2. Selecting The Hours/Cycles And Size Of The Ventilation System


How to choose the right extractor fan

 The choice of extractor fan for your ventilation system depends largely on the following parameters:

  • volume of the room
  • number of air exchanges per hour needed

To calculate the first parameter its sufficient to multiply LENGTH x WIDTH x HEIGHT and its read in m3. Multiplying the m3 by the number of air exchanges necessary, the correct capacity for the extraction is obtained and is expressed in m3/h. Therefor the capacity of the extractor fan must coincide with this result.

When we are considering ducted fans( or fans installed with ducts attached) it is necessary to consider also the loss of capacity, deriving from the length of the ducts and type of ducts. For the choice of the fan its advise to raise by 10-15% the theoretical data obtained.

The number of air exchanges per hour, indicate how many times in hour it is necessary to change the air in a room or area to obtain a sufficient ventilation.
To simplify this calculation we have developed an air exchange tool, in which you can fill in the fields to obtain an estimate for the air exchange’s needed.

Calculation for air flow exchanges and extractor fan capacity

Unit of measure

Room size
XX m

Room volume

Type of room/environment

N° of Air exchanges

Air capacity m3/h

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