Insulation options for half-height basement foundation

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wetcoast
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Joined: Tue Jul 02, 2019 9:31 pm

Insulation options for half-height basement foundation

Post by wetcoast » Tue Jul 02, 2019 9:54 pm

Hey everyone. I'm working on remodeling my 1984 basement. The house sits on a hill, so the basement foundation is half-height in the front, and full height in the back. The foundation is uninsulated (concrete touches the earth). I'm on the west coast of Canada (near Vancouver) so it doesn't really get cold (very rarely below freezing) but it's wet outside during winter.

The builder stuck some drywall in front of the concrete without insulation to provide a "finished" look. No insulation, just an air gap around 1". The plan is add a bit of insulation and fully cover the foundation with drywall. Attached is a photo of the foundation on the inside.

I've been watching a lot of Shannon's videos, but I'm struggling with the best insulation option for my project. I am thinking 1-1.5" rigid foam box around the concrete (secured using plastic anchors) followed by 2x2 framing or strapping then mold-resistant drywall. Maybe even a bit more foam within the framing if I go with the 2x2. I like the character and function of a half-height ledge, but don't want the ledge to stick out too far, hence why I don't want to go with 2x4.

Do I need a vapor barrier before the drywall? How do I protect against mold between the concrete and the foam? I've read a lot of contradictory information online and could use some help.

Thanks
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Shannon
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Re: Insulation options for half-height basement foundation

Post by Shannon » Wed Jul 03, 2019 6:52 am

Well your first step will be to see what your local building code office will allow as far as foam and vapour barrier. Some areas will allow no vapour barrier if you use 2" or more of foam ,some will require it . So check with them first.
As far as mould between the foam and concrete you should have no issues with that.
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wetcoast
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Joined: Tue Jul 02, 2019 9:31 pm

Re: Insulation options for half-height basement foundation

Post by wetcoast » Thu Jul 04, 2019 1:54 am

Thanks Shannon. I'm in climate zone 4 (Victoria, BC). From what I've read, 2" XPS should be acceptable. No mention of a vapor barrier.

I've attached an illustration of my plan so far. 2" XPS next to concrete (spray foam used to seal around gaps), followed by 1x3" strapping screwed through the foam into concrete (or glued?), then mold-resistant drywall. Does this sound reasonable? Anything you would improve upon? Thanks.
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Shannon
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Re: Insulation options for half-height basement foundation

Post by Shannon » Thu Jul 04, 2019 6:44 am

Nope, looks like you have it correct. Good luck!
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wetcoast
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Re: Insulation options for half-height basement foundation

Post by wetcoast » Thu Jul 04, 2019 11:36 pm

Awesome, thanks Shannon.

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