Part F · England · Free to use
Part F ventilation and trickle vent calculator
Whole-dwelling rate, extract rates, background ventilators and purge openings for a home under the 2021 edition.
Approved Document F Volume 1 (2021)
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Part F · Result
25 l/s whole-dwelling rate
Trickle vent and extract sizes below. Only for less airtight homes (design permeability above 5 m³/(h·m²)).
Calculated result- Whole-dwelling ventilation rate: Calculated resultgreater of 25 l/s (2 bed) or 0.3 l/s per m²25 l/s
- Kitchen extract (intermittent): Calculated resultcooker hood to outside30 l/s
- Bathroom extract (intermittent): Calculated resulteach15 l/s
- WC extract (intermittent): Calculated resulteach6 l/s
- Background ventilator, each habitable room and kitchen: Calculated resultsingle-storey dwelling10,000 mm² EA
- Background ventilator, each bathroom: Calculated result4,000 mm² EA
- Number of ventilators in habitable rooms and kitchens: Checks passedmin 5 for a 2-bed home5
- Total equivalent area: Calculated result54,000 mm²
- Purge: openable area, largest room: Calculated result1/20 of floor area (Table 1.4)1.3 m²
- Table 1.7 does not apply where all openings are on one façade or the kitchen has no external wall; use continuous extract instead.
- Open-plan kitchen-living rooms need at least three habitable-room-size ventilators (para 1.58).
Clauses this relies on
Source edition and scope
Approved Document F Volume 1 (2021).
Uses the 2021 edition. The 2026 standards have future commencement dates and different scope conditions; confirm the edition applicable to your project.
This is a preliminary check of the conditions shown. Confirm the edition, project circumstances and any additional requirements with your architect or building control.
A design aid, not legal advice. Checked against the Building Regulations 2010 for England; confirm with building control.