Approved Document L: volume 1 (dwellings) (takes effect on 4 March 2027)

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The Building Regulations 2010

L

Conservation of fuel and power and the minimisation of greenhouse gases

2026 version - For use in Wales*

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This approved document supports Part L of Schedule 1 to the Building Regulations 2010.

This approved document takes effect on 4 March 2027 for use in Wales. It does not apply to work on a particular building where a building notice, full plans application or initial notice have been submitted before that date, provided the work for each building is started before 4 March 2028.Full detail of the transitional arrangements can be found in Circular Letter 003/2026 published on Building regulations | Sub- topic | GOV.WALES

*This approved document gives guidance for compliance with the Building Regulations for building work carried out in Wales.

© Crown copyright 2026, Welsh Government,

WG54476, Digital ISBN 978-1-83745-485-3

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The Approved Documents

What is an Approved Document?

This Approved Document, which takes effect on 4 March 2027, has been approved and issued by the Welsh Ministers to provide practical guidance on ways of complying with the energy efficiency requirements of the Building Regulations 2010 for Wales, as amended, which are referred to throughout the remainder of this document as ‘the Building Regulations’.

These Approved Documents give guidance on each of the technical parts of the regulations and on regulation 7 (see the back of this document). The Approved Documents provide guidance for common building situations.

It is the responsibility of those carrying out building work to meet the requirements of the Building Regulations 2010. Although it is ultimately for the courts to determine whether those requirements have been met, the Approved Documents provide practical guidance on potential ways to achieve compliance with the requirements of the regulations in Wales.

Although Approved Documents cover common building situations, compliance with the guidance set out in the Approved Documents does not provide a guarantee of compliance with the requirements of the regulations because the Approved Documents cannot cater for all circumstances, variations and innovations. Those with responsibility for meeting the requirements of the regulations will need to consider for themselves whether following the guidance in the Approved Documents is likely to meet those requirements in the particular circumstances of their case.

Note that there may be other ways to comply with the requirements than the method described in an approved document. If you prefer to meet a relevant requirement in some other way than described in an Approved Document, you should seek to agree this with the relevant building control body at an early stage.

Where the guidance in the Approved Document has been followed, a court or inspector will tend to find that there is no breach of the regulations. However, where the guidance in the approved document has not been followed, this may be relied upon as tending to establish breach of the regulations and, in such circumstances, the person carrying out building works should demonstrate that the requirements of the regulations have been complied with by some other acceptable means or method.

In addition to guidance, some Approved Documents include provisions that must be followed exactly, as required by regulations or where methods of test or calculation have been prescribed by the Welsh Ministers.

Each approved document relates only to the particular requirements of the Building Regulations 2010 that the document addresses. However, building work must also comply with all other applicable requirements of the Building Regulations 2010 and all other applicable legislation.

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How to use this approved document

This document uses the following conventions.

a. Text against a blue background is an extract from the Building Regulations 2010 or the Building (Registered Building Control Approvers etc.) (Wales) Regulations 2024 (both as amended). These extracts set out the legal requirements of the regulations.

b. Key terms, printed in blue, are defined in Appendix A.

c. References are made to appropriate standards or other documents, which can provide further useful guidance. When this approved document refers to a named standard or other reference document, the standard or reference has been clearly identified in this document. Standards are highlighted in bold throughout. The full name and version of the document referred to is listed in Appendix C (other documents) or Appendix D (standards). However, if the issuing body has revised or updated the listed version of the standard or document, you may use the new version as guidance if it continues to address the relevant requirements of the Building Regulations.

d. Standards and technical approvals also address aspects of performance or matters that are not covered by the Building Regulations and may recommend higher standards than required by the Building Regulations. Nothing in this Approved Document precludes you from adopting higher standards.

e. Additional commentary in italic text appears after some numbered paragraphs. This commentary is intended to assist understanding of the immediately preceding paragraph or sub-paragraph, or to direct readers to sources of additional information, but is not part of the technical guidance itself.

User requirements

The Approved Documents provide technical guidance. Users of the Approved Documents should have adequate knowledge and skills to understand and apply the guidance correctly to the building work being undertaken.

Where you can get further help

If you are not confident that you possess adequate knowledge and skills to apply the guidance correctly or if you do not understand the technical guidance or other information in this approved document or the additional detailed technical references to which it directs you, you should seek further help. Help can be obtained through a number of routes, some of which are listed below:

a. If you are the person undertaking the building work: either from your local authority building control service or from a registered building control approver.

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ADs b. If you are registered with a competent person scheme: from the scheme operator c. If your query is highly technical: from a specialist or an industry technical body for the relevant subject.

The Building Regulations

The following is a high level summary of the Building Regulations relevant to most types of building work. Where there is any doubt you should consult the full text of the regulations, available at www.legislation.gov.uk .

Building work

Regulation 3 of the Building Regulations defines ‘building work’. Building work includes among other things:

a. the erection or extension of a building b. the provision or extension of a controlled service or fitting in or in connection with a building c. the material alteration of a building or a controlled service or fitting.

Regulation 4 states that building work should be carried out in such a way that, when work is complete:

a. For new buildings or work on a building that complied with the applicable requirements of the Building Regulations: the building complies with the applicable requirements of the Building Regulations.

b. For work on an existing building that did not comply with the applicable requirements of the Building Regulations:

i. the work itself must comply with the applicable requirements of the Building Regulations and ii. the building must be no more unsatisfactory in relation to the requirements than before the work was carried out.

Material change of use

Regulation 5 defines a ‘material change of use’ in which a building or part of a building that was previously used for one purpose will be used for another.

The Building Regulations set out requirements that must be met before a building can be used for a new purpose. To meet the requirements, the building may need to be upgraded in some way.

Materials and workmanship

In accordance with regulation 7, building work must be carried out in a workmanlike manner using adequate and proper materials. Guidance on regulation 7(1) is given in Approved Document 7, and guidance on regulation 7(2) is provided in Approved Document B.

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Independent third party certification and accreditation

Independent schemes of certification and accreditation of installers can provide confidence that the required level of performance for a system, product, component or structure can be achieved.

Building control bodies may accept certification under such schemes as evidence of compliance with a relevant standard. However, a building control body should establish before the start of the building work that a scheme is adequate for the purposes of the Building Regulations. The local authority still retains inspection and enforcement powers in these circumstances.

Energy efficiency requirements

Part 6 of the Building Regulations imposes additional specific requirements for energy efficiency.

If a building is extended or renovated, the energy efficiency of the existing building or part of it may need to be upgraded.

Notification of work

Most building work and material changes of use must be notified to a building control body unless one of the following applies.

a. It is work that will be self-certified by a registered competent person or certified by a registered third party.

b. It is work exempted from the need to notify by regulation 12(6A) of, or Schedule 4 to, the Building Regulations.

Responsibility for compliance

People who are responsible for building work (e.g. agent, designer, builder or installer) must ensure that the work complies with all applicable requirements of the Building Regulations. The building owner may also be responsible for ensuring that work complies with the Building Regulations. If building work does not comply with the Building Regulations, the building owner may be served with an enforcement notice.

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Section 0

Section 0

Introduction

0.1This Approved Document, Approved Document L, Volume 1: Dwellings, gives guidance on how to comply with Part L of Schedule 1 to the Building Regulations and the energy efficiency requirements for dwellings. For guidance for non-domestic buildings, use Approved Document L, Volume 2: Buildings other than dwellings.

0.2This Approved Document contains the following sections.

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Application

0.3The guidance in this volume 1 of Approved Document L applies to dwellings only. In a mixed-use building, Approved Document L Volume 2 should be consulted for building work in those parts of the building that are not dwellings.

Note: Dwellings are self-contained units. Rooms for residential purposes and buildings that contain only rooms for residential purposes are not dwellings, and so Approved Document L Volume 2 applies to them.

New Dwellings

0.4Guidance for newly constructed dwellings is given in Sections 1 to 9 of this Approved Document.

New dwellings with conservatories and porches

0.5Conservatories and porches should be included in the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity rating calculations only if they are constructed at the same time as a new dwelling, and:

a. there is no thermal element between the dwelling and the conservatory and/or porch; or b. the conservatory and/or porch will be heated via fixed heating.

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Section 0

Common areas in buildings with multiple dwellings

0.6The common areas of buildings containing more than one dwelling fall outside the scope of this document. For the common areas:

a. If they are heated follow Approved Document L, volume 2: Buildings other than dwellings.

b. if they are unheated, individual fabric elements should meet the minimum standards set out in Section 3.

Extensions and work in existing dwellings

0.7Guidance for building work on existing dwellings is given in the relevant paragraphs within Sections 3 to 12 of this Approved Document.

Exemptions for historic and traditional buildings

0.8Work to the following types of dwellings does not need to comply fully with the energy efficiency requirements where to do so would unacceptably alter the dwelling’s character or appearance:

a. Those listed in accordance in accordance with section 76 of the Historic Environment (Wales) Act 2023.

b. Those in a conservation area designated in accordance with section 158 of the Historic Environment (Wales) Act 2023.

c. Those included in the schedule of monuments maintained under section 3 of the Historic Environment (Wales) Act 2023.

0.9Work to a dwelling in paragraph 0.8 must comply with the energy efficiency requirements where this would not unacceptably alter the dwelling’s character or appearance. The work should comply with standards in this Approved Document to the extent that it is reasonably practicable.

Historic and traditional dwellings where special considerations apply

0.10In addition, special considerations apply to works to the following three classes of non-exempt existing buildings:

a. of architectural and historic interest and are referred to as a material consideration in a local authority’s development plan or local development framework; or b. of architectural and historic interest and are within national parks, areas of outstanding natural beauty, registered historic parks and gardens, registered battlefields, the curtilages of scheduled monuments, and world heritage sites; or c. of traditional construction with permeable fabric that both absorbs and readily allows the evaporation of moisture.

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Section 0

0.11Work to such buildings is required to comply with the energy efficiency requirements as far as is reasonably practicable. In considering what is reasonably practicable, the work should not unacceptably alter or mar the character of the building or increase the risk of long-term deterioration of the building’s fabric or fittings.

0.12Additional guidance on how to implement specific energy efficiency or renewable energy measures is available in Cadw’s How to Improve Energy Efficiency in Historic Buildings in Wales (2022) and Renewable energy and your historic building (2010).

0.13In general, new extensions to dwellings of historic and architectural interest should comply with the energy efficiency requirements: guidance on how to comply is set out within Sections 9 and 10. The only exception would be where there is a need for the extension to be consistent with the character of the existing building.

0.14Particular issues relating to work to dwellings of historic and architectural interest warrant sympathetic treatment and would benefit from further specialist professional advice. These issues include:

a. restoring the historic character of a building that has been subject to a previous inappropriate alteration, for example, replacement windows and doors; or b. rebuilding a former historic building, for example, following a fire or infilling a gap site in a terrace; or c. enabling the fabric of historic buildings to control moisture (as originally designed) and avoid potential long-term deterioration.

0.15When assessing dwellings of historic and architectural interest where special consideration may apply, it is important that the building control body takes into account the advice of the local authority’s conservation officer, particularly where the work requires planning permission and/or listed building consent.

Exemptions for covered areas, conservatories and porches

0.16Parts of a building which are not heated, for example garages, carports and outbuildings are exempt. Conservatories and porches are also exempt from the energy efficiency requirements if they fulfil all of the following requirements:

a. be at ground level; and b. have an internal floor area that is less than 30m 2; and c. be thermally separate from the heated area of the dwelling, and d. the conservatory or porch contains no fixed heating appliance or the buildings heating system is not extended into the conservatory or porch.

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Section 0

Live–work units

0.17A unit that contains both living accommodation and space to be used for commercial purposes (e.g. as a workshop or office) should be treated as a dwelling, as long as the commercial part can revert to domestic use.

0.18The commercial part of a building can revert to domestic use if, all of the following apply:

a.there is direct access between the commercial space and the living accommodation; and

b.the commercial space and the living accommodation are within the same

thermal envelope; and

c.the living accommodation comprises a substantial proportion of the total area of the unit. What constitutes a ‘substantial proportion’ should be assessed on a case-by-case basis.

Note: A large non-domestic building that contains a small flat for a manager is not treated as a dwelling. A dwelling that contains a room used as an office or utility space is still treated as a dwelling.

Mixed-use developments

0.19When constructing a dwelling as part of a larger building that contains other types of accommodation, sometimes called a mixed-use development, refer to the two volumes of Approved Document L as follows:

a.For guidance on each individual dwelling, use this Approved Document (Approved Document L volume 1).

b.For guidance on the non-dwelling parts of the building, such as heated common areas and the commercial or retail space, use Approved Document L, volume 2: Buildings other than dwellings

Selected key interactions with other parts of the Building Regulations

0.20The Approved Documents set out, what in ordinary circumstances, may be accepted as one way to comply with the Building Regulations. It remains the responsibility of those designing or undertaking building work to assess, on a case-by-case basis, whether specific circumstances require additional or alternative measures to achieve compliance with the regulatory requirements.

There are interactions between many of the requirements of the Building Regulations, here is guidance on some key interactions.

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Section 0

Interaction with Part B

0.21This Approved Document provides guidance for fixed building services and on- site electricity generation. Where on-site electricity is provided for occupant use in dwellings and buildings containing dwellings, the guidance on the fire safety requirements (including means of escape) for the building in Approved Document B should be followed. Where insulation is installed and becomes part of the external wall in a relevant building as defined in regulation 7(2), the guidance of Approved Document B, Volume 1, should be followed.

Interaction with Part C

0.22This Approved Document provides guidance and examples on upgrading thermal elements. A lesser standard may be acceptable in order to ensure thermal elements comply with the requirements of Part C of interstitial and surface condensation. Guidance in Approved Document C should be followed.

Interaction with Part E

0.23This Approved Document provides guidance on insulation that is reasonably continuous and limits thermal bridging. Construction junctions should limit noise transfer where Part E of the Building regulations sets a requirement. Approved Document E should be followed.

Interaction with Part F

0.24This Approved Document provides guidance on reducing unwanted heat loss, by achieving optimum airtightness. The air infiltration of a dwelling should be considered when specifying the minimum amount of purpose-provided ventilation, following Approved Document F.

Interaction with Part J

0.25This Approved Document provides guidance on airtightness. Guidance on permanent ventilation openings for open flued appliances in very airtight dwellings should be followed in Approved Document J.

Interaction with Part K and M

0.26This Approved Document provides guidance on controls for fixed building services and on-site electricity generation. Where manual controls are provided, they should be within reasonable reach of the occupants. Guidance is provided in Approved Documents K and M.

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Section 0

Interaction with Part O

0.27This document provides guidance on conserving energy use and avoiding CO 2 emissions associated with active cooling. Guidance on mitigating the risk of overheating in new dwellings in relation to the health and comfort risks to occupants is provided in Approved Document O.

Interaction with Part P

0.28This Approved Document provides guidance for on-site electricity generation and energy storage. Where on-site electricity generation or energy storage is installed, the electrical safety requirements of the Building Regulations should be met, Approved Document P should be followed.

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Section 0

Regulations 24, 25, 25C(b), 25D 26, 26A, 26B, 26C, 27, 27A, 27B and 27C: Energy performance of dwellings calculations

This Approved Document deals with the requirements of regulations 24, 25, 25C(b), 25D, 26, 26A, 26B, 26C, 27, 27A,27B and 27C of the Building Regulations 2010 (as amended).

Regulation 24 - Methodology of calculation and expression of energy performance

(1) The Secretary of State shall approve–

(a) a methodology of calculation of the energy performance of buildings, including methods for calculating asset ratings and operational ratings of buildings; and

(b) ways in which the energy performance of buildings, as calculated in accordance with the methodology, shall be expressed.

(2) In this regulation–

‘asset rating’ means an energy performance indicator determined from the amount of energy estimated to meet the different needs associated with a standardised use of the building; and

‘operational rating’ means an energy performance indicator determined from the amount of energy consumed during the occupation of a building over a period of time and the energy demand associated with a typical use of the building over that period.

Regulation 25 - Minimum energy performance requirements for new buildings

The Secretary of State shall approve minimum energy performance requirements for new buildings, in the form of target CO 2 emission rates, which shall be calculated and expressed in accordance with the methodology approved pursuant to regulation 24.

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Section 0

Regulation 25C (b) – New Buildings: Minimum energy performance requirements

Minimum energy performance requirements must be approved by the Welsh Ministers, calculated and expressed in accordance with the methodology approved pursuant to regulation 24, for- new dwellings, in the form of target fabric performance values.

Regulation 25D - Energy use intensity rating

Energy use intensity ratings must be approved by the Welsh Ministers, applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulations 24 for new buildings.

Regulation 26 – CO 2 emission rates for new buildings

Where a building is erected, it shall not exceed the target CO 2 emission rate for the building that has been approved pursuant to regulation 25, applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulation 24.

Regulation 26A - Primary energy rates for new buildings

Where a building is erected, it must not exceed the target primary energy rate for the building which has been approved pursuant to regulation 25C(a), applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulation 24.

Regulation 26B – Fabric performance values for new dwellings

Where a dwelling is erected, it must not exceed the target fabric performance values for the dwelling which have been approved pursuant to regulation 25C (b), applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulation 24.

Regulation 26C – Minimum energy use intensity rating

Where a dwelling is erected, it must equal or exceed the energy use intensity rating for the dwelling which has been approved pursuant to regulation 25D applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulation 24 for new buildings.

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Section 0

Regulation 27 - CO 2 emission rate calculations

(1) This regulation applies where a building is erected and regulation 26 applies.

(2) Not later than the day before the work starts, the person carrying out the work shall give the local authority a notice which specifies–

a.the target CO 2 emission rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

b.the CO 2 emission rate for the building as designed, calculated and expressed in and accordance with the methodology approved pursuant to regulation 24; and

c.a list of specifications to which the building is to be constructed.

(3) Not later than five days after the work has been completed, the person carrying out the work shall give the local authority–

a.a notice which specifies–

i. the target CO 2 emission rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

ii. the CO 2 emission rate for the building as constructed, calculated and expressed in and accordance with the methodology approved pursuant to regulation 24; and iii. whether the building has been constructed in accordance with the list of specifications referred to in paragraph (2) (c), and if not a list of any changes to those specifications; or

b.a certificate of the sort referred to in paragraph (4) accompanied by the

information referred to in sub-paragraph (a).

(4) A local authority is authorised to accept, as evidence that the requirements of regulation 26 have been satisfied, a certificate to that effect by an energy assessor who is accredited to produce energy performance certificates for that category of building.

