Approved Document L: volume 2 (buildings other than dwellings) (takes effect on 4 March 2027)

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The Building Regulations 2010

Approved Document

Volume 2

Buildings other than dwellings

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 978-1-83745-487-7

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The Approved Documents

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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The Approved Documents

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 F (standards) or Appendix G (other documents). 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.

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 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.

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The Approved Documents

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:

a. the erection or extension of a building b. the provision or extension of a controlled service or fitting 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.

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.

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The Approved Documents

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.

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

Introduction

0.1This Approved Document is Approved Document L, volume 2: buildings other than dwellings. It gives guidance on how to comply with Part L of Schedule 1 of the Building Regulations and the associated energy efficiency requirements for buildings other than dwellings. For guidance relating to domestic buildings, use Approved Document L, volume 1: dwellings.

0.2This Approved Document contains the following sections:

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Application

0.3The guidance in Approved Document L, Volume 2 applies only to buildings other than dwellings. In a mixed-use building, this document should be consulted for building work in those parts of the building that are not dwellings. The document gives guidance for building work in both new and existing buildings.

Note: Dwellings are self-contained units. This document applies to both of the following, which are not dwellings.

i.Rooms for residential purposes.

ii.Buildings that contain only rooms for residential purposes.

0.4In the Welsh Ministers' view, for the purposes of the energy efficiency requirements of the Building Regulations, a building means either of the following.

a. The whole of the building.

b. Part of a building designed or altered to be used as a separate premises.

Common areas in buildings that contain multiple dwellings

0.5For the common areas of buildings that contain more than one dwelling, the following guidance applies.

a. If the common areas are heated, the guidance in this Approved Document should be followed.

b. If the common areas are unheated, individual fabric elements should meet the minimum standards set out in Section 3 of Approved Document L, Volume 1: Dwellings.

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New buildings

0.6Guidance for new buildings is given in Sections 1 to 8 of this Approved Document.

0.7For a conservatory or porch installed as part of the construction of a new building, if both the following apply:

a.there is adequate thermal separation between the building and the conservatory or porch

b.the building’s heating system is not extended into the conservatory or porch

The conservatory or porch should follow the guidance in Section 9, treating the conservatory or porch as if it were an extension being added onto an existing building.

Where a conservatory or porch is provided in a new building and both a. and b. have not been achieved, the guidance for the whole new building should be followed, including for Primary Energy Rate and Building Emission Rate calculations, treating the conservatory or porch as a room in the new building.

0.8For the first fit-out works in buildings, such as shell-and-core office buildings, guidance for new buildings covering first fit-out should be followed. For any subsequent fit-out works the guidance for existing buildings should be followed.

0.9For constructing a building from modular subassemblies, or for relocating a modular or portable building, guidance for new buildings should be followed, taking note of the special considerations for these building types outlined in Section 2. If the work extends an existing building, consequential improvements may also be required - guidance is given in Section 11.

Extensions to and work on existing buildings

0.10Guidance on complying with the energy efficiency requirements is given for the following.

a.Limiting heat gains and losses: Section 3.

b.Building services: Section 4 and 5.

c.New elements in existing buildings, including replacement of a thermal element and constructing an extension: Section 9.

d.Existing elements in existing buildings, including renovating or retaining a thermal element, material change of use and change to energy status: Section 10.

e.Consequential improvements: Section 11.

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Exemptions

0.11The following classes of buildings or parts of buildings other than dwellings are exempt from the energy efficiency requirements.

a.Places of worship – buildings or parts of a building that are used primarily or solely for formal public worship, plus adjoining spaces the function of which is directly linked to that use (e.g. a vestry in a church).

Note: Parts of the building that are designed to be used separately, such as offices, catering facilities, day centres, meeting halls and accommodation, are not exempt from the energy efficiency requirements.

b.Temporary buildings with a total planned time of use of two years or less.

c.Buildings with low energy demand which are industrial sites, workshops and non-residential agricultural buildings;

Note: Low energy demand only relates to the energy used by fixed heating or cooling systems, not to energy required for or created by process needs. This includes buildings or parts of buildings where the space is not generally heated or cooled other than by process heat or buildings or parts of buildings that only require heating or cooling for short periods each year, such as during critical periods in the production cycle (e.g. plant germination, egg hatching) or during very severe weather conditions.

Note: Portable or modular buildings with a planned service life longer than two years, whether on one or more sites, are not exempt. See paragraphs 2.17 to 2.25.

d.New and existing stand-alone buildings other than dwellings, with a total useful floor area of less than 50 m 2.

e.Carports, covered yards, covered ways and some conservatories and porches (see paragraphs 0.19 to 0.20).

Exemptions for listed buildings, buildings in conservation areas and scheduled monuments

0.12Work to the following types of buildings do not need to comply fully with the energy efficiency requirements, where to do so would unacceptably alter the buildings character or appearance.

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

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

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

0.13Work to a building in paragraph 0.12 must comply with the energy efficiency requirements where this would not unacceptably alter the building’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 buildings where special considerations apply

0.14In 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.

0.15Work to such buildings is required to comply with the energy efficiency requirements as far as is reasonably practicable. Historic and traditional buildings should only have their energy efficiency improved to the extent that it does not risk the long-term deterioration of the building fabric or fittings, in particular those that have a vapour permeable construction that both absorb and readily allow moisture to evaporate. Examples include wattle and daub, cob, stone and constructions using lime render or mortar.

0.16New extensions to historic or traditional buildings should comply fully with the standards of energy efficiency in this Approved Document unless there is a need to match the external appearance or character of the extension to that of the host building. The work should comply with standards in this Approved Document to the extent that it is reasonably practicable.

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0.17In determining whether full energy efficiency improvements should be made, the building control body should take into account the advice of the local authority’s conservation officer.

0.18Additional guidance on how to implement specific energy efficiency measures is available in Cadw’s How to Improve Energy Efficiency in Historic Buildings in Wales (2022).

Exemptions for conservatories and porches

0.19Where building work creates an extension to an existing building and the extension is a conservatory or porch, the extension is exempt from the energy efficiency requirements, under Regulation 21 of the Building Regulations, if all of the following criteria are met.

a.The extension is at ground level.

b.The internal floor area does not exceed 30 m2.

c.The glazing complies with Part N of Schedule 1 to the Building Regulations.

d.Any wall, door or window separating the conservatory or porch from the building has been retained or, if removed, replaced with a wall, door or window.

Note: Replacement walls, windows and doors should meet the requirement in regulation 23(2). See Section 9.

e.The conservatory or porch contains no fixed heating appliance or the buildings heating system of the building is not extended into the conservatory or porch.

Exemptions for covered areas

0.20Where a building is extended through the addition of a carport open on at least two sides, a covered yard, covered walkway or covered driveway, the work is exempt from the energy efficiency requirements if both of the following are met.

a.It is at ground level.

b.The floor area of that extension does not exceed 30 m2.

Live–work units

0.21A unit 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. Guidance for dwellings can be found in Approved Document L, volume 1: dwellings.

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Section 0

0.22The 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.

b.The commercial space and the living accommodation are within the same thermal envelope.

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 by the building control body.

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

0.23When constructing a building that contains dwellings and 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 Approved Document L, volume 1: dwellings.

b. For guidance on the non-dwelling parts of the building, such as heated common areas, and in the case of mixed-use developments, the commercial or retail space, use this Approved Document.

Selected key interactions with other parts of the Building Regulations

0.24The 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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Interaction with Part B

0.25This Approved Document provides guidance for fixed building services and on-site electricity generation. Where on-site electricity is provided for occupant use, the guidance on the fire safety requirements 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 2, should be followed.

Interaction with Part C

0.26This 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

0.27This Approved Document provides guidance on insulation that is reasonably continuous and limits thermal bridging. Construction junctions should have adequate edge sealing, following Approved Document E.

Interaction with Part F

0.28This Approved Document provides guidance on reducing unwanted heat loss through 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

0.29This Approved Document provides guidance on airtightness. Guidance on permanent ventilation openings for open flued appliances in very airtight buildings should be followed in Approved Document J.

Interaction with Part K and M

0.30This Approved Document provides guidance on controls for fixed building services, building automation control systems and on-site electricity generation. Where manual controls are provided, they should be within reasonable reach of the occupants. Guidance provided in Approved Documents K and M.

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Regulations 24, 25, 25C, 26, 26A, 27, 27A, new regulations for primary energy: Energy performance of building calculations

This Approved Document deals with the requirements of regulations 24, 25, 25C, 26, 26A, 27 and 27A and new regulations for primary energy of the Building Regulations 2010.

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 CO2 emission rates, which shall be calculated and expressed in accordance with the methodology approved pursuant to regulation 24.

Regulation 25C (a) – 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 buildings, in the form of target primary energy rates.

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Section 0

Regulation 26 – CO2 emission rates for new buildings Where a building is erected, it shall not exceed the target CO2 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 27 - CO2 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 CO2 emission rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

b.the CO2 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 CO2 emission rate for the building, calculated and expressed in accordance with the methodology approved pursuant to regulation 24;

ii.the CO2 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

CO2 emission rate.

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Section 0

Regulation 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 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 sub-paragraph (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.

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.

Intention

Regulation 24

Regulation 24 of the Building Regulations set requirements for Welsh Ministers to approve a methodology of calculation of the energy performance of a building. For a new non-domestic building, the approved methodologies are the Simplified Building Energy Model or other software tools approved under the Notice of Approval.

Calculation methodologies are set out in Section 1 and Section 2.

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 and a Target Emission Rate. The targets are set out in Section 1 of this Approved Document.

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Regulation 26 and 26A

A newly constructed building must be shown to meet regulations 26 and 26A by producing calculations to show that the building meets both of the following.

a.Target Primary Energy Rate.

b.Target Emission Rate.

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

Regulation 27 and 27A

Both before and after a newly constructed building 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 Primary Energy Rate and Target Emission Rate

1.1A new building must be built to a minimum standard of energy performance. The building primary energy rate and the building emission rate for the new building, as set out in Section 2, must be equal or better than the emission rate and primary energy rate calculated for the notional building. The building primary energy rate and building emission rate must be calculated at the design stage and when building work is complete.

Note: How to calculate the Building Primary Energy Rate and Building Emission Rate is set out in Section 2.

1.2The notional building is of the same size and shape as the actual building and has standardised properties for fabric and services. The properties of the notional building are set out in the Building Research Establishment’s National Calculation Methodology modelling guide, which is available from NCM (uk-ncm.org.uk)

1.3The energy performance of the notional building, is described using the following metrics:

a.The Target Primary Energy Rate, in kWhPE /m2 per year.

b.The Target Emission Rate, in kgCO 2/m 2 per year.

1.4The Target Primary Energy Rate and Target Emission Rate must be calculated using the approved methodology. Software packages that implement this methodology can be either of the following:

a.The Simplified Building Energy Model (SBEM), for buildings with design features that can be adequately modelled by it.

b.Other software tools approved under the relevant Notice of Approval.

The software packages should be used in line with the version policy as stated in the National Calculation Methodology Modelling Guide.

As part of the submission to the building control body, it should be shown that the software package used is appropriate to the application.

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Section 1

Note: An up-to-date list of approved software can be found on the Welsh Government Part L webpages.

District heat networks and communal heat networks

1.5For a building connected to a district heat network the notional building will use primary energy and CO2 emission factors for heat and hot water as listed in Table 1.1.

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

1.6For a building connected to a communal heat network the notional building will use the characteristics of the heat network and associated services as defined in the National Calculation Methodology Modelling Guide.

1.7For 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.

1.8The 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 building.

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Section 1

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

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

d.That at least 90% of the thermal energy delivered by the district heat network to the building 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 building 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 heat network within 5 years of the ‘as-built’ 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’ 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

Low-carbon heat sources

Electrically powered heat pumps(1)

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 building should include both electrical energy consumed and ‘source’ thermal energy (e.g. heat from the air).

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Section 2

Section 2

Calculating the Building Primary Energy Rate and Building Emission Rate

2.1The same software package implementing the approved calculation methodology should be used to calculate the Target Primary Energy Rate, the Target Emission Rate, the Building Primary Energy Rate and the Building Emission Rate.

2.2The Building Primary Energy Rate and the Building Emission Rate must be calculated at both of the following points.

a.Before work starts, using design values.

b.When work is complete, using values for the building as constructed, and incorporating both of the following.

i.Any changes that have been made during construction to the list of specifications (for example any changes to specific fan powers / air handing units where applicable).

ii.The measured air permeability (see Section 7).

2.3At both of these points in paragraphs 2.2(a) and (b), the Building Primary Energy Rate and Building Emission Rate must not exceed the Target Primary Energy Rate and the Target Emission Rate, respectively.

The specification of the actual building may vary from that of the notional building if the building meets the Target Primary Energy Rate, Target Emission Rate 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 Building Primary Energy Rate (calculated using design values).

b.The Target Emission Rate and the Building Emission Rate (calculated using design values).

c.A list of specifications used in the calculations.

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Section 2

Items (a) to (c) can be reported using the design stage Building Regulations United Kingdom Part L Compliance report (BRUKL report) which is produced as a standardised output from the Approved Software detailed in paragraph 1.4. For further details of the design stage BRUKL report, see Appendix C.

2.5The building control body must be notified once the work is complete of all of the following.

a.The Target Primary Energy Rate and the Building Primary Energy Rate.

b.The Target Emission Rate and the Building Emission Rate.

c.A list of specifications used in the calculations made for the building as constructed, and whether the specifications have changed from those provided in the design stage.

Building control bodies can accept evidence of (a) to (c) above as reported in the as-built BRUKL report, provided by an accredited energy assessor. This should also be supported by photographic evidence. The BRUKL report is produced as a standardised output from the BRUKL module within the Approved Software package detailed in paragraph 1.4. For further details of the as-built BRUKL report and photographic evidence, see Appendix C.

Note: Developers/clients may wish to provide building control bodies with the required photographs as work progresses, allowing any potential issues to be identified at an early stage. Photographs are not a replacement for site inspections by building control bodies.

Heating in the Building Primary Energy Rate and the Building Emission Rate calculations

2.6When systems can be powered by more than one fuel, the following applies, according to the fuel(s).

a.Biomass heating supplemented by an alternative appliance (e.g. electric heat pump) - the CO 2 emission factor and primary energy factor should be based on a weighted average for the two fuels. The weighting should be based on the usage of each fuel that would be expected to meet the heating demands as calculated from the Part L compliance model.

