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Blower door testing  

Energy Efficiency

A method to determine air leakage is called a blower door test. This involves installing a temporary door covering consisting of a fan and various gauges. This fan either pressurizes or depressurizes the home, depending on which direction it is blowing. Once the home is pressurized, the gauges are used to determine the amount of air leaking out of the home. Smoke tracers can be used to determine where the leakages are occurring.


The following table shows the test results of an air leakage study (blower door test) performed on a 1,728 square foot home in Dallas, Texas.


Area of leakage Air leakage
Soleplates 25%
Wall outlets 20%
Exterior windows 13%
Duct systems 13%
Vent hoods 6%
Fireplace 6%
Recessed spot lights 5%
Exterior doors 4%
Dryer vent 3%
Sliding glass door 2%
Bath vent 1%
Other 2%




















Infiltration factors

The amount of heat lost or gained through infiltration depends on the following five factors:

Volume of air. The volume of air inside a building is constant. The volume used for calculation is the air only within the conditioned portion of the building.

Time. The amount of energy lost due to infiltration is proportional to the length of time involved. This length of time must be expressed in hours since the air changes are on an hourly basis.

Air changes per hour. The number of times, in one hour, that the entire volume of air inside a structure leaks out and must be replaced. The figure represents the tightness of the building. The following Table can be used as a rough estimate of air changes per hour for rooms in residential type buildings.


Room type Air changes per hour
No windows or exterior doors 0.5
Windows or exterior doors on 1 side 1.0
Windows or exterior doors on 2 sides 1.5
Windows or exterior doors on 3 sides 2.0
Entrance halls 2.0


















Information provided by the National Food and Energy Council. 





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