(5) In this regulation ‘specifications’ means specifications used for the calculation of the

CO 2 emission rate.

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Section 0

27A - Primary energy rate calculations.—

(1) This regulation applies where a building is erected and regulation 26A applies.

(2) Not later than the day before the work starts, the person carrying out the work must give the local authority a notice which specifies—

(a) the target primary energy rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

(b) the primary energy rate for the building as designed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24; and

(c) a list of specifications to which the building is to be constructed.

(3) Not later than five days after the work has been completed, the person carrying out the work must give the local authority—

(a) a notice which specifies—

(i) the target primary energy rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

(ii) the calculated primary energy rate for the building as constructed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24; and

(iii) whether the building has been constructed in accordance with the list of specifications referred to in paragraph 2(c), and if not a list of any changes to those specifications; or (b) a certificate of the sort referred to in paragraph (4) accompanied by the information referred to in subparagraph (a).

(4) A local authority is authorised to accept, as evidence that the requirements of regulation 26A have been satisfied, a certificate to that effect by an energy assessor who is accredited to produce energy performance certificates for that category of building.

(5) In this regulation, “specifications” means specifications used for the calculation of the primary energy rate.

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Section 0

Regulation 27B - Fabric performance values calculations

(1) This regulation applies where a dwelling is erected and regulation 26B applies.

(2) Not later than the day before the work starts, the person carrying out the work must give the local authority a notice which specifies—

(a) the target fabric performance values for the dwelling, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

(b) the fabric performance values for the dwelling as designed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24; and

(c) a list of specifications to which the dwelling is to be constructed.

(3) Not later than five days after the work has been completed, the person carrying out the work must give the local authority—

(a)a notice which specifies—

(i) the target fabric performance values for the dwelling, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

(ii) the calculated fabric performance values for the dwelling as constructed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24; and

(iii) whether the dwelling has been constructed in accordance with the list of specifications referred to in paragraph 2(c), and if not a list of any changes to those specifications; or

(b) a certificate of the sort referred to in paragraph (4) accompanied by the information referred to in sub-paragraph (a).

(4) A local authority is authorised to accept, as evidence that the requirements of regulation 26B have been satisfied, a certificate to that effect by an energy assessor who is accredited to produce energy performance certificates for that category of building.

(5) In this Regulation, “specifications” means specifications used for the calculation of the fabric performance values.”

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Section 0

27C – Minimum energy use intensity rating calculations

(1) This regulation applies where a dwelling is erected and regulation 26C applies.

(2) Not later than the day before the work starts, the person carrying out the work must give the local authority a notice which specifies—

(a) the energy use intensity rating for the dwelling as designed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24, and

(b) a list of specifications to which the dwelling is to be constructed.

(3) Not later than five days after the work has been completed, the person carrying out the work must give the local authority—

(a) a notice which specifies—

(i) the target energy use intensity rating for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24,

(ii) the energy use intensity rating of the building as constructed, calculated and expressed in accordance with the methodology approved pursuant to regulation 24, and

(iii) whether the building has been constructed in accordance with the list of specifications referred to in paragraph (2)(b), and if not, a list of any changes to those specifications, or

(b) a certificate of the sort referred to in paragraph (4) accompanied by the information referred to in sub-paragraph (a).

(4) A local authority is authorised to accept as evidence that the requirements of regulation 26C have been satisfied, a certificate to that effect by an energy assessor who is accredited to produce energy performance certificates for that category of building.

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Section 0

Note: Where the building control body is a registered building control approver, see regulation 5 of the Building (Registered Building Control Approvers etc.) (Wales) Regulations 2024.

Regulation 24

Regulation 24 requires Welsh Ministers to approve a methodology of calculation of the energy performance of a building. For a new dwelling, the approved methodology is the Standard Assessment Procedure. Calculation methodologies are set out in Section 1 and Section 2 of this Approved Document.

Regulation 25

Regulation 25 requires Welsh Ministers to approve minimum energy performance requirements. These requirements are in the form of a target primary energy rate, a target emission rate, target fabric performance values and a target energy use intensity. The targets are set out in Section 1 of this Approved Document.

Regulations 26, 26A, 26B and 26C

A newly constructed dwelling must be shown to meet regulations 26, 26A, 26B and 26C by producing calculations to show that the dwelling meets all of the following.

a.Target primary energy rate.

b.Target emission rate.

c.Target fabric performance values.

d.Target Energy Use Intensity.

Section 2 of this approved document sets out how to produce these calculations.

Regulations 27, 27A, 27B and 27C

Both before and after a newly constructed dwelling is built, a notice must be given to the building control body of the calculations.

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Section 1

Section 1

Calculating the target emission rate, target primary energy rate, target fabric performance values and target energy use intensity rating.

Target primary energy rate, target emission rate and target energy use intensity rate

1.1A new dwelling must be built to a minimum standard of total energy performance. This is evaluated by comparing calculations of the performance of the dwelling against calculations of the performance of a theoretical dwelling called the ‘notional dwelling’. This must be carried out both at the design stage and when work is complete.

The notional dwelling is of the same size and shape as the actual dwelling and has standardised properties for fabric and services. The full properties of the notional dwelling are set out in the UK Government’s Standard Assessment Procedure (SAP) for energy rating of dwellings.

1.2The energy performance of the notional dwelling is described using following metrics.

a.The Target Primary Energy Rate, in kWhPE /m2/year: this is the maximum primary energy used by the dwelling.

b.The Target Emission Rate, in kgCO 2e/m 2/year: this is the minimum standard for CO 2 emissions from the dwelling.

c.The Target Energy Use Intensity, in kWh/m 2/yr: this is the maximum energy use by the dwelling.

1.3The Target Primary Energy Rate, Target Emission Rate and Target Energy Use Intensity must be calculated using the UK Government’s Standard Assessment Procedure for energy rating of dwellings, version 10.3. The standardised properties are in Appendix R and summarised in Appendix E of this Approved Document.

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Section 1

Target fabric performance values

1.4A new dwelling must also meet the Target Fabric Performance Values for elements of the fabric. Target Fabric Performance Values can be met by adopting the mandatory minimum energy efficiency standards for the building fabric, which are set out in Section 3 (table 3.1).

Notional dwelling specification

1.5The full notional dwelling specification used in the Standard Assessment Procedure is given in Appendix R of SAP version 10.3: Standard Assessment Procedure SAP 10 The notional dwelling specification is summarised in Appendix E.

District heat networks and communal heat networks – determining the target CO2 and Primary Energy (the notional dwelling)

1.6For a dwelling connected to a district heat network the notional building will use primary energy and CO 2 emission factors for heat and hot water as listed in Table 1.1.

1.7For a dwelling connected to a communal heat network the notional building will use the characteristics of the heat network and associated services as defined in Appendix R of the SAP 10.3 specification.

Note: Software platforms, and interfaces relating to them which are approved for use with the approved methodology includes functionality to allow the notional dwellings to be modelled as connected to heat networks

Table 1.1 Primary energy and CO 2 factors to be used for heating and hot water for dwellings connected to district heat networks

Note:

1.The heat network status of ‘sleeved’ means that a declaration has been made as described in paragraphs 1.8 and 1.9

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Section 1

1.8For a district heat network to have the status of ‘sleeved’ a declaration of sleeving capacity should be made to the building control body. The declaration should be signed by both of the following.

a.The body responsible for the operation of the district heat network.

b.A suitably qualified person.

Note: Only district heat networks can be sleeved. Communal heat networks are not able to be sleeved.

1.9The declaration of sleeving capacity should state all of the following:

a.That the district heat network is providing both space heating and water heating to the dwelling.

b.The thermal energy (in kWh per year) that is required by the dwelling for space heating and hot water, as calculated using the same version of the approved methodology as used to calculate the dwelling emission rate.

c.The proportion of this thermal energy which will delivered by the district heat network to the dwelling.

d.That at least 90% of the thermal energy delivered by the district heat network to the dwelling will be provided by new or unused capacity of the types described in Table 1.2. Any temporary plant also needs to be of the types described in Table 1.2.

e.That the new or unused capacity which is being allocated to the dwelling through this process has not been declared to any building control body for any other applications which are ongoing, or which have received a completion certificate.

f.Any new capacity should be added to the district heat network within 5 years of the ‘as-built stage’ assessment. The change in capacity should be described and evidence of both of the following provided.

i.That planning permission, if required, has been granted for the new capacity.

ii.That the district heat network will connect to the new source. A signed contract to connect and supply heat should be provided.

Note: Any new capacity which is to be added later than 5 years after the ‘as-built stage’ assessment should not be included in the declaration of sleeving capacity.

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Section 1

Table 1.2 Low-carbon heat sources which can be included in a declaration of sleeving capacity (1)

Low-carbon heat sources

Electrically powered heat pumps

Waste heat (including from power stations)

Geothermal heat

Electric boiler

Solar thermal

Biofuels

Note

1.The declaration of low carbon thermal energy (kWh) from heat pumps to the dwelling should include both the ‘source’ thermal energy (e.g. heat from the air) and the electrical power consumed as an input to the heat pump.

Buildings that contain multiple dwellings

1.10For a building containing flats, an average target primary energy rate, average target emission rate and average target energy use intensity may be calculated as an alternative to an individual target for each dwelling.

Calculating an average target primary energy rate, average target emission rate or average target energy use intensity for separate buildings on the same site is not considered a reasonable method to show compliance.

Calculating an average target primary energy rate, average target emission rate or average target energy use intensity for a row of terraced houses is not considered a reasonable method to show compliance.

1.11The floor-area-weighted average of the target primary energy rate for all the dwellings in the building should be calculated using the following formula:

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Section 1

{(target primary energy rate1 × 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎1) + (target primary energy rate2 × 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎2) + (target primary energy rate3 × 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎3) + … } (𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎1 + 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎2 + 𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 𝑎𝑎𝐹𝐹𝑎𝑎𝑎𝑎3 + … )

1.12The average target emission rate should be calculated using the formula above, but replacing target primary energy rate with target emission rate.

The average target energy use intensity should be calculated using the formula above in paragraph 1.10 but replacing target primary energy rate with target energy use intensity.

1.13Each individual dwelling in a building that contains more than one dwelling should meet the Target Fabric performance values.

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Section 2

Section 2

Calculating the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity

2.1The same approved methodology used to calculate the target primary energy rate, target emission rate and target energy use intensity must be the same as that used to calculate the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity.

2.2The dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity must be calculated at both of the following points using the same approved methodology:

a. Before work starts, using design values.

b. When work is complete, using figures for the building as constructed, and incorporating both ofthe following:

i. Any changes that have been made during construction to the list of specifications.

ii. The measured air permeability.

2.3At both of these points the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity must not exceed the target primary energy rate, target emission rate and target energy use intensity. The specification of the actual dwelling may vary from that of the notional dwelling if the dwelling meets the target primary energy rate, target emission rate, target energy use intensity, target fabric performance values and the guidance in this approved document.

Building control notification

2.4The building control body must be notified before the work starts, of all of the following:

a.The target primary energy rate and the dwelling primary energy rate (calculated using design values).

b.The target emission rate and the dwelling emission rate (calculated using design values).

c.The target energy use intensity and the dwelling energy use intensity (calculated using design values).

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Section 2 d. The dwelling fabric performance values (calculated using design values).

e. A list of specifications used in the calculations.

2.5Items (a) to (e) above may be reported using the ‘design stage’ Building Regulations Wales Part L compliance report (BRWL report). For further details of the design stage BRWL report, see Appendix B.

2.6The building control body must be notified once the work is complete of all of the following.

a.the as-built target primary energy rate and as-built dwelling primary energy rate

b.the as-built target emission rate and as-built dwelling emission rate

c.the as-built target energy use intensity and as-built dwelling energy use intensity

d.the as-built dwelling fabric performance values

e.A list of specifications used in the as-built calculations, and whether the specifications have changed from those used in the design stage calculations.

Building control bodies are authorised to accept notification of (a) to (e) above as reported in the ‘as-built’ stage BRWL report together with photographic evidence of compliance. For further detailsof the post-completion BRWL report and photographic evidence, see Appendix B.

Note: Developers may wish to provide building control bodies with the required photographs as the work progresses on site, however, photographs are not a replacement for site inspections by building control bodies.

Buildings that contain multiple dwellings

2.7Buildings that contain more than one dwelling must comply with one of the following.

a.every individual dwelling meets all of the following conditions:

i.a dwelling primary energy rate that is no greater than the individual dwelling’s target primary energy rate

ii.a dwelling emission rate that is no greater than the individual dwelling’s target emission rate

iii.a dwelling energy use intensity that is no greater than the individual dwelling’s target energy use intensity

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Section 2

Or

b.all of the following are met:

i.the average dwelling primary energy rate for the whole building, calculated in accordance with paragraph 2.8, is no greater than the average target primary energy rate for the whole building.

ii.the average dwelling emission rate for the whole building, calculated in accordance with paragraph 2.8, is no greater than the average target emission rate for the whole building.

iii.the average dwelling energy use intensity for the whole building, calculated in accordance with paragraph 2.8, is no greater than the average target energy use intensity for the whole building.

Note: Guidance on how to calculate an average target primary energy rate, an average target emission rate and average target fabric energy efficiency rate is given in paragraph 1.7.

2.8The average dwelling primary energy rate, average dwelling emission rate, and average dwelling energy use intensity are the floor-area-weighted averages of the dwelling primary energy rates, dwelling emission rates and dwelling energy use intensities for all the individual dwellings in the building.

The average dwelling primary energy rate, average dwelling emission rate, and average dwelling energy use intensity should be calculated using the same averaging methodology set out in paragraphs 1.9 to 1.12.

An average dwelling primary energy rate, average dwelling emission rate or average dwelling energy use intensity should not be calculated across separate buildings on a site.

An average dwelling primary energy rate, average dwelling emission rate or average dwelling energy use intensity should not be calculated for a row of terraced houses.

Note: Information and photographic evidence must be provided for each individual dwelling, as described in Section 9 and Appendix B.

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Section 2

Special considerations when calculating dwelling primary energy rate, dwelling primary energy rate and dwelling energy use intensity

Secondary heating

2.9When calculating the dwelling primary energy rate, dwelling emission rate, and dwelling energy use intensity for a dwelling with a secondary heating appliance, all of the following apply.

a.The value used in the calculation for the fraction of heat provided by the secondary heating system must be as defined by the approved methodology for the particular combination of main heating system and secondary heating appliance.

b. The efficiency of the secondary heating appliance with its appropriate fuel should be used in the calculation of all of the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity.

c. No chimney or flue should be provided when no appliance is installed.

Community heating systems and district heat networks

2.10If thermal energy is supplied from a district heat network or communal heat network, CO 2 emission factors and primary energy factors for the heat delivered to the dwelling by the district heat network should be determined by considering the details of the scheme and all of the following guidance. These factors should be used in the calculations of the dwelling primary energy rate and dwelling emission rate.

a. The CO 2 emission factor and primary energy factor for heat delivered to the dwelling are entered as inputs into the approved methodology for calculating the dwelling primary energy rate and dwelling emission rate.

b. Calculations should take account of the performance of the whole system in all cases, including where a declaration of sleeving capacity has been made. This should include the performance of the distribution circuits, all heat generating plants, combined heat and power (CHP), storage, and any waste heat recovery or heat dumping.

Note: If a declaration of sleeving is made, the CO2 emission factor and primary energy factor are still required to be calculated

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Section 2 c. The electricity generated by any CHP or trigeneration scheme should be credited using the appropriate CO 2 emission and primary energy factors.

d. CO 2 emissions and primary energy associated with the thermal energy streams of a trigeneration scheme should be attributed in proportion to the output energy streams.

e. When calculating the dwelling primary energy rate and dwelling emission rate for a dwelling connected to a district heat network, the calculation should include all of the following i) heat sources already connected to the district heat network ii) any significant changes to the planned heat supply as a result of the connection of new heat sources to the district heat network within 5 years of the ‘as-built stage’ assessment.

f. When there will be a change to the planned heat supply to the district heat network within 5 years of the ‘as-built stage’ assessment as described in (e)(ii) above, a submission to the building control body should be made providing details of the additional source(s) and showing both of the following.

i. That planning permission, if required, has been granted for the change.

ii. That the heat network will connect to the new source. A signed contract to connect and supply heat should be provided.

g.For communal heat networks, the CO2 emission factors and primary energy factors that are used to calculate the dwelling emission rate and dwelling primary energy rate should be calculated as follows.

The primary energy factor for heat output should be calculated as:1/H × (F × PE F – E × PE E ) where:

H is the useful heat (excluding heat rejected) in kWh

F is the fuel input in kWh

PE F is the primary energy factor for the input fuel in kWh PE /kWh E is the electricity production from the scheme in kWh

PE E is the primary energy factor for district heat CHP generated electricity in kWh PE /kWh.

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Section 2

The CO2 emission factor for the heat output should be calculated as:

1/H × (F × CO2F – E × CO2E ) where:

H is the useful heat (excluding heat rejected) in kWh F is the fuel input in kWh

CO 2F is the emission factor for the input fuel in kgCO 2 /kWh E is the electricity production from the scheme in kWh

CO 2E is the emission factor for district heat CHP generated electricity in kgCO 2 /kWh.

h.The dwelling primary energy rate and dwelling emission rate submitted to the building control body should be accompanied by a report, signed by the body responsible for the operation of the district heat network and a suitably qualified person, detailing how the CO2 emission factors and primary energy factors were derived.

Swimming pool basins

2.11When determining the dwelling primary energy rate, the dwelling emission rate and dwelling energy use intensity for a dwelling with a swimming pool, the thermal performance of the pool basin should not be included in the calculation. Instead, the dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity should be calculated as if the area covered by the pool were replaced with the equivalent area of floor with the same U-value as the pool surround.

Party walls

2.12When calculating the dwelling primary energy rate, dwelling emission rate and dwelling fabric energy efficiency rate, one of the following should be followed.

a.If the approved methodology used in the calculation of the dwelling emission rate and dwelling primary energy rate is the Standard Assessment Procedure (SAP) version 10.3, use the values given in section 3.7 of the SAP version 10.3.

b.If the approved methodology used in the calculation of the dwelling emission rate and dwelling primary energy rate is the Home Energy Model (HEM), the HEM condition for the party wall should be selected from Table 2.1 for the type of construction adopted.

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Section 2

Table 2.1 HEM condition for party walls 1

Taking account of internal lighting when calculating dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity

2.13The calculations of dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity should account for the efficacy of light sources installed in the fixed lighting locations.