The Building Emission Rate and Building Primary Energy Rate submitted to the building control body should be accompanied by a report, signed by a suitably qualified person, detailing how the combined emission factor was derived.

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Section 2

b.Appliances that can burn both biomass fuel and fossil fuel: the CO 2 emission factor and primary energy factor for dual-fuel appliances should be used, except where the building is in a smoke control area, when the anthracite figure should be used.

c.In all other cases, the calculation should use the fuel with the highest CO 2 emission factor from those used by the system.

District heat networks and communal heat networks

2.7If 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 building 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 Building Primary Energy Rate and Building Emission Rate.

a.The CO 2 emission factor and primary energy factor for heat delivered to the building are entered as inputs into the Approved Methodology for calculating the Building Primary Energy Rate and Building 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 CO 2 emission factor and primary energy factor are still required to be calculated.

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 Building Primary Energy Rate and Building Emission Rate for a building 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.

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Section 2

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) 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 CO 2 emission factors and primary energy factors that are used to calculate the Building Emission Rate and Building Primary Energy Rate should be calculated as follows.

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

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

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

PEE is the primary energy factor for district heat CHP generated electricity in kWhPE /kWh.

The CO 2 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

CO2F is the emission factor for the input fuel in kgCO2 /kWh E is the electricity production from the scheme in kWh

CO2E is the emission factor for district heat CHP generated electricity in kgCO 2 /kWh.

h.The Building Primary Energy Rate and Building 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 CO 2 emission factors and primary energy factors were derived.

Note: See the National Calculation Methodology Modelling Guide for further information.

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Section 2

Management and control features in the Building Primary Energy Rate and the Building Emission Rate calculations

2.8Where enhanced management and control features are provided in the building, the Building Primary Energy Rate and Building Emission Rate can be reduced. The appropriate adjustment factor in Table 2.1 should be applied to both of the following, for the system(s) to which the enhanced management and control feature is being applied.

a.The CO 2 emissions.

b.The primary energy.

Note: For example, if the CO 2 emissions due to electrical energy consumption were 70kgCO 2 / (m2 ·year) without enhanced management and control features, and if power factor correction equipment were provided to achieve a power factor of greater than 0.95, the Building Emission Rate could be reduced by 70 x 0.025 = 1.75kgCO 2 /(m2·year).

Table 2.1 Enhanced management and control features

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Section 2

Achieving the Target Primary Energy Rate and Target Emission Rate

2.9Provided the building satisfies the minimum standards for fabric set out in Section 3, the designer can achieve the Target Primary Energy Rate and Target Emission Rate by using any combination of the following.

a.Fabric energy efficiency.

b.Efficient building services.

c.Low and zero carbon technologies integrated in an appropriate mix.

Note: The Target Primary Energy Rate and Target Emission Rate are not likely to be met by using the minimum standards for fabric set out in Section 3 alone.

Special considerations when calculating Building Primary Energy Rate and Building Emission Rate

2.10Special considerations apply to certain classes of building. These building types include all of the following.

a.Buildings with low energy demand, follow paragraphs 2.11 to 2.16.

b.Modular and portable buildings with a planned service life of more than two years (at one or more sites), follow paragraphs 2.17 to 2.25.

c.Swimming pools, follow paragraph 2.26.

d.Shell and core developments, follow paragraphs 2.27 to 2.31.

e.Industrial sites, workshops and non-residential agricultural buildings other than those with low energy demand, follow paragraph 2.32.

Note: Industrial sites, workshops and non-residential agricultural buildings with low energy demand and buildings with a planned service life of less than two years are exempt from the energy efficiency requirements. See paragraph 0.11.

Buildings with low energy demand

2.11Buildings with low energy demand are those buildings or parts of buildings, which are not exempt from the energy efficiency requirements for reasons outlined in Section 0, where any of the following apply.

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Section 2

a.Fixed building services for heating and/or cooling are not provided.

b.Fixed building services for heating and/or cooling are provided only to heat or cool a localised area rather than the entire enclosed volume of the space concerned (e.g. localised radiant heaters at a workstation in a generally unheated space).

c.Fixed building services are used to heat space in the building to temperatures that are substantially less than those normally provided for human comfort (e.g. to protect a warehouse from frost).

2.12A Target Primary Energy Rate, Building Primary Energy Rate, Target Emission Rate and Building Emission Rate should be calculated for non-exempt buildings with low energy demand. Zones that correspond to the definitions in paragraph 2.11 should be modelled as outlined in the National Calculation Methodology Modelling Guide paragraph 122 as ‘unconditioned’, i.e. not served by a space heating or space cooling system.

2.13For a building with low energy demand both of the following apply:

a.Every fixed building service that is installed should meet the energy efficiency standards in Section 4 and 5.

b.The building envelope should be insulated to a degree that is reasonable in the particular case. If some general heating is provided, as in paragraph 2.11c, then no part of the opaque fabric should have a U-value higher than 0.7 W/(m 2.K).

2.14If part of a building with low energy demand is both:

a.partitioned off

b.heated normally

(for example, an office area in an unheated warehouse), then the separately heated area should be treated as a separate building or zone and the normal procedures for demonstrating compliance with the energy efficiency requirements of the Building Regulations should be followed.

2.15If a building that had low energy demand no longer has low energy demand, consequential improvements may need to be made in some circumstances. See Section 11.

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Section 2

2.16If a building or part of a building with low energy demand was designed as a shell and core building, and first fit-out work results in it no longer being classed as having low energy demand (in line with paragraph 2.11), then normal procedures for demonstrating compliance with the energy efficiency requirements of the Building Regulations should be followed.

Modular and portable buildings with a planned service life of more than two years

2.17Placing an existing module on a new site is considered by the Building Regulations to be the construction of a new building

2.18Special considerations apply to modular and portable buildings with a planned service life of more than two years.

a.For modular and portable buildings at one location, follow paragraphs 2.19 to 2.21.

b.For modular and portable buildings intended for use at more than one location, for example under hire agreements, follow paragraphs 2.22 to 2.25.

Buildings at one location

2.19Modular and portable buildings with a planned service life of more than two years at one location should be shown to comply with the energy efficiency requirements.

2.20If more than 70% of the external envelope of this type of building will be created from sub-assemblies manufactured before the date when this Approved Document came into force, the Target Primary Energy Rate and Target Emission Rate should be adjusted by the relevant factors from Table 2.2.

Note: One way to show the date of manufacture of each sub-assembly is by relating the serial number to the manufacturer’s records.

2.21After a modular building is manufactured, any later work on a module should meet the standards in this document, treating it as work on an existing building as follows.

i.Fabric elements that will be refurbished or replaced in modular sub- assemblies should meet the minimum standards given in Section 3.

ii.Fixed building services elements that will be replaced in modular sub- assemblies should meet the minimum standards in Section 4 and 5.

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Section 2

Table 2.2 Multiplying factors for Target Primary Energy Rate and Target Emission Rate for modular and portable buildings with a service life of more than 2 years at one location

Buildings at more than one location

2.22Modular and portable buildings with a planned service life of more than two years but with an intended time of use in one location of less than two years should be shown to comply with the energy efficiency requirements. An example of this type of building is a modular or portable building for short term hire to multiple locations.

Note: An example of evidence that the planned time of use in the given location is less than two years is the hire agreement for the unit.

2.23For a modular or portable building of the type described in paragraph 2.22, the Target Primary Energy Rate, Building Primary Energy Rate, Target Emission Rate and Building Emission Rate should be calculated when the portable building or its modular components are first constructed. The calculation can be based on a standard generic configuration of modules.

Whenever the building is moved to a new location, in which its intended time of use is less than two years, these calculations can be provided as evidence that the energy efficiency requirements are met. The supplier should provide all the following in writing.

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Section 2

a.Details of the calculation.

b.Confirmation that the modules as provided meet or exceed the energy standards of the elements of the generic module on which the calculation was based.

c.Confirmation that the activities assumed in the generic module are reasonably representative of the planned use of the actual module.

2.24If the planned time of use of a modular or portable building in one location is less than two years, the only practical heating technology may be electric resistance heating. In such cases, the notional building will use electric resistance heating.

2.25If more than 70% of the external envelope of this type of building will be created from sub-assemblies manufactured before the date when this Approved Document came into force, the Target Primary Energy Rate and Target Emission Rate should be adjusted by the relevant factors from Table 2.3.

Note: One way to show the date of manufacture of each sub-assembly is by relating the serial number to the manufacturer’s records.

Table 2.3 Multiplying factors for Target Primary Energy Rate and Target Emission Rate for modular and portable buildings with a planned service life of more than 2 years but intended time of use at one location of less than 2 years

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Section 2

Swimming pool basins

2.26When calculating the Building Primary Energy Rate and Building Emission Rate for a building with a swimming pool, the thermal performance of the pool basin should not be included. Instead, the Building Primary Energy Rate and Building Emission Rate should be calculated as if the area covered by the pool was replaced with the equivalent area of floor with the same U-value as the pool surround.

Shell and core developments

2.27If a building is offered to the market as a shell for fit-out work by the incoming occupier, the developer should calculate a design-stage Target Primary Energy Rate, Building Primary Energy Rate, Target Emission Rate and Building Emission Rate. These calculations should be submitted to the building control body and be based on a realistic fit-out which achieves the energy efficiency requirements.

2.28If some systems are not installed when a building is put on the market, reasonable assumptions should be made when calculating the Building Primary Energy Rate and Building Emission Rate and in the model for the efficiencies of services that will be installed during first fit-out work. The specification provided to the building control body should give all of the following.

a.Details of the services (including any on-site electricity generation) not provided in the base build.

b.The efficiency values assumed for these services.

c.A statement on how access will be provided to install any services, including on-site electricity generation, during first fit-out work.

2.29When the base building in a shell and core development is completed, the as-built Target Primary Energy Rate, Building Primary Energy Rate, Target Emission Rate and Building Emission Rate should be calculated based only on the building and systems as constructed. The fit-out areas should be assumed to be conditioned to temperatures appropriate to their designated use, but no associated energy demand included.

2.30If an incoming occupier does first fit-out work on all or part of a building in a shell and core development by providing or extending fixed services for any of the following.

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Section 2

a.Heating.

b.Hot water.

c.Air-conditioning.

d.Mechanical ventilation.

then a Target Primary Energy Rate, Building Primary Energy Rate, Target Emission Rate and Building Emission Rate should be submitted to the building control body when work is complete to show compliance with the energy efficiency requirements of the Building Regulations for the part(s) of the building covered by the fit-out work.

Note: Photographic evidence must be provided for the fit-out work for each individual fit- out unit.

2.31If fit-out work does not include providing or extending any of the fixed services for any of the following:

a.Heating.

b.Hot water.

c.Air-conditioning.

d.Mechanical ventilation.

then any lighting systems that are installed should be at least as efficient as those assumed in the shell developer’s initial submission.

Note: Paragraph 8.11 outlines requirements for the building log book to be completed for shell and core developments when first fit-out work takes place.

Industrial sites, workshops and non-residential agricultural buildings other than those with low energy demand

2.32Special considerations may apply to industrial sites, workshops and non-residential agricultural buildings, if the National Calculation Methodology Modelling Guide cannot adequately account for the building’s use. For example, if using the National Calculation Methodology Modelling Guide would lead to negative impacts on cost- effectiveness and/or significant technical risk.

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Section 2

Requirement L1(a): Limiting heat gains and losses

This section deals with the requirements of Part L1(a) of Schedule 1 to the Building Regulations 2010.

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Section 2

Intention

In the Welsh Minister’s view, requirement L1(a) is met in a new building by achieving both of the following.

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

i.The building fabric, including walls, floors, roof, windows and openings - paragraphs 3.1 to 3.6 and paragraphs 3.9 to 3.14.

ii.Airtightness – the required air permeability from table 3.1

iii.The pipework and services – paragraphs 3.18 to 3.26.

b.Limiting unwanted heat gains to the building, throughout the year, through any of the routes listed in point a. as set out in Section 3 and specifically for new buildings - paragraphs 3.16 to 3.17.

In the Welsh Minister’s view, requirement L1(a) is met for the work being done to an existing building by achieving both of the following, where relevant to the work being done.

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

i.Any building fabric to which building work is being carried out, including walls, floors, roof, windows and openings – paragraphs 3.1 to 3.14. Further guidance is given in the following sections.

•o For new elements, replacement elements and extensions – Section 9.

•o For renovated elements, retained elements, a change to energy status and a material change of use – Section 10.

ii.Any work which might result in making airtightness worse – paragraph 3.15.

iii.Any pipework and services to which building work is carried out following paragraphs 3.18 to 3.21 and 3.25.

b.Limiting unwanted heat gains to the building, throughout the year, through any of the routes listed in point (a) as set out in Section 3.

Note: If work includes an extension to an existing building, initial provision of fixed building services, or an increase in the installed capacity of fixed building services, consequential improvements may be required - Section 11.

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Section 3

Section 3

Limiting heat gains and losses

U-values

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

3.2The U-value of a window should be calculated for one of the following.

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

b. For windows in buildings similar to dwellings, calculated for a standard window 1.23m (±25%) wide × 1.48m (–25%) high and the actual configuration of the window.

c. For windows in buildings similar to dwellings, calculated for a standard window 1.23m (±25%) wide × 1.48m (–25%) high and one of the following standard configurations. Standard configurations should not be used for commercial windows.

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 as set out in BS EN ISO 12567-1 for windows and BS EN ISO 12567-2 for roof windows.

e. Calculated using the standard window size, depending on the overall product area, and methodology as defined in BS EN 14351-1.

Note: For domestic-type windows in buildings similar to dwellings if there are no test data or calculated performance values, the default value from table 6e of the Standard Assessment Procedure may be used.

3.3The U-value of a door should be calculated for either of the following.

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

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Section 3 b. Calculated using one of the following standard sizes.

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

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

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

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

d. Calculated using the standard window size, depending on the overall product area, and methodology as defined in BS EN 14351-1.

3.4To correctly assess whether an element meets the limiting U-value, the U- value must be calculated for the element in the appropriate plane – either horizontal or vertical. Windows and roof windows should have their U-values calculated based on a vertical position. Rooflights should have their U-values calculated based on a horizontal position. If the data available for the element is in the incorrect plane, its U-value should be adjusted according to the guidance in The Building Research Establishment’s BR 443.

