As our wall assemblies and building practice evolve (more on that here) the numbers for our Passive House projects’ blower door tests have steadily improved. Blower door tests are used to determine the building envelope’s air tightness, one of three performance metrics for Passive House certification (the other two are heating/cooling load and primary energy demand). To pass, the home must fall under 0.6 ACH50 (0.6 air changes per hour at 50 pascals of pressure).
Our most recently completed Passive House, the Madrona Passive House in Seattle, came in at 0.32 ACH50. Last week, our almost-finished Wallingford Passive House project (also in Seattle) snuck in below that at 0.315 ACH50!
A couple complexities with the project made this number especially exciting. “We were pleased to get these low numbers while incorporating a vented range hood and make up air ducting,” said Dan Whitmore, H&H CPHC. “Both of which penetrated the air barrier and require motorized dampers but leak approximately 10cfm each.”
Wallingford Passive House in-progress.
Certified Passive House Consultant and Building Analyst Skylar Swinford of ESCO performed the blower door test:
Skylar monitors the blower door testing using a manometer, flow rate meter, and Tectite software.
To conduct the test, Skylar mounted a duct blaster fan into one of the home’s exterior door frames to pressurize and depressurize the house. Note that for a conventional home, this test would require a larger blower door fan, but when we build to Passive House levels of airtightness the much lower flow of a duct blaster fan (usually used to test duct systems) is a better fit. The pressurizing and depressurizing not only allows us to take the airtightness measurement, it also allows us to suss out any air leaks and address them.
The duct blaster fan installed in the exterior door at Wallingford Passive House
With this passing airtightness score we’re that much closer to finishing up this soon-to-be-certified Passive House project!
For more on the blower door test at Wallingford Passive House, check out this video with Skylar:Back to Field Notes