Most of my unconditioned basement has studded walls with panelling and no insulation which makes it uninhabitable for most of the year. The house was build in the early 50s. The studs are smaller than 2 X 4s. Peeling back a panel I guess there is 2 inches to the poured concrete wall. Keep in mind I rent the home from a family member and maybe I will own it in the future. Therefore I hesitate to go all out in any renovation but want to make in habitable. Here are my questions. Can I insert rigid foam insulation between the studs? Should I install it over the studs? Either way, can I put the panelling over the insulation or is Sheetrock required? Thanks for your advice
You can insert rigid foam between the studs. If you really have 2" there then you can expect anywhere from R-10 to R-12 depending on the type and density of the foam that you use. Overall, this will be the easiest and most cost effective method of getting some insulation in there. This will also be the easiest way of having something to reattach either paneling or drywall as they can go directly on top of the studs or furring strips that are already there.
You can also install your foam over the studs, but this will make it harder to install your interior wall surface. If you went with the 2" between studs as above but wanted more insulation, then you could add a layer of 1/2" or 3/4" rigid foam across both the studs and the inset foam. This could bump your insulation up by another R-3 to R-5.
Or, you can just install the thin layer of foam on top of the studs, without installing the inset 2" thick layer. You would not get as much insulation as you would have your R-3 surface layer and a dead air space. this will help, but not as effective as the solid foam fill.
Even if you install on top of the studs, you can install paneling or drywall directly on top of the foam. However, the thicker the foam layer is on top of the stud surface the greater amount of cushion you will have. This could result is some uneven seams for both paneling or drywall. If it were me, I would not put more than 3/4" of the closed-cell type foam (commonly known as blue board or pink board)on top of the studs. Any screws you use must be long enough to hit the studs as the foam has no grip.
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