Note: These orientations should only be used when calculating U-values to check that they meet the limiting standards outlined in paragraphs 3.5 to 3.8 below. They should not be used in the energy calculations in Sections 1 and 2, where the U-value of each element is calculated based on the plane in which it is constructed or installed.

Limiting standards for new and replacement elements

3.5New insulating elements should meet the limiting standards in Table 3.1. This includes all of the following.

a.Elements in new buildings.

b.New elements in extensions to existing buildings.

c.New or replacement elements in existing buildings.

Guidance on when a new element in an existing building must meet the requirements in Table 3.1 is given in Section 9.

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Section 3

3.6If windows or fully glazed pedestrian doors cannot meet the requirements of Table 3.1 in an existing building, because of the need to maintain the character of the building, either of the following should be met.

a.These fittings should not exceed a centre pane U-value of 1.2 W/(m 2.K).

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

Table 3.1 Limiting U-values for new or replacement elements in new and existing buildings; and air permeability for new buildings

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3.The U-value of the floor of an extension may be calculated using the exposed perimeter and floor area of either the whole enlarged building or the extension alone.

4.The U-value of a swimming pool basin (walls and floor) calculated according to BS EN ISO 13370.

5.For example, student accommodation, care homes and similar uses where the occupancy levels and internal heat gains are essentially domestic in character.

6.If other performance (e.g. wind load, safety, security or acoustic attenuation) requires thicker glass to be used, an equivalent window unit with standard thickness glazing should be shown to meet the required standard.

7.The methods for calculating Window 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.

8.No maximum U-value is set for display windows and similar glazing. For new buildings, however, the impact of windows and similar glazing must be taken into account when calculating primary energy and CO 2 emissions.

9.In buildings with high internal heat gains, the average U-value for windows can be higher than the values given above if this can be shown to be an appropriate way of reducing overall CO 2 emissions and primary energy. However, individual values should be no higher than 2.7 W/(m 2 .K).

10.U-values for rooflights or rooflight-and-kerb assemblies should be based on the developed surface area of the rooflight (U d values), which is often greater than the area of the roof opening. Further guidance on U d values is given in the Building Research Establishment’s BR 443 and the National Association of Rooflight Manufacturers’ Technical Document NTD02.1.

11.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 have a maximum U-value of 0.35W/m 2·K.

12.If meeting such a standard in an existing building would reduce by more than 5% the internal floor area of the room bounded by the wall, a lesser provision may be appropriate.

13.If meeting such a standard in an existing building, would create significant problems in relation to adjoining floor levels, a lesser provision may be appropriate.

Limiting standards for renovated and retained elements

3.7Existing elements that are being renovated or retained may need to meet the limiting standards in Table 3.2. The following elements should meet the standards in Table 3.2.

a.Thermal elements that are being renovated in existing buildings. Renovated elements should achieve or better the U-values in Table 3.2, column (b). Renovation of a thermal element is defined in Section 10.

b.Elements that are being retained in existing buildings, following a material change of use or change to energy status (see Section 10). Retained elements with a U-value higher than (worse than) the threshold value in Table 3.2, column (a), should be upgraded to achieve (or better) the U- values in Table 3.2, column (b). For all retained thermal elements not listed in Table 3.2, expert advice should be sought to determine an appropriate improved U-value.

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Section 3

Section 10 should also be referred to.

Note: When renovating thermal elements, the work should comply with all the requirements in Schedule 1, but particular attention should be paid to Parts B, F and J.

Note: A retained thermal element can be:

-an existing element that becomes a thermal element where previously it was not (for example, in an existing building where an internal wall is removed so that a previously unconditioned store room with an external wall becomes a cellular office), or

-an existing thermal element in a building that is subject to a material change of use (for example a thermal element in a dwelling which is to be converted and used a public building)

Note: Where the suitability of a retained thermal element needs to be assessed prior to being upgraded or where it is recommended that expert advice be sought, the person carrying out this work should be appropriately trained in risk assessment and management. For non-domestic buildings, an example may be a Retrofit Lead Professional working in accordance with PAS 2038:2021 – Retrofitting non-domestic buildings for improved energy efficiency – Specification. PAS 2035:2023 – Retrofitting dwellings for improved energy efficiency – Specification and guidance – may be used only in those limited cases where PAS 2038:2021 explicitly permits its application to smaller, simpler non-domestic buildings.

3.8If achieving the U-value in Table 3.2, column (b) is not economically, functionally or technically feasible, the thermal element should be upgraded to as close as possible to the U-values given in Table 3.2 column (a).

Note: Technically and functionally feasible. An energy efficiency measure is not deemed to be technically or functionally feasible if the thickness of insulation needed to achieve the U-values set out in Table 3.2 column (b) 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.

In 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 possible to the U-values given in Table 3.2 column (a). 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.

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Section 3

Generally, a thermal element once upgraded should not have a U-value greater than 0.7 W/(m2.K). A worse U-value for the thermal element may be acceptable where this is necessary to comply with Part C of the Building Regulations on protection from the harmful effects of interstitial and surface condensation.

Note: Economically feasible. The definition of whether an energy efficiency measure is economically feasible is provided in Appendix A.

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Section 3

Table 3.2 Limiting U-values for existing elements in existing buildings

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Section 3

Continuity of insulation

3.9In new and existing buildings, both of the following apply.

a.The insulation is reasonably continuous across newly built elements.

b.Thermal bridging, including at the party wall, should be reasonably limited.

Note: Any solution to edge sealing or thermal bridging in new buildings should take particular account of Part E (noise) of the Building Regulations.

3.10To avoid air movement within thermal elements in new and existing buildings, either of the following measures should be implemented.

a. The insulation layer should abut the air barrier at all points across newly built elements.

b. The space between the air barrier and the insulation layer should be filled with solid material.

3.11Thermal bridging should be addressed in the design and construction of a building by one of the following.

a.Using construction joint details calculated by a person with suitable expertise and experience using both of the following.

i.The guidance set out in The Building Research Establishment’s BR 497.

ii.A process flow sequence that has been provided to the building control body indicating the way in which the detail should be constructed.

Construction joint details can then be used to calculate the Building Primary Energy Rate and Building Emission Rate.

b.Using construction joints without quantifying the thermal bridge values. The values for generic linear thermal bridge values given in The Building Research Establishment’s Information Paper 1/06 and increased by 0.04 W/(m.K) or 50%, whichever is greater, should be used to calculate the Building Primary Energy Rate and Building Emission Rate.

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Section 3

Note: Evidence of suitable expertise and experience for calculating linear thermal transmittance would be to demonstrate all of the following:

i.the person has been trained in the software used to carry out the calculation

ii.the person has applied that model to the example calculations in the Building Research Establishment’s Report BR 497

iii.the person has achieved results within the stated tolerances.

3.12To calculate linear thermal transmittances and temperature factors in support of the approaches in paragraph 3.11a, the guidance in the Building Research Establishment’s Report BR 497 should be followed. The construction details specified should achieve a temperature factor that is greater than or equal to that set out in the Building Research Establishment’s Information Paper 1/06.

3.13To support the approaches in paragraph 3.11a, the builder should demonstrate to the building control body that an appropriate system of site inspection is in place to give confidence that the construction procedures achieve the required standards.

3.14When thermal elements are replaced or renovated, a report should be produced, signed by a suitably qualified person which confirms both of the following.

a.Appropriate design details and building techniques have been specified.

b.The specified details, as constructed, provide adequate protection against surface condensation using the guidance in the Building Research Establishment’s Information Paper 1/06 and BR 497.

Airtightness in existing buildings

3.15When carrying out work in existing buildings, care should be taken to reduce unwanted heat loss through air infiltration by doing all of the following:

a.When installing pipework or services, taping and sealing around openings and services penetrations.

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

c.When installing controlled fittings, ensuring that the controlled fitting is well fitted and reasonably draft-proof.

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

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Section 3

Limiting the effects of solar gains in summer

3.16In certain residential type buildings (including some buildings which are categorised as ‘buildings other than dwellings’), solar gains should be limited in summer in accordance with Approved Document O (Mitigation of overheating risk). The buildings in scope are defined in Table 0.1 of Approved Document O.

3.17For all buildings not covered by paragraph 3.16, the following applies, irrespective of whether the building is air-conditioned. For each space in the building that is occupied or mechanically cooled, the solar gains through the glazing - aggregated from April to September inclusive – should be no greater than would occur through the relevant reference glazing systems in Table 3.3. The g-value should be calculated according to BS EN 410. In this context, an occupied space means a space that is intended to be occupied by the same person for a substantial part of the day. This excludes circulation spaces and other areas of transient occupancy, such as toilets.

The intention is to limit solar gains during the summer, in order to achieve one of the following:

a.reduce the need for air-conditioning; or

b.reduce the capacity of any air-conditioning system that is installed.

Table 3.3 Reference glazing systems for calculating solar gain

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Section 3

Limiting heat losses and gains from building services

Direct hot water and heating pipework

3.18Hot water and heating pipework should be insulated in all areas inside and outside the building unless it can be shown that the heat is ‘always useful’. Insulation should be reasonably continuous including at bends, T-branches, wall brackets and around any obstruction.

3.19Insulation should be designed so that the permissible heat losses in BS 5422 for hot water and heating services in non-domestic buildings are not exceeded. For low temperature systems, meeting the standards in Table 3.4 is one way of showing that heat losses will not exceed those given in BS 5422. For domestic hot water systems, meeting the standards in Table 3.5 is one way of showing that heat losses will not exceed those given in BS 5422.

3.20Insulation thickness should be calculated in accordance with BS EN ISO 12241.

Note: in most cases, manufacturers will be able to supply information and required thicknesses for their products to comply with heat loss standards in paragraph 3.19. However, Tables 3.4 and 3.5 give indicative thicknesses for typical applications.

3.21Heating pipework insulation on building heat distribution systems should meet the standards in one of the following, as applicable.

a. For communal heat networks and new buildings that contain multiple dwellings that are connected to a district heat network, the minimum insulation thicknesses for building heat distribution systems should follow CIBSE CP1 Heat Networks: Code of Practice.

Note: The thicknesses given in CIBSE CP1 Heat Networks: Code of Practice are minimum thicknesses and project specific calculations should be carried out to justify the insulation specification, in accordance with CIBSE CP1 Heat Networks: Code of Practice.

b.For other types of new buildings, not covered by 3.21(a), connected to a district heat network, the insulation thicknesses on building heat distribution systems should follow BS 5422.

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Section 3

Table 3.4 Minimum thickness of pipework insulation for low temperature hot water space heating applications in non-domestic buildings

Table 3.5 Minimum thickness of pipework insulation for domestic hot water services in non-domestic buildings

Cooling Pipework

3.22Cooling pipework should be insulated along its whole length. Control against heat gain should be maximised and heat gain to uninsulated pipes permitted only where the cooling load of the distribution pipework is less than 1% of the total load.

3.23Insulation should be designed so that the maximum permissible heat gains in BS 5422 are not exceeded.

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Section 3

3.24Provision should be made to control condensation, by following BS 5422.

Insulating ductwork

3.25Ductwork that carries warm or cold air should be insulated throughout its whole length to achieve heat transfer no greater than that given in Table 3.6. Meeting the indicative insulation thicknesses which are also given in Table 3.6 is one way of demonstrating that the heat transfer value has not been exceeded.

Condensation should also be controlled by following BS 5422

Table 3.6 Maximum heat losses and gains for ducts delivering air for heating and/or cooling

Domestic hot water storage vessels

3.26Domestic hot water storage vessels should meet either of the following.

a.Maximum heat losses in Table 3.7.

b.Maintenance consumption values in BS EN 89, for gas-fired storage water heaters.

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Section 3

Table 3.7 Maximum heat losses from domestic hot water storage vessels 1,2

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Section 3

Requirement L1(b)(i) (ai) and (ii): Fixed building services efficiency and controls

This section deals with the requirements of Part L1(b)(i),(ai) (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

Intention

In the Welsh Minister’s view, requirement L1(b)(i),(ai), (ii), (iii) and L2 are met in a new building by providing:

a.fixed building services meet the minimum efficiencies in Section 5.

b.controls to fixed building services that both:

i.meet the general controls for heating systems in paragraphs 4.13, 4.14 and 4.16 to 4.18.

ii.meet system specific controls in Section 5.

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

In the Welsh Minister’s view, Requirement L1(b)(i), (ai), (ii), (iii) and L2 are met for work in existing buildings by achieving all of the following.

a.Any fixed building services installed meet the minimum efficiencies in Section 5 and meet the criteria in paragraph 4.6.

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

i.meet the general controls for heating systems in paragraphs 4.8, 4.13, 4.14 and 4.16 to 4.18.

ii.meet standards for system specific controls in Section 5.

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

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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 building, the efficiency of the service should be no lower than the value in Section 5. If a proposed service is not covered in Section 5, the service should be shown to be 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 4 or 5.

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

4.3For heating systems and cooling systems, paragraphs 4.11 to 4.19 should be followed, in addition to system specific advice in Section 5.

New building services in new buildings

4.4For heating and hot water systems in new buildings one of the following should apply.

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

i. A CO 2 emissions factor, as listed in the consultation National Calculation Methodology Modelling Guide, of less than or equal to 0.086 kgCO 2/kWh ii. A primary energy factor, as listed in the consultation National Calculation Methodology Modelling Guide, 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 highest emission factor.

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Section 4

4.5Backup heating and hot water systems should meet the standard in paragraph 5.4(a) unless both of the following conditions are met.

a.There is no suitable low carbon alternative to provide backup heating or hot water.

b.The failure of primary heating or hot water systems would present either:

i. a significant life safety risk ii. a significant risk to the operation of critical national infrastructure.

Replacement building services in existing buildings

4.6A replacement fixed building service should be at least as efficient as the value 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 delivery energy than the service being replaced, and

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

Note: If the efficiency of the appliance being replaced is unknown, this should be established in line with the hierarchy in Appendix E.

Worked example:

Replacing an old fuel oil-fired boiler that has emissions of 0.319kgCO 2/kWh and primary energy of 1.180kWh PE/kWh at 85% efficiency with an LPG boiler that has emissions of 0.240kgCO 2/kWh and primary energy of 1.104kWh PE /kWh) at 93% efficiency.

