July 20, 2015
A blower door test is an integral part of a comprehensive home energy audit. It measures a home's rate of air infiltration, helps identify energy-wasting air leaks, and can help verify the effectiveness of weatherization and energy retrofit work like air sealing and insulation when done after the work is complete. In this post, we'll explain exactly how a blower door works, and walk through the same process our highly trained auditors use to identify the optimal way to maximize your home's energy efficiency.
The blower door seeks to answer the two questions of how much air is leaking in and out of a home, and exactly where that air is leaking out. Normally, this information is very hard or nearly impossible to find, as even fairly large leaks are difficult to identify with the naked eye. The blower door at its core is simply a large, finely calibrated fan paired with a manometer-- a sensitive device that measures air pressure. A door is set up to create a tight seal over the front door of a home, and the manometer is set up to read the air pressure both inside and outside the home. All exterior doors and windows are shut, and all interior doors are opened for the test.
The fan is turned on and slowly dialed up in speed, blowing air out of the home. This causes the home to drop in pressure relative to the outside. The temporarily depressurized home sucks in air from outside through whatever cracks and leaks it has in its exterior at a rapid rate. These are the areas to be targeted for air sealing-- the major problem areas of the home's shell. During a blower door test, an auditor is able to walk around a home to identify what rooms, windows, attic spaces, or other parts of the home are the leakiest. Paired with an infrared camera, even the tiniest of cracks or temperature differences are brought out with a blower door.
In addition to these qualitative observations, the blower door gives us a quantitative measurement about the leakiness of a home. When a home levels out at a predetermined depressurization (normally 50 Pascals below the pressure of outside), the rate of air leaking into the home is equal to the rate of air being blown out of the home through the blower door fan. This rate of air, measured in cubic feet per minute, can be converted to determine the air change rate of the home.
A blower door test is one of the most powerful tools in an auditor's arsenal. One of the easiest ways to see the results of a comprehensive home energy project is to compare the pre and post work blower door tests. Properly installed air sealing and insulation should reduce a home's blower door reading significantly, indicating that the home is much less leaky throughout the entire year.\
Call us now to schedule a home energy audit with a blower door test to find out where the leaks in your home are-- and how we can work with you to fix them!
