Rigid Foam Basement Insulation in Unfinished Basement – Best Practices
I read the article “How to Insulate a Basement Wall” and “The High Cost of Deep-Energy Retrofits” and just wanted to run my plan across GBA members to make sure I’m not missing anything.
I am in climate Zone 5A and have 3 rooms in my basement. There are two unfinished rooms in the basement with bare concrete walls – a utility room with the furnace and water heater and a large storage room with only 68″ of headroom, but you can stand better between the joists. There is also a finished room in the basement. All 3 rooms are separated by doors.
For my two unfinished rooms, I am planning on:
1) Install 2″ XPS on the concrete with insulation glue and tape the seams and then 2″ Dupont/Dow Thermax polysio with staggered seams on top of that. This should give R-23 and the XPS should do better with my 5A climate zone according to your articles.
2) I’ll keep the insulation 1/2″ off the concrete floor and I’ll fill the gap with Great Stuff foam insulation.
1) Do I need to insulate the interior concrete walls that connect to the exterior walls at a right angle? Or maybe insulate the first 5 feet?
2) Is it okay to sandwich electrical conduit between the insulation and the concrete wall? Or in one case where I have an outlet, should I re-mount the outlet on 4″ of wood that is attached to the concrete so I can insulate all around the wood?
3) Is it worth it to insulate the floor in these unfinished rooms? There are no heat vents in these areas, just heat in the utility room from the actual furnace and the vents running in these rooms. I have minimal headroom in both the unfinished rooms, so I don’t think the traditional rigid foam and sleepers will work. I used Dricore R+ in the finished room, and although it wasn’t cheap, the floors are noticeably warmer with the R-3 on the floor. Any other cheaper options or just skip insulating the floor?
Thank you for your time and help.
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