A blower door is a diagnostic piece of equipment used by qualified energy auditors and weatherization contractors to determine building air tightness and pinpoint leaks in a house. The blower door uses a powerful fan that mounts into the frame of an exterior door.
During a blower door test, the fan typically pulls air out of the house by drawing air through all unsealed cracks and openings. The air flow is measured by gauges to determine how tight the house is. To assure the house is not too tight before weatherization work is done, the blower door test is performed before any air sealing and insulation work takes place. Also, to assure that any weatherization work has not over tightened the house, another blower door test is performed when work is completed.
For supporting information and a diagram of a blower door, visit the U.S. Department of Energy web site
