Insulating on Inside of Foundation Walls
This is kind of a follow-up to another post (insulating and sealing rim joist in house with no sill plate) but I thought the two issues were disconnected enough to warrant two discussions.
My (fairly) newly built house (build around 2000) in Atlantic Canada (Zone 6) has a wrapped foundation (brown dimpled membrane) that was installed afterwards to remediate some moisture ingress issues observed after a pretty heavy spring thaw – I don’t know the exact details but that was what was told to me by the past owners. They also improved the drainage around the house when doing this. I can only assume it’s all-good as we had record rainfall this fall and the sump barely ran and I did not observe moisture on the foundation walls (basement was still humid in the summertime though!)
Anyhow, past improvements aside – with the foundation being wrapped with what I assume is a mostly vapour-impermeable membrane, I was not sure if all of the advice on installing a vapour barrier on the inside of the foundation is still applicable.
My main worry if I install a vapour barrier on the interior is that whatever moisture makes it past the exterior barrier might then get trapped in the foundation walls/concrete and without the ability to dry at a reasonable rate and may cause issues with the foundation itself. Is there any logic to that?
Since there doesn’t seem to be any interior basement moisture issues at the moment anymore, I was thinking that I should leave well-enough alone and just use mineral wool board to insulate the exposed foundation walls, allowing any moisture in the concrete to dry to the inside.
I know this would result in condensation forming on the foundation walls when they are cooler due to the insulation, but the mineral wool is not affected by this I understand, and I would think the water would eventually run to the floor and dry. There will also soon be a heat-pump water heater in the room presumably dehumidifying the space (though I don’t want to rely on this, just secondary).
Any thoughts on this?
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