The most rigorous way to locate duct leaks is with a blower door or
similar analysis performed by a professional. This analysis measures the
magnitude of your duct leakage and identifies its location.
Blower Door Tests
A blower door is a special instrument used to measure air leakage in a
building shell and its ductwork. The equipment consists of a temporary door
covering which is installed in an outside doorway and a blower which forces
air into or out of the building. The blower door measures how leaky the
building and ductwork are, and can be used to find the location of the major
leaks. Without a blower door, finding the leaks in the ductwork can be
difficult since the ducts are often in hard to reach areas such as the attic
or crawl space and the leaks are usually hidden from view by duct
insulation.
Why should you care about air leakage in houses? Everyone
knows that air leakage can cause uncomfortable drafts in houses, but energy
researchers have discovered that sealing air leaks is one of the simplest
and least expensive way to save energy in homes. A typical house may lose
about 1/3 of its heat through walls and ceilings, 1/3 through windows and
doors, and 1/3 through air leakage. A few hours of air sealing with
inexpensive sealants can often reduce the air leakage by about 1/4 to 1/2,
resulting in a saving of 10% to 20% of the total house heating and cooling
bill. Each house has different amounts and types of air leakage, and the
most efficient technique is to spend the most time sealing the leakiest
houses. Duct leakage is probably the worst type of house air leak.
Therefore, you need a tool that can quickly identify the leaky houses and
show you where the leaks are.