Achieving the target primary energy rate, target emission rate, target energy use intensity and target fabric performance values

2.14Provided the dwelling satisfies the minimum standards for fabric elements set out in Section 3, the target primary energy rate, target emission rate and target energy use intensity can be achieved by using any combination of the following.

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Section 2

a.fabric energy efficiency

b.efficient building services/systems

c.low and zero carbon technologies (including renewable energy generation) integrated in an appropriate mix.

2.15The target fabric performance values can only be achieved through fabric energy efficiency as set out in section 3.

.

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Section 2

Requirement L1(a): Limiting heat gains and losses

This Approved Document deals with the requirements of Part L1 of Schedule 1 to the Building Regulations 2010.

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Section 2

Intention

In the Welsh Minister’s view, Regulation L1(a) for new dwellings will be met where both of the following are achieved.

a.Limiting unwanted heat losses from the dwelling by meeting the standards for all of the following.

i.the building fabric, including walls, floors, roof, windows and openings paragraphs 3.1 to 3.3 and paragraphs 3.13 to 3.15.

ii.uncontrolled air loss – paragraph 3.16.

iii.the pipework and services paragraphs 3.18 to 3.22 and paragraphs 3.24 to 3.33.

b.Limiting unwanted heat gains to the dwelling, throughout the year, through any of the routes listed in (a) above as set out in Section 34.

In the Welsh Minister’s view, Regulation L1(a) for existing dwellings will be met by meeting the standards in paragraphs 3.8 to 3.10 and Sections 10, 11 and 12.

Regulation 25C(b) and 26B

Regulation 25C (b) – New Buildings: Minimum energy performance requirements

Minimum energy performance requirements must be approved by the Welsh Ministers, calculated and expressed in accordance with the methodology approved pursuant to regulation 24, for- new dwellings, in the form of target fabric performance values.

Regulation 26B – Fabric performance values for new dwellings

Where a dwelling is erected, it must not exceed the target fabric performance values for the dwelling which have been approved pursuant to regulation 25C (b), applying the methodology of calculation and expression of the energy performance of buildings approved pursuant to regulation 24.

Intention

In the Welsh Minister’s view, Regulation 25C(b) and 26B will be met where the new dwelling meets or is better than the worst acceptable fabric values set out in paragraph 3.7 Table 3.1.

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Section 3

Section 3

Limiting heat losses and gains, and target fabric performance values

U-values

3.1U-values should be assessed using the methods and conventions set out in the Building Research Establishment’s BR 443. U-values should be assessed for the whole fabric element (e.g. in the case of a window, the combined performance of the glazing and the frame).

New Dwellings

3.2For new dwellings, the U-value of a window or door should be determined using one of the following.

a. Measured using the hot-box method set out in BS EN ISO 12567-1 for windows or doors, and in BS EN ISO 12567-2 for roof windows.

b. Calculated using the actual size and configuration of the window in line with BS EN ISO 10077-1 and BS EN ISO 10077-2.

3.3For new dwellings, determination of a window or door U-value is to include all of the following where present.

a.Actual frame sections, e.g. different width outer frames.

b.Sills/thresholds.

c.Add-ons/frame extenders (any additional non-structural element that extends the size of the frame), e.g. 15mm, 30mm etc.

d.Dummy sashes (non-opening sash/vent fixed in place)

e.Dummy transoms/mullions

f.Decorative glazing bars within the glazing unit cavity, e.g. Georgian bars/duplex, both internal.

g.Non dead-load-bearing coupling components, e.g. PVC H-coupler.

For new dwellings, determination of a window or door U-value is to exclude the following where present.

h.Any dead-load-bearing component items, e.g. bay poles.

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Section 3

Existing dwellings

3.4For existing dwellings, the U-value of a window should be determined using one of the following.

a. Calculated using the actual size and configuration of the window.

b. Calculated for a standard window 1.23m (±25%) wide × 1.48m (±25%) high and for the actual configuration of the window.

c. Calculated for a standard window 1.23m (±25%) wide × 1.48m (±25%) high and for one of the following standard configurations.

i. For a casement window: a central vertical divider with one opening light and one fixed light.

ii. For a vertical sliding sash window: a central horizontal divider with two opening lights.

iii. For a roof window: no divider.

d. Measured using the hot-box method set out in BS EN ISO 12567-1 for windows and in BS EN ISO 12567-2 for roof windows.

e. Taken from the default values in the Standard Assessment Procedure, version 10.3, Table 6e.

3.5For existing dwellings, the U-value of a door should be determined using one of the following.

a. Calculated using the actual size and configuration of the door.

b. Calculated using one of the following standard sizes.

i. 1.23m (±25%) wide × 2.18m (±25%) high, for doors ≤ 3.6m2.

ii. 2.00m (±25%) wide × 2.18m (±25%) high, for doors > 3.6m2.

Note: When a single U-value is calculated for a product range of doors, the configuration of door chosen for the calculation should be the worst performing in the product range.

c. Measured using the hot-box method in BS EN ISO 12567-1.

d. Taken from the default values in the Standard Assessment Procedure, version 10.3, Table 6e.

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Section 3

3.6To correctly assess whether an element meets the limiting U-value, the U-value must be calculated for the element in the appropriate plane – horizontal or vertical. For windows and roof windows, U-values should be calculated based on a vertical position. For rooflights, U-values should be calculated based on a horizontal position. If the data available is for the element in the incorrect plane, it should be adjusted according to the guidance in the Building Research Establishment’s BR 443.

Note: Paragraph 3.6 does not apply to Home Energy Model or Standard Assessment Procedure calculations, where the U-value of each element is calculated based on the plane in which it is constructed or installed.

Target performance values in new dwellings

3.7For a new dwelling, it must be demonstrated that the target fabric performance values have been met. The calculated fabric performance values for the new dwelling must be entered into the approved methodology. For new dwellings, in order to demonstrate compliance with regulation 26B, the fabric performance values must be as good as or better than the worst acceptable values set out in Table 3.1.

Limiting standards in existing dwellings

New and replacement elements in existing dwellings

3.8New fabric elements in existing dwellings (such as those constructed as part of an extension) should meet the limiting standards in Table 3.1.

3.9The U-value of a replacement fabric element in an existing dwelling should both:

a.be no worse than that of the element being replaced

b.meet the limiting standards in Table 3.1.

3.10Guidance on when a new element must meet the standards in Table 3.1 is given in Section 10. Elements that should meet the standards include both of the following.

a.Elements in extensions to existing dwellings.

b.New or replacement elements in existing dwellings.

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Section 3

3.11If windows or fully glazed external pedestrian doors cannot meet the requirements of Table 3.1 because of the need to maintain the character of the building, as set out in paragraph 0.8, one of the following should be met.

a.These fittings should not exceed a centre pane U-value of 1.2W/(m2·K).

b.Single glazing should be supplemented with low-emissivity secondary glazing.

Renovated and retained elements

3.12Further guidance for existing dwellings in relation to renovated and retained thermal elements, extensions and consequential improvements is given in Sections 10, 11 and 12.

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Section 3

Table 3.1 Worst acceptable fabric performance values

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7.The limiting value for rooflights also applies to kerbs that are supplied as part of a single rooflight-and-kerb assembly sourced from the same supplier and for which the supplier can provide a combined Ud-value for the assembly. An upstand built on site should exceed a U-value of 0.35W/(m 2·K).

8.The methods for calculating Window Energy Rating and Doorset Energy Rating are set out in the Glass and Glazing Federation’s Glazing Manual Data Sheet 2.3, Guide to the Calculation of Energy Ratings for Windows, Roof Windows and Doors.

9.For external fire doorsets, as defined in Appendix A of Approved Document B, Volume 1, a maximum U-value of 1.8W/(m2·K) is permissible.

10.The U-value of the floor of an extension can be calculated using the exposed perimeter and floor area of the whole enlarged dwelling.

11.If there are problems with the load-bearing capacity of the frame or height of the upstand, for a flat roof or roof with integral insulation, a lesser standard may be appropriate.

12.If meeting such a standard would create significant problems in relation to adjoining floor levels, a lesser standard may be appropriate.

13.If, due to boundary constraints, meeting such a standard would reduce the internal floor area of the bounded room by more than 5%, a lesser thermal performance may be appropriate, provided the wall achieves the best practicable thermal performance.

Continuity of insulation

3.13Gaps in insulation can have a significant impact on heat loss and thermal bypass and create a risk of condensation and mould. The building fabric should be constructed so that the insulation is reasonably continuous across newly built elements. To ensure continuity of insulation in new dwellings, the applicable guidance in Appendix F should be followed.

Thermal Bridging

3.14Thermal bridges occur when an area of a building has significantly higher heat transfer than the surrounding parts. Breaks in insulation, reduced insulation or more conductive materials can contribute to thermal bridge effects. The building fabric should be constructed so that thermal bridging, including at the party wall, is reasonably limited.

3.15To limit thermal bridging in new and existing dwellings, the applicable guidance in Appendix G should be followed.

Airtightness in new dwellings

3.16For a new dwelling, the minimum standard for air permeability is given in Table 431. When carrying out work in new dwellings, care should be taken to reduce

unwanted heat loss through air infiltration. To ensure airtightness in new dwellings, the applicable guidance in Appendix H should be followed.

Airtightness in existing dwellings

3.17When carrying out work in existing dwellings, care should be taken to reduce unwanted heat loss through air infiltration by doing all of the following.

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Section 3 a. When installing pipework or services, taping and sealing around service penetrations.

b. When installing or renovating thermal elements, the element being installed should be draught-proofed, and air-leakage gaps should be filled.

c. When installing windows, roof windows, rooflights or doors (all of which are controlled fittings), the controlled fitting should be well fitted and reasonably draught-proof.

Note: Particular attention should be paid to Approved Document F and Approved Document J when making an existing dwelling more airtight.

Limiting heat losses and gains from building services

Hot water and heating pipework

Note: In dwellings with low levels of fabric heat loss, including new dwellings, heat lost from pipework and hot water storage vessels may lead to overheating in the summer. Where overheating may be a risk, it is recommended that greater levels of insulation than given in paragraphs 3.25 to 3.34 are installed where practical.

3.18In a new system, all of the following new pipework should be insulated. This includes where pipework passes through a void outside the heated living space, such as a roof void or ground floor void.

a.All primary circulation pipework for both of the following.

i.Heating circuits where pipework extends outside the heated living space.

ii.Domestic hot water systems.

b.All hot water pipework connected to a hot water storage vessel. This includes pre-plumbed pipework. The insulation should extend to the greater of the following.

i.The point at which the pipework first meets a building element (i.e. a wall, ceiling or floor).

ii.At least 1m from the point at which the pipework connects to the hot water storage vessel.

c.All secondary circulation pipework for a domestic hot water system.

Note: For minimum standards for insulation of district and communal heating see paragraphs 3.28 to 3.31.

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Section 3

3.19Any primary circulation pipework for heating or domestic hot water which passes through the thermal envelope should meet all of the following.

i.Outside the thermal envelope, insulation should be continuous up to the thermal envelope.

ii.Inside the thermal envelope, insulation should be continuous up to the thermal envelope.

iii.Interruptions to the thermal envelope should be as few as possible. Any interruptions should be airtight.

3.20All pipework insulation should be reasonably continuous, including at bends, T- branches, wall brackets and around any obstructions including valves.

3.21Refrigerant pipework for heat pumps in dwellings should be fully insulated. Refrigerant pipework should be insulated in accordance with paragraphs 3.18 to 3.20.

3.22For new dwellings, heat pumps which serve individual dwellings should be located as close to the dwelling as practical and meet all of the following

a.Minimise the length of pipework required between the heat pump and dwelling

b.Ensuring sufficient airflow

c.Meeting requirements for safe operation

d.Allowing access for servicing.

Heat pumps that are part of a communal heat network should be located as close as practical to the building to minimise the length of pipework between the heat pump and the dwelling.

3.23In an existing system, when a heating appliance or hot water storage vessel is replaced, all accessible pipes in the dwelling should be insulated as described in paragraphs 3.18 to 3.19.

3.24Heat losses from insulated pipework should not exceed those given in BS 5422 for base level thickness of insulation for hot water services at 60°C, regardless of the actual design temperature. Meeting the standards in Table 3.2 is one way of demonstrating that heat losses will not exceed those given in BS 5422.

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Section 3

Note: BS 5422 provides base level thicknesses and enhanced level thicknesses of insulation for domestic hot water and heating services. Adopting enhanced level thicknesses is encouraged where feasible to further reduce heat losses from hot water and heating pipework.

Table 3.2 Minimum thicknesses of pipework insulation for hot water services and space heating applications

Hot water storage vessels

3.25Hot water storage vessels should comply with the following.

a.Copper hot water storage combination units should comply with BS 3198.

b.Vented cylinders should comply with the heat loss and heat exchanger requirements of BS 1566-1 or BS EN 12897 as appropriate.

c.Unvented hot water storage system products should comply with BS EN 12897.

3.26Primary storage systems should meet the insulation requirements of the Hot Water Association’s ‘Performance Specification for Thermal Stores’.

3.27 Vessels that store heated water for a heating or domestic hot water system should have standing losses that do not exceed the heat loss given in Table 3.3.

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Section 3

Table 3.3 Maximum daily heat loss for a hot water storage vessels in dwellings (1)

Heat networks

External pipework for district heat networks

3.28For new dwellings connected to a district heat network, the pipework of the primary heat network up to the point of connection with the building should be designed according to the minimum requirements in CIBSE CP1 Heat Networks: Code of Practice.

3.29Pipework for district heat networks should be insulated to meet either of the following.

a. the standards in BS EN 253 for pre-insulated pipes b. an equivalent performance for conventionally heated pipes.

3.30Where pipework is run above ground, the performance of the pipe insulation should be at least as high as the insulating performance of pipework in the buried part of the system.

Internal pipework for district heat networks

3.31 For new buildings that contains multiple dwellings, the building heat distribution should be insulated. The insulation thickness for the building heat distribution system in Approved Document L, Volume 2 should be followed.

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Section 3

Note: Where the building heat distribution system is external, paragraphs 3.28 to 3.30 should be followed

Heat interface units

3.32In new dwellings, heat loss from the heat interface unit should not exceed 1.0 kWh/day, tested in accordance with the regime set out in CIBSE CP1 Heat Networks: Code of Practice.

3.33Hot water storage vessels connected to a heat interface unit for a heating or domestic hot water system should have standing losses that do not exceed the heat losses given in Table 3.3.

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Section 3

Requirement L1(b)(i), (ii), (iii) and L2: Fixed building services’ energy efficiency and controls and on-site generation of electricity

This section deals with the requirements of Part L1(b)(i), (ii) and L2 of Schedule 1 to the Building Regulations 2010.

Schedule 1 – Part L Conservation of fuel and power and the minimisation of greenhouse gas emissions

L1.Reasonable provision shall be made for the conservation of fuel and power and the minimisation of greenhouse gas emissions in buildings by—

(a) limiting heat gains and losses–

(i) through thermal elements and other parts of the building fabric; and

(ii) from pipes, ducts and vessels used for space heating, space cooling and hot water services;

(b)providing fixed building services which–

(i) are energy efficient;

(ai) minimise greenhouse gas emissions

(ii) have effective controls; and

(iii) are commissioned by testing and adjusting as necessary to ensure they use no more fuel and power than is reasonable in the circumstances.

On-site generation of electricity

L2.Where a system for on-site electricity generation is installed—

(a) reasonable provision must be made to ensure that—

(i) the system and its electrical output are appropriately sized for the site and available infrastructure;

(ii) the system has effective controls; and

(b) it must be commissioned by testing and adjusting as necessary to ensure that it produces the maximum electricity that is reasonable in the circumstances.

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Section 3

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Intention

In the Welsh Minister’s view, requirements L1(b)(i),(ai), (ii), (iii) and L2 are met in a new dwelling by achieving all of the following.

a. Fixed building services that both:

i. meet the minimum efficiencies in Section 5.

ii. are appropriately sized, following paragraphs 4.9 to 4.10 and 4.12 to 4.15.

b. Controls to fixed building services are provided that both:

i. meet the general controls for heating and hot water systems in paragraphs 4.16 to 4.24 ii. meet the system specific controls in Section 5.

c. Any on-site electricity generation is both appropriately sized and has controls.

In the Welsh Ministers’ view, requirement L2 is met, when a dwelling is erected, by following the guidance in paragraphs 4.68 to 4.79.

Requirement L2 does not apply to a building which is a relevant building for the purposes of regulation 7(4) of the Building Regulations 2010.

Requirement L2 does not apply to a building on which it is not possible to install a system for on-site renewable electricity generation capable of generating a reasonable output, taking account of the building’s design and surroundings. The guidance in paragraphs 4.73 and 4.74 describes the reasonable output.

In the Welsh Minister’s view, requirements L1(b)(i), (ii), (iii) and L2 are met in an existing dwelling by achieving all of the following.

a. Fixed building services that both:

i. meet the minimum efficiencies in Section 5 and the criteria in paragraphs 4.5 and 4.6 ii. are appropriately sized, following paragraphs 4.9 to 4.14.

b. Any fixed building services installed have controls that both:

i. meet the standards for general controls for heating and hot water systems in paragraphs 4.17 to 4.29 ii. meet the standards for system specific controls in Section 5.

c.Any on-site electricity generation provided is both appropriately sized, following paragraph 4.8, and has controls.

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In the Welsh Ministers’ view, requirement L2A is met, when a dwelling is erected, by following the guidance in paragraphs 5.69 to 5.78. Requirement L2A does not apply to a building which is a relevant building for the purposes of regulation 7(4) of the Building Regulations 2010. Requirement L2A does not apply to a building on which is it not possible to install a system for on-site renewable electricity generation capable of generating a reasonable output taking account of the building’s design and surroundings. The guidance in paragraphs 4.73 and 4.74 describes the reasonable/equivalent output.

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Section 4

Section 4

Carbon and energy performance of building services – general guidance

New building services

4.1For each new fixed building service in a new or existing dwelling, the efficiency of the service should be no lower than the value set out in Section 5. If a proposed service is not covered in Section 5, it should be demonstrated that it is no less efficient than a comparable service that is covered.

4.2Both of the following apply to the efficiency claimed for a fixed building service.

a.The efficiency should be based on the appropriate test standard set out in Section 5.

b.The test data should be certified by a conformity assessment body accredited by UKAS to carry out this work.

New building services in new dwellings

4.3For heating and hot water systems in new dwellings, paragraphs 4.9 to 4.10, 4.12 to 4.15 and 4.16 to 4.24 should be followed, in addition to system specific guidance in Section 5.

