Insulation and vapor management for walls against earth
Background: I have cement walls for a walkout basement and concrete slab on grade floor and I am trying to insulate without trapping moisture. I would like vapor permeable insulation and am trying to figure out how to both trap vapor from the outside earth outside, and prevent heat of the inside conditioned space from meeting the cold exterior surfaces. There is exterior drainage and some rigid foam outside the house protecting it but I once say wetness at the base of one wall. The floors are dry.
Floor: I don’t want to have a vapor impermeable strate that, while protecting the flooring could create a greenhouse effect for rising vapor. Im am considering 1/4 inch rigid insulation with parallel slits cut into it to allow breathability, and no plastic sheeting. Then flooring on that, or boards and then flooring on them.
Walls: a contractor wants to put rigid against the concrete wall against the earth and seal with spray foam to protect from having warm conditioned air touching the cold cement. I don’t want to trap moisture that could possibly seep in from the foundation into the walls. So Im thinking of build the framing out from the walls a few inches and sealing the back of it with rigid and using batts between framing 2x4s.
For both walls and floor im considering using a sealant but I understand these decay.
Please give me your best formula to address both problems of need to keep warm air from hitting cold exterior surfaces, and needing to allow inward vapor to breath without being trapped.
Also is there a hard flooring that is more breathable than ceramic tile?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part