Calculating air volume

Technicians and other people in the business often tell us that it can be difficult to find the most suitable ventilation system for the customer or task.

Not everyone feels like digging down into advanced mathematical formulas or going through the building regulation with a fine toothcomb.

Nor do you need to.

The engineers at Genvex have collected all the requirements and instructions of the building regulation Bygningsreglementet 2015 and reduced them to very simple guidelines that you can use next time you need to calculate air volume.

Guide: How to calculate air volume in 3 easy steps

NB: If the house has a self-contained extractor hood and if it has its own engine, you can reduce the total exhaust volume by 20l/s. This requires, of course, maintaining a minimum air exchange of 0.3l/s pr. m2. However, we always recommend a basic air exchange in the kitchen using the ventilation system when the hood is not in use.

Recommendations for BR2015.


How many square metres is the house?

On Plan 1, look for: “Air exchange” and enter the air volume of the house.

For example: Your house is 130m2. Minimum air amount will be: 140m3/h or 39l/s.

Air exchange schema: With regards to BR2015, minimum air exchange in a heated living space should be 0.30l/s pr. m2 living space (gross).

tabel beregning af luftmængde engelsk


How many rooms in use are there?

On Plan 2, find: “Exhaust amount” and enter the air amount of a residential living space with corresponding rooms.

For example: Your house has a kitchen, 1 bathroom, a guest bathroom and a utility room. The minimum air amount here should be: 198m3/h or 55l/s.

Exhaust amount schema: The minimum exhaust amounts depend on what kind of and how many utility rooms house has.

Tabel beregning af luftmængde engelsk 2


Which air amount was the highest?

You have now entered two different air amounts. The highest of the two numbers is the recommended amount of air for your house, see building regulation Bygningsreglementet BR2015.

For example:
The air amount according to Schema1 is 140m3/h or 39l/s.
The air amount according to Schema 2 is 198m3/h or 55l/s.

The last air amount is the highest one and is the one that suits your house best.

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