4.4For heating and hot water systems in new dwellings one of the following should apply for all services:

a.The service is limited to using fuels that meet both of the following:

i.A CO 2 emissions factor, as listed in the Part L 2026 notional dwelling of less than or equal to 0.086 kgCO 2/kWh

ii.A primary energy factor, as listed in the Part L 2026 notional dwelling of less than or equal to 1.969 kWhPE /kWh.

b.The service is provided by a district heat network.

Note: If a heating or hot water system is able to use more than one type of fuel, then the assessment in paragraph 4.4(a) should be made using the fuel with the greatest emissions factor.

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Section 4

Replacement building services in existing dwellings

4.5A replacement fixed building service should be at least as efficient as the value set out in Section 5 and should comply with either of the following:

a.If the service uses the same fuel as the service being replaced, it should have an efficiency that is not lower than that of the service being replaced

b.If the service uses a different fuel than the service being replaced, it should both:

i.not produce more CO 2 emissions per kWh of heat than the service being replaced

ii.not have a higher primary energy demand per kWh of heat than the service being replaced.

Note: If the efficiency of the appliance being replaced is not known, the Standard Assessment Procedure version 10.3, Tables 4a and 4b, should be used but with no adjustments from Tables 4c and 4d.

Note: CO 2 emission factors and Primary Energy Factors should be taken from the Standard Assessment Procedure version 10.3, Table 12.

•Note: Where a heat pump is installed which meets the minimum efficiency standards in this Approved Document, it should be deemed to be compliant with paragraph 4.5, without the need to carry out this calculation.

Worked example:

Replacing an old oil-fired boiler that has emissions of 0.298kgCO2/kWh and primary energy of 1.180kWhPE/kWh at 85% efficiency with an LPG boiler that has emissions of 0.241kgCO2/kWh and primary energy of 1.141kWhPE/kWh at 93% efficiency.

CO 2 emissions

Oil-fired boiler: 0.298/0.85 = 0.35 kgCO 2/kWh

LPG boiler: 0.241/0.93 = 0.26 kgCO 2/kWh

Primary energy

Oil-fired boiler: 1.180/0.85 = 1.39kWhPE /kWh

LPG boiler: 1.141/0.93 = 1.23kWh PE /kWh

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Section 4

The new LPG boiler has both lower CO 2 emissions and lower primary energy than the oil-fired boiler being replaced, and therefore complies with paragraph 4.5. The new boiler is also at least as efficient as the minimum efficiency set out in Section 5.

4.6Where a replacement fixed building service uses a different fuel than the service being replaced in a home with very low heat loss, a higher primary energy demand for the new heating appliance may be acceptable. For example, a higher primary energy demand may be acceptable when replacing a gas boiler with direct electric heaters as part of a deep retrofit project, where the resulting heat loss of the dwelling is less than 25kWh/m2 per year.

4.7Facilitating future connection to a district heat network should be considered - for example by providing capped off connections in pipework to allow later connection to a local district heat network).

Replacing on-site electricity generation in existing dwellings

4.8If renewable technology such as a wind turbine or photovoltaic array is replaced, the new system should have a kWp capacity that is at least that of the original installation. For further guidance on replacing on-site electricity generation systems, see Section 5.

Sizing heating systems

Sizing space heating systems in new and existing dwellings

4.9The size of space heating systems should be designed using both of the following.

a. The heat loss calculation in BS EN 12831-1 for the dwelling.

b. A sizing methodology that takes account of the properties of the dwelling.

Systems should not be oversized.

Note: Guidance for the appropriate design and sizing of different types of space heating system, in line with paragraph 4.9(a), is produced by a number of technical and professional bodies. These include the Chartered Institute of Plumbing and Heating Engineering, the Chartered Institution of Building Services Engineers, the Heat Pump Association and the Microgeneration Certification Scheme.

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Note: When installing a new heating system including the heating appliance and/or emitters, a room-by-room heat loss calculation should be used. When only a heating appliance is being replaced, a whole dwelling heat loss calculation is appropriate. Sizing a replacement heating appliance using the heat output of the currently installed appliance is not appropriate

4.10Where a wet heating system is either:

a. newly installed or b. fully replaced, including both the heating appliance, emitters, and associated pipework all parts of the system (including pipework and emitters) should be sized to allow the space heating system to operate effectively and in a manner that meets the needs of the dwelling, at a maximum flow temperature of 45°C or lower.

In existing dwelling, where it is not technically or functionally feasible to install a space heating system which can operate at a maximum flow temperature of 45°C (for example, where there is not enough space for larger radiators, or the existing distribution system receives higher temperature heat from a low carbon district heat network), the space heating system should be designed to the lowest design temperature that will meet the heating needs of the dwelling.

•Note: Low temperature requirements apply to space heating only. Further guidance can be found in the Building Research Establishment’s FB 59 Design of Low-temperature Domestic Heating Systems.

4.11In existing dwellings, where a gas combination boiler is used, the boiler type should be selected to modulate down to the typical mid-season heating load of the dwelling.

Sizing heat pump heating systems

4.12Reversible heat pump systems (i.e. those that provide both cooling and heating) should be designed to be optimised for heating in most circumstances. A primary heating system containing heat pumps, i.e. heat pump only systems and hybrid systems, should be selected to meet the full space heating requirement at the design condition chosen for heat loss calculations in paragraph 4.9. It should not be assumed that any heat will be supplied by additional secondary heaters to meet the calculated design demand of a dwelling.

4.13The space heating flow temperature of the heat emitter circuit(s) should be designed to optimise efficiency of the heat pump.

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Section 4

4.14Air source heat pump systems should be inverter driven and selected to modulate to the typical mid-season heating load of the dwelling.

Sizing domestic hot water systems

Note: For temperature limits to control legionella in domestic hot water systems, see Approved Document G. Guidance on commissioning hot water storage vessels can be found in Section 7.

4.15Domestic hot water systems should be sized for the anticipated demand for domestic hot water in the dwelling, based on BS EN 12831-3. Systems should not be significantly oversized.

Note: The following design guides can be used to carry out this calculation.

a.The Chartered Institution of Building Services Engineer’s Domestic Heating Design Guide.

b.The Chartered Institute of Plumbing and Heating Engineering’s Plumbing Engineering Services Design Guide – Heating and hot water systems design.

Controls for heating and domestic hot water systems

System controls and zoning

4.16For wet heating systems in new dwellings with a floor area of 150m2 or greater, a minimum of two independently controlled heating circuits should be provided.

4.17System controls should be wired so that when there is no demand for space heating or hot water, the heating appliance and pump are either of the following.

a.Switched off.

b.Set back to a reduced output temperature.

4.18Domestic hot water circuits that are supplied from a hot water store should have both of the following.

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a.Time control which is independent of space heating circuits.

b.Electronic temperature control

4.19Primary hot water circuits for domestic hot water or heating should have fully pumped circulation where this is compatible with the heat generator.

4.20Wet heating systems should ensure a minimum flow of water to avoid short- cycling.

4.21For space heating systems, temperature control should be installed for the heating appliance.

Thermostatic room controls

4.22For heating systems in new dwellings, or when a heat generator such as a boiler is replaced in an existing dwelling, each room should be provided with thermostatic room controls. These controls should be able to separately adapt the heating output in each room served by the heating appliance, or, where justified in accordance with paragraph 4.23, in each heating zone.

Note: There is no need to install thermostatic room controls in rooms/zones without heating in new or existing dwellings.

Note: Installing thermostatic room controls may not be technically feasible in some cases. These may include the following.

a. Dwellings with low heat demand (e.g. less than 10W/m2).

b. Dwelling with buffer zones for heat absorption or dissipation with high thermal mass.

4.23It may be justified to control a heating zone rather than individual rooms in either of the following cases.

a.In single-storey open-plan dwellings in which the living area is greater than 70% of the total floor area. In such cases, the dwelling should be considered as one heating zone.

b.Where two adjacent rooms have a similar function and heating requirements (e.g. kitchen and utility room). In such cases, the adjacent rooms should be considered as one heating zone.

Note: For exhaust air heat pump systems, which extract heat from the exhaust air of a dwelling, it may not be necessary to provide independent thermostatic control to individual rooms. Providing room/ zone control on this type of system is unlikely to be economically and/or technically viable. However, other space heating systems also in

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Section 4 use in the same dwelling should be controlled using thermostatic room controls as described above.

•Note: Commissioning heating systems is covered in Section 7.

4.24The standards in paragraphs 4.22 and 4.23 may be satisfied by providing any of the following.

a.Both of the following.

i.A thermostat in a room that the heating circuit serves.

ii.An individual thermostatic room control for each heat emitter, such as a thermostatic radiator valve, on all heat emitters outside the room which

contains the thermostat. Thermostatic radiator valves should not be used in the same room as the thermostat. Heat emitters in the same room as the thermostat should have manual controls.

b.An individual room/heating zone thermostat or fan coil thermostat for each room/heating zone.

c.An individual networked heat emitter control for each emitter.

Controls in existing heating and domestic hot water systems

4.25In addition to paragraphs 4.22 to 4.24, work on existing systems should incorporate the controls detailed in paragraphs 4.26 to 4.29.

4.26If domestic hot water and space heating are controlled by a single time controller in the existing system, then these may continue to be controlled together after the work is complete. Otherwise, domestic hot water and space heating should each have separate time controls.

4.27If work is carried out on a system which includes a boiler, a boiler interlock should be installed.

4.28If a hot water storage vessel is replaced, the replacement hot water storage vessel should have an electronic temperature control, such as a cylinder thermostat.

4.29If a boiler is replaced, the boiler controls should meet the standards in Section 5 for the relevant wet heating system. (Boiler controls are considered to be part of the boiler installation.)

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Section 4

Smart meter readiness of new dwellings

Note: It is recommended that new dwellings are designed and constructed to enable the installation and commissioning of smart meters. For good practice, see DESNZ guidance: Guidance on designing and constructing new builds to be smart-meter-ready.

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Section 5

Section 5

Carbon and energy performance of building services - system specific guidance

Note: This section sets out minimum Building Regulations standards for fixed building services and other systems. Best practice is to achieve higher efficiencies than these minimum standards.

Note: The Ecodesign for Energy-Related Products Regulations 2010 set the efficiencies and standards that must be met when introducing new energy-using products to the market. This approved document sets standards that should be met when installing fixed building services or on-site electricity generation. In cases where the Energy-Related Products Regulations and the Building Regulations both apply, both standards should be met.

Heat pump heating systems

Note: For heat pumps that provide comfort cooling, guidance is also given in paragraphs 5.48 to 5.52.

5.1All heat pumps should meet Ecodesign product regulations. The applicable Ecodesign Regulations for different types of heat pump and uses are set out in Table 5.1.

Note: Table 5.1 references domestic size heat pumps. For larger heat output heat pumps and heat pumps used for domestic hot water heating only see Section 5 of Approved Document L, Volume 2: Buildings other than dwellings.

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Section 5

Table 5.1: Ecodesign Regulations applicable to different types of heat pump

5.2The heat pump unit should include all of the controls applicable to that type of heat pump set out in Table 5.2.

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Section 5

Table 5.2 Minimum requirements for controls for different types of heat pump units in new and existing dwellings

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5.3The heat pump should have controls that include both of the following.

a. Weather compensation or internal temperature control.

b. A timer or programmer for space heating.

5.4When a heat pump is installed in a dwelling in which other heat sources are available, all heat sources should be controlled by one control system.

5.5Heat pumps should be located and installed in line with the manufacturer’s guidance. For air source heat pumps, this includes considering factors that may adversely affect their performance, for example not recirculating cold exhaust air, and the removal of condensation from the outdoor coil during a defrost cycle.

5.6Heat pumps should not be sited next to sleeping areas or on materials that readily transmit vibration. Also, external fans and heat pump compressors should be appropriately selected to minimise disturbance to neighbours while remaining in compliance with planning requirements.

5.7Anti-vibration instruments and flexible hose connections should be installed in line with the manufacturer’s guidance in order to limit the effects of harmful vibrations on building structures.

Gas-fired heating systems

5.8A gas-fired heating system in an existing dwelling should meet both of the following:

a.The minimum efficiencies in Table 5.3.

b.The general requirements for heating and hot water systems in Section 4.

.

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Section 5

Table 5.3 Minimum efficiencies for gas-fired heating systems in existing dwellings

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Section 5

5.9If a gas-fired combination boiler is installed in an existing dwelling, at least one of the following energy efficiency measures, appropriate to the system, should be installed.

a.Flue gas heat recovery.

b.Weather compensation.

c.Load compensation.

d.Smart thermostat (with remote access) with automation and optimisation.

5.10A gas-fired range cooker with an integral central heating boiler (within a single appliance body) that is either part of a new system or is a replacement component in an existing system should have two independently controlled burners (one for the cooking function, and one for the boiler).

Note: This paragraph does not apply to appliances with fully independent boiler and cooker parts within a shared case. In this case, the boiler should be treated in the same way as a conventional gas-fired boiler.

5.11If a gas-fired warm air system is installed in an existing dwelling, all the following should be met.

a.The system should be installed in accordance with BS 5864.

b.All new or replacement ductwork should be insulated in accordance with BS 5422.

c.Where controls are external to the heater, the system should be provided with a time switch/programmer and room thermostat, or programmable room thermostat.

d.Where controls are integrated in the heater, the system should be provided with a time switch/programmer and room temperature sensor linked to heater firing and fan speed control.

e.Independent temperature control of the hot water circuit should be implemented with a cylinder thermostat and a timing device. When there is no demand for hot water both the pump and circulator should switch off.

5.12A gas-fired fixed independent space heating appliance that is installed in an existing dwelling, should meet the applicable standard(s) as follows:

a.an appliance for primary space heating should meet the standards i to iv below,

i.BS EN1266

ii.BS 7977-1

iii.BS EN 613

iv.BS EN 13278

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Section 5

b.an appliance for secondary space heating should meet one or more of the standards below:

i.BS EN1266

ii.BS 7977-1

iii.BS EN 613

iv.BS EN 13278

v.BS EN 14829

vi.BS EN 449.

5.13If a gas fire is provided as a secondary heat source as part of a combined fire and back boiler unit in an existing system, the standards in BS 7977-2 should be met.

5.14If a gas-fired fixed decorative fuel-effect fire is installed in an existing dwelling, both of the following should apply:

a.the standards in BS EN 509 should be met

b.There should be a maximum of one appliance per 100 m 2 of dwelling floor area.

Oil-fired heating systems

5.15An oil-fired heating system in an existing dwelling should meet both of the following.

a.The minimum efficiencies in Table 5.4.

b.The general requirements for heating and hot water systems in Section 4.

Table 5.4 Minimum efficiencies for oil-fired heating systems in existing dwellings

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5.16An oil-fired range cooker with an integral central heating boiler (within a single appliance body) is part of a new system or replacement component in an existing dwelling, the appliance should have two independently controlled burners (one for the cooking function, and one for the boiler).

Note: This paragraph does not apply to appliances with fully independent boiler and cooker parts within a shared case. In this case, the boiler should be treated in the same way as a conventional oil-fired boiler.

5.17If a continuously burning oil-fired vaporising appliance is provided for secondary heating or hot water, one of the following should be met, depending on the type of appliance.

a.For a manually operated appliance, no further control is required above the integral manual controls that the appliance manufacturer provided.

b.For an electrically operated appliances, an integral remote or thermostatic control should be provided.

Note: This guidance does not apply to appliances that have been converted from another fuel.

Electric heating systems

Note: Electric resistance heating is assumed to be 100% efficient, therefore no minimum efficiency is set for these types of system. Electric radiant heating systems should not be assumed to have an efficiency greater than 100%.

•Note: This section of the guidance does not cover either of the following.

a. Electric heat pumps (guidance is provided in paragraphs 5.1 to 5.7).

b. Portable electric heating devices.

5.18Electric heating systems should follow paragraphs 5.19 to 5.21, in addition to the general requirements for heating and hot water systems in Section 4.

5.19For electric storage heaters, both of the following apply.

a. Automatic control of input charge should be provided.

b. The rate of heat release from the appliance should be adjustable, using an adjustable damper or other thermostatically controlled method.

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Section 5

5.20For electric panel heaters that are either part of a new system or replacement components, time and temperature control should be provided to allow separate control for either of the following.

a.Each room.

b.Each appliance, where this meets the guidance for thermostatic room controls in paragraphs 4.22 to 4.24.

5.21For an electric warm air system that is either a new system or is a replacement component, both of the following should be provided.

a.A programmable room thermostat or a time switch and room thermostat.

b.Separately controllable heating zones which meet the guidance for thermostatic room controls in paragraphs 4.22 to 4.24.

Solid fuel heating systems

5.22Solid fuel appliances in new and existing dwellings should have a minimum efficiency (gross calorific value) as specified in Table 5.5 for the category of appliance.

5.23A solid fuel appliance belonging to category D1/2/3/4, F, G2, J2 or J5 of Table 5.5, that is used to deliver primary heating as part of a central heating system should comply with all of the following.

a.Meet the general requirements for heating and hot water systems in Section 4.

b.Have separate time control for space heating and hot water circuits.

c.Have automatic control of the burning rate.

d.Follow the manufacturer’s instructions on the size and position of heat leek radiators designed to keep the system operating effectively by leaking heat.

5.24A solid fuel appliance that is either part of a new central heating system or is a replacement component of a central heating system should meet both of the following.

a.The appliance should be from categories D, F, G and J in Table 5.5.

b.The appliance should have a ratio of room heat to water heat appropriate for the room and the total property.

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Section 5

Table 5.5 Solid fuel appliance categories and minimum efficiencies

District heat networks and communal heat networks

5.25Paragraphs 5.26 to 5.31 apply where work involves connecting dwellings to a district heat network or communal heat network that achieves both of the following.

a.Has a central source such as a boiler, combined heat and power unit, or heat pumps.

b.Distributes heat to six or more dwellings.

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Section 5

Connecting to a new communal heat network

5.26The central heat source in a new communal heat network should comply with the standards in section 5 of Approved Document L, Volume 2, buildings other than dwellings.

Note: Where a district heat network or communal heat network connects to fewer than six dwellings, the central heat source should meet the standards in this Approved Document

Minimising energy used by pumps

5.27New district heat networks or communal heat networks should meet both of the following.

a.The design temperature difference for the primary circuit of the district heat network or communal heat network should be a minimum of 20°C. Heat pump-led district heat networks or communal heat networks may, however, need to run at a lower temperature difference.

b.Variable volume control systems should be used to reduce the volume of water and the pressure difference required from the pumps under part load.

Controls for district heat networks and communal heat networks

5.28For wet heating systems, the maximum design flow rate from a district heat network or communal heat network into the dwelling’s heating system or into the hydraulic break between the dwelling’s heating system and the network should be limited by suitable control and balancing valves to maintain the overall balance in the network and avoid excessive pumping energy.