CO 2 emissions

Fuel oil-fired boiler: 0.319/0.85 = 0.375 kgCO 2/kWh

LPG boiler: 0.240/0.93 = 0.258 kgCO 2/kWh

Primary energy

Fuel oil-fired boiler: 1.180/0.85 = 1.388 kWhPE/kWh

Biomass boiler: 1.104/0.93 = 1.188 kWhPE/kWh

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Section 4

The new LPG boiler has both lower CO 2 emissions and lower primary energy than the fuel oil-fired boiler being replaced, and therefore complies with paragraph 5.4. The new boiler is also at least as efficient as the minimum efficiency set out in Section 5.

4.7If renewable technology such as a wind turbine or photovoltaic array is being 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.

4.8When a new heating appliance is installed in an existing building, the heating system after the work is complete should have the following controls.

a. Timing.

b. Temperature.

c. Where appropriate and technically feasible, weather compensation.

4.9For heating systems that are being replaced, both of the following apply.

a.Paragraphs 4.11 to 4.14 should be followed, in addition to system specific guidance in Section 5.

b.Facilitating future connections to a district heat networks should be considered (e.g. providing capped off connections in pipework to allow a later connection to a district heat network).

4.10If work involves providing or extending fixed building services, both of the following apply:

a.Energy meters should be installed following paragraph 4.19, and

b.Consequential improvements may be needed (see section 11).

Sizing new and replacement space heating systems

4.11The specification of space heating systems should be based on an appropriate heat loss calculation for the building, based on BS EN 12831-1 and CIBSE’s Guide B1. Systems should not be significantly oversized.

4.12Where a wet heating system is either

a.newly installed or

b.fully replaced, including the heating appliance, emitters and associated pipework,

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Section 4 all parts of the system, including pipework and emitters, should be sized to allow the space heating system to operate effectively, and to meet the heating needs of the building, at a maximum flow temperature of 55°C. To maximise the efficiency of the wet heating system, it is preferable to design to a lower flow temperature than 55°C.

In existing buildings, where it is not feasible to install a space heating system which can operate at a maximum flow temperature of 55°C (e.g. where there is not enough space for larger radiators, or the existing distribution system received 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 building.

Controls and zoning for new and replacement space heating systems.

4.13For heating systems, all of the following apply.

a.The systems should be subdivided into separate control zones for areas of the building for which any of the following are significantly different:

i.solar exposure

ii.pattern of use

iii.type of use.

b.For each control zone it should be possible to control all of the following independently of other control zones:

i.timing

ii.temperature

c.The service should be appropriate to the requirements of the space. If both heating and cooling are provided, the controls should prevent both operating simultaneously.

d.Central plant should operate only when the zone systems require it. The default condition should be off.

e.Where appropriate and technically feasible, heating systems should have weather compensation.

4.14System controls should be wired so that when there is no demand for space heating, the heating appliance and pump are switched off.

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Section 4

System treatment for hot water systems for space and domestic hot water heating

4.15Before a new heating appliance is installed, it should be commissioned as follows.

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.

Thermostatic room controls

4.16For heating systems and cooling systems in a new non-domestic building, or when a heat generator such as a boiler is replaced in an existing non-domestic building, each room must be provided with thermostatic room controls. These controls should be capable of being used to separately adapt the heating or cooling output in each room served by the heating or cooling appliance or, where justified in accordance with paragraph 4.17, in each heating zone.

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

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

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

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

4.17It may be justified to control a heating zone rather than individual rooms in either of the following cases:

a.in open-plan spaces in which heating demand and patterns of use are similar across the whole space, sub-zoning of temperature control might not be appropriate. In such cases, the space should be considered as one heating zone.

b.where two adjacent rooms have a similar function and heating or cooling requirements. In such cases, the adjacent rooms should be considered as one heating zone.

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Section 4

Note: For exhaust air heat pump systems, which extract heat from the exhaust air of a building, 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 use in the same building should be controlled using thermostatic room controls as described above.

4.18The standards in paragraphs 4.16 and 4.17 may be satisfied by providing any of the following.

a.An individual networked heating or cooling emitter control for each emitter.

b.Both of the following:

i.a thermostat in a room that the heating or cooling 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 located in the same room as the thermostat.

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

Energy submeters

4.19Energy submetering systems should be installed in new buildings, or when fixed building services are provided or extended in an existing building. The system should meet all of the following requirements.

Note: In addition to submetering arrangements, it is recommended that new non-domestic buildings are designed and constructed to be suitable for smart meter installations and commissioning. For good practice, see DESNZ guidance: Guidance on designing and constructing new builds to be smart- meter-ready.

a.The various end-use categories, such as heating, lighting, and cooling should be sub-metered in such a way that at least 90% of the annual energy consumption of each fuel can be assigned to an end-use. Detailed guidance on how to achieve this is given in CIBSE’s TM39.

b.Metering should enable forecast energy use to be compared with in- performance energy use, and should facilitate energy reporting. This requirement can be met by basing the sub-metering strategy on a design-stage energy forecast for the building, using one of the methodologies in paragraph 9.4.

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Section 4

c.Metering should measure the energy use of each tenant within the building.

d.The output of any renewable systems should be monitored separately.

e.In buildings with a total useful floor area greater than 1000 m 2, automatic meter reading and data collection facilities should be installed.

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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.

5.1This section sets out minimum standards for specific types of building services. The minimum efficiencies are based on documented manufacturers’ test data. Note that test results are always based on the equipment when operating under particular conditions. Equipment should be designed, specified and installed with the aim of maximising its efficiency as-installed.

Heat pumps

5.2All heat pumps, except those defined in paragraph 5.3 should meet Ecodesign product regulations. The applicable Ecodesign product regulations for different types of heat pump and uses are set out in Table 5.1.

5.3The following types of heat pump should have a coefficient of performance (COP) of 2.5 or higher as rated at the applicable rating conditions below.

a. Heat pumps other than air-to-air with an output between 400kW and 1000kW as rated at the applicable conditions in BS EN 14511-2.

b. Heat pumps used for domestic hot water heating only as rated at the applicable conditions in BS EN 16147.

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Section 5

Table 5.1 Ecodesign product regulations applicable to different types of heat pump installed in new buildings and new or replacement heat pumps in existing buildings

Controls for heat pumps

5.4For heat pump installations in which other heat sources are available to the same building, each of these heat sources should be appropriately incorporated into a single control system. This includes interlinked systems for coordinated operation.

Note: Example sequencing control routines for systems consisting of multiple heat pumps can be found in CIBSE AM17: Heat pump installations for large non-domestic buildings.

Controls for heat pumps in new buildings

5.5For heat pumps in new buildings, in addition to meeting the general requirements for heating and hot water systems in Section 4, the 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 buildings

Controls for heat pumps in existing buildings

5.6For heat pumps in existing buildings, in addition to the general guidance for controls and zoning in Section 4, any outdoor fans, including those in cooling towers or dry coolers, should be controlled.

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Section 5

Boilers in existing buildings

Note: This subsection applies to wet central heating systems that use commercial boilers fired by natural gas, liquid petroleum gas, oil or biomass. Steam boilers are not covered. Electric boilers are dealt with in paragraph 5.19.

5.7In addition to meeting the general requirements for heating systems in Section 4 and following paragraphs 5.11 to 5.12, new boiler plant installed in existing buildings should meet the seasonal efficiencies, or the overall seasonal efficiency for multiple-boiler systems using non-identical boilers (i.e. non-identical in terms of capacity and efficiency), in Table 5.3

Table 5.3 Minimum heat generator seasonal efficiency for boiler systems in existing buildings 1,2

Single-boiler systems and multiple-boiler systems with identical boilers

5.8The seasonal efficiency of the boiler should be determined using equation 5.1.

Boiler seasonal efficiency = 0.81η 30% + 0.19η100% Equation 5.1 where:

η 30% is the gross boiler efficiency measured at 30% load η 100% is the gross boiler efficiency measured at 100% load.

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Section 5

Note: Efficiencies based on net calorific value should be converted to efficiencies based on gross calorific value, using the appropriate conversion factor in the Standard Assessment Procedure version 10 Table E4.

Note: Equation 5.1 assumes that the efficiency at 15% load is the same as that at 30% load.

5.9Equation 5.1 applies to both of the following.

a.Single-boiler systems that:

i.produce low temperature hot water

ii.have an output of 400 kW or less.

b.Multiple-boiler systems that:

i.produce low temperature hot water

ii.comprise individual boilers with identical efficiencies

iii.have an output of 400 kW or less.

Note: For boilers with an output of more than 400 kW, the manufacturer’s declared efficiencies should be used.

Multiple-boiler systems with non-identical boilers

5.10In existing systems, if both of the following apply, equation 5.2 should be used to calculate the overall boiler seasonal efficiency.

a.More than one boiler is installed on the same heating system.

b.The efficiencies of the boilers are not identical.

Note: All boilers should be used in the calculation, including any that are identical.

Where:

ηOBSE is the gross overall boiler seasonal efficiency ηBSE is the gross boiler seasonal efficiency of each individual boiler calculated using equation 5.1

R is the rated output in kW of each individual boiler (at 80/60°C flow/return temperature).

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Section 5

Boiler controls

5.11Boiler systems with an output of more than 100kW should have both of the following.

a.Optimum start or optimum stop control that either:

i.provides night set-back

ii.provides frost protection outside occupied periods.

b.Either:

i.a two-stage high/low firing facility in the boiler

ii.multiple boilers with sequence control to provide efficient part-load performance.

5.12Gas-fired boilers and multi-stage oil-fired boilers with an output of more than 500kW should have fully modulating burner controls.

Biomass boilers

5.13The efficiency of biomass boilers at their nominal load and tested to BS EN 16510-1 and BS EN 16510-2-4 should be no lower than the following:

a.for independent gravity-fed boilers with an output of less than 20.5 kW: 65%

b.for independent automatic pellet/woodchip boilers: 75%

Gas and oil-fired warm air heaters

5.14In addition to meeting the general requirements for heating systems in Section 4, warm air systems in existing buildings should meet the heat generator seasonal efficiency in Table 5.4.

Table 5.4 Minimum heat generator seasonal efficiency for gas and oil-fired warm air heaters

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Gas and oil-fired radiant heaters

5.15In addition to meeting the general requirements for heating systems in Section 4, radiant heaters in existing buildings should meet the heat generator seasonal efficiency in Table 5.5.

5.16For flued appliances, thermal efficiency (net calorific value) should be measured to either of the following test standards, as applicable:

a.BS EN 17082

b.BS EN 13842.

The calculation of the thermal efficiency should both:

a.exclude fans

b.take account of the radiant heater and associated flue pipe/tailpipe within the building envelope.

Table 5.5 Minimum performance standards for radiant heaters

Electric space heating systems

Note: Electric resistance and radiant 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 5.2 to 5.6).

b.Portable electric heating devices.

5.17Electric space heating systems should meet the guidance in paragraphs 5.18 to 5.23, in addition to the general requirements for heating systems in Section 4

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5.18Electric boiler systems should comply with all of the following.

a.Systems should both:

i.have flow temperature control

ii.be able to modulate the power input to the primary water depending on space heating conditions.

b.Timing and temperature demand control should be provided.

c.If the building has a floor area greater than 150m 2, heating should be split into different heating zones and each zone should have separate controls for timing and temperature demand.

5.19Electric warm air systems should comply with both of the following.

a.Have timing and temperature demand control provided.

b.If the building has a floor area greater than 150m 2, heating should be split into different heating zones and each zone should have separate controls for timing and temperature demand.

5.20Electric radiant heaters should have either automatic zone control (where electric radiant heaters provide zone heating) or automatic occupancy control, through occupant presence detection.

5.21Electric panel or skirting heaters should have controls for timing and temperature demand.

5.22For electric storage heaters, both of the following apply.

a.The input charge should adjust automatically, based on the internal air temperature.

b.Manual control of heat release from the appliance should be possible.

5.23Electric fan convectors should have switching to control both of the following.

a.The local fan.

b.The temperature of individual fan convectors.

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Section 5

Combined heat and power systems

Note: This section of the guidance covers the installation of combined heat and power (CHP) systems in existing buildings that both:

a.have a total power capacity between 5 kWe and 5 MWe

b.are used in commercial applications.

For systems with a total power capacity less than 5 kWe, follow the guidance in Approved Document L, volume 1: dwellings.

5.24CHP plant should, under annual operation, have both of the following.

a.A minimum CHPQA quality index (QI) of 105.

b.Power efficiency greater than 20%.

5.25CHP plant should have a control system that ensures that the CHP unit operates as the lead heat generator unless there is a lower carbon heat source supplying the same system. In this case, the control system should ensure that the system provides the lowest carbon intensity of delivered heat.

5.26Metering should be provided that measures all of the following.

a.Hours run.

b.Electricity generated.

c.Fuel supplied to the CHP unit.

Dedicated domestic hot water heaters

5.27The recommended minimum standards set out in this section apply only to dedicated water heaters. Central heating boilers which provide space heating and domestic hot water should meet the minimum standards in paragraphs 5.7 to 5.13. Heat pumps which provide domestic hot water should meet the minimum standards in paragraphs 5.2 to 5.6.

5.28In addition to meeting the general requirements for heating systems in Section 4, domestic hot water systems in new and existing buildings should meet the minimum thermal efficiencies in Table 5.6 When considering thermal efficiency, both of the following apply

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a.include the heat generator and any integral storage vessel.

b.Exclude the following, where present.

i.Secondary pipework.

ii.Fans and pumps.

iii.Diverter valves, solenoids, actuators.

iv.Supplementary storage vessels.

5.29Domestic hot water systems should be sized for the anticipated domestic hot water demand of the building, based on BS EN 12831-3. Systems should not be significantly oversized.

Table 5.6 Minimum thermal efficiencies for domestic hot water (DHW) systems

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5.30Where efficiency data is not readily available, efficiencies should be calculated using manufacturers’ recovery rates and equations 5.3 and 5.4.

Gross thermal efficiency = heater output / gross input Equation 5.3

Controls for combustion-heated domestic hot water systems in existing buildings

5.31Domestic hot water systems should have both of the following.

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

b.Electronic temperature control.

5.32Primary hot water circuits for domestic hot water or heating should have fully pumped circulation where this is compatible with the heat generator.

5.33Direct-fired circulator systems, direct-fired storage systems and indirect-fired circulator systems should have automatic thermostatic control to both of the following.

a.Shut off the burner/primary heat supply when the desired water temperature is reached.

b.Shut off primary flow if the system temperature is too high.

