I often get requests for a Blower door test, or “what is the Blower door?” In short it’s a fan that temporarily mounts usually in the front door of the house. This fan will usually depressurize your home to a specific point. Don’t worry; it won’t pop your ears. I am told that pets are sensitive to the pressure changes but I have found that not to be true at least yet. If you open a door or window slightly you will get a gush of air rapidly coming in to equalize the pressure differences.
In simple terms taken from Wikipedia, this is what they say,
“A blower door is a machine used to measure the air tightness of buildings. It can also be used to measure airflow between building zones, to test duct work air tightness and to help physically locate air leakage sites in the building envelope.
There are three primary components to a blower door: (1) a calibrated, variable-speed fan, capable of inducing a range of airflows sufficient to pressurize and depressurize a variety of building sizes, (2) a pressure measurement instrument, called a manometer, to simultaneously measure the pressure differential induced across the face of the fan and across the building envelope, as a result of fan airflow, and (3) a mounting system, used to mount the fan in a building opening, such as a door or a window.”
So what’s the deal about the pressure change?
The deal is if the house is depressurized below the outside pressure, air will try to leak in to stabilize the pressure differences. This is how we find out how leaky(heat escaping or cold air coming in) a house is. Coupled with that air infiltration, a thermal camera can more effectively find those leakage areas. Additional tests, called Zonal Tests can help test room by room which is the leakiest. Often used going from bedroom to bedroom or from the basement to the first floor. Sometimes a house can leak so much that the pressure we seek to achieve cannot be reached. These drafty homes are the homes in dire need of tightening up. Tightening up the home will have a positive effect on both heating in the winter, and cooling in the summer, thereby reducing your energy costs.
So don’t be afraid of a blower door, they are a really cool tool and an energy audit of any kind needs a blower door test.