What DB HS 3 requires
Table 2.1 gives the minimum continuous flow rate in l/s for each room, by the type of dwelling: its number of bedrooms. Dry rooms (bedrooms and living rooms) receive air; wet rooms (kitchen, bathrooms, toilets) are extracted.
Minimum flow rates (Table 2.1)
All values in l/s.
| Dwelling | Main bedroom | Other bedrooms | Living and dining rooms | Wet rooms, total minimum | Wet rooms, minimum per room |
|---|---|---|---|---|---|
| 0 to 1 bedrooms | 8 | not applicable | 6 | 12 | 6 |
| 2 bedrooms | 8 | 4 | 8 | 24 | 7 |
| 3 or more bedrooms | 8 | 4 | 10 | 33 | 8 |
Mixed rooms and cooking
Where a room has several dry functions, the function with the largest flow rate applies. Where dry and wet functions are mixed, each zone gets its own flow rate. In addition, the cooking area must allow separate extraction of at least 50 l/s, independent of the general ventilation.
Worked example
A three-bedroom home with a living room, a kitchen, a bathroom and a toilet. Dry rooms: 8 l/s for the main bedroom, 4 + 4 l/s for the two other bedrooms and 10 l/s for the living room, 26 l/s in total. Wet rooms: at least 33 l/s in total and 8 l/s per room, for example 11 l/s each for the kitchen, bathroom and toilet.
How Aira applies it
Aira counts the bedrooms on the plan to find the dwelling type. Each bedroom and each living or dining room gets the flow rate of Table 2.1; the largest bedroom counts as the main bedroom. The wet-room total of Table 2.1 is divided equally over the kitchen, bathrooms and toilets, and no room gets less than the minimum per room. Supply and extract are made equal: the lower is raised to the higher. You can correct the room functions and every flow rate in the table before you download the plan.
Source
The figures are taken from the official document, checked on 14 October 2026. Always check the version that applies to your project.