5.34Direct-fired continuous flow systems should include both of the following.

a.A flow sensor to control the rate at which water flows through the heat exchanger. This should both:

i.control outlet temperatures

ii.if the sensor detects insufficient flow, shut off the burner/heat input.

b.A high limit thermostat to shut off the primary flow if the system temperature is too high.

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Controls for electrically heated domestic hot water systems

5.35Point-of-use electrically heated, local electrically heated and centralised electrically heated domestic hot water systems should have automatic thermostatic control to interrupt the electrical supply when either of the following occurs.

a.The setpoint storage temperature is reached.

b.The system temperature gets too high.

Manual reset should be possible if there is an over-temperature trip.

5.36Local and centralised electrically heated domestic hot water systems should have both of the following.

a.Seven-day time control.

b.The facility to increase the water temperature by using an immersion heater in the hot water cylinder.

5.37Water heaters in Instantaneous electrically heated domestic hot water systems should have both of the following.

a.A flow sensor to control the rate at which water flows through the heat exchanger. If the sensor detects insufficient flow, it should shut off the electrical input.

b.A high limit thermostat to shut off the primary flow if the system temperature is too high.

Comfort cooling

Note: Evaporative cooling and desiccant cooling systems are not within the scope of this guidance.

5.38In addition to cooling systems meeting the general requirements for

Building services in Section 4, the seasonal energy efficiency ratio (SEER) of each cooling unit should meet the minimum standards in Table 5.7.

5.39The specification of comfort cooling systems should be based on an appropriate heat gain calculation for the building, based on CIBSE’s Design Guide A. Systems should not be significantly oversized. In most circumstances this means that the cooling appliance should not be sized for more than 120% of the design cooling load.

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Table 5.7 Minimum seasonal energy efficiency ratio (SEER)1 for comfort cooling

Controls for comfort cooling

5.40Comfort cooling/air-conditioning systems should have all of the following controls.

a.The systems should be subdivided into separate control zones for areas of the building for which any of the following are significantly different:

i.solar exposure

ii.pattern of use

iii.type of use.

b.For each control zone and for each terminal unit (the point at which conditioned air is delivered to the space), it should be possible to control both of the following independently of other control zones.

i.Timing.

ii.Temperature.

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

d.Where a system has multiple cooling units, controls should be provided to ensure that the combined plant operates in its most efficient mode. Central plant should operate only when the zone systems require it. The default condition should be off.

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e.Controls for comfort cooling systems should meet BS EN SIO 52120-1 Class C.

f.Controls should meet the requirements for thermostatic room controls in paragraphs 4.16 to 4.18.

Calculating the seasonal energy efficiency ratio (SEER)

5.41The value of the seasonal energy efficiency ratio (SEER) should be determined using BS EN 14825 with average climate data; in conjunction with the Ecodesign Commission Regulation (EU) 2016/2281. The SEER of the cooling unit is given by equation 5.5.

SEER = a(EER100% ) + b(EER75% ) + c(EER50%) + d(EER25% ) Equation 5.5 where:

EERx is the EER measured at the load conditions of 100%, 75%, 50% and 25% at the operating conditions detailed for the part load energy efficiency ratio.

a, b, c and d are the load profile weighting factors relevant to the proposed application. The load profile weighting factors can be taken from either of the following.

a.Table 5.8, for office-type accommodation.

b.A detailed simulation or prediction of the load profile of the building. The calculation should include the desired indoor condition as well as the ambient loads in which the system will work.

Table 5.8 Standard cooling load profile weighting factors for office accommodation

5.42For cooling units for which there is no part load data, the value used for SEER is the full load EER.

5.43For applications where the load profile is not known but there is some data on chiller part load EER, the following apply.

•5.44

a.for chillers where the full and half load (50%) EERs are known: the value used for the SEER is the average of the full load and half load EERs.

b.for chillers with four points of part load EER: the SEER should be calculated using Equation 5.5 with each EER weighted equally.

c.if the chiller used does not have data for four steps of load: the weights should be apportioned appropriately.

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5.45For plants with multiple chillers, a plant seasonal energy efficiency ratio (SEER) should be calculated based on the sum of the energy consumption of all the operating chillers. All the following factors should be included:

a.degree of oversizing of the total installed capacity

b.sizes of individual chillers

c.EERs of individual chillers in operating conditions

d.control mode used, e.g. parallel, sequential, dedicated low load unit

e.load profile of the proposed building

f.building location (which determines ambient conditions).

5.46For systems that can use free cooling or heat recovery, the SEER should be calculated for the specific application, including free cooling or heat recovery elements. For variable refrigerant flow (VRF) systems, any calculations must include indoor and outdoor conditions, the power input from controls, and indoor units.

5.47For absorption chillers used in conjunction with on-site CHP, a district heat network or a communal heat network, the following apply.

a.The CO 2 emissions and primary energy should be calculated in the same way as when using CHP for heating.

b.The control system should ensure as far as possible that heat from boilers is not used to supply the absorption chiller.

c.The full load EER of the absorption chillers should be at least 0.7.

5.48For district cooling schemes, the CO 2 factor and primary energy factor of the cooling energy supply should be calculated. These values should be used to calculate the Building Emission Rate and Primary energy rate.

Heating and cooling system circulators and water pumps

5.49In variable volume systems, variable speed glandless circulators should be used.

5.50In any variable volume system, if a water pump is used on a closed loop circuit and the motor is rated at more than 750 W, then it should be fitted with or controlled by an appropriate variable speed controller.

5.51In new buildings, pumps should be selected to minimise energy consumption following CIBSE Guide B1. Pumps should not be oversized.

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Section 5

Mechanical ventilation

5.52Ventilation systems should be specified based on the ventilation needs of the building, in accordance with Approved Document F, volume 2: buildings other than dwellings.

5.53Air handling systems should be able to achieve a specific fan power (SFP) at 25% of design flow rate no greater than the SFP at 100% design flow rate.

5.54Fans used for general air distribution that are rated at more than 1100W should be fitted with variable speed drives.

5.55Ventilation ductwork should be made and assembled to be reasonably airtight. Ductwork should comply with the specifications in either of the following.

a.BESA’s DW/144.

b.British Standards BS EN 1507, BS EN 12237 and BS EN 13403.

5.56Air handling units should be made and assembled to be reasonably airtight. Air handling units should comply with Class L2 air leakage given in BS EN 1886.

5.57The specific fan power of systems at the design air flow rate should be no greater than the value in Table 5.9.

SFP should be calculated in accordance with BS EN 13779-3 at the full design load. For fan coil units, use BS 8850.

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Table 5.9 Maximum specific fan power (SFP) in air distribution systems in new and existing buildings

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Controls for mechanical ventilation

5.58For mechanical ventilation systems, all of the following apply:

a. The systems should be subdivided into separate control zones for areas of the building for which any of the following are significantly different:

i.solar exposure

ii.pattern of use

iii.type of use.

b. For each control zone it should be possible to control all of the following independently of other control zones:

i.timing

ii.where appropriate, temperature

iii.where appropriate, ventilation rate

iv.where appropriate, air recirculation rate.

c. Central plant should operate only when the zone systems require it. The default condition should be off.

5.59Central mechanical ventilation systems should have both of the following:

a.time control at room level

b.on/off time control at air handler level.

5.60Heat exchangers should have both of the following.

a.defrost control to protect the heat exchanger

b.control to ensure that heat recovery can be stopped, modulated or bypassed during periods where heat recovery is undesirable.

5.61Supply temperature control should be provided via a variable set point with outdoor temperature compensation.

5.62Local and zonal systems should have on/off air flow control at room level.

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Heat recovery

5.63Ventilation systems that provide supply and extract ventilation should be fitted with a heat recovery system where technically feasible.

Lighting

Internal lighting

5.64Any fixed internal lighting should achieve lighting levels appropriate to the activity in the space. Spaces should not be over-illuminated. Lighting should be designed based on CIBSE’s SLL Code for Lighting or an equivalent design guide.

Note: For smaller spaces where total lighting power is likely to be low (toilets, store rooms etc.) there is no expectation that lighting calculations should be produced.

5.65Internal lighting should be as follows:

a.General lighting should either:

i.have an average luminaire efficacy of greater than 105 luminaire lumens per circuit-watt

ii.have a Lighting Energy Numeric Indicator (LENI) calculated using the method in Appendix B and no greater than the applicable values set out in Table B1.

b.Display lighting should meet any one of the following:

i.have an average light source efficacy of greater than 95 light source lumens per circuit-watt.

ii.have a rated power use no greater than 0.3W/m 2 in each space

iii.have a Lighting Energy Numeric Indicator (LENI) calculated using the method in Appendix B and no greater than the applicable values set out in Table B1.

c.High excitation purity light sources should have an average light source efficacy of greater than 65 light source lumens per circuit-watt.

d.Colour-tuneable light sources (CTLS), including tuneable-white and dim- to-warm should have an average light source efficacy of greater than 80 light source lumens per circuit-watt.

Note: This approved document does not include minimum standards for specialist lighting, such as theatrical spotlights, stage lighting, gobo projectors, wall-washers or colour-tuneable light sources (CTLS), including tuneable-white and dim-to-warm.

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5.66Internal general lighting and display lighting should be metered by one of the following methods:

a.dedicated lighting circuits with a kilowatt-hour meter for each circuit.

b.local power meter coupled to or integrated in the lighting controllers of a lighting management system.

c.a lighting management system that can both:

i.calculate the consumed energy

ii.make this information available to a building management system.

5.67Lift car lighting and display lighting in lift cars should achieve an average light source efficacy of 105 luminaire lumens per circuit watt or greater.

Note: Suitable lighting systems or activation points should be located near the lift landing doors to provide illumination as individuals exit the lift to ensure safe access and egress.

Lighting controls for internal lighting

5.68Lighting controls in new and existing buildings should follow the guidance in the Building Research Establishment’s Digest 498.

5.69Automatic controls to turn the general lighting off when the space is not in use (e.g. through presence detection) should be fitted in both of the following.

a.All unoccupied spaces

b.Occupied spaces where suitable for the use of the space.

5.70In hotel bedrooms, controls such as key-card switches and/or controls that automatically detect occupation should be installed to turn off internal lights during unoccupied periods.

5.71General lighting in occupied spaces should have daylight controls (e.g. photo- switching and dimming) for parts of the space which are likely to receive high levels of natural light, where compatible with space function.

5.72Display lighting should be controlled on dedicated circuits that can be switched separately from those for lighting provided for general illuminance.

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Section 5

Fixed external lighting in new buildings

5.73In new buildings, fixed external lighting levels should be appropriate to the activity in the space. External lighting should be designed based on CIBSE’s SLL Code of Lighting or an equivalent design guide.

5.74Illuminance from fixed external lighting in new buildings should be directed to where the light is needed using shields, reflectors and baffles. Light should be directed downwards where feasible. Light spill and wasted light to the sky should be kept to a minimum in line with the Institution of Lighting Professionals’ Guidance Note GN01/21 The Reduction of Obtrusive Light.

Note: For further guidance, see CIE 150:2017 Guide on the Limitation of the Effects of Obtrusive Light from Outdoor Lighting Installations.

Lighting controls for fixed external lighting in new buildings

5.75Fixed external lighting in new buildings should be fitted with automatic controls that switch off external lights during both of the following.

a.Daylight hours.

b.Periods of the night when the building is not in operational use.

These requirements do not apply if either of the following conditions are met.

i.Lighting in either period (a) or (b) is essential for safety or security purposes.

ii.The maximum power consumption of the luminaire (or group of luminaires to be controlled by a single sensor) is less than 4W.

Note: The maximum power consumption of the luminaire is to be determined based on the maximum power rating of lamp(s) which can be safely fitted into the luminaire as determined by the manufacturer. This should be determined using the rated power for LED luminaires..

Building automation and control systems

5.76If a new building has a space heating or air-conditioning system with an effective rated output of greater than 180 kW, a Building Automation and Control System must be installed.

5.77If an existing building has a space heating or air-conditioning system with an effective rated output greater than 180kW, and a Building Automation and Control System is being replaced or installed, a Building Automation and Control System being replaced or installed should follow paragraphs 5.83 to 5.84.

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Note: The requirements in paragraphs 5.75 and 5.76 also apply to buildings containing heating and air-conditioning systems which are combined with ventilation systems.

5.78For building systems that do not satisfy paragraph 5.75 or 5.76, consideration should be given to providing centralised controls to allow the facilities manager to switch off appliances when they are not needed. Where appropriate, controls should be automated (with manual override) to maximise energy savings. Consideration should be given to the power requirements of essential (e.g. life safety) systems.

Determining the effective rated output

5.79The effective rated output of a space heating or air conditioning system is the combined output of the equipment in the building which is provided for heating or cooling the internal space in normal operation for the comfort of occupants.

5.80The effective rated output should be assessed based on the final installed capacity of the heating or air-conditioning system. When estimating the effective rated output at the design stage, designers should make allowances for the final installed capacity, including potential oversizing and equipment substitution.

5.81When determining the effective rated output of air-conditioning systems, the combined maximum output of both of the following, as specified by the manufacturer, should be included.

a.Air-conditioning systems

b.Air-conditioning systems combined with or as part of a ventilation system.

5.82When determining the effective rated output of heating systems, the combined maximum output of all the following, as specified by the manufacturer, should be included

a.Primary space heating systems.

b.Space heating systems combined with or as part of a ventilation system.

c.Secondary space heating systems.

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Note: The effective rated output of a heating or cooling system does not include any of the following.

a.Heating or cooling equipment only intended for emergency or occasional backup use.

b.Heating equipment for frost protection.

c.Heating for domestic hot water.

d.Heating or cooling for industrial processes.

5.83If the building is heated through a district heat network or communal heat network, the effective rated output should be based on the capacity of the equipment installed in the building, making reasonable assumptions for the operation of the district heat network or communal heat network, including flow temperatures.

Building Automation and Control System specification

5.84Where a Building Automation and Control System is installed in a new or existing building, and the building meets the space heating or cooling criteria in paragraphs 5.80 and 5.81, the system should meet all of the following.

a.Fully complies with EN ISO 16484.

b.Continuously monitors, logs, analyses and allows for adjusting energy use.

c.Benchmarks the building’s energy efficiency, detects losses in efficiency of heating, ventilation and air conditioning systems, and informs the person responsible for the facilities or building management about opportunities for energy efficiency improvement.

d.Allows communication with connected fixed building services and other appliances inside the building and be interoperable with fixed building services across different types of proprietary technologies, devices and manufacturers.

