Rigid w/ reflective or without in Basement
Jarret
| Posted in Expert Exchange Q&A on
I am building a conditioned basement in Los Angeles. I’m installing rigid on the 12″ foundation walls to keep heated air off the cold concrete. I thought I would use foil faced rigid to accomplish that. However, I’m thinking I’d like some permeability. If moisture does collect on the foundation wall, it should be able to dry to the inside, so in this case I should not use foil faced rigid, right?
Which is the better way to go, foil or no foil?
Fyi, I will also fur off the rigid with 2×6 framing and fill with R-21 batts. The house has a lot of glazing, so California (Title 24) requires it meets robust insulation standards
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Replies
Jarret,
From Martin's blog: https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall
"Does interior basement insulation need to be vapor-permeable? No. The idea that a damp concrete wall should be able to dry towards the interior — in other words, that any insulation on the interior of a basement wall should be vapor-permeable — is mistaken. In fact, you don’t want to encourage any moisture to enter your home. Your concrete wall can stay damp for a century; that dampness won’t hurt the concrete."
Thank you Malcolm. I had remembered reading that somewhere, but could not recall where.