Removing stapled kraft-faced fiberglass batts
BuildingNewb
| Posted in General Questions on
I have an attic with Kraft Faced Fiberglass Batts that are stapled between the joists. I’m looking to air seal the attic floor but this will entail ripping the kraft facing in order to remove them.
Am I better off leaving it alone and not ripping the paper (I know it acts as a vapor retarder) or does it not really matter if I rip the paper where it’s stapled and then just place the batts back in between the joists after air sealing?
Thanks for the input!
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Replies
Building Newb,
If I were you, I would remove the batts and the kraft facing as best I could, tearing where necessary, and would replaced the (somewhat damaged) batts after air sealing work is completed. I wouldn't worry too much about damaged kraft paper -- the attic will still perform well.
Thanks for your help. Also, is it dangerous to seal the top plate on exterior walls? I worry about warm, moist air getting trapped in the exterior wall cavities and unable to vent up into the attic.
Building Newb,
Sealing air leaks is always good. You don't want warm moist air to escape -- you want it to stay right where it is.
I was just worried that the warm, moist air in the exterior walls would build up and eventually condense on the sheathing. Maybe I don't understand the building science well enough.
Building Newb,
You're correct that you don't want warm, moist interior air to contact cold sheathing. The way to prevent that from happening is to seal air leaks -- including air leaks at the top of your wall.
If your wall is leaky, you'll have streams of air moving through the wall. When warm moist air hits cold wall sheathing or enters your attic, you can get condensation or moisture accumulation. So nip the problem in the bud by sealing those air leaks.
What Martin said. If you leave the top plate leaky the convecting air moving through will keep replenishing the cavity with moist air being drawn from the conditioned interior, depositing orders of magnitude more moisture in the leaky wall cavity than it would otherwise. By blocking the leak at the top, it slows the rate of air-transported moisture.