Fan Capacity Calculator

The ATTMA Trade Association has developed a Blower Door Fan Capacity Calculator to help ATTMA members calculate how many fans are required for Level 2 buildings.

The fan capacity calculator works on the basis of some assumptions such as a quality power supply and running into a free air unobstructed route.  The fans that can be used are: Infiltec, Retrotec (1000, 2000, 3000, 5000 and 6000 series) and The Energy Conservatory (Model 3, Model 4 and Ductblasters).

The tool requires the blower door fan, the target air permeability and the size of the building (surface area) to be identified. The calculator will provide you a reasonable estimate for the number of fans that will be needed.

Please note, as per the ATTMA guidance, you should always take approximately 20% more fan power than required to allow for a higher result. It is not uncommon for the target to be changed post test. Taking an extra 20% fan power will allow the result to still be valid and used for compliance.

Tests must always meet 50Pa Induced Pressure to be valid.

The following tool was provided to ATTMA by Stroma Technology Ltd.

Make Model Air Permeability
(m³/h.m² @ 50Pa)
Envelope (m²)
No. of Fans

This tool should only be used for guidance and is based on the 240v 50hz equipment specifications from new. ATTMA take no responsibility for errors.