Part F ventilation rates calculator.
Extract and whole-dwelling rates for a house or flat. For ventilation and mvhr installers, m&e, site supervisors. Free, no sign-up.
3-bed figure vs 0.3 l/s × 85 m². The higher wins.
- 1 × kitchens: 30 l/s each
- 1 × bathrooms: 15 l/s each
- 1 × wcs: 6 l/s each
Minimum rates from Approved Document F 2021, Tables 1.1 to 1.3, for new dwellings. Not a ventilation design: terminals, ducts, background ventilators and commissioning are separate.
The whole-dwelling rate is the higher of two figures from Approved Document F (2021): the bedroom-count figure in Table 1.3, and 0.3 litres per second for every square metre of internal floor area. Bigger flats with few bedrooms usually hit the floor-area figure first.
Intermittent extract (System 1) uses Table 1.1: 60 l/s in a kitchen, or 30 l/s if the hood is over the hob, 30 in a utility, 15 in a bathroom, 6 in a WC. Continuous extract (System 3, and the extract side of an MVHR) uses Table 1.2: 13, 8, 8 and 6. For a continuous system the sum of the wet rooms must also be at least the whole-dwelling rate, so the tool shows both and takes the higher.
Where it stops: this is the minimum air the regulations ask for. It says nothing about duct sizing, terminal positions, background ventilators, noise or the airtightness route. That is the designer's job and the commissioning engineer's certificate.
Free, no sign-up, no tracking inside the frame. Paste it into any page; the credit line stays.