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Old 04-05-2019, 11:17 AM   #1
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Rim Joist insulation - insect considerations


I've been going back & forth on how to insulate my basement rim joists (Zone 6)

Spray foam vs Rigid XPS w/picture-framed 'loctite foam'

But after a ton of reading on possible offgassing, and being a paranoid dad of 3 little girls that play in the basement all the time I decided to go the XPS route.

Every spring we have sugar ants that find their way and I discovered they come in through micro-openings in my rim joists. I figure insulating will take care of this issue.

Will rigid XPS serve as a good block for insect sealing? Should I picture-frame with canned foam before putting the rigid foam in, then foam again once it's in, to really seal any potential openings up? Or should the rigid foam be pressed tight against the band joist?

Considering I'm in zone 6 should I use 2" rigid foam? How about doubling up, not much extra $ but would I see any benefit to 4"?

Any advice welcome.
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Old 04-05-2019, 12:15 PM   #2
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Re: Rim Joist insulation - insect considerations


Is the framing pretty consistent?



If so, you can cut the foam and tuck in in there and seal with regular caulking.



I would use 2" minimum in your region and I would seal the gaps in the framing before you put in the foam with the same caulking. Make sure it is airtight before you put the foam in.



Be sure to seal the gap between the mudsill and the wall as well.


Foam should be covering in my opinion unless the foam says it can otherwise be left uncovered.
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Old 04-05-2019, 12:32 PM   #3
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Re: Rim Joist insulation - insect considerations


Keeping ants out is hope and a prayer but I would caulk the seams in the wood.

Put 2 layers of 2" foam loosely fit and caulked in place then cover that with a piece of drywall caulked on place. The drywall is to fire protect the foam because in a fire that is dangerous and we always want to cover it.
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Old 04-05-2019, 12:50 PM   #4
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Re: Rim Joist insulation - insect considerations


Thanks gentlemen. I will caulk the seams and sill plate. Any reason why I shouldn't Goodstuff or Loctite foam the pieces in place? This is the technique I see most often on various home improvement sites and youtube videos.
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Old 04-05-2019, 12:51 PM   #5
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Re: Rim Joist insulation - insect considerations


Also - what kind of caulk? 100% Silicone?
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Old 04-05-2019, 01:28 PM   #6
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Re: Rim Joist insulation - insect considerations


Quote:
Originally Posted by MoreCowbell70 View Post
Also - what kind of caulk? 100% Silicone?
Wait for others who have done more of this but I would use Quad
https://www.homedepot.ca/product/lep...5ml/1000671610
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Old 04-06-2019, 09:39 AM   #7
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Re: Rim Joist insulation - insect considerations


No need for anything that expensive like silicone or Quad in my opinion. Quad has some decent off gassing to it as well.



Any latex or acrylic should work fine. Its basically entirely covered so it isn't getting near the work out that any exterior sealant would get.
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