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Insulating an Unfinished Basement

I have a 5 year old house with an unfinished basement. I would like to insulate it and was hoping someone could give me an idea as how to do it. I used to have wet walls, but since had JES Basements come in and put a system in. Since then, my walls have been dry. I still, however, keep a dehumidifier in the basement. I was planning on framing the basement and then putting insulation. But I keep reading about "vapor barrier". My basement is "below grade". Any help or suggestions would be greatly appreciated. I also wanted to note that the basement walls are cinder block.


Re: Insulating an Unfinished Basement

Seems like the current view is to:
1. insulate along the block wall with rigid foam, adhered with concrete adhesive, and seal joints with builders tape
2. spray foam, or rigid foam with expanding foam in tight spots along rim joist, or batt insulation at least
3. erect walls and drywall with NO vapour barrier (batt insulation can be added between studs as well)

The rigid foam will act as a moisture and temperature barrier from the block walls. A plastic vapour barrier will trap moisture if any, in the cavity between the rigid foam and drywall, leading to mold problems.

This is what I have gleaned from the interwebs, so it is by no means standard practice or code. Do your own research and take it as you will. I am not a contractor or builder, just a DIYer.


Re: Insulating an Unfinished Basement

If there are utilities (ie wiring, plumbing, or HVAC lines) along the wall, you may have to frame in space away from the current walls to access them for inspection and service by code. This varies from area to area so you'll have to check locally.

If nothing otherwise prevents it, just apply 3/4" rigid foam panels over the existing walls, apply furring strips or studding over that, then drywall using moisture-resistant type sheetrock. If you do it this way, all wiring and piping behind the wall will need to be suitably encased (EMT conduit for electrical) to prevent someone from driving a nail into it later on. Maintain at least 1/4" space from all materials except the foam and the floor so that casual moisture cannot wick up into them. Wood, PVC, or preferably vinyl cove base will seal that on finishing. So long as you mind the future servicing details, this is a great DIY project and adds a lot of useable floorspace to a home at minimal cost.


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