Air Changes per Hour (ACH)

Testing by CSIRO found that a typical ACH of the tested houses was 0.77 ACH, or 15.4 ACH50.

The Passive House standard requires air tightness so that there will be less than 0.6 ACH50  with a pressure difference between inside and outside of 50 Pa. Under normal conditions this should mean a ACH of 0.03.


  • 0.5 ACH50 - 0.03 ACH - Passive House, very tight
  • 3 ACH50 - 0.15 ACH - A good aim - Just Right and Airtight
  • 15.4 ACH50 - 0.77 ACH - Average in CSIRO study

Note I am using a conversion of 1 ACH50 = 20 ACH based on a statement by CSIRO.

How to measure ACH

Blower door test

References


  1. Air changes per hour - Wikipedia
  2. How Much Air Leakage in Your Home Is Too Much?

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