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Old 05-08-12, 06:24 PM   #5
S-F
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The fan on a blower door is pretty intense. In fact, if the door isn't installed properly it will suck itself out of the door jamb. That being said, if you can get a powerful enough fan/fans, I recommend pressurizing the house to find air leaks. That way your smoke pen or whatever smoke source you use, will make a B line to the leak. The depressurization is strictly for testing the overall leakiness of a house. For spot testing everyone uses pressurization. You turn the blower door fan around. There are a few exceptions to this rule. Houses generally have the thermal boundary at the sheathing except in the attic which uses an airtight drywall approach. In this case you would depressurize the house and test for ceiling leaks from up in the attic to see the smoke scoot down into the house. Once more exception is when it's bitter cold out and you can use an IR camera to see the cold air being sucked in. That's pretty cool.
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S-F: "What happens when you slam the door on a really tight house? Do the basement windows blow out?"

Green Building Guru: "You can't slam the door on a really tight house. You have to work to pull it shut."
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