Blower Door Test
We performed the initial pre drywall blower door test last Friday. The blower door test is a big part of the energuide rating system, which in turn is a requirement under Built Green Canada.
What’s a blower door test?
The best way to describe it is that you basically put a big fan in the door, one that is hooked up to a computer, close all the windows and suck the air out of the house. You have a pressure gauge inside, and one outside. Once the pressure difference is 50 Pascals, you measure the amount of air passing through the fan.
What does that tell you?
If you add up all the little holes in the envelope of the house, you get what is called an equivalent leakage area, which can be anywhere from the size of a 4” pipe to a hole that is 4 square feet. Compare that leakage area with the total volume of the house and it tells you how many air changes you get per hour.
What’s the big deal with air leakage?
When you have warm, moist air going through wall and roof assemblies, you have the potential for condensation, mold and of course heat loss. In fact, air leakage is anywhere from 50 to 100 times more significant in terms of heat loss and moisture problems than heat loss and vapour movement through the materials of your wall and roof assemblies.
An average house built to today’s building code standards will get you about 5 air changes per hour at 50 pascals of pressure difference. Our initial, pre drywall test results were 0.85 air changes per hour at 50 pascals. My energy advisor, Jerry Sawkins thinks we should be at 0.6 for the final blower door test. The pre drywall blower door test reveals a lot about the house and most people find it quite enlightening.