Leaky homes are hard to heat and hard to cool. The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower door. A blower door is a tool that depressurizes a house; this depressurization exaggerates the home’s air leaks, making the leaks easier to measure and locate.
An energy-efficient house must be as airtight as possible. Many older U.S. homes are so leaky that a third to a half of the home’s heat loss comes from air leaks.
There is no such thing as a house that is too tight. However, it’s also true that there is no such a thing as an airtight house. Every house leaks, and that’s why we perform blower-door tests — to measure a building’s leakage rate.
Who needs a blower door?
Blower-door testing is useful for both new construction and existing homes. By testing a new home, a builder:
- Can determine whether a certain airtightness target has been met;
- Can document airtightness levels needed to qualify for certain home labeling programs, including Energy Star and Passivhaus;
- Can do a better job calculating heat loss and heat gain the next time he or she builds a similar house;
- Can brag about the home’s airtightness to prospective homebuyers or drinking buddies.
If you’re building a new home, the best time to conduct a blower-door test is after the home is insulated but before the drywall is hung. If the test reveals major problems, the leaks will be easier to fix at that point than later on.
Testing existing homes
There are at least two reasons to conduct a blower-door test on an existing house: to determine how leaky it is, and to help locate and fix the leaks.