Note: A BS EN ISO 52120-1 Class A Rated type system meets these requirements.

5.85Where a Building Automation and Control System is installed, its control capabilities should be appropriate for the building, the building’s expected usage, and the building services specification.

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Section 5

On-site electricity generation and storage

Note: For buildings which contain dwellings, the guidance in Approved Document L, Volume 1: Dwellings applies.”

5.86Where 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, planning constraints and on-site energy demand.

5.87On-site electricity generation and storage systems should be specified, installed and commissioned according to the manufacturer’s instructions to ensure the overall performance of the system meets a reasonable standard and to maximise the generating or storage capacity.

5.88When replacing an existing on-site electricity generation and storage system, the installed generation capacity of the new system should be no less than that of the existing system, except where it can be demonstrated that a smaller system would be more appropriate or effective (for example, replacing an existing system with a system which is better matched to the building’s energy demand).

5.89On-site generation electricity generation should be provided with automated controls that support the design of the system and the intended use. This is particularly the case where storage systems, such as batteries, are used.

Lifts, escalators and moving walkways

5.90The energy consumption of passenger lifts, escalators and moving walkways (moving walks) in new buildings should be minimised by performing calculations for alternative designs using the methods described in BS EN ISO 25745-2 or BS EN ISO 25745-3.

Note: Please see paragraph 0.8 which refers to work in relation to shell and core type developments

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Lifts

5.91Passenger lifts in new buildings should operate in a standby condition, where they remain stationary and at a reduced level of energy demand, during periods of low passenger demand.

5.92Passenger lifts in new buildings should achieve at least energy efficiency classes shown in Table 5.10 using the methodology described in BS EN ISO 25745-2.

Table 5.10 Minimum energy efficiency classes for lifts

Escalators and moving walkways

5.93Escalators and moving walkways (moving walks) in new buildings should incorporate an autostart feature or operate in slow speed condition when no passengers are using the equipment.

5.94Escalators and moving walkways in new buildings should achieve at least energy efficiency class A+ using the methodology described in BS EN ISO 25745-3.

Communal heat networks

5.95The central heat source for a communal heat network should comply with the minimum standards in this section (Section 5) as relevant for the heat source.

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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.

Pressure testing

43.(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 regulation 26A 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 Testing and Measurement 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.

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Intention

In the Welsh Minister’s view, the requirements of regulation 43 are met when a building is erected, by carrying out pressure testing in accordance with paragraphs 6.2 to 6.6 and 6.9.

In the Welsh Minister’s view, results from a pressure test must be used to demonstrate compliance with regulation 26 and 26A of the Building Regulations 2010 in accordance with paragraphs 6.6 to 6.8, and with L1(a)(i) of Schedule 1 of the Building Regulations 2010, 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 building 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 airtightness testing methodology, CIBSE’s TM23 Testing Buildings for Air Leakage. The procedures set out in that document have been approved by Welsh Ministers.

Showing compliance and reporting pressure test results

6.3The Building Control Body should be given evidence that pressure testing equipment has been calibrated using a UKAS-accredited facility or by the original manufacturer in accordance with all of the following:

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

b.At least once every 24 months

c.CIBSE’s 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.

6.5Buildings that are not dwellings, including extensions that are being treated as new buildings to comply with Part L, must be pressure tested - except those buildings listed in paragraph 6.6.

6.6Welsh Ministers’ have approved that pressure testing does not need to be carried out in the following buildings.

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Section 6

a.Buildings with less than 500 m 2 total useful floor area. A pressure test may be avoided provided that the air permeability used to calculate the Building Primary Energy Rate and Building Emission Rate is taken as 15 m 3/(h.m 2) at 50Pa.

b.A factory-made modular building that meets the following criteria:

i.the floor area is less than 500 m 2

ii.the building has a planned service life of more than two years, but the intended time of use in one location is less than two years

iii.no site assembly work is needed other than linking standard modules using standard link details.

If the building as installed conforms to a standard configuration of modules and link details for which the installer has pressure test data, these test data may be used to estimate the air permeability. Test data must be from a minimum of five in-situ measurements of the same module types and link details as used in the actual building. Air permeability should be in m 3/(h.m 2) at 50 Pa. When calculating the Building Primary Energy Rate and Building Emission Rate for a factory-made modular building as described above, the value that should be used for design air permeability is the average air permeability test result at 50Pa plus 1.0m 3/(h.m 2).

c.Large extensions. If the Building Control Body agrees that sealing off and testing the extension separately from the existing building is impractical, the extension should be treated as a large, complex building – see paragraph 6.6 d.

d.Large complex buildings. If pressure testing is impractical due to the size or complexity of the building, the developer may produce both of the following.

i.A detailed justification of why pressure testing is impractical.

ii.A detailed strategy to give confidence that a continuous air barrier will be achieved.

It is reasonable for the building control body to accept this strategy in place of a pressure test to assess compliance.

The developer should seek expert advice to confirm the justification and strategy in paragraph 6.6d. Any justification and strategy should be in line with the approved air tightness testing methodology, CIBSE's TM 23 Testing Buildings for Air Leakage. It would not be reasonable to claim that air permeability lower than 5.0 m 3/(h.m 2) @ 50 Pa had been achieved.

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Section 6

e.Compartmentalised buildings. If buildings are compartmentalised into self- contained units with no internal connecting openings, it is reasonable for the building control body to accept a pressure test carried out on a representative area of the building as evidence of the building’s air permeability.

If the results of the pressure test on the representative area of the building do not meet the criteria in paragraphs 6.1 and 6.7, the building air permeability should be improved and retested until the criteria are achieved. The developer should also carry out a further test on another representative area to confirm that all parts of the building achieve the expected standard.

6.7The Building Primary Energy Rate and Building Emission Rate (detailed in Section 2) calculated using the measured air permeability must not be higher than the Target Primary Energy Rate and Target Emission Rate respectively.

6.8If a building does not achieve the criteria in paragraphs 6.1 and 6.7, the building air permeability should be improved and retested until the criteria are achieved.

6.9The results of all pressure tests on buildings, including any test failures, should be reported to the building control body.

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Section 6

Regulations 44 and 44ZA and requirements requirements L1(b)(iii) and L2(b): Commissioning

This section deals with the requirements of Part L1(b)(iii) and L2(b) of Schedule 1 to the Building Regulations and regulations 44 and 44ZA.

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–

(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.

(c) for the purposes of this Part—

“greenhouse gas”has the meaning given by section 37(1) of the Environment (Wales) Act 2016.

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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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 complying 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

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

Intention

In the Welsh Minister’s view, requirements L1(b)(iii) and L2(b) and the requirements of regulations 44 and 44ZA is 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 should 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. This should include commissioning ventilation fans to demonstrate that their specific fan powers are no worse than the minimum standards and aligned with the Building Primary Energy Rate and Building Emission Rate calculations.

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

7.2The commissioning process should involve testing and adjusting the fixed building services (including for any energy metering arrangements and/or Building Automation and Control Systems where required by section 4 or 5) and on-site electricity generation as necessary with the aim of optimising their in-use performance and in accordance with the manufacturer’s instructions.

7.3When installing a fixed building service, or installing on-site electricity generation that is subject to the energy efficiency requirements, a commissioning plan should be prepared. The commissioning plan should also include including any energy metering arrangements where required by Sections 4 or 5. The commissioning plan should identify all of the following:

a.the systems (including any energy metering arrangements) to test;

b.the tests to complete;

c.schedule of commissioning;

d.roles and responsibilities;

e.documentation requirements

A way of documenting the commissioning plan to the building control body would be through the use of the templates in the Model Commissioning Plan (BSRIA BG 8/2009).

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Section 7

a.The building control body should be given the commissioning plan (along with the design stage TER/BER and TPER/BPER for new buildings), so that they can then check that commissioning is being done as the work proceeds.

Large buildings

7.4For large buildings with the following size thresholds:

a.a new non-domestic building that has a useful floor area over 1000 m 2;

b.a new extension to an existing building, where the extension has a useful floor area over 1000 m2;

c.an existing building that has a useful floor area over 1000 m 2 and either of the following applies:

i.there is an initial provision of any fixed building service i.e. the initial installation of heating, hot water, air conditioning or mechanical ventilation, internal or external lighting, metering and sub-metering, automatic meter reading system, Building Automation and Control System or renewable energy generators, or

ii.there is an increase in the installed capacity of any fixed building service.

The commissioning plan should be completed by a Specialist Commissioning Manager (who should be suitably qualified or experienced), and given to the Building Control Body before the work begins on site (unless the work is carried out by a person registered with a competent person scheme, in which case the notice must be given to the Building Control Body within 30 days of the works being completed).

Other buildings

Note: (Other buildings that are not applicable to items a, b, or c in paragraph 7.4)

7.5If the only controls for a fixed building service, or on-site electricity generation are ‘on’ and ‘off’ switches, this service does not need to be commissioned.

7.6Any commissioning should be carried out in accordance with all of the following procedures:

a.CIBSE’s Commissioning Code M

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Section 7

b.Any of the following:

i.The specific CIBSE Commissioning Codes relevant to each service being commissioned

ii.The specific BSRIA Commissioning Guides relevant to each service being commissioned

iii.A combination of i and ii

c.the procedures for air leakage testing of ductwork given in paragraphs 7.10 to 7.13.

Notice of completion of commissioning

7.7A notice of completion of commissioning must be given to the relevant building control body and the building owner to confirm that that the installed fixed building services and on-site electricity generation were commissioned according to the procedures in 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 the performance of the system is reasonably in accordance with the actual building design (including calculation of specific fan powers). For any areas where building services do not perform as well as intended, written commentary should be included along with guidance on how to improve performance.

7.8The 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 5 days of the commissioning 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 inspector 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 relevant local authority with the application for a completion certificate.

d.In other cases - for example where 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.

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Section 7

7.9Where 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.

Air leakage testing of ductwork

7.10For ducted systems that are served by fans with a design flow rate greater than 1 m 3/s, ductwork leakage tests should be carried out. Tests should follow the procedures in the Building and Engineering Services Association (BESA) documents DW/143 and DW/144.

7.11For low-pressure ductwork, if at least 10% of the ductwork is tested at random and achieves the low-pressure standard as defined by DW/143, a calculated improvement in both the Building Primary Energy Rate and Building Emission Rate may be claimed. Details are given in the National Calculation Methodology Modelling Guide.

7.12Membership of the BESA Specialist Ductwork Group or the Association of Ductwork Contractors and Allied Services (ADCAS) is one way of demonstrating that a contractor has suitable competency for ductwork pressure testing work.

7.13Air leakage rates are given in Table 7.1. If a ductwork system fails to meet the air leakage limit in Table 7.1, both of the following apply:

a.remedial work should be carried out to achieve satisfactory performance in retests;

b.further ductwork sections should be tested as set out in DW/143.

Table 7.1 Ductwork pressure classes

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Section 7

Regulation 40 and 40A: Providing Information to the owner about the building, fixed building services and maintenance requirements

This section 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 to 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 building is erected, the requirements of Regulation 40 and 40A are met by providing the owner of the building with all of the following information.

a.Operating and maintenance instructions for fixed building services and on-site electricity generation, in accordance with paragraphs 8.1 to 8.3.

b.Other important documentation as detailed in paragraphs 8.4 to 8.7.

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Section 7

In the Welsh Minister’s view, regulations 40 and 40A are met when work is carried out on an existing building by providing the owner with both of the following.

a.Operating and maintenance instructions for the work on fixed building services and on-site electricity generation, provided in accordance with paragraphs 8.1 and 8.3.

b.Relevant information for work on existing systems as detailed in paragraphs 8.8 to 8.13.

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Section 8

Section 8

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

Operating and maintenance instructions

8.1For a new building and for work to an existing building, operating and maintenance instructions should be given to the owner of the building in a building log book.

Note: Information in the log book may draw on or refer to information available as part of other documentation, such as the Operation and Maintenance Manuals or the Health and Safety file. Further advice is provided in BSRIA’s BG 26/2011.

8.2For new buildings and for the work that has been carried out on existing buildings, the information provided should contain all of the following.

a.Information so that the building can be operated in an energy efficient manner, including information about:

i.the building

ii.the fixed building services and on-site electricity generation

iii.the maintenance requirements of the fixed building services and on- site electricity generation the metering and sub-metering, and automatic meter reading systems.

b.A copy of the completed commissioning records.

c.The additional information specified below for new buildings (paragraphs 8.4-8.5.) or existing buildings (paragraphs 8.6-8.11).

8.3Before work begins on site, for both new and existing buildings, the proposed Log Book contents list should be submitted to the building control body (unless the work is being carried out by a person registered with a competent person scheme where it is only necessary to notify the building control body within 30 days of completing the works). At building completion:

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Section 8

a.Where a commissioning completion checklist is being produced for a large building (as required in paragraph 7.7): A declaration should be completed in the commissioning completion checklist that the Log Book has been handed over to the owner of the building.

b.Where a commissioning completion checklist is not being produced: A declaration should be provided to the building control body with the commissioning notice required in paragraph 7.7. It should confirm that the Log Book has been handed over to the owner of the building and it must be signed by the person carrying out the work.

The Building Control Body is unlikely to be able to provide a certificate of compliance until the declaration is received.

Additional information for new buildings

8.4For new buildings, the log book should also include all of the following.

a.Data on the inputs used to calculate the Target Primary Energy Rate, Target Emission Rate, Building Primary Energy Rate and Building Emission Rate.

b.The recommendations report generated with the ‘on-construction’ energy performance certificate.

c.Photographic evidence of the details outlined in Appendix C. This may be an appendix to the log book.

8.5Where Building Automation and Control Systems are installed in a new building, information about their energy performance must also be given to the building owner.

Additional information for work in existing buildings

8.6For work that has been carried out in existing buildings, information added to a new or existing log book should also include information about all of the following.

a.Any new, renovated or upgraded thermal elements.

b.Any new or renovated windows, roof windows, rooflights or doors (controlled fittings).

c.Any newly installed energy meters.

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Section 8

8.7For existing buildings, when any 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 on-site electricity generation affected by the work must be assessed and documented.

8.8For existing buildings, when installing a complete new or replacement system (for example, replacing a heating system including the heating appliance, pipework and heat emitters) the energy performance of the whole system must be assessed. The results should be recorded and give to the building owner with the manufacturer’s supporting literature. The record of energy performance results may be any of the following.

a.A documented assessment using an approved methodology, such as a new Energy Performance Certificate.

b.A documented assessment of the installed system produced in accordance with Ecodesign and associated energy labelling requirements.

c.A documented assessment of a reasonably representative complete system produced by the product manufacturer.

d.Another equivalent assessment carried out by a suitably qualified person.