5.29For new district heat networks or communal heat networks, the domestic hot water system should have variable volume controls to maintain low return temperatures in the primary circuit of the network.

Heat interface units and hot water storage in new dwellings

5.30Where domestic hot water is stored (either centralised or in individual dwellings), heat exchange between the heat interface unit supply and the hot water storage vessel should be provide through a direct plate heat exchanger to minimise the return temperature of the water.

Note: Heat interface units and any dedicated ancillary products such as hot water storage vessels should meet minimum standards in Section 3 and 4 for domestic hot water and heating systems.

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Section 5

Metering for district heat networks and communal heat networks

5.31District heat networks and communal heat networks should be designed to accommodate heat meter(s) for each dwelling.

Micro combined heat and power systems

5.32The heating plant emission rate of a micro combined heat and power system (micro-CHP) should be no greater than the emission rate of a regular boiler using the same fuel.

5.33The heating plant emission rate should be calculated using all of the following.

a. The method in DEFRA’s Method to Evaluate the Annual Energy Performance of Micro-cogeneration Heating Systems in Dwellings.

b. The performance data for the micro-CHP packaged according to BSI PAS 67.

c. A plant size ratio that uses the nominal heat output of the heating plant divided by the average heat loss of the building when there is a temperature difference of 24.2°C.

Underfloor heating systems

Note: Guidance on underfloor heating systems can be found in BS EN 1264 and BS EN ISO 11855.

Zoning and Controls

5.34In addition to meeting the general requirements for heating and hot water systems in Section 4, new underfloor heating systems should meet all of the following.

a.All underfloor heating systems should have controls to adjust the operating temperature.

b.Room thermostats for electric underfloor heating systems should have a manual override.

c.Heating systems for screed floors greater than 65mm thick should automatically reduce the room temperature at night or when the room is unoccupied.

d.Heat loss should be minimised by following the guidance in paragraphs 6.35 to 6.39.

Note: Standards on thermostatic room controls in paragraphs 4.22 to 4.24 apply to underfloor heating.

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Section 5

Minimising heat losses

5.35Ground floors and those in contact with the outside of the dwelling should be insulated to limit downwards heat losses to not more than 10 W/m 2.

5.36Floors with underfloor heating should be insulated to reduce downwards heat transmission, providing a thermal conduction resistance of at least 1.25 (m 2.K)/W, if they are installed directly above any of the following.

a.An unheated space.

b.An intermittently heated space.

c.The ground.

5.37The intermediate floor should have a layer of insulation to reduce downwards heat transmission with a thermal resistance of one of the following.

a.The performance in paragraph 5.35.

b.Thermal resistance of either of the following

i.For electric systems, not less than 0.5 (m 2.K)/W.

ii.For wet systems, not less than 0.75 (m 2.K)/W.

5.38Underfloor systems should be designed to account for the thermal resistance of floor coverings in order to provide the heat output required.

Note: Guidance on thermal resistance of floor coverings can be found in the Contract Flooring Association’s Beyond Installation: Guidance on Underfloor Heating and BEAMA’s BEAMA guide on the use of floor coverings with underfloor heating (UFH) systems.

5.39Distribution pipework which does not provide useful heat to a room should be insulated to the standards of paragraph 3.24.

Specific standards for electric underfloor heating

5.40Electric cables for underfloor heating installed within screeds should meet the following.

a.For direct electric systems, within screeds not exceeding 60mm.

b.For night energy storage systems, within screeds of at least 65mm.

Note: Screeds in this context include any wet applied material. This includes tile adhesive or levelling compound.

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Section 5

5.41Where electric cable underfloor heating systems that use night energy storage are used, both of the following should be met.

a.A minimum of 20% of the floor area of the dwelling should have fast- response systems such as panel heaters.

b.Controls should be installed which are designed to modify the input charge in response to both of the following.

i.The room thermostat.

ii.Floor temperature sensing.

5.42Programmable room thermostats with an override feature should be provided for all direct electric zones of the electric underfloor heating system. Thermostats should have air and floor temperature sensing capabilities, which may be used individually or together.

Solar water heating systems

Note: The guidance for solar water heating in this document applies to indirect solar systems that supply domestic hot water and have both of the following.

a.A solar collector area of less than 20 m2.

b.A solar heated water storage volume of less than 440 litres.

5.43New solar hot water collectors should be independently certified as complying with all tests required by BS EN 12975-1 and BS EN ISO 9806 for both of the following.

a.Thermal performance.

b.Reporting and identification.

5.44The electrical input power of the primary pump in the solar system should be less than the higher of the following.

a.50W.

b.2% of the peak thermal power of the collector.

5.45For a heat exchanger between a solar primary and secondary system, a minimum of 0.1m 2 or equivalent of heat exchanger area should be provided or every 1m 2 of the net absorber area of the solar collector.

5.46For work on new or existing solar domestic hot water heating system, controls should be fitted to or upgraded to do all of the following.

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Section 5

a.Maximise the useful energy gain from the solar collectors.

b.Minimise the accidental loss of stored energy.

c.Ensure that hot water produced by back-up sources is not used when adequate solar pre-heated water is available.

d.Provide a means to control the adverse effects of excessive temperatures and pressures.

e.Where a separate domestic hot water heating appliance is pre-heated by a solar system, the appliance should be controlled to add no extra heat if the target temperature is met from the solar pre-heated vessel.

5.47The dedicated storage volume of solar heated water relative to the area of the collector should be either of the following.

a.A minimum volume of 25 litres for every 1m 2 of the net absorber area of the solar collector.

b.Equivalent to at least 80% of the daily hot water demand (as defined by the Standard Assessment Procedure for new and existing dwellings)

Note: Domestic hot water storage vessels and pipework associated with the solar water heating system should follow the minimum standards in Section 3 to minimise heat losses.

Comfort cooling

5.48The specification of comfort cooling systems should be based on a calculated heat gain for the dwelling. To calculate heat gain, both CIBSE Guide A and the manufacturer’s guidance should be followed.

Systems should not be significantly oversized: in most circumstances, the cooling appliance should not be sized for more than 120% of the design cooling load.

5.49The seasonal energy efficiency ratio of an air conditioner working in cooling mode should be one of the following.

a. For new dwellings, a minimum of 4.6.

b. For existing dwellings, a minimum of 4.0.

The seasonal energy efficiency ratio should be calculated according to BS EN 14825.

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Section 5

5.50Comfort cooling systems should have all of the following controls.

a.For each control zone and for each terminal unit, it should be possible to independently control both of the following:

i.Timing.

ii.Temperature.

b.If both heating and cooling are provided in the same space, the controls should prevent them operating simultaneously.

5.51For cooling systems that serve multiple dwellings, follow the guidance in Approved Document L, Volume 2: Buildings other than dwellings.

5.52Exposed refrigeration pipework should be both of the following.

a.Insulated in accordance to paragraph 3.21.

b.Enclosed in protective trunking.

Mechanical ventilation

5.53Ventilation systems should meet the ventilation needs of the dwelling, in accordance with Approved Document F Volume 1: Dwellings. Systems should be designed so that they can be commissioned to suitable ventilation rates so that spaces are not significantly overventilated.

5.54The specific fan power for mechanical ventilation systems should be no greater than the values in Table 5.6.

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Section 5

Table 5.6 Maximum specific fan power (SFP) for mechanical ventilation systems in new and existing dwellings

5.55All ventilation systems providing both supply and extract ventilation should be fitted with all of the following.

a.A heat recovery system with a minimum efficiency of 73%.

b.A summer bypass facility (giving the ability to bypass the heat exchanger or to control its heat recovery performance).

c.A variable speed controller.

Lighting

5.56Any fixed lighting should achieve lighting levels appropriate to the activity in the space. Spaces should not be over-illuminated.

•Note: In many cases, householders will be able to choose the lamp installed in the individual space.

5.57Where installed in a new or existing dwelling, each internal luminaire should have light sources with one of the following.

a.A minimum luminous efficacy of 105 light source lumens per circuit-watt.

b.For non-standard specialist light sources, a minimum luminous efficacy as listed in Table 5.7.

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Section 5

5.58Where installed in a new or existing dwelling, internal luminaires should have local controls to allow for the separate control of lighting in each space or zone. Controls may be either manual, automatic or a combination of both.

5.59Where fixed external lighting is installed in a new or existing dwelling, each external luminaire should have light sources with either of the following.

a.A minimum luminous efficacy of 105 light source lumens per circuit-watt.

b.For non-standard specialist light sources, a minimum luminous efficacy as listed in Table 5.7.

Table 5.7 Minimum luminous efficacies for specialist light sources

5.60Where installed in a new or existing dwelling, fixed external lighting should have both of the following controls.

a.Automatic controls which switch the luminaire off in response to daylight.

b.Controls which switch the luminaire off after the area lit becomes unoccupied as follows.

i. For a luminaire with a total luminous flux of greater than 1200lm, automatic proximity sensors should be used.

ii. For a luminaire with a total luminous flux of 1200lm or less, manual control is acceptable.

Building Automation and Control Systems

5.61Where a building automation and control system is installed, it should have appropriate control capabilities for the dwelling, based on the type of building, its expected use and potential energy savings.

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Section 5

5.62The building automation and control system should be specified and installed according to the manufacturer’s instructions to ensure that its overall performance meets a reasonable standard.

5.63For large or complex buildings, the guidance in Approved Document L, Volume 2: buildings other than dwellings should be followed.

On-site electricity generation and storage

5.64Where on-site electricity generation (including renewable electricity) and storage is installed, such as photovoltaic panels or battery storage, systems should be an appropriate size for the site, available infrastructure and on-site energy demand.

5.65On-site electricity generation and storage systems should be specified, installed and commissioned according to the manufacturer’s instructions to ensure that the overall performance of the system meets a reasonable standard and to maximise the generating or storage capacity.

Note: Guidance for commissioning for on-site electricity generation systems is also given in Section 7.

5.66When replacing an existing on-site electricity generation system, the installed generation capacity of the new system should be no less than that of the existing system, except where a smaller system can be shown to be more appropriate (e.g. replacing an existing system with one which is better matched to the dwelling’s energy demand).

5.67On-site electricity generation and storage systems should be provided with controls to allow proper operation of the system without the need for user intervention. This is particularly relevant where storage systems, such as batteries, are used.

5.68On-site renewable electricity can be generated by photovoltaic panels, or another renewable technology. Where another renewable technology is used to generate electricity, the amount produced by all technologies should be equivalent to the output of the standards in paragraphs 5.70 and 5.71.

Systems for on-site renewable electricity generation on dwellinghouses and buildings containing one or more dwellings

5.69When a new dwellinghouse or a building containing one or more dwellings is erected, the following paragraphs 5.72 to 5.73 provide guidance on how to meet requirement L2A.

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Section 5

5.70When a dwellinghouse or a building containing one or more dwellings is erected and a system for renewable electricity generation is required to be installed on- site, the minimum amount produced by renewable technologies should be equivalent to the output described in paragraph 5.73 (dwellings) or paragraph 5.74 (buildings containing dwellings).

5.71Paragraph 5.70 does not require off-site renewable technologies (e.g. microgrids) to meet requirement L2A, however, these may be used as an alternative option to meet the requirement, if an equivalent renewable electricity generation output as described in paragraph 5.73 (dwellings) or paragraph 5.74 (buildings containing dwellings) is directly available and prioritised for the use of residents of the dwellings.

5.72The calculations in paragraphs 5.73 to 5.74 should use the same version of the approved methodology as used to calculate the dwelling emission rate and dwelling primary energy rate.

5.73Roof-mounted photovoltaic arrays on dwellinghouses should be designed to achieve a reasonable output using one of the following.

a. An annual output (in kWh) for the dwellinghouse as calculated using the approved methodology of at least equal to that of a photovoltaic array with all of the following characteristics.

i. Installed peak power (kWp) equal to photovoltaic panels with an efficiency of 0.22kWp per m2 installed over an area equivalent to 40% of the dwellinghouse’s ground floor area (see Equation 1).

ii. Orientated south-east to south-west.

iii. Pitch of 45 degrees.

iv. Not overshaded.

b. An annual output (in kWh) for the dwelling as calculated using the approved methodology at least equal to that of a photovoltaic array covering the reasonably practicable roof area with a panel efficiency of 0.22 kWp/m2.

Equation 1: An appropriate level of installed peak power (PPDWELLING) in kWp for an individual dwellinghouse can be calculated using the following.

PPDWELLING = APVD × EFFPV where:

EFFPV = PV Panel Efficiency (kWp/m2) of 0.22kWp/m2 or higher

APVD = area available for photovoltaic panels (m2) equivalent to at least 40% of the ground floor area.

5.74Roof-mounted photovoltaic arrays on buildings containing one or more dwellings should be designed to achieve one of the following.

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Section 5

a.An annual output (in kWh) for the building as calculated using the approved methodology of at least equal to that of a photovoltaic array with all of the following characteristics.

i.Installed peak power (kWp) equal to photovoltaic panels with an efficiency of 0.22kWp per m 2 installed over an area equivalent to 40% of the building’s ground floor area (see Equation 2).

ii.Orientated south-east to south-west.

iii.Pitch of 45 degrees.

iv.Not overshaded.

b.An annual output (in kWh) for each dwelling within the building as calculated using the approved methodology of at least equal to that of a photovoltaic array with all of the following characteristics.

i.Installed peak power (kWp) equal to photovoltaic panels with an efficiency of 0.22kWp per m 2 installed over an area equivalent to 40% of the individual dwelling’s ground floor area (see Equation 3).

ii.Orientated south-east to south-west.

iii.Pitch of 45 degrees.

iv.Not overshaded.

c.An annual output (in kWh) for the building as calculated using the approved methodology at least equal to that of a photovoltaic array covering the reasonably practicable roof area with a panel efficiency of 0.22 kWp/m 2.

Equation 2: For buildings with multiple storeys, the ground floor area (AGRND) in m2 of the building can be calculated using the following.

AGRND = ATOTAL / Number of Storeys where:

ATOTAL = total floor area of all spaces within the building (m2)

Equation 3: For buildings containing dwellings, the ground floor area allocated to an individual dwelling

(AGRNDDWELL) in m2 can be calculated using the following.

AGRNDDWELL = (ADWELL / ATOTAL) × AGRND where:

ADWELL = floor area of dwelling (m2)

ATOTAL = total floor area of all spaces within the building (m2)

AGRND = building ground floor area from Equation 2 (m2).

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Section 5

Note for equations 1, 2 and 3:

-0.22kWp/m2 is the photovoltaic panel power output in kWp/m2 with an efficiency of 1kWp per 4.5m2.

-Ground floor area does include certain unheated spaces within dwellings, which is defined in section 8.05 of SAP 10 conventions.

-The floor area of a building is measured to the internal face of the external perimeter wall.

-The total floor area of all spaces within the building is the gross internal area (GIA).

-The number of storeys in the building is defined in section 2.08 of SAP 10 conventions.

5.75The system for renewable electricity generation should be designed so that generated electricity is available to residents of the dwellings. In buildings containing dwellings, this could be to individual dwellings and communal spaces where the electricity can be used for the benefit of the residents of the dwellings.

Note: Where on-site electricity generation or energy storage is installed, the fire safety (including means of escape) and electrical requirements of the Building Regulations should be met. Approved Documents B and P should be followed. Manufacturer instructions should also be followed.

5.76Where the standards in paragraphs 5.73(a) and 5.74(a) and (b) cannot be met, efforts should be made to maximise the generation output where it is possible. This should include modifying designs to specify higher performance panels, alternative orientations of panels and other modifications (for example, positions of roof vents or architectural features) to accommodate additional photovoltaic panels where possible. Examples of layouts which maximise the reasonably practicable area available for roof-mounted photovoltaic arrays for a variety of roof types are given in Appendix B.

5.77In exceptional circumstances it may not be possible to install a system for on-site renewable electricity generation on a dwellinghouse or a building containing dwellings which is capable of a reasonable output. These circumstances include the following.

a.Dwellinghouses where it can be demonstrated by following the guidance in paragraph 5.73 and Appendix B that there is insufficient roof area available to install photovoltaic arrays capable of generating an annual output of 720kWh (calculated using the Approved methodology).

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Section 5

b.Buildings containing dwellings where it can be demonstrated by following the guidance in paragraph 5.74 and Appendix B that there is insufficient roof area available to install photovoltaic array capable of generating an annual output for each dwelling of 720kWh (calculated using the Approved methodology) divided by the number of storeys.

5.78Any photovoltaic arrays which do not achieve either of the standards in paragraphs 5.73(a) and 5.74(a) and (b) will be highlighted in the BRWL report. Evidence to support the reasonably practicable area of roof available for photovoltaic array or lower provision should be provided to the relevant building control body as outlined in Appendix B.

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Section 5

Regulation 43: Pressure testing

This Approved Document deals with the requirements of regulation 43 of the Building Regulations 2010.

Regulation 43 - Pressure testing

(1) This regulation applies to the erection of a building in relation to which paragraph

L1(a)(i) of Schedule 1 imposes a requirement.

(2) Where this regulation applies, the person carrying out the work shall, for the purpose of ensuring compliance with regulation 26 and paragraph L1(a)(i) of Schedule 1:

(a) ensure that:

i. pressure testing is carried out in such circumstances as are approved by the

Secretary of State; and ii. the testing is carried out in accordance with a procedure approved by the

Secretary of State; and

(b) subject to paragraph (5), give notice of the results of the testing to the local authority.

(3) The notice referred to in paragraph (2)(b) shall:

(a) record the results and the data upon which they are based in a manner approved by the Secretary of State; and

(b) be given to the local authority not later than seven days after the final test is carried out.

(4) A local authority is authorised to accept, as evidence that the requirements of paragraph (2)(a)(ii) have been satisfied, a certificate to that effect by a person who is registered by Elmhurst Energy Systems Limited or the Air Tightness and Testing and Measuring Association in respect of pressure testing for the air tightness of buildings.

(5) Where such a certificate contains the information required by paragraph (3)(a), paragraph (2)(b) does not apply.

Note: Where the building control body is a registered building control approver, see regulation 5 of the Building (Registered Building Control Approvers etc.) (Wales) Regulations 2024(as amended).

Intention

In the Welsh Minister’s view, the requirements of regulation 43 are met, when a dwelling is erected, by carrying out pressure testing in accordance with paragraphs 6.2 to 6.5 and 6.7 to 6.8.

