Code-Blower Door Testing a Small Home

This post originally appeared on the Green Building Advisor website.

Code compliant blower door testing of a small home can be very frustrating for both the person performing the test and the homeowner or contractor who are required to have the test.  A few months ago, I tested a 952 square foot, newly constructed home with a volume of 7616 cubic feet, one of the smallest I’ve tested.  The house had a leakage rate of 416 cfm which resulted in a 3.28 ACH50 number.  A failed blower door test (my climate requires 3 ACH50 or less).  If we take that same CFM rate but increase the ceiling height to 9 feet, which changes the volume to 8568 cubic feet, 2.91 ACH50, a passing test.  Either way, 416 CFM of air moving through the blower door isn’t much, some kitchen exhaust hoods can move more air than that.  Seems unfair to punish smaller homes when blower door testing, especially when the blower door test is testing the surface of a structure, not it’s volume.

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