A Blower Door test is a comprehensive test measuring the Air Infiltration of your entire house. A large blower door fan is used to depressurize your house by blowing a large volume of air from inside your house to the outside. Thinking of your house as a system, this depressurization of your home will pinpoint any holes and other leakage areas in the envelope of your house. The best way to think of your home is as an entire energy system. When everything is working perfectly, you feel comfortable and enjoy low energy bills. But when one part is not working properly the other parts either amplify the problem or compensate to make up for the problem. The best examples are found on the Energy Star website:
http://www.energystar.gov/index.cfm?fuseaction=popuptool.atHome

Using our state-of-the-art infrared camera, Infrared Imaging (IR) detects all the areas where air enters your house, captured as IR pictures, and noted for your report.Also included in your report are regular digial photos showing the exact location of the air leakage shown in the infrared camera picture.

Ceiling not insulated and heat loss from recessed lights as well as leaking down the walls.	Old insulation crumbling down the walls.
Heat from attic leaking into the wall due to poor air sealing in attic.	Recessed light allowing heat from attic to flow into room.