Insulation

basement insulation on top half-frost line

Anonymous user 05/03/2026 - 2:20 PM

Dear experts, I am on a project to finish my basement by myself. My basement has the pink insulation with poly on the top half, above grade and nothing on bottom half. Existing insulation is looks okay and I really don’t want to rip it off to install new full insulation. My plan is to cover bottom half with rigid foam board, seal it all around with low expansion spray foam. Also spray foam where rigid foam meets the existing insulation. Then install 2x4 on top of it and maybe optionally fill the frame cavity with wool batt up from floor to existing insulation level. No poly! do you think it is a good solution? Appreciate your comments.

Insulation Police Ltd

Rating: 4.9 out of 5

4.9/5124 reviews

Edmonton

Fiberglass is an air filter the same as Rocksul batts. They are both conductors and allow cold and warm to touch.Styrofoam has a true field R value but it is only as good as its smallest crack where the cold gets behind it. If you seal the styrofoam with the foam cans 100% you will be fine. I put a life time gaurantee on my work so i only trust spray foam and cellulose injected tight because of the perfect fit and density. They both have a hollow cell which creates is own vapor barrier. They have a true field R value. I hope this helps

Answered7 March 2026

Like

1

---