Building tight houses is a fundamental step toward energy efficiency, and figuring out how well you’ve done is actually pretty simple.
Air leakage is calculated with a blower-door test. A technician depressurizes the house with a blower sealed into a doorway and measures how much air can pass through the building envelope.
The result is typically described either as air changes per hour at a pressure difference of 50 pascals — ach50 in industry lingo — or cubic feet per minute (CFM) @ 50 pascals. Either way, air leakage becomes a known value. If the house is too leaky, the builder can take corrective steps to tighten it up.
The process isn’t intended to be onerous. But Frank Keeler, who wants to build his own house in Washington state, has concluded that the required blower-door test is enough for him to abandon the idea of building altogether, as he explains in a recent Q&A post at GreenBuildingAdvisor.
“We are building a new home ourselves,” he writes, “and are looking for a checklist to help us prepare for the blower door test.”
Requirements for the test in Washington state have only recently been enforced, he adds, and it’s proving hard to get solid advice. Moreover, costs can range from $75 an hour to thousands of dollars, depending on where you live, and there’s no telling how many tests he’ll need to pay for.
His dilemma is the subject of this week’s Q&A Spotlight.
Where to get help
General information about blower-door testing is available online. Resources include an article by GBA senior editor Martin Holladay explaining the protocol for conducting a blower-door test and the locations of common air leaks.
Another, pointed out by Robert…