Hi I’m currently finishing my basement. My basement wall is poured concrete and has 3.5 inches of EPS foam on the interior and 1/2 inch drywall cover. The drywall is literally screwed to the foam. The house is about 10 years old. I don’t see evidence of poly on the wall from the exposed perimeter of the drywall. My best guess is the inspector allowed the foam to be counted as a vapour barrier but as from my understanding EPS foam isn’t a vapour barrier but maybe the perm rating was close enough to be acceptable.
I was originally planning to build a 2×4 wall against the existing wall. Leave it uninsulated and run my electrical through it and drywall it. That way I leave the existing wall untouched. Some friends are telling me I should insulate the new wall and install a poly vapour barrier. I’m not sure if this is the best approach. I’m unsure if the added insulation could effect the wall assembly in a negative way on a building science standpoint. As for the vapour barrier installation I’m a lot more hesitant for retaining moisture and have have a potential double vapour barrier since I’m in a cold climate.
The reason why I’ve wanted to build a 2×4 wall was that I do not want to cut in the existing foam and drywall to run my electrical wires. I was told by electricians that the wire needs to be stapled to something structural every so many feet and I don’t have any proper supporting elements. The only element I would have is the concrete foundation. Anyways it seemed like a lot of work and was significantly more costly that method on a electrical stand-point from the electrical quotes. Installing the electrical on with the 2×4 wall was something I could complete partially if not all on my own and safe significant amount of money.
Any thoughts? Should I just leave the new 2×4 wall and drywall as originally planned? Add the insulation? Add the poly vapour barrier as well? Or simply scrap the 2×4 wall and install the electrical on the existing wall.
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