8.9When carrying out work on an existing system, such as installing or replacing components (for example, replacing a boiler but retaining the pipework and heat emitters), the energy performance of the new components should be assessed. The results should be given to the building owner. This record of energy performance documentation may be any of the following:

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.

8.10If work on an existing system alters the energy performance or CO 2 emissions performance of the system, then the complete altered system should be assessed and the guidance for new or replacement systems in paragraph 8.9 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.

8.11Where building work is carried out on first fit-out (for example, shell and core buildings or partially occupied buildings) the building log-book should be updated, following paragraphs 8.8-8.10.

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Section 8

Regulation 23(2) and requirement L1(a): Replacing thermal elements and limiting heat gains and losses in existing buildings, including extensions

This section deals with the requirements of regulation 23(2) and L1(a) of the Building Regulations 2010.

Requirements for the renovation or replacement of thermal elements

23.(2) Where the whole or any part of an individual 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.

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Intention

In the Welsh Minister’s view, regulation 23(2) and L1(a) are met for new or replacement elements in existing buildings by following the standards in Section 9.

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Section 9

Section 9

Replacing thermal elements and limiting heat gains and losses in existing buildings, including extensions

General

9.1This section provides guidance for new elements in existing buildings, which includes all of the following types of work.

a.Providing a new thermal element in an existing building – follow paragraph 9.2.

b.Providing a replacement thermal element in an existing building – follow paragraph 9.2.

c.Replacing windows, doors or rooflights (controlled fittings) in an existing building – follow paragraphs 9.3 to 9.5.

d.Extending an existing building – follow paragraphs 9.6 to 9.12.

e.Adding a conservatory or porch to an existing building – follow paragraphs 10.12 to 10.13.

Note: Guidance for renovating or retaining elements in existing buildings is given in Section 10.

New and replacement thermal elements

9.2The minimum standards in paragraphs 3.5 and 3.6 and Table 3.1 should be met for both of the following.

a.New thermal elements installed in an existing building.

b.Thermal elements constructed to replace existing thermal elements.

New and replacement windows, roof windows, rooflights and doors (controlled fittings)

9.3If the entire unit of a window, roof window, rooflight or door is replaced, all the following apply.

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Section 9

a.Units should be draught-proofed.

b.Units should meet the minimum standards in Table 3.1 (or paragraph 3.6 if applicable).

c.Insulated cavity closers should be installed where appropriate.

9.4For windows in buildings that are domestic in character, building control bodies may accept as evidence of compliance with the standards given in Table 3.1, a Window Energy Rating from a certification scheme that provides a quality assured process and a supporting audit trail from calculating the performance of the window through to the window being installed.

9.5If a window, pedestrian door or rooflight is enlarged or a new one created, either of the following should be met.

a.The areas of windows, rooflights and pedestrian doors should not exceed the relevant percentage from Table 9.1.

b.If the area of windows, rooflights or pedestrian doors exceeds the relevant percentage from Table 9.1, compensating measures should be included elsewhere in the work to improve the energy efficiency of the building.

Extension of buildings other than dwellings

9.6Constructing an extension in a building with a total useful floor area greater than 1000m 2 triggers the requirement for consequential improvements. Section 11 should be followed.

9.7An extension should be regarded as a new building, and guidance in Sections 1 to 8 should be followed, if the proposed extension has a total useful floor area that is both:

a.greater than 100 m 2

b.greater than 25% of the total useful floor area of the existing building.

If the proposed extension does not meet criteria a. and/or b, the guidance in paragraphs 9.8 to 9.12 should be met.

9.8When a building is extended, the fixed building services or on-site electricity generation that are provided or extended should comply with the guidance in Sections 4 and 5.

9.9When a building is extended, elements should meet the standard in one of the following: paragraph 9.10, 9.11 or 9.12.

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Section 9

9.10When a building is extended, elements should satisfy all of the following.

a.New thermal elements should meet the standards in Table 3.1.

b.Replacement thermal elements should meet the standards in Table 3.1.

c.New windows, roof windows, rooflights and doors (controlled fittings) should meet standards in Table 3.1.

d.Existing fabric elements that will become thermal elements should meet the limiting standards in Table 3.2, by following the guidance in paragraphs 10.2 to 10.4.

In addition, if either of the following areas is greater than that of the existing building, the area of openings in the extension should not exceed that given in Table 9.1.

a.Window and pedestrian doors as a percentage of exposed wall.

b.Rooflights as a percentage of area of roof.

Table 9.1 Maximum area of openings in the extension

Note: Vehicle access doors, display windows and similar glazing and smoke vents can be as large an area of wall or roof as required for the purpose.

9.11As an alternate approach to paragraph 9.10, the area-weighted U-value of all thermal elements in the extension should be shown to not exceed the area- weighted U-value of an extension of the same size and shape that complies with paragraph 9.9. This includes the standards of areas of openings in Table 9.1.

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Section 9

The area-weighted U-value is given by the following expression.

{(U1 × A1) + (U2 × A2) + (U3 × A3) + … )} (A1 + A2 + A3 + … )

Where:

U1= the U-value of element type 1

A 1 = the area of element type 1 and so on.

9.12As an alternative approach to paragraphs 9.10 or 9.11, an approved calculation tool may be used to demonstrate that the Building Primary Energy Rate and the Building Emission Rate for the existing building plus proposed extension do not exceed those for the existing building plus a notional extension. The notional extension should be the same size and shape as the proposed extension and comply with paragraph 9.10.

All calculations should include all consequential improvements that may apply.

Conservatories and porches

9.13Conservatories 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 building, and d. the conservatory or porch contains no fixed heating appliance or the building’s heating system is not extended into the conservatory or porch.

New conservatories or porches

9.14A conservatory or porch is considered as thermally separate where the existing walls, windows and doors between the building and the conservatory or porch are left in place or if they are removed, they are replaced by walls, windows and doors that that achieve or better a U-value given for new and replacement elements in existing buildings given in Table 3.1.

9.15Where a conservatory or porch is not exempt, it should fulfil the following requirements:

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Section 9 a. Glazed and opaque elements should meet the standards set out for new and replacement elements in existing buildings given in Table 3.1 (The limitations on the total area of windows, roof windows and doors as set out in paragraph 9.10 of Extensions do not apply here); and b. be thermally separate from the heated area of the building (see paragraph 9.14); and c. any fixed space heating installed in the conservatory or porch should comply with Sections 4, 5 and 7.

9.16Adding a non-exempt conservatory to increase the conditioned volume of an existing building triggers a requirement for consequential improvements, these are set out in Section 11.

9.17There are two alternative optional approaches that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere. These are set out below.

a.Average U-value approach

As an alternate approach to paragraph 9.15, the area-weighted U-value of all thermal elements in the conservatory or porch should be demonstrated to be no greater than that of a conservatory or porch of the same size and shape that complies with paragraph 9.14.

The area-weighted U-value is given by the following expression. {(U1 × A1) + (U2 × A2) + (U3 × A3) + … )} (A1 + A2 + A3 + … )

Where:

U1= the U-value of element type 1

A 1 = the area of element type 1 and so on.

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Section 9

b.Modelling approach

An approved calculation tool may be used to demonstrate that the Building Primary Energy Rate and the Building Emission Rate for the existing building and the proposed conservatory or porch is no greater than for the existing building plus a notional conservatory or porch. The notional conservatory or porch should be the same size and shape as the proposed conservatory or porch and comply with paragraph 9.15. The specification of the existing building using in conjunction with the notional conservatory or porch as the basis of setting the Building Primary Energy Rate and the Building Emission Rate should include all consequential improvements that will be undertaken in the existing building.

Where upgrades over the minimum requirements of consequential improvements are made to the existing building to compensate for lower performance in the conservatory or porch, then such upgrades should be implemented to a standard that is no worse than set out in the relevant guidance in this Approved Document. The relevant standards for upgrading retained thermal elements are set out in Table 3.2.

9.18If the proposed addition is not thermally separated from the dwelling and therefore does not meet all of the requirements in paragraphs 9.13 and 9.14, it should be treated as an extension and follow the guidance set out in paragraphs 9.6 to 9.12 including the limitation on the total area of windows and doors.

Existing conservatories or porches

9.19An 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 building are removed (and not replaced); or b. the conservatory or porch is provided with a fixed heating appliance or the building’s heating system is extended into the conservatory or porch.

9.20In 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 paragraphs 10.7 to 10.8 should be followed.

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Section 9

Regulation 23 (1) and L1(a): Renovation of thermal elements and limiting heat gains and losses

This section deals with the requirements of regulation 23(1) and L1(a) to the Building Regulations 2010.

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Section 9

Intention

In the Welsh Minister’s view, regulation 23(1) and L1(a) are met for work to elements in existing buildings by renovating a thermal element to the standards in Section 10.

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Section 9

Regulations 6 and 22: Material change of use and change to energy status

This section deals with the requirements of regulation 6 and 22 of the Building Regulations 2010.

Requirements relating to material change of use

6.

1)Where there is a material change of use of the whole of a building, such work, if any, shall be carried out as is necessary to ensure that the building complies with the applicable requirements of the following paragraphs of Schedule 1—

a)in all cases, B1 (means of warning and escape), B2 (internal fire spread— linings), B3 (internal fire spread—structure), B4(2) (external fire spread— roofs), B5 (access and facilities for the fire service), C2(c) (interstitial and surface condensation), F1 (ventilation), G1 (cold water supply), G3(1) to (3) (hot water supply and systems), G4 (sanitary conveniences and washing facilities), G5 (bathrooms), G6 (kitchens and food preparation areas), G2 (bathrooms), H1 (foul water drainage), H6 (solid waste storage), J1 to J4 (combustion appliances), L1 (conservation of fuel and power and the minimisation of greenhouse gas emissions), P1 (electrical safety);

b)in the case of a material change of use described in regulation 5(c), (d), (e) or (f), A1 to A3 (structure);

c)in the case of a building exceeding fifteen metres in height, B4(1) (external fire spread—walls);

d)in the case of a material change of use described in regulation 5(a), (b), (c), (d), (g), (h), (i) or, where the material change provides new residential accommodation, (f), C1(2) (resistance to contaminants);

e)in the case of a material change of use described in regulation 5(a), C2 (resistance to moisture);

f)in the case of a material change of use described in regulation 5(a), (b), (c), (g), (h) or (i), E1 to E3 (resistance to the passage of sound);

g)in the case of a material change of use described in regulation 5(e), where the public building consists of or contains a school, E4 (acoustic conditions in schools);

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h)in the case of a material change of use described in regulation 5(a) or (b), G2 (water efficiency) and G3(4) (hot water supply and systems: hot water supply to fixed baths);

i)in the case of a material change of use described in regulation 5(c), (d), (e) or (j), M1 (access and use).

2)Where there is a material change of use of part only of a building, such work, if any, shall be carried out as is necessary to ensure that—

a)that part complies in all cases with any applicable requirements referred to in paragraph (1)(a);

b)in a case in which sub-paragraphs (b), (e), (f), (g) or (h) of paragraph (1) apply, that part complies with the requirements referred to in the relevant sub- paragraph;

c)in a case to which sub-paragraph (c) of paragraph (1) applies, the whole building complies with the requirement referred to in that sub-paragraph; and

d)in a case to which sub-paragraph (i) of paragraph (1) applies—

i.that part and any sanitary conveniences provided in or in connection with that part comply with the requirements referred to in that sub-paragraph; and

ii.the building complies with requirement M1(a) of Schedule 1 to the extent that reasonable provision is made to provide either suitable independent access to that part or suitable access through the building to that part.

(3) Subject to paragraph (4), where there is a material change of use described in regulation 5(k), such work, if any, must be carried out as is necessary to ensure that any external wall, or specified attachment, of the building only contains materials of a minimum European Classification A2-s1, d0 or A1, classified in accordance with BS EN 13501- 1:2018 entitled "Fire classification of construction products and building elements. Classification using test data from reaction to fire tests" (ISBN 978 0 580 95726 0) published by the British Standards Institution on 14th January 2019.

(4) Paragraph (3) does not apply to the items listed in regulation 7(3).

Requirements relating to a change to energy status

22.Where there is a change to a building’s energy status, such work, if any, shall be carried out to ensure that the building complies with the applicable requirements of Part L of Schedule 1.

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Section 9

Intention

Regulations 6 and 22 of the Building Regulations set requirements for buildings to comply with Schedule 1 of the Building Regulations when a material change of use or a change to energy status occurs.

In the Welsh Minister’s view, the requirements of regulations 6 and 22 are met by following the guidance in Section 10.

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Section 10

Section 10

Work to thermal elements in existing buildings

General

10.1This section provides guidance for work to existing elements in buildings, including all of the following.

a.Renovating an existing thermal element in an existing building – follow paragraphs 10.2 to 10.4.

b.If a building is subject to a material change of use – follow paragraphs 10.5 to 10.8.

c.If a building is subject to a change to energy status – follow paragraphs 10.6 to 10.8.

Note: For new and replacement elements in existing buildings, the guidance in Section 9 should be followed.

Renovating thermal elements

10.2Renovating a thermal element means one of the following.

a.Providing a new layer through cladding or rendering the external surface of the 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 etc.) and then rebuilding.

d.Replacing the waterproof membrane on a flat roof.

e.Providing cavity wall insulation.

10.3If a thermal element is renovated and one of the following applies, then the whole of the thermal element should be improved to achieve at least the U-value in Table 3.2, column (b).

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> > | | | | | | | | | | | > | | | | | |

Section 10

More than 50% of the surface of the individual thermal element will be renovated (see paragraph 10.4).

b.The work constitutes a major renovation. A major renovation is when more than 25% of the surface area of the external building envelope is renovated.

10.4When assessing the percentage area that will be renovated of an individual thermal element, consider whether the individual element is being renovated from the outside or inside, following Figure 10.1 and Figure 10.2 respectively.

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Section 10

Figure 10.2. Renovation of a thermal element from the inside

For example, if the plaster is being removed from the inside of a wall, the area of the thermal element is the area of external wall as viewed from inside the room.