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In the Welsh Minister’s view, results from a pressure test must be used to show that work complies with both of the following.

a. Regulations 26 and 26A of the Building Regulations, in accordance with paragraphs 6.6 to 6.8.

b. The requirements of Part L1(a)(i) of Schedule 1 to the Building Regulations, in accordance with paragraphs 6.1 and 6.6.

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Section 6

Section 6

Air permeability and pressure testing

6.1The minimum standard for air permeability of a new dwelling is given in Table 3.1 of Section 3. Measured air permeability is established by an air pressure test.

Air pressure testing procedure

6.2Air pressure tests should be performed following the guidance in the approved air tightness testing methodology, CIBSE’s TM23 Testing Buildings for Air Leakage. The procedures for testing and reporting in that document have been approved by Welsh Ministers.

Showing compliance, and reporting pressure test results

6.3The building control body should be given provided with evidence that pressure testing equipment has been calibrated using a UKAS-accredited facility or by the original manufacturer with all of the following.

a. A period in accordance with the manufacturer’s guidance.

b. At least once every 24 months.

c. CIBSE TM23 Testing Buildings for Air Leakage.

6.4Building control bodies may accept a pressure test certificate from a person registered by any organisation listed in Regulation 43(4) as evidence that the testing has been carried out in accordance with the approved procedure in paragraph 6.2.

The building control body should be given evidence that the person who provides the pressure test certificate meets both of the following.

a.Has received appropriate training

b.Is registered to test the specific class of building.

6.5An air pressure test should be carried out on every new dwelling.

6.6The dwelling primary energy rate, dwelling emission rate, and dwelling energy use intensity (detailed in Section 2), all calculated using the measured air permeability, must not be higher than the target primary energy rate, target emission rate, and target energy use intensity, respectively.

6.7If a dwelling does not achieve the criteria in paragraphs 6.1 and 6.6, the dwelling air permeability should be improved and retested until the criteria are achieved.

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Section 6

6.8The results of all pressure tests on dwellings, including any test failures, should be reported to the building control body.

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Section 6

Requirement L1(b)(iii) and L2(b) and Regulation 44 and 44ZA: Commissioning

This Approved Document deals with the requirements of Part L1 of Schedule 1 to the Building Regulations 2010 and Regulation 44.

Schedule 1 – Part L Conservation of fuel and power and the minimisation of greenhouse gas emissions

L1.Reasonable provision shall be made for the conservation of fuel and power and the minimisation of greenhouse gas emissions in buildings by—

(b) providing fixed building services which–

(iii) are commissioned by testing and adjusting as necessary to ensure they use no more fuel and power than is reasonable in the circumstances.

L2.Where a system for on-site electricity generation is installed—

(b) it must be commissioned by testing and adjusting as necessary to ensure that it produces the maximum electricity that is reasonable in the circumstances.

Commissioning

44.—(1) This regulation applies to building work in relation to which paragraph F1(2) of Schedule 1 imposes a requirement, but does not apply to the provision or extension of any fixed system for mechanical ventilation or any associated controls where testing and adjustment is not possible.

(2) This regulation applies to building work in relation to which paragraph L1(b) of Schedule 1 imposes a requirement, but does not apply to the provision or extension of any fixed building service where testing and adjustment is not possible or would not affect the energy efficiency of that fixed building service.

(3) Where this regulation applies the person carrying out the work shall, for the purpose of ensuring compliance with paragraph F1(2) or L1(b) of Schedule 1, give to the local authority a notice confirming that the fixed building services have been commissioned in accordance with a procedure approved by the Secretary of State.

(4) The notice shall be given to the local authority –

(a) not later than the date on which the notice required by regulation 16(4) is required to be given; or

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(b) where that regulation does not apply, not more than 30 days after completion of the work.

Commissioning in respect of a system for on-site electricity generation

44ZA. (1) This regulation applies to building work in respect of a building in relation to which paragraph L2 of Schedule 1 imposes a requirement, but does not apply to the provision or extension of any system for on-site electricity generation where testing and adjustment is not possible.

(2) Where this regulation applies the person carrying out the work must, for the purpose of ensuring compliance with paragraph L2 of Schedule 1, give to the local authority a notice confirming that the system for on-site electricity generation has been commissioned.

(3) The notice must be given to the local authority—

(a) not later than the date on which the notice required by regulation 16(4) is required to be given; or

(b) where that regulation does not apply, not more than 30 days after completion of the work.

Note: Where the building control body is a registered building control approver, see regulation 5 of the Building (Registered Building Control Approvers etc.) (Wales) Regulations 2024(as amended).

Intention

In the Welsh Minister’s view, requirements L1(b)(iii) and L2(b) and the requirements of regulations 44 and 44ZA are met by commissioning fixed building services and on-site electricity generation in accordance with Section 7.

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Section 7

Section 7

Commissioning fixed building services and on-site electricity generation systems

7.1Both of the following must be commissioned.

a.Fixed building services must be commissioned to ensure that they use no more fuel and power than is reasonable in the circumstances.

b.On-site electricity generation systems must be commissioned to ensure that they produce as much electricity as is reasonable in the circumstances.

A fixed building service, or on-site electricity generation that, by design, cannot be adjusted, or for which commissioning would not affect energy use, does not need to be commissioned.

7.2The commissioning process should involve testing and adjusting the fixed building services and on-site electricity generation as necessary and in accordance with the manufacturer’s instructions.

7.3A commissioning plan should be produced that identifies the following.

a.Which systems to test.

b.How these systems will be tested.

c.The fixed building services and on-site electricity generation that do not need to be commissioned and why they do not need to be commissioned.

For new dwellings, the commissioning plan should be given to the building control body with calculations of the design stage dwelling primary energy rate, dwelling emission rate, and dwelling energy use intensity.

Notice of completion of commissioning

7.4A notice of completion of commissioning must be given to the relevant building control body to confirm that the installed fixed building services and on-site electricity generation systems were commissioned according to the procedure in Section 7.

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Section 7

The notice should confirm all of the following.

a.That the commissioning plan was followed.

b.That all systems have been inspected in an appropriate sequence and to a reasonable standard.

c.That test results confirm that performance is reasonably in accordance with the design requirements.

The notice of completion of commissioning should be given the following number of days after commissioning work is completed.

a.If a building notice or full plans have been given to a local authority building control body, the notice of completion of commissioning should be given within five days of the work being completed.

b.If the building control body is a registered building control approver, the notice should generally be given to the registered building control approver within five days of the work being completed.

c.If the building work is higher-risk building work that requires a completion certificate, the notice must be given to the local authority with the application for a completion certificate.

d.In other cases - for example, if the work is carried out by a person registered with a competent person scheme - the notice must be given to the building control body within 30 days of the work being completed.

7.5Where any fixed building services and on-site electricity generation systems that require commissioning are installed by a person registered with a competent person scheme, that person may give the notice of completion of commissioning.

7.6Until the building control body receives the notice of completion of commissioning, it may decide not to give a completion/final certificate.

System specific guidance for commissioning

Hot water systems for space and domestic hot water heating

7.7Before a new heating appliance is installed, it should be commissioned as follows.

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Section 7

a.all central heating and primary hot water circuits should be thoroughly cleaned and flushed out.

b.A suitable chemical inhibitor should be added to the primary heating circuit to protect against scale and corrosion.

c.In hard water areas, suitable measures should be taken to treat the feed water to water heaters and the hot water circuit of combination boilers to reduce limescale accumulation.

d.Domestic central heating systems should be prepared and commissioned to BS 7593.

Note: The Benchmark commissioning checklist can be used to show that commissioning has been carried out satisfactorily for the heating and hot water system and its heat generation source.

7.8Hot water storage vessels should be commissioned in accordance with the manufacturer’s instructions.

Note: An example commissioning checklist can be found in the Microgeneration Certification Scheme’s MIS 3005-I:The Heat Pump Standard (Installation).

Note: For guidance on temperature control of hot water storage vessels see Health and Safety Executive guidance, including L8 Legionnaire’s disease. The control of legionella bacteria in water systems. Approved code of practice and HSG 274 Legionnaire’s disease. Part 2: The control of legionella bacteria in hot and cold water systems.

Heat pump heating systems

7.9Heat pumps and any dedicated ancillary products, e.g. integrated hot water cylinders, should be commissioned in accordance with both the manufacturer’s instructions and the appropriate system design parameters.

7.10The notice of commissioning given to the local authority should include a checklist to confirm that the relevant commissioning steps have been carried out. This should be provided in one of the following formats.

a.The Commissioning Checklist in Appendix A of MIS 3005-I:2025.

b.The Heat Pump Association’s Air to Water Heat Pump Commissioning Checklist.

c.An equivalent commissioning checklist.

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Section 7

7.11The person carrying out commissioning should be a member of an organisation which regularly and independently verifies their competence, training and performance. This should be demonstrated by any of the following.

a.Membership of a relevant competent person scheme that is designated in the regulations.

b.Membership of the Microgeneration Certification Scheme.

c.Evidence showing an equivalent level of competency to (a) or (b).

7.12A ground source heat pump should be commissioned as follows.

a.Ground arrays, including header pipes and manifolds, should be flushed as one system to remove all debris and purged to remove all air. Vertical, horizontal and slinky ground arrays in particular should be flushed in both directions. During this process, the heat pump (along with its accompanying pipework) should be isolated from the ground heat exchanger to avoid damage to the internal heat exchanger inside the heat pump.

b.The heat pump and its accompanying pipework should be flushed and purged as a separate system while isolated from the ground array system.

c.In a closed-loop ground source heat pump installation, after the complete purging of micro air bubbles, a pressure test (in accordance with BS EN 805, section 11.3.3.4) should be conducted to prove the integrity of the systems. This test should be conducted on the entire system, which typically comprises the heat pump, header pipes, manifold and all ground arrays.

d.Antifreeze and biocide should be added to ground heat exchangers as appropriate, in line with the manufacturer’s instructions.

7.13Commissioning information provided to the dwelling owner should include details of the fluids used and their commissioned concentrations.

District heat networks and communal heat networks

7.14For district heat networks and communal heat networks, both of the following apply.

a.Systems should be commissioned to optimise the use of energy for pumping.

b.Flow rates in individual heat emitters should be balanced using either of the following.

i.appropriate return temperatures.

ii.calibrated control valves.

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Section 7

Underfloor heating

7.15All installed equipment in underfloor heating systems should be commissioned in accordance with BS EN 1264-4.

On-site electricity storage systems

7.16On-site electricity storage and battery systems that are connected to on-site electricity generation should be designed, installed and commissioned in accordance with both of the following.

a.the manufacturer’s instructions.

b.A commissioning procedure such as the commissioning requirements of Microgeneration Certification Scheme’s MIS 3012: The Battery Standard (Installation).

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Section 7

Regulation 11W: Competence: general requirement

This section deals with the requirements of regulation 11W of the Building Regulations 2010 (as amended).

Regulation 11W

11W.—

(1) Any person carrying out any building work or any design work must have—

(a) where the person is an individual, the skills, knowledge, experience and behaviours necessary; (b) where the person is not an individual, the organisational capability, to carry out—

(i) the building work in accordance with all relevant requirements;

(ii) the design work so that the building work to which the design relates, if built, would be in accordance with all relevant requirements.

(2) Any person carrying out any building work as a contractor or any design work as a designer must have—

(a) where the person is an individual, the skills, knowledge, experience and behaviours necessary,

(b) where the person is not an individual, the organisational capability, to fulfil the duties of a contractor or designer, under these Regulations in relation to the work.

(3) The requirements in paragraphs (1) and (2) do not apply to an individual (T) who is in training to fulfil those requirements.

(4) The person who asked T to carry out any building work or, any design work must ensure T is adequately supervised when carrying out the work.

(5) A person who is in training to fulfil the requirements of a principal contractor or a principal designer may not be appointed as a principal contractor or a principal designer.

In the Welsh Ministers’ view, the requirements of regulation 11W are met for the installation of heat pumps in new and existing dwellings by following the procedures for installation, certification, inspection and testing of heat pump systems in Section 8 of this Approved Document.

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Section 8

Section 8

Installation, certification, inspection and testing of heat pump systems

General

8.1For the installation of systems which use heat pumps as a heating source, extra care should be taken to ensure both of the following.

a. The person carrying out the work is suitably competent (for example, they are a registered competent person).

b. The work meets the requirements of the Building Regulations.

8.2For heat pump installation work, one of the following two procedures must be used to certify that the work complies with the requirements set out in the Building Regulations.

a.Self-certification by a registered competent person.

b.Certification by a building control body.

8.3To verify that the design, installation and commissioning of heat pumps meets the energy efficiency requirements of the Building Regulations, the heat pump installation work should be inspected and tested to show that it meets all of the following:

a. heat losses from hot water and heating pipework are limited, following paragraph 3.18 to 3.24.

b. heat losses from hot water storage vessels are limited, following paragraph 3.25 to 3.27.

c. heat pump systems have been sized appropriately, following paragraphs 4.9 to 4.14.

d. new hot water storage vessels in dwellings have been appropriately sized, following paragraph 4.15.

e. the system has adequate controls, following paragraphs 4.16 to 4.29.

f. the heat pump system meets the system requirements set out in 5.1 to 5.7.

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Section 8

Self-certification by a registered competent person

8.4Heat pump installers who are registered competent persons should do both of the following.

a. Install and commission the system to the standards set out in this Approved Document.

b. Give notice to the building control body that commissioning has been carried out in accordance with this approved document.

Note: Using an installation checklist of the standards in paragraph 8.3 is recommended to make sure that the relevant standards have been met.

8.5The heat pump installer or the installer’s registration body must within 30 days of the work being completed do both of the following.

a. Give a copy of the Building Regulations compliance certificate to the occupier.

b. Give the certificate, or a copy of the information on the certificate, to the building control body.

Certification by a building control body

8.6If a heat pump installer is not a registered competent person, then before work begins the installer must notify an appropriate building control body to oversee the work.

8.7The building control body will determine the extent of inspection and testing needed for it to establish that the work is compliant with the Building Regulations requirements, based on the nature of the heat pump installation work and the competence of the installer. The building control body should be given notice of when the work has reached relevant stages. The building control body will set out the notification procedure.

8.8Once an appropriate building control body has decided that, as far as can be ascertained, the work meets all the Building Regulations requirements, it will issue a Building Regulations completion certificate (if a local authority) or a final certificate (if a registered building control approver).

Note: Using an installation checklist of the standards in paragraph 8.3 is recommended to make sure that the relevant standards have been met.

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Section 8

Regulation 40: Providing information

This Approved Document deals with the requirements of regulation 40 and 40A of the Building Regulations 2010.

Information about use of fuel and power

40.(1) This regulation applies where paragraph L1 of Schedule 1 imposes a requirement relating to building work.

(2) The person carrying out the building work shall not later than five days after the work has been completed provide to the owner sufficient information about the building, the fixed building services and their maintenance requirements so that the building can be operated in such a manner as to use no more fuel and power than is reasonable in the circumstances.

Information about systems for on-site generation of electricity

40A. (1) This regulation applies to building work in respect of a building in relation to which paragraph L2 of Schedule 1 applies.

(2) The person carrying out the work must, not later than five days after the work has been completed, provide to the owner sufficient information about the system for on- site electricity generation in respect of its operation and maintenance requirements so that the system may be operated and maintained in such a manner as to produce the maximum electricity that is reasonable in the circumstances and delivers this electricity to the optimal place for use.

Intention

In the Welsh Minister’s view, when a new dwelling is erected, the requirements of regulation 40 and 40A are met by providing the owner with information about all of the following.

a.Operating and maintenance instructions for fixed building services and on-site electricity generation, in accordance with paragraphs 9.1 to 9.3.

b.Other important documentation as detailed in paragraphs 9.4 to 9.8.

In the Welsh Minister’s view, the requirements of regulation 40 and 40A are met for when work is carried out on an existing dwelling by providing the owner with information about both of the following.

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Section 8

a.Operating and maintenance instructions for the work on any fixed building services and on-site electricity generation that has been carried out, in accordance with paragraphs 9.1 to 9.3.

b.Relevant information for work on existing systems as detailed in paragraphs 9.9 to 9.12.

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Section 9

Section 9

Providing information to owners about the building, fixed building services and maintenance requirements

Operating and Maintenance instructions

9.1For a new dwelling and for work to an existing dwelling, operating and maintenance instructions for any fixed building services and any on-site electricity generation installed as part of the work installed as part of the work should be given to the dwelling owner.

The instructions should be sufficient to help occupiers achieve the expected level of energy efficiency and to verify that any fixed building services and any (where applicable) on-site electricity generation complies with the energy performance requirements of the Building Regulations.

The documentation should be all of the following.

a. easy to understand, b. specific to the dwelling c. specific to the model of services and controls installed.

d. durable e. in an accessible format.

9.2The operating and maintenance instructions should do all of the following in a user focused manner.

a. Explain the following for the fixed building services any on-site electricity generation and any other technologies.

i.what they are

ii.what they are for

iii.where they are located, using a floor plan

iv.how to operate them efficiently, including the location and operation of timers and sensors and any tariff considerations.

v.how to maintain them

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Section 9 b. Identify where to find other important documentation, such as appliance manuals.

c. Include a completed commissioning sheet, where relevant.

d. Include the additional information specified below for new dwellings (paragraphs 9.4 to 9.5), newly erected dwellings (paragraphs 9.6 to 9.8) or for work in existing dwellings (paragraphs 9.9 to 9.12).

9.3For a newly erected dwelling and for work on an existing dwelling, the operating and maintenance instructions should also do all of the following.

a.Explain the following for on-site electricity generation and any other technologies.

i.What they are.

ii.What they are for.

iii.Where they are located, using a floor plan.

iv.How to operate them, including the location and operation of timers and sensors.

v.How to maintain them.

b.Identify where to find other important documentation, such as appliance manuals.

c.Include a completed commissioning sheet, where relevant.

d.Include the additional information specified below for newly erected dwellings (paragraphs 9.6 to 9.8) or for work in existing dwellings (paragraphs 9.9 to 9.12).

Additional information for new dwellings

9.4For a new dwelling, the operating and maintenance instructions should include a Home Energy Guide. The Home Energy Guide should contain non-technical advice on how to operate and maintain the dwelling in a healthy and energy efficient manner. The guide should advise on the following.

a.Heating and domestic hot water.

b.Any on-site electricity generation system (if applicable).

c.Ventilation (see Approved Document F).

d.Staying cool in hot weather (newly erected dwellings) (see Approved Document O).

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Section 9

A paper copy of the Home Energy Guide should be provided, and a digital copy made available. A template for a Home User Guide can be viewed at Building regulations guidance: part L (conservation of fuel and power) | GOV.WALES

.

