Finished Basement insulation Guidance
I am preparing to finish my basement (Rhode Island – zone 5). It is a walkout basement with poured concrete walls on 3 sides and a framed wall (insulated with batts) on one side).
I have been researching how to properly insulate the poured concrete walls and slab, and have settled on:
– R-6 or greater rigid foam insulation, 2×4 framed wall, mineral wool batts for wall and
– R-6 or greater rigid foam insulation under osb/plywood subfloor on slab floor
I have a few primary questions:
1. It seems that EPS is preferable to XPS for a host of reasons, but most importantly as it doesn’t absorb as much water. Planning to use the R-Tech product from Home Depot (2″ R7.7 – https://www.homedepot.com/p/R-Tech-2-in-x-48-in-x-8-ft-R-7-7-EPS-Rigid-Foam-Board-Insulation-310891/202532856#overlay). Is this ok for both walls and floors?
2. Do I need to put down a layer of 6mm poly under the foam on interior of slab (I’m uncertain as to whether it exists below slab.
3. Are there any special considerations on the above given the fact that it’s a walkout basement?
4. Can I just let the rigid foam and subflooring ‘float’ on the floor?
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Replies
Dean,
1. EPS absorbs and releases water more readily that XPS, but it’s not really an issue on either your walls or floor.
2. You need a continuous vapour-barrier over the slab. The two most common solutions are poly or a dimple matt.
3. No
4. The two most common stack-ups are: one layer of subfloor secured though the foam into the slab, or two layers staggered, glued and screwed, which can float over the foam.
https://www.insofast.com/insofast-products-applications/insofast-interior-applications/interior-uses
This product is specifically designed for basements (walls & floor) plus has an "integrated stud" ...