Material change of use and change to energy status

10.5A material change of use, in relation to buildings other than dwellings, is when a building satisfies any of the following:

a.is used as a hotel or a boarding house, where previously it was not

b.is used as an institution, where previously it was not

c.is used as a public building, where previously it was not

d.is not described in Classes I to VI in Schedule 2, where previously it was

e.contains a room for residential purposes, where previously it did not

f.contains more or fewer rooms for residential purposes than previously, but still contains at least one

g.is used as a shop where previously it was not.

Note: A material change of use may result in a change to energy status.

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Section 10

10.6A change to energy status is when a building was previously exempt from the energy efficiency requirements but now is not. The change to energy status applies to the whole building or parts of the building that have been designed or altered to be used separately. For example, when a previously un-heated space becomes part of the heated building, a change to energy status applies to that space.

10.7If there is a material change of use and/or a change to energy status, all of the following should be met.

a.Existing thermal elements should meet the limiting standards as outlined in paragraphs 3.7 to 3.8.

b.If both of the following apply to existing windows, roof windows, rooflights and doors (controlled fittings), they should be replaced to meet the limiting standards in Table 3.1.

i.They separate a conditioned space from an unconditioned space or the external environment.

ii.They have a U-value higher than either of the following:

•for windows, roof windows and doors – 3.30 W/(m 2.K)

•for rooflights – 3.80 W/(m 2.K) calculated by following paragraph 3.4.

Note: Paragraph 10.7b does not apply to display windows or high-usage entrance doors.

c.New or replacement thermal elements should meet the standards in Table 3.1.

d.New or replacement windows, roof windows, rooflights and doors (controlled fittings) should meet the standards in Table 3.1.

e.The area of openings in the newly created building should not be more than 25% of the total floor area. However, a large area of openings may be achieved by following paragraph 10.8.

f.Any fixed building services, including Building Automation and Control Systems, and/or on-site electricity generation, that are provided or extended should meet the standards in Sections 4 and 5.

Note: Consequential improvements may be required when there is a material change of use or change to energy status and Section 11 should be followed.

10.8Outlined below are two alternative optional approaches to paragraph 10.7 that offer more design flexibility by allowing some elements of the design to be relaxed if compensated for elsewhere. This applies to a material change of use or a change to energy status.

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Section 10

a.Average U-value approach

As an alternate approach to paragraph 10.7, the area-weighted U-value of all thermal elements subject to the building works should be demonstrated to be no greater than the same building works that comply with the minimum standards given in paragraph 10.7.

The area-weighted U-value is given by the following expression. {(U1 × A1) + (U2 × A2) + (U3 × A3) + … )} (A1 + A2 + A3 + … )

Where:

U1= the U-value of element type 1

A 1 = the area of element type 1 and so on.

Although U-value requirements may be relaxed, the U-value of any individual thermal element (wall, floor or roof) should not be worse than in the U-values set out in column (a) in Table 3.2 to ensure resistance to surface condensation and mould growth.

b.Modelling approach

An approved calculation tool may be used to demonstrate that the Building Primary Energy Rate and the Building Emission Rate for the building is no greater than for the existing building plus building works associated with the material change of use or a change to energy status which comply with paragraph 10.7. The specification of the existing building used as the basis of setting the Building Primary Energy Rate and the Building Emission Rate should include all consequential improvements that will be undertaken in the existing building.

Where upgrades over the minimum requirements of consequential improvements are made to the existing building to compensate for lower performance of the works associated with the material change of use or a change to energy status, then such upgrades should be implemented to a standard that is no worse than set out in the relevant guidance in this Approved Document. The relevant standards for upgrading retained thermal elements are set out in Table 3.2.

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Section 10

Regulation 28: Consequential improvements to energy performance

This section deals with the requirements of regulation 28 of the Building Regulations 2010.

Regulation 28 - Consequential improvements to energy performance

(1) Paragraph (3) applies to an existing building with a total useful floor area of over 1000m2 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;

(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.

Intention

In the Welsh Ministers view, where regulation 28 applies, the requirements of this regulation are met for existing buildings by carrying out consequential improvements that are technically, functionally and economically feasible, by following the guidance in Section 11.

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Section 11

Section 11

Consequential improvements to energy performance

11.1Consequential improvements describe additional energy efficiency improvements that should be undertaken when the following buildings works are undertaken:

a. The existing building is extended or part of the building is converted to include fixed heating in a previously unheated space, increasing the conditioned volume. The building could be extended by means of a conventional extension or a non-exempt conservatory or porch b. the initial provision of any fixed building service i.e. the initial installation of heating, hot water, air conditioning or mechanical ventilation, or internal or external lighting (not including emergency escape lighting or specialist process lighting), or c. an increase in the installed capacity of any fixed building service

Note: Photovoltaics or other microgeneration technology are generally not fixed building services

The requirement in item (a) applies to all existing non-domestic buildings. The requirements in items (b) and (c) only apply to existing non-domestic buildings where the total useful floor area is over 1000m².

Note: Consequential improvements should be carried out so that the entire building complies with Part L of the Building Regulations to the extent that the improvements are technically, functionally and economically feasible.

Note: If the building already complies with the current requirements of Part L of the Building Regulations, consequential improvements are not required.

11.2Where work other than the items listed in paragraph 11.1 is planned as part of the principal works, if they improve the energy performance of the building, these are consequential improvements. Work carried out to compensate for the poorer standard of an extension, using the alternative approach to demonstrating compliance described in paragraph 9.11, does not count as a consequential improvement.

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Section 11

Consequential improvements when extending a building

Note: A new free-standing building constructed on an existing site is a new building, not an extension.

11.3When an existing building is being extended or the habitable area is being increased, consequential improvements should be installed. The measures listed in Appendix D, Table D.1, may be considered technically, functionally and economically feasible in normal circumstances.

11.4For an extension or increase in habitable area, the value of the principal works is used to determine the minimum value of the consequential improvement works. The value of the consequential improvement works should not be less than 10% of the value of the principal works.

11.5As part of the initial notice or deposit of plans, a chartered quantity surveyor or other suitably qualified person should produce a signed report that gives the value of the principal works and the value of the consequential improvements. The prices used should be those at the date when the building control body is informed of the proposals.

Consequential improvements on installing or extending the capacity of fixed building services

Note: Increasing the size of central boiler plant to serve a new extension would not generally increase the installed capacity of a fixed building service per unit area, unless the heating provision in the existing building is increased at the same time. Unless the heating provision in the existing building is increased at the same time as the size of central boiler plant, paragraph 11.6 would not apply, but paragraphs 11.3 to 11.5 would continue to apply as a result of the extension.

11.6If it is proposed to install a fixed building service in an existing building with a total useful floor area of over 1000 m 2, either as a new fixed building service or to increase the installed capacity of a fixed building service per unit area, then both of the following consequential improvements should be made to meet the requirements of Part L, where this is practical and technically, functionally and economically feasible.

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Section 11

a.Energy efficiency improvements should be made to fixed building services. All of the following apply.

i.When installing or extending the capacity of fixed building services, the value of the principal works is used to determine the minimum value of the energy efficiency improvements made to fixed building services as consequential improvements. The value of these consequential improvements should not be less than 10% of the value of the principal works, excluding the value of any work to improve other energy efficiency aspects of the building served by the services in meeting paragraph 11.6b.

ii.The measures listed in Appendix D, Table D.1 relate to this requirement, 11.6(a), and may be considered technically, functionally and economically feasible in normal circumstances.

iii.As part of the initial notice or deposit of plans, a chartered quantity surveyor or other suitably qualified person should produce a signed report that gives the value of the principal works and the value of the consequential improvements. The prices used should be those at the date when the building control body is informed of the proposals.

b.Other energy efficiency aspects of those parts of the building served by the fixed building service should be improved.

i.All technically, functionally and economically feasible measures to improve the fabric of the building served should be made. The extent of the improvements to the fabric should not be determined by the value of the principal works.

ii.The measures in Appendix D, Table D.2 relate to this requirement, 11.6(b), and may be considered technically, functionally and economically feasible in normal circumstances.

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Appendix A

Appendix A

Key terms

Note: Except for the items marked * (which are from the Building Regulations 2010), these definitions apply only to Approved Document L, Volume 2: Buildings other than dwellings.

Air permeability is the measure of airtightness of the building fabric. It is defined as the air leakage rate per hour per m 2 of envelope area at the test reference pressure differential of 50 pascals.

-The limiting air permeability is the worst allowable air permeability.

-The design air permeability is the target value set at the design stage.

-The assessed air permeability is the measured air permeability of the building concerned. The assessed air permeability is the value used to establish the Building Emission Rate and the Building Primary Energy Rate.

Airtightness The resistance of the building envelope to infiltration when ventilators are closed. The greater the airtightness at a given pressure difference across the envelope, the lower the infiltration.

Building Automation and Control System means a system comprising all products, software and engineering services that can support energy efficient, economical and safe operation of heating, ventilation and air conditioning systems through automatic controls and by facilitating the manual management of those building systems.

Building Control Body is either a local authority building control department or a registered building control approver.

Building Emission Rate is the building’s CO 2 emission rate expressed as kgCO 2/(m 2.year).

*Building Envelope in relation to a building is defined in regulation 35 as:

the walls, floor, roof, windows, doors, roof windows and rooflights.

Building heat distribution system is the heat network distribution pipework for hot water and heating for a building connected to a heat network, between the primary district heat network and the connection(s) with any dwelling or building. Building distribution pipework is normally internal but may be external. This does not include heat distribution within individual dwellings, for example the heat interface unit and space heating and hot water systems within dwellings. Also sometimes referred to as secondary

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Appendix A heat network. Note that CIBSE CP1 Heat Networks: Code of Practice sets insulation standards for the primary district heat network and for the distribution pipework within multi-residential buildings that are connected to a heat network; but not for any other pipework (e.g. pipework within non-residential buildings that are connected to district heat networks nor buildings not connected to a district heat network).

Building Primary Energy Rate is the primary energy use per square metre of floor area per year of a new building other than a dwelling. Expressed as kWhPE /(m 2.year) and determined using the approved methodology. The approved methodology is given in the National Calculation Methodology Modelling Guide.

Centralised electrically heated is a domestic hot water system in which the water is supplied to the draw-off points from a device in which water is heated by an electric element or elements immersed in the stored water. The water heater is situated centrally with a distribution system to supply water to the draw off-points and has a capacity greater than 300 litres.

Centre pane U-value means the U-value determined in the central area of the glazing unit, making no allowance for edge spacers or the window frame.

*Change to energy status is defined in regulation 2(1) as:

Any change which results in a building becoming a building to which the energy efficiency requirements of those Regulations apply, where previously it was not.

CHPQA quality index is an indicator of the energy efficiency and environmental performance of a CHP scheme, certified by the Combined Heat and Power Quality Assurance scheme.

Circuit-watt is the power consumed in lighting circuits by light sources and, where applicable, their associated control gear (including transformers and drivers) and power factor correction equipment.

CO 2 emission factor is an estimate of CO 2 equivalent emissions produced by the use of different fuels per kWh of delivered energy.

Coefficient of performance (COP) is a measure of the efficiency of a heat pump at specified source and sink temperatures, measured using the procedures in BS EN 14511-2:

- Heating COP = heat output / power input

- % COP (COP×100) is the heat generator efficiency.

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Appendix A

Commissioning is when after all or part of the fixed building service or on-site electricity generation system has been installed, replaced or altered, the system is taken from a state of static completion to working order. Testing and adjusting are carried out for fixed building services, as necessary, to ensure that the whole system uses no more fuel and power than is reasonable in the circumstances. Testing and adjusting are carried out for on-site electricity generation systems, as necessary, to ensure that the whole system produces the maximum amount of electricity that is reasonable in the circumstances.

For each system, commissioning includes all of the following:

a.setting-to-work

b.regulation (that is, testing and adjusting repetitively) to achieve the specified performance

c.calibration

d.setting up and testing the associated automatic control systems

e.recording the system settings and the performance test results that have been accepted as satisfactory.

Communal heat network is a heat network by means of which heating, cooling and/or hot water is supplied to a single building only divided into separate premises, for example to both dwellings and non-dwellings in a mixed-use building or a building divided into separate premises.

Conformity assessment body is an organisation that is responsible for carrying out activities such as testing, inspection and certification (conformity assessment) which provides assurance that what is being supplied meets the expectations specified or claimed. In the UK, the United Kingdom Accreditation Service (UKAS) is the sole organisation that grants accreditation to a conformity assessment body to carry out conformity assessment activities.

Consequential improvements mean those energy efficiency improvements required by regulation 28.

Control Zone means independent control of rooms or areas within buildings that need to be heated to different temperatures at different times.

*Controlled service or fitting is defined in Regulation 2(1) as:

a service or fitting in relation to which Part G, H, J, L or P of Schedule 1 imposes a requirement.

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Appendix A

Direct-fired circulator is a domestic hot water system in which the water is supplied to the draw-off points from a hot water vessel in which water is heated by combustion gases from a primary energy source. The unit has no storage volume, as water is stored in a supplementary storage vessel.

Direct-fired continuous flow is a domestic hot water system in which the water is supplied to the draw-off points from a device in which cold water is heated by combustion gases from a primary energy source as it flows through the water heater. The water heater is close to the draw-off points. The unit has no storage volume, as water is instantaneously heated as it flows through the device.

Direct-fired storage is a domestic hot water system in which the water is supplied to the draw-off points from an integral hot water vessel in which water is heated by combustion gases from a primary energy source.

Display lighting means lighting to highlight displays of exhibits or merchandise, or lighting used in spaces for public leisure and entertainment such as dance halls, auditoria, conference halls, restaurants and cinemas.

Display window means an area of glazing, including glazed doors, to display products or services on offer to the public within a building, positioned as in all of the following:

a.at the external perimeter of the building

b.at an access level

c.immediately adjacent to a pedestrian thoroughfare.

If there is a permanent workspace within one glazing height of the window, the window cannot be considered to be a display window.

Glazing more than 3 m above an access level should not be considered part of a display window except where either of the following applies:

a.The products on display require a greater height of glazing

b.Both of the following apply

i.where building work involves changes to the façade and glazing that require planning consent

ii.planning requirements mean that a greater height of glazing is necessary, e.g. to fit with surrounding buildings or to match the character of the existing façade.

District heating network is a system that supplies heat from a central source/s to consumers in two or more buildings, via a network of pipes carrying hot/warm liquids (generally water). Heat networks can cover a large area or even an entire city, or can be relatively local, supplying a small cluster of buildings.

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