When performing a blower door test the goal is typically to depressurize the thermal envelope so you can either feel or test with smoke or infrared camera , areas of air infiltration or lack of insulation
If one wanted to test the area behind kneewalls in the “cold area” or outside the the thermal envelope for air leakage. Can you simply pressurize the house to force warm air leakage out. Then use the smoke test or infrared camera to identify the problematic areas.
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First, I think you have the basic blower door test procedure wrong in that "the goal is typically to depressurize the thermal envelope". Blower door tests with which I am familiar, pressurize the entire structure and measure the volume of air required to bring the pressure up to a certain point. Leakage is then calculated in ACH or air changes per hour, flow being measured and volume of the house in cubic feet, i.e. CFM x60/house volume = ACH.
To answer your question, yes, during a positive pressure blower door test, you could try to observe specific leaks via smoke or other means. Infrared is very good at identifying large areas and/or problem areas, but not going to be too useful in pinpointing individual leaks.
Tim,
This comes straight from are energy companys website
"The house is depressurized and any leaks (air infiltration) in the home are accounted for through the air being blown out of the door.
By using the volume of the home, the air changes per hour (ACH) is calculated. This number is used, along with the other thermal characteristics of the house, to determine the Energy Rating of the home"
It's also not uncommon to test various rooms individually.
From what others have said who used blower doors on every house, at first they would do a test, go back and seal, and repeat the test to see how they did. Over time it was always the same areas that needed attention so they simply do one test on each house now and the results are generally quite predictable.
Sealing all the standard areas before the test is problably a good idea, and it at least reduces the number of things to focus on after the test.
The Taunton "For Pros" book on insulation and weatherization is a good primer on sealing from top to bottom.
Good luck
Beer was created so carpenters wouldn't rule the world.