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Air Sealing Attic

pmsmith2032's Avatar

Join Date: Sep 2013
Posts: 20

08-16-16, 06:36 AM   #1  
Air Sealing Attic

Any tips on how to air seal the attic? Has anyone tackled a project like this after the attic is already insulated (12-18" of loose fill insulation)? I could suck up old insulation with a shop vac but I would imagine this would take forever and I'm not sure insulation can be reused.

Is Great Stuff the best product to use to seal the air leaks?

Is there a good way to navigate in the attic? I tried this once before using 2'x8' strips of plywood but had issues. I had a hard time laying the plywood flat with the insulation over the joists and pipes and ducting "hidden" under the insulation.


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marksr's Avatar
Forum Topic Moderator

Join Date: Mar 2005
Posts: 42,787

08-16-16, 06:49 AM   #2  
The best time to seal any leaks is before the insulation is put down. If you have a good idea of where the air leaks are you could 'rake' the insulation away from that area, seal the voids and put the insulation back.

No easy way to navigate an attic. If you aren't adept at walking/setting on the top of the joists you need to use plywood/lumber to span the joists. You should be able to feel any duct work or other obstructions prior to putting much weight on the board.

retired painter/contractor avid DIYer

Tony P.'s Avatar

Join Date: Jan 2015
Posts: 422

08-16-16, 07:11 AM   #3  
I sealed my attic and can't imagine doing it properly after blown insulation is applied. In fact, my suggestion is to focus on those areas where sealing is most important rather than attempting to do the impossible. If you're inclined, get yourself an infrared thermometer and use it to find those places where the temperature difference is greatest and use that to focus.

Alternatively and my preference, is to focus on a few specific areas where sealing is most widely considered worthwhile: probably the attic access point, above lighting fixtures and bathroom vents, around the chimney, and plumbing ventilation. I wouldn't bother with rest of it and I'd leave the blown insulation alone everywhere else. As the doctors say, first do no harm.

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