Note: There is no requirement to follow the layout, format or example text used in the template.

9.5For heat pump heating systems installed in a new dwelling, operating and maintenance information provided to the dwelling owner should include all of the following.

a.Details of the heat loss calculation carried out for the heat pump heating system. Details should include all of the following.

i.Design internal room temperature(s).

ii.Design external air temperature.

iii.Date of calculation.

b.Design flow temperature of the heat pump heating system.

c.Confirmation of whether the person carrying out commissioning is registered with a competent person scheme. If so, the name of that scheme should be provided.

d.Size of emitter circuit.

e.Minimum setback temperatures.

The maintenance and operating information in (a) to (e) should be fixed to or as close as practical to the heat pump unit or the hot water storage vessel, for example on a sticker or information plate, for future heating engineers to use. This information should be in a shielded location if outside, for example on the rear of the heat pump unit.

Additional information for newly erected dwellings

9.6For a newly erected dwelling, the Home Energy Guide should also advise on on-site electricity generation (if applicable).

9.7For a newly erected dwelling. both of the following should be given to the dwelling owner.

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Section 9 a. a signed copy of the Building Regulations Wales Part L compliance report (BRWL report) b. photographic evidence of the build quality

9.8For a newly erected dwelling, the operating and maintenance instructions should direct readers to both of the following.

a. The as-built BRWL report, which includes data used to calculate dwelling primary energy rate, dwelling emission rate and dwelling energy use intensity.

b. The recommendations report generated with the ‘on-construction’ energy performance certificate.

Additional information for work in existing dwellings

9.9For an existing dwelling, when building work is carried out for which Section 4 and/or Section 5 sets a standard, the energy performance of the fixed building services and/or on-site electricity generation affected by the work should be assessed and documented.

9.10For an existing dwelling, when installing a complete new or replacement system (e.g. replacing a heating system including the heating appliance, pipework and heat emitters), the energy performance of the whole system should be assessed. The results should be recorded and given to the dwelling owner with the manufacturer’s supporting literature. The record of energy performance results may be any of the following.

a. Full records of commissioning the system in accordance with Section 7.

b. A documented assessment using the approved methodology, such as a new energy performance certificate.

c. Another equivalent assessment carried out by a suitably qualified person.

9.11For an existing dwelling, when carrying out work on an existing system, such as installing or replacing components (e.g. replacing a boiler but retaining the pipework and heat emitters), the energy performance of the new components should be assessed. The results should be recorded and given to the dwelling owner. The record of energy performance results may be in either of the following forms.

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Section 9 a. Product data sheets from the product manufacturer.

b. Other documented results of energy assessment of the product carried out in accordance with relevant test standards.

9.12For an existing dwelling, if work on an existing system alters the energy performance or CO2 emissions performance of the system, then the complete altered system should be assessed and the guidance for new or replacement systems in paragraph 9.11 should be followed. Such work may include the following:

a. A change in heating fuel for a space heating or domestic hot water system.

b. Extending or expanding the capacity of a space heating, comfort cooling or ventilation system by over 25% of its previous capacity.

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Section 9

Requirement L1(a): Limiting heat gains and losses

This Approved Document deals with the requirements of Part L1 of Schedule 1 to the Building Regulations 2010.

Intention

In the Welsh Minister’s view, requirement L1(a) is met for new elements in existing dwellings by following the standards in section 10.

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Section 10

Section 10

New elements in existing dwellings, including extensions

General

10.1This section provides guidance for the following types of work on existing dwellings.

a. For extensions or new thermal elements in existing dwellings – follow paragraphs 10.2 to 10.8.

b. For new and replacement windows and doors – follow paragraphs 10.9 to 10.15 (for extensions) and 10.20 to 10.29 (for windows in an existing dwelling) c. For conservatories and porches - follow paragraphs 10.30 to 10.36 d. For indoor swimming pools – follow paragraphs 10.37 to 10.39

New and replacement thermal elements

10.2The minimum standards in paragraphs 3.7 and 3.8 and Table 3.1 should be met for both of the following.

a. New thermal elements installed in an existing dwelling.

b. Replacement thermal elements in an existing dwelling.

Extensions

10.3In this Approved Document, extension describes when new building fabric is added to an existing dwelling to create an extra room or rooms.

10.4Adding an extension to increase the habitable volume of an existing dwelling triggers a requirement for additional energy efficiency improvements – consequential improvements – that are set out in Section 12.

10.5Two alternative optional approaches to the guidance below, that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere, are set out in Section 13.

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Section 10

Building Fabric

10.6New thermal elements constructed as part of an extension should achieve or better the U-values set out in the final column of Table 3.1 (existing dwellings).

10.7Thermal element is used in the Building Regulations to describe a wall, floor or roof, which separates a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature.

10.8If an extension incorporates a part of the existing structure, which previously was not subject to the energy efficiency requirements, for example if the extension is built against a garage, this part should be treated as a retained thermal element and follow the guidance set out in Section 11, paragraphs 11.7-11.11.

Windows and Doors

10.9New windows and doors installed as part of an extension should be draughtproofed units that achieve or better the U-values set out in the column (a) of Table 10.1. Insulated cavity closers should be installed around the windows and doors where appropriate.

Table 10.1 Windows and doors

10.10In this Approved Document, windows and doors refers to windows and external doors that separate a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature. Windows and doors are described as controlled fittings in the Building Regulations, i.e. windows and doors on which various parts of the Building Regulations impose a requirement.

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Section 10

10.11In the case of dwellings of architectural and historic interest where special consideration applies or in other cases where there is a need to maintain the character of a façade, if the windows or doors are unable to achieve the U-values set out in column (a) of Table 10.1, then they should achieve or better the lesser U-values set out in column (b) of Table 10.1.

10.12The total area of windows and doors in the extension should not exceed the sum of:

a. 25% of the internal floor area of the extension; plus b. the total area of any windows and doors which, as a result of the new extension, no longer exist or are no longer exposed.

10.13It is advisable to ensure that the total area of windows and doors in the extension is not less than 20% of the internal floor area of the extension, as this would mean that the extension and the part of the existing building that it abuts are likely to experience low levels of daylight, resulting in increased use of electric lighting and consumption of fuel and power. For further guidance see; BS 8206-2:2008 Lighting for buildings. Code of practice for daylighting.

10.14In the case of dwellings of architectural and historic interest where special consideration applies, a greater total area of windows and doors may be acceptable. For example, there may be a need for the extension to be consistent with the character of the existing building. In such cases, where practicable, the performance of the windows and doors should be improved or other compensating improvements undertaken following either of the alternative approaches set out in Section 13.

10.15Where low-e secondary glazing is installed, the edge of the secondary glazing element should be fully air sealed to the existing window frame or reveal to minimise the risk of condensation forming between the primary and secondary glazing.

Building Services

10.16Where an extension to an existing dwelling includes the provision, extension, alteration or replacement of any fixed building services systems, those systems should comply with the appropriate standards in Sections 4, 5 and paragraphs 3.18 to 3.33, and commissioned according to Section 7.

Design and Installation Standards

10.17When extending an existing dwelling, new, upgraded and renovated building fabric should be carefully designed, detailed and constructed to:

a. avoid gaps in the insulation; and b. minimise air leakage; and c. limit reasonably avoidable thermal bridges.

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Section 10

10.18Particular attention should be paid around window and door openings, to junctions between building elements, such as between the walls and roof, and at changes of geometry, for example a corner in a wall or a hip in a roof.

10.19Thermal bridges are instances where heat loss is worse than through the main building fabric. They allow heat to flow between the outer and inner skins of a wall, floor or roof by bridging the insulation.

Windows and doors

10.20This Section of the Approved Document gives guidance for the following building works to an existing dwelling:

a. installing replacement windows and doors; and/or b. enlarging existing windows and doors; and/or c. creating new windows and doors.

10.21In this Approved Document, windows and doors refers to windows and external doors that separate a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature. Windows and doors are described as controlled fittings in the Building Regulations, i.e. windows and doors on which various parts of the Building Regulations impose a requirement.

10.22Separate guidance is given in other parts of Section 10 and in Section 11 for windows and doors in extensions, conversions (also known as a change of energy status), material changes of use and conservatories and porches.

10.23Two alternative optional approaches to the guidance below, that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere, are set out in Section 13.

Window and Door standards

10.24For new or replacement windows and doors, if the entire unit of that fitting is provided, all of the following apply

a. Units should be draughtproofed b. Units should achieve or better the U-values set out in column (a) of Table 10.1.

c. Insulated cavity closers should be installed around the windows and doors where appropriate.

10.25Windows and doors refer to the whole units, i.e. including the frames. Consequently replacing just the glazing or door leaf while retaining an existing frame is not building work and so does not have to meet the energy efficiency requirements. However, in such cases it would be sensible to upgrade the

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Section 10 window or door to as close to the U-values set out in column (a) of Table 10.1 as is practicably possible.

10.26Building control bodies may accept, as evidence of compliance with the standards given in Table 10.1, a Window Energy Rating and/or Doorset Energy Rating from a certification scheme that provides a quality assured process and a supporting audit trail from calculating the performance of the window or door through to the window or door being installed.

10.27Where an existing window or door is enlarged or a new one created, either of the following should be met.

a.The total area of windows, roof windows, rooflights and doors should not exceed 25% of the total floor area of the dwelling.

b.If the area of windows, roof windows, rooflights and doors exceeds 25% of the total floor area of the dwelling, measures should be taken to improve the energy efficiency of the dwelling.

Note: Where the area of windows, roof windows, rooflights and doors exceeds 25%, consideration may also be needed to mitigate the risk of summertime overheating. Please see Approved Document O for further guidance.

10.28In the case of dwellings of architectural and historic interest where special consideration applies or in other cases where there is a need to maintain the

character of a façade, if the windows or doors are unable to achieve the U-values set out in column (a) of Table 10.1, then they should achieve or better the lesser U-values set out in column (b) of Table 10.1.

10.29Where low-e secondary glazing is installed, the draughtproofing should be on the secondary glazing to minimise the risk of condensation forming between the primary and secondary glazing.

Conservatories and porches

10.30Conservatories and porches are exempt from the energy efficiency requirements if they fulfil all of the following requirements:

a. be at ground level; and b. have an internal floor area that is less than 30 m 2; and c. be thermally separate from the heated area of the dwelling, and d. the conservatory or porch contains no fixed heating appliance or the buildings heating system is not extended into the conservatory or porch.

New conservatories or porches

10.31A conservatory or porch is considered as thermally separate where the existing walls, windows and doors between the dwelling and the conservatory or porch are left in place or if they are removed, they are replaced by walls that achieve or

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Section 10 better U-values given in column (a) of Table 10.1. The U-values for windows and doors should be calculated as Paragraphs 3.1 to 3.5.

a.Glazed and opaque elements should meet the standards set out in the final column of Table 3.1 (The limitations on the total area of windows, roof windows and doors as set out in paragraph 10.12 of Extensions do not apply here); and

b. be thermally separate from the heated area of the dwelling (see paragraph 11.29); and c. any fixed space heating installed in the conservatory or porch should comply with Sections 4, 5 and 7.

10.32Adding a non-exempt conservatory to increase the habitable volume of an existing dwelling triggers a requirement for additional energy efficiency improvements – consequential improvements – that are set out in Section 12.

10.33Two alternative optional approaches that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere are set out in Section 13.

10.34If the proposed addition is not thermally separated from the dwelling and therefore does not meet all of the requirements in paragraphs 10.30 and 10.31, it should be treated as an extension and follow the guidance set out in

paragraphs 10.2 to 10.19 including the limitation on the total area of windows and doors.

Existing conservatories or porches

10.35An existing conservatory or porch ceases to be exempt if:

a. any or all of the walls, windows and doors that thermally separate an existing exempt conservatory or porch from the dwelling are removed (and not replaced); or b. the conservatory or porch is provided with a fixed heating appliance or the buildings heating system is extended into the conservatory or porch.

10.36In such situations, this constitutes a change in energy status and the previously exempt conservatory or porch should be treated as a conversion and the guidance set out in Section 11 paragraphs 11.2 to 11.11 should be followed.

Indoor Swimming Pools

10.37New indoor swimming pool basins (walls and floors) should achieve or better a U- value of 0.25 W/m 2.K.

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Section 10

10.38Two alternative optional approaches that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere are set out in Section 13.

10.39Design consideration should be taken with regards to compressive creep, insulation boards not fully supported and the effects of point loading. Care should be taken to avoid thermal bridging particularly around basin wall and floor junctions with foundations.

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Section 10

Regulation 22: Change to energy status and 23: Requirements for the renovation or replacement of thermal elements

This Approved Document deals with the requirements of regulation 22 and 23 to the Building Regulations 2010.

Regulation 22 - Requirements relating to a change to energy status

Where there is a change to a building’s energy status, such work, if any, shall be carried out as is necessary to ensure that the building complies with the applicable requirements of Part L of Schedule 1.

Regulation 23 - Requirements for the renovation or replacement of thermal elements

(1) Where the renovation of an individual thermal element—

(a) constitutes a major renovation; or

(b) amounts to the renovation of more than 50% of the element’s surface area;

the renovation must be carried out so as to ensure that the whole of the element complies with paragraph L1(a)(i) of Schedule 1, in so far as that is technically, functionally and economically feasible.

(2) Where the whole or any part of an individual thermal element is proposed to be replaced and the replacement—

(a) constitutes a major renovation; or

(b) (in the case of part replacement) amounts to the replacement of more than 50% of the thermal element’s surface area;

the whole of the thermal element must be replaced so as to ensure that it complies with paragraph L1(a)(i) of Schedule 1, in so far as that is technically, functionally and economically feasible.”

Regulation 2(1) - Interpretation

“change to a building's energy status” means any change which results in a building becoming a building to which the energy efficiency requirements of these Regulations apply, where previously it was not

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Section 10

Intention

In the Welsh Minister’s view, the requirements of L1(a) in relation to regulations 22 and 23 are met by following the guidance in Section 11 for renovation or replacement of a thermal element and a change to energy status.

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Section 11

Section 11

Work to thermal elements in existing dwellings

General

11.1This section covers the following building works.

a. For conversions (change of energy status) – follow paragraphs 11.2 to 11.13 b. For renovations – following paragraphs 11.14 to 11.25 c. For material change of use - follow paragraphs 11.26 to 11.45 d. For replacement thermal elements – follow paragraph 11.46

Conversions (change of energy status)

11.2In this Approved Document, conversion describes when part of a dwelling, which previously was not subject to the energy efficiency requirements, is converted into a heated space, for example a loft or garage conversion where the space is now to be heated. This is described as a change of energy status in the Building Regulations.

11.3In the case of a conversion, a retained thermal element is an existing element that becomes a thermal element where previously it was not, for example the gable wall in a loft conversion.

11.4Thermal element is used in the Building Regulations to describe a wall, floor or roof, which separates a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature.

11.5Converting part of an existing dwelling to increase the habitable volume triggers a requirement for additional energy efficiency improvements – consequential improvements – that are set out in Section 12.

11.6Two alternative optional approaches to the guidance below, that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere, are set out in Section 13.

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Section 11

Building Fabric

11.7Retained thermal elements should be upgraded to achieve or better U-values set out in column (a) of Table 11.1.

Table 11.1: Standards for retained fabric elements

1For dormer windows, ‘roof’ includes the roof parts of the windows and ‘wall’ includes the wall parts (cheeks).

2Area-weighted average U- values.

3Where existing wall cavities are unfilled, they should be insulated (where suitable) to achieve the maximum U-value in column (a). Prior to installing cavity wall insulation, the wall should be assessed to ensure its condition, construction type, and location are suitable for insulating by this method. Where the assessment identifies a significant risk (e.g. for sites exposed to driving rain) the wall is exempt from meeting the maximum U-value in column (a) using only this method. In such cases, other methods of insulation should be considered, e.g. internal or external wall insulation.

4Where existing wall cavities are partially insulated, they are exempt from meeting the maximum U-value in column (a). The air gap on the cold side of the existing insulation should not be compromised through the application of additional insulation (unless expert advice is sought) as this may present a moisture risk.

5Where internal wall insulation is intended, the maximum U-value in column (a) should be achieved. The wall should be assessed to ensure it is suitable for insulating by this method, which should include a moisture risk assessment.

6.If a wall is suitable for the application of external wall insulation, the maximum U-value in column (a) should be achieved provided suitable specifications have been followed, such as those published by SWIGA (Solid Wall Insulation Guarantee Agency): External wall insulation specification for weathering and thermal bridge control. A wall may be suitable to receive external wall insulation if it is of solid construction or has fully filled and insulated cavities. Cavity walls that are uninsulated or partially insulated should be assumed as not suitable for the application of external wall insulation (unless expert advice is sought).

7.The U-value of the floor of an extension can be calculated using the exposed perimeter and floor area of the whole enlarged dwelling.

8.If meeting such a standard would limit headroom, a worse U-value may be appropriate. In such cases, both the following should be achieved.

a. The depth of the insulation plus any required air gap should be at least to the depth of the rafters.

b. The insulant should be chosen to achieve the lowest practicable U-value

9.If meeting such a standard would reduce the internal floor area of the room bounded by the wall by more than 5%, a lesser provision may be appropriate.

10.If meeting such a standard would create significant problems in relation to adjoining floor levels, a lesser standard may be appropriate.

11.If for a flat roof or roof with integral insulation there are problems with the load-bearing capacity of the frame or height of the upstand, a higher U-value may be appropriate.

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Section 11

11.8Where the U-value set out in column (a) of Table 11.1 is not economically, functionally or technically feasible, the thermal element should be upgraded as close as is practicably possible to the U-values in column (a) of Table 11.1. Generally, the U-value of the thermal element should not be worse than the limiting U-values set out in column (b) of Table 11.1 to minimise the risk of surface condensation and mould growth.

Note: Where the suitability of an element needs to be assessed prior to the application of insulation, or where it is recommended that expert advice be sought in Table 11.1, the person carrying out this work should be appropriately trained in risk assessment and management (for example a Retrofit Coordinator as identified in PAS 2035). Following the procedures given in ‘PAS 2030/2035: 2019 - Retrofitting dwellings for improved energy efficiency. Specification and guidance’ is one way of demonstrating to the Building Control Body that the suitability of an element has been adequately considered.

11.9The test of the economic feasibility of an energy efficiency measure is to calculate if the measure achieves a payback of the initial cost within 15 years through energy savings. This is calculated by dividing the cost of implementing the measure (not the whole cost of the project) by the annual energy saving achieved by that measure, estimated using the latest version of SAP, taking account of VAT in both the cost and the saving.

