How do I prepare for a blower door test in new construction?
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I’m interested in doing a blower door test on my new construction house.
I have read some of the articles on here about blower door testing, and most appear to focus on existing construction.
One article said to preform the test on new construction after insulation, but before drywall.
In the typical insulation / drywall progression, wouldn’t the walls be insulated, then everything drywalled (including the ceiling), and then ceiling insulation laid on top of the ceiling drywall?
It seems like ceiling drywall would need to be installed prior to doing a blower door test, and then have the drywall guys come back to do the walls.
Is this correct?
The only other alternative I could see to this would be stapling up a vapor barrier to the underside of the ceiling trusses and then running the blower door.
Neither option seems ideal.
Either I would need to hire drywall guys to do their job in stages, or I would need to rely on staple ridden vapor barrier that could potentially be ripped from the ceiling during a blower test (is this even possible?).
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Replies
Since you are measuring air tightness, your air barrier, wherever and whatever it is, needs to be in place. If your ceiling drywall is your air barrier, then it needs to be in place.
You want to be able to use the test to find and fix any leaks.
The test must be done prior to insulation, so you can easily find and repair the leaks. Be prepared to spend a few hours looking, and if you don't get the number you want, rent a fog machine and get that going; you'll see the leaks. Leaks around windows are common, so they should be foamed ahead of time.
Adam,
Another GBA reader, Lawrence Martin, just posted a nearly identical question on a blog page (Ten Common Mistakes Made By New Home Builders). Here's how I answered Lawrence's question:
The scheduling of the blower-door test depends on the air barrier details. At a minimum, you'll need to have your primary air barrier installed (including your ceiling air barrier or roof air barrier) and your windows and doors in place before you can perform the blower-door test.
In a house where the primary air barrier is at the sheathing layer (including the roof sheathing), the blower-door test can usually be performed before any drywalling.
If the ceiling drywall will be the primary air barrier, then of course the ceiling drywall needs to be installed and taped before the blower-door test can be performed.
For more information on these issues, see Blower Door Basics.