A Blower Door Test Doesn’t Lie

As the HERS rater set up his equipment he explained to the audience, including the homeowner and the GC, what  he was doing.  The homeowner was interested because the test had been included as a way to confirm good workmanship and the future benefit of energy savings. The GC was interested because this was his first blower door test after thirty years as a builder. As the fan started to spin and the structure’s interior went  to a negative pressure, the GC began telling me all the reasons why his company’s work was synonymous with high levels of energy efficiency. He recalled how the studs had been caulked and the plates had been sealed with gaskets. He relayed the painstaking details his crew had used to seal the windows with foam and tape. However, when the differential pressure hit the target of 50 Pascals, it was plainly obvious that the GC’s suggestion of energy efficiency was a far cry from what was delivered. The air leaking around the windows didn’t require a thermal imaging camera or smoke pencil to highlight the offending areas.  All I had to do was stand near the window and let the breeze blow through my hair.

The builder asked me how the test was going, to which I replied that his crew had failed to seal the window. His response was one of shock and denial. He insisted that they had and attempted to explain why I was wrong. My only response was to show him where to stand and how to hold the back of his hand against the corner of the window.  “The test shows us where air is leaking into or out of the envelope. It doesn’t lie.” His response? “Well, my crew does the best job they can.”

The rater packed up his gear and handed the homeowner the less than impressive report.  I’ve often wondered about the conversation that followed between the homeowner and GC.  Did the owner question the GC’s claim of being an “energy efficient builder”? And without the blower door test, would the owner have ever known otherwise?  And more importantly, did the builder change his approach with the next energy efficient home he built, or does he continue just to do “the best he can”?

In my opinion, many builders lie to themselves and mislead clients about energy efficiency. They make claims of energy performance, and still only build a code-minimum house. On the other hand, many builders are waking up to the realities of the demands made by homebuyers and the new energy codes. Many of these builders are also smart enough to back up their claims and ensure their record of performance with a blower door test.  A blower door test doesn’t lie. It is a tool that can be unimaginably helpful at confirming both past workmanship and future energy consumption. Does your next build include a blower door test?

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