11.10An energy efficiency measure is not deemed to be functionally or technically feasible if the thickness of insulation needed to achieve the U-values set out in column (a) of Table 11.1 would:

a. reduce the internal floor area of a room by more than 5%; or b. cause significant problems with adjoining floor levels; or c. create insufficient headroom; or d. could not be supported by the existing structure.

11.11In such cases, the choice of insulation should be based on achieving a U-value as close as is practicably possible to the U-values in column (a) of Table 11.1.

11.12If any new or replacement thermal elements are constructed as part of a conversion the guidance for new thermal elements set out in paragraphs 3.8 and 3.9, should be followed.

Windows and Doors, Building Services, Design and Installation Standards

11.13Paragraphs 11.36 to 11.42 should be followed in relation to windows and doors. Paragraph 11.43 should be followed in relation to building services, and paragraphs 11.44 to 11.46 should be followed in relation to Design and Installation Standards.

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Section 11

Renovations

11.14Renovating a thermal element means one of the following.

a.Providing a new layer through cladding or rendering the external surface of a thermal element.

b.Providing a new layer through dry-lining the internal surface of a thermal element.

c.Replacing an existing layer through stripping down the thermal element to expose basic structural components (e.g. bricks, blocks, rafters, joists, frame) and then rebuilding.

d.Replacing the waterproof membrane on a flat roof.

e.Providing cavity wall insulation.

11.15In this Approved Document, where a thermal element is subject to a renovation the performance of the whole of the thermal element should be improved provided the area to be renovated is:

a. greater than 50% of the surface of the individual thermal element or b. constitutes a major renovation where more than 25% of the surface area of the building envelope undergoes renovation.

Note: When a building undergoes a major renovation this may represent an opportunity to consider and take into account the technical, environmental and economic feasibility of installing high-efficiency alternative systems (see section 3).

Note: When thermal elements are being renovated, the work should comply with all the requirements in Schedule 1, but particular attention should be paid to Parts B, C, F and J.

11.16Thermal element is used in the Building Regulations to describe a wall, floor or roof, which separates a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature.

11.17The provision of a new layer means cladding or rendering the external surface or dry lining the internal surface. The replacement of an existing layer means either stripping down the element to its basic structural components (masonry, timber frame, steel frame, etc.) and then rebuilding or replacing the waterproof membrane of a flat roof.

11.18When assessing the proportion of the area to be renovated in paragraph 11.15 the area of the element to be renovated should be taken as that of the individual element, not all the elements of that type in the building. For example, if stripping down the roof of an extension the area of the element is the area of the extension roof, not the total roof area of the dwelling. The area of the element also differs

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Section 11 whether the element is being renovated from the inside or the outside. For example, if removing all the plaster finish from the inside of a wall, the area of the element is the area of the wall in the room, however, if removing the external render, it is the area of the elevation in which that wall sits.

11.19Two alternative optional approaches to the guidance below, that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere, are set out in Section 13.

Building Fabric

11.20Where a thermal element is renovated through the provision of a new layer or the replacement of an existing layer, as described in paragraph 12.15, the performance of the whole element should be improved to achieve or better the U-values set out in column (a) of Table 11.1 including any risk assessments specified in the table are undertaken.

11.21Where the U-value set out in column (a) of Table 11.1 is not economically, functionally or technically feasible, then the thermal element should be upgraded as close as is practicably possible to the U-values in column (a) of Table 11.1. Generally, the U-value of the thermal element should not be worse than the limiting U-values set out in column (b) of Table 11.1 to minimise the risk of surface condensation and mould growth.

Note: Where the suitability of an element needs to be assessed prior to the application of insulation, or where it is recommended that expert advice be sought in Table 11.1, the person carrying out this work should be appropriately trained in risk assessment and management (for example a Retrofit Coordinator as identified in PAS 2035). Following the procedures given in ‘PAS 2030/2035: 2019 - Retrofitting dwellings for improved energy efficiency. Specification and guidance’ is one way of demonstrating to the Building Control Body that the suitability of an element has been adequately considered.

11.22The test of the economic feasibility of an energy efficiency measure is to calculate if the measure achieves a payback of the initial cost within 15 years through energy savings. This is calculated by dividing the cost of implementing the measure (not the whole cost of the project) by the annual energy saving achieved by that measure, estimated using the latest version of SAP, taking account of VAT in both the cost and the saving.

Note: For the purposes of determining whether a measure is economically, functionally or technically feasible, the criteria set out in paragraphs 11.9, 11.10 and 11.11 should be applied.

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Section 11

Design and Installation Standards

11.23When renovating part of an existing dwelling, renovated building fabric should be carefully designed, detailed and constructed to:

a. avoid gaps in the insulation; and b. minimise air leakage; and c. limit reasonably avoidable thermal bridges.

11.24Particular attention should be paid around window and door openings, to junctions between building elements, such as between the walls and roof, and at changes of geometry, for example a corner in a wall or a hip in a roof.

11.25Thermal bridges are instances where heat loss is worse than through the main building fabric. They allow heat to flow between the outer and inner skins of a wall, floor or roof by bridging the insulation.

Material Change of Use

11.26A material change of use, in relation to dwellings, is any of the following.:

a. the building is now used as a dwelling, where previously it was not; or b. the building now contains a flat, where previously it did not; or c. The building contains a greater or lesser number of dwellings than it did, having previously contained at least one dwelling.

Note: The following standards apply if either the whole building or part of a building is undergoing a material change of use.

11.27Where a previously unheated building is converted into a dwelling, it is described as a “change in energy status” in the Building Regulations and paragraphs 11.2 to 11.12 should be followed.

11.28Thermal element is used in the Building Regulations to describe a wall, floor or roof, which separates a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature.

11.29Two alternative optional approaches to the guidance below, that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere, are set out in Section 13.

Building Fabric

11.30Existing thermal elements in a building subject to a material change of use should be upgraded to achieve or better the U-values set out in column (a) of Table 11.1 including any risks assessments specified in the table are undertaken.

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Section 11

11.31Where the U-value set out in column (a) of Table 11.1 is not economically, functionally or technically feasible, then the thermal element should be upgraded as close as is practicably possible to the U-values in column (a) of Table 11.1. Generally, the U-value of the thermal element should not be worse than the limiting U-values set out in column (b) of Table 11.1 to minimise the risk of surface condensation and mould growth.

Note: Where the suitability of an element needs to be assessed prior to the application of insulation, or where it is recommended that expert advice be sought in table 11.1, the person carrying out this work should be appropriately trained in risk assessment and management (for example a Retrofit Coordinator as identified in PAS 2035). Following the procedures given in ‘PAS 2030/2035: 2019 - Retrofitting dwellings for improved energy efficiency. Specification and guidance’ is one way of demonstrating to the Building Control Body that the suitability of an element has been adequately considered.

11.32The test of the economic feasibility of an energy efficiency measure is to calculate if the measure achieves a payback of the initial cost within 15 years through energy savings. This is calculated by dividing the cost of implementing the measure (not the whole cost of the project) by the annual energy saving achieved by that measure, estimated using the latest version of SAP, taking account of VAT in both the cost and the saving.

11.33An energy efficiency measure is not deemed to be functionally or technically feasible if the thickness of insulation needed to achieve the U-values in column (a) of Table 11.1 would:

a. reduce the internal floor area of a room by more than 5%; or b. cause significant problems with adjoining floor levels; or c. create insufficient headroom; or d. could not be supported by the existing structure.

11.34In such cases, the choice of insulation should be based on the best thermal performance that is practicable to achieve a U-value as close as is practicably possible to the U-values in column (a) of Table 11.1. In cases of insufficient headroom, the depth of the insulation plus any required air gap should be at least equal to the depth of the rafters.

11.35If any new or replacement thermal elements are constructed as part of a material change of use, the guidance for new thermal elements set out in paragraphs 3.7 and 3.8 should be followed.

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Section 11

Windows and Doors

11.36If an existing window or door has a U-value worse than the threshold U-values set out in column (c) of Table 10.1, then it should be replaced with draught- proofed units that achieve or better the U-values set out in column (a) of Table 10.1. Insulated cavity closers should be installed around the windows and doors, where appropriate.

11.37New and replacement windows and doors should be draught-proofed units that achieve or better the U-values set out in column (a) of Table 10.1. Insulated cavity closers should be installed around the windows and doors, where appropriate.

11.38In this Approved Document, windows and doors refers to windows and external doors that separate a heated space from the external environment, the ground, and any parts of the building which are not heated or, where another part of the building which is not a dwelling, is heated to a different temperature. Windows and doors refer to the whole units, i.e. including the frames.

11.39Consequently replacing just the glazing or door leaf while retaining an existing frame is not building work and so does not have to meet the energy efficiency requirements. However, in such cases it would be sensible to upgrade the window or door to as close to the U-values set out in column (a) of Table 10.1 as is practicably possible. Windows and doors are described as controlled fittings in the Building Regulations, i.e. windows and doors on which various parts of the Building Regulations impose a requirement.

11.40Where an existing window or door is enlarged or a new one created the total area of windows and doors should not exceed 25% of the total floor area of the dwelling.

11.41In the case of dwellings of architectural and historic interest where special consideration applies or in other cases where there is a need to maintain the character of a façade, if replacement windows or doors are unable to achieve the U-values set out in column (a) of Table 10.1, then they should achieve or better the lesser U-values set out in column (b) of Table 10.1.

11.42Where low-e secondary glazing is installed, the draughtproofing should be on the secondary glazing to minimise the risk of condensation forming between the primary and secondary glazing.

Building Services

11.43Where a material change of use of a building to become a dwelling includes the provision, extension, alteration or replacement of any fixed building services systems, those systems should comply with the appropriate standards in Sections 4, 5 and paragraphs 3.15 to 3.32, and commissioned according to Section 7.

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Section 11

Design and Installation Standards

11.44When undertaking a change of use, the building fabric should be carefully designed, detailed and constructed to:

a. avoid gaps in the insulation; and b. minimise air leakage; and c. limit reasonably avoidable thermal bridges.

11.45Particular attention should be paid around window and door openings, to junctions between building elements, such as between the walls and roof, and at changes of geometry, for example a corner in a wall or a hip in a roof.

11.46Thermal bridges are instances where heat loss is worse than through the main building fabric. They allow heat to flow between the outer and inner skins of a wall, floor or roof by bridging the insulation.

Replacement thermal element in an existing dwelling

11.47Replacement thermal elements constructed in an existing dwelling should achieve the minimum standards in paragraphs 3.8 and the final column of table 3.1. If minimum standards are not technically feasible, they should be constructed to as close to the minimum standards as is practicably possible.

Note: A thermal element does not include windows, doors, roof windows or roof-lights.

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Section 11

Regulation 28: Consequential improvements

This Approved Document deals with the requirements of regulation 28 of the Building Regulations 2010 (as amended).

Regulation 28 - Consequential improvements to energy performance

(1) Paragraph (3) applies to an existing building with a total useful floor area over 1000m 2 where the proposed building work consists of or includes—

(a) the initial provision of any fixed building services; or

(b) an increase to the installed capacity of any fixed building services.

(2) Paragraph (3) applies to an existing building where the proposed building work consists of or includes--

(a) an extension; or

(b) the extension of the building’s heating system or the provision of a fixed heating appliance, to heat a previously unheated space.

(3) Subject to paragraph (4), where this paragraph applies, such work, if any, shall be carried out as is necessary to ensure that the building complies with the requirements of Part L of Schedule 1.

(4) Nothing in paragraph (3) requires work to be carried out if it is not technically, functionally and economically feasible.

Note: Where the building control body is a registered building control approver, see regulation 5 of the Building (Registered Building Control Approvers etc.) (Wales) Regulations 2024(as amended).

Intention

In the Welsh Minister’s view, where regulation 28 applies, the requirements of this regulation are met for existing dwellings by carrying out consequential improvements that are technically, functionally and economically feasible, by following the guidance in Section 12.

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Section 12

Section 12

Consequential improvements

What are consequential improvements?

12.1Consequential improvements (see regulation 28) describes additional energy efficiency improvements that should be undertaken where an existing dwelling is extended or part of the dwelling is converted increasing the habitable volume. The dwelling could be extended by means of a conventional extension or a non- exempt conservatory or porch. A conversion (also known as a change of energy status) is where there is an extension of the building’s heating system or the provision of a fixed heating appliance in a previously unheated space, e.g. a garage or loft conversion.

12.2Where consequential improvements are triggered by extensions (including non- exempt conservatories or porches) and conversions, the work should still comply with the relevant guidance: see Section 10 for guidance on extensions; see Section 11 for guidance on conversions and on conservatories and porches.

12.3Where consequential improvements are undertaken they should only be undertaken where they are technically, functionally or economically feasible. Those improvement measures identified here should typically be feasible.

Note: The test of the economic feasibility of an energy efficiency measure is to calculate if the measure achieves a payback of the initial cost within 15 years through energy savings. This is calculated by dividing the cost of implementing the measure (not the whole cost of the project) by the annual energy saving achieved by that measure, estimated using the latest version of SAP, taking account of VAT in both the cost and the saving.

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Section 12

Consequential improvement measures: energy efficiency

12.4Where an existing dwelling is extended or converted, as a result increasing the habitable area by no more than 10m 2, if there is no loft insulation or it is less than 200 mm thick, provide 250 mm of loft insulation or increase it to 250 mm (figures are based on mineral wool/or equivalent insulation).

12.5Where an existing dwelling is extended or converted, as a result increasing the habitable area by more than 10m 2, the following energy efficiency improvements should be undertaken:

a. if the dwelling has uninsulated cavity walls, fill with insulation where suitable (cavity wall insulation may not be suitable in some circumstances, such as sites exposed to driving rain)1; and

b. if there is no loft insulation or it is less than 200 mm thick, provide 250 mm insulation or increase it to 250 mm (figures are based on mineral wool/or equivalent insulation); and c. upgrade any hot water cylinder insulation as follows:

i. if the hot water cylinder is uninsulated, provide a 160 mm insulated jacket; or ii. if the hot water cylinder has insulated jacket less than 100 mm thick, add a further insulated jacket to achieve a total thickness of 160 mm; or

iii.if the hot water cylinder has factory-fitted solid foam insulation less than 25 mm thick, add an 80 mm insulated jacket.

12.6Where the consequential improvement to increase the thickness of the loft insulation to 250 mm is triggered by a loft conversion, the consequential improvement will still be necessary if there are some areas of the loft floor remaining around the new heated volume, for example near the eaves.

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Section 12

12.7Care should be taken when installing insulation to avoid any gaps and not compromise the existing ventilation requirements. Particular attention should be paid around window and door openings, to junctions between building elements, such as between the walls and roof, and at changes of geometry, for example a corner in a wall or a hip in a roof.

Consequential improvement measures: Significant extensions

12.8Where a significant extension is proposed for an existing dwelling, consequential improvements should be provided to the existing dwelling and/or extension following the simplified approach in paragraph 12.9 or the alternative approach in paragraph 12.10.

Note: For the purposes of paragraph 12.8, an extension is classed as a significant extension where it involves new construction that increases the footprint of the dwelling, and where:

(a) the total gross internal floor area of the extension (including conditioned and unconditioned spaces, e.g. such as a garage, but excluding rooms in the roof space) is 40 m² or greater; and

(b) the extension has at least the same number of storeys (excluding room in the roof storeys) as the existing dwelling.

Simplified Approach

12.9Installation of one of the following renewable technology’s:

a.Photovoltaic installation following the system specific guidance in paragraphs 5.64 to 5.67 with an array at least 2.0 kWp.

b.Solar water heating system that serves both the existing dwelling and extension by following the system specific guidance in paragraphs 5.43 to 5.47.

Note: Electrical generation systems using renewable technology on dwellings connected to the electricity distribution network will generally require either Distribution Network Operator (DNO) notification for smaller systems, or DNO connection approval for larger systems. Further guidance and information should be obtained from the relevant DNO.

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Section 12

Note: Renewable technology systems should be compatible with energy storage systems to maximise self-consumption by storing site-generated energy during periods when renewable generation is inactive.

Note: Where the work involves a significant change in the applied loading to an existing roof, the structural integrity of the roof structure and the supporting structure should be checked to ensure that upon completion of the work the building is not less compliant with Requirement A1 than the original building. Approved Document A (Structure) should be followed.

Alternative Approach

12.10As an alternative to the simplified approach, alternative energy efficiency improvements should be provided following either paragraph 12.11 or 12.12.

12.11Heat pump technology should be designed and installed to provide space heating and/or domestic hot water to the dwelling and extension, following the system specific guidance in paragraphs 4.9 to 4.24 and 5.1 to 5.7.

12.12The ‘Equivalent Primary Energy and Carbon Emissions Target’ approach as set out in section 13 may be used with the following limits applied to the benchmark.

a.The proposed extension benchmark should include a 2.0 kWp solar photovoltaic system and

b.The array modelled with the following inputs:

i.Orientation: south-facing

ii.Overshading: none or very little

iii.Roof pitch: 35°

12.13The ‘Equivalent Primary Energy and Carbon Emissions Target’ approach offers greater design flexibility and allows other renewable or low and zero carbon technologies and/or enhanced fabric/service efficiencies, to contribute toward the reduction of the primary energy and carbon emissions of the dwelling and proposed significant extension.

Note: Non-renewable technology and fabric improvement measures may be used to meet the primary energy and carbon emissions target for a dwelling where the provision of renewable technology is not chosen.

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Section 12

Note: Fabric improvement measures used to meet the primary energy and carbon emissions target should be additional to the measures identified in paragraphs 12.4 to 12.7.

Exemptions for significant extensions

12.14A significantly extended dwelling is exempt from the requirements in paragraph 12.8 where the dwelling:

a.Already has renewable technology installed that has a capacity equivalent to or better than the sizes set out in paragraph 12.9.

b.Already has a heat pump that serves the dwelling and can be extended to serve the proposed extension.

c.Meets the exemption guidance in paragraphs 0.8 to 0.15.

d.cannot reasonably accommodate the renewable technologies in paragraph 12.9 because they are not technically, functionally or economically feasible (see paragraph 12.3).

Note: Where a dwelling is considered unsuitable for solar renewable technology following paragraph 12.9, evidence of the technical or economic constraints should be submitted to the building control body, unless the alternative approach described in paragraphs 12.10 to 12.13 is followed.

Note: Evidence of technical or economic constraints may include for example an MCS- accredited installer feasibility report or equivalent.

Note: Where a DNO does not approve a connection, this should be treated as not technically feasible as described in paragraph 12.14 d. Evidence in the form of a DNO refusal letter should be submitted to the building control body.

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