What the decree requires
Section 9 sets three minimums for the outdoor air flow:
| Requirement | Minimum outdoor air flow |
|---|---|
| Rooms for staying, per person, in the planned period of use | 6 dm³/s |
| The whole building, per m² of floor area | 0.35 dm³/s |
| A dwelling | 18 dm³/s |
Extract per room
The decree sets the air flow for the dwelling as a whole. For the extract per room, designers use the industry guide below.
Room values from the industry guide
Designers commonly use the FINVAC guide for dimensioning ventilation in dwellings, which refers to the decree. It is an industry guide, not law. In normal use, in dm³/s:
A home sauna adds 6 dm³/s of supply and 6 dm³/s of extract. Room flows may deviate by at most 20 per cent from the design value.
| Room | Flow (dm³/s) |
|---|---|
| Largest or only bedroom, supply | 12 (draft 2019: 6 per person above two people) |
| Other bedrooms, supply | 8 |
| Other living space, supply | 8 (living room under 22 m²), otherwise 0.35 per m² |
| Kitchen, extract | 8 (at least 25 when boosted) |
| Bathroom, with or without toilet, extract | 10 |
| Separate toilet, extract | 7 |
| Separate utility room, extract | 8 |
| Dressing room and storage, extract | 6 |
| Technical space, extract | 3 |
Worked example
A home of 100 m² for four people. By floor area: 0.35 × 100 = 35 dm³/s. By persons: 4 × 6 = 24 dm³/s. The dwelling minimum is 18 dm³/s. The highest value, 35 dm³/s, is the total outdoor air flow.
How Aira applies it
Aira takes the floor area from the plan and the number of occupants from the bedrooms (two in the largest bedroom and one in each other, shown as an assumption you can change), and uses the highest of the three minimums as the total outdoor air flow. Supply is divided over the habitable rooms by floor area and the extract equally over the kitchen, bathroom, toilet and utility room. Because the flow must be adjustable upwards by at least 30 per cent (section 10), the installation must be able to deliver 1.3 times the total; this is shown under the table. You can adjust every figure in the table before you download the plan.
Source
The figures are taken from the text of the decree on Edilex, checked on 16 October 2026. The room values come from the FINVAC industry guide (2017 version and draft of 18 June 2019, with equal tables).