Hi everyone. I am preparing to insulate my basement walls and rim joist. I am located in southern Maine along the coast, zone 6a. I have a general plan and looking for advice/inputs and a few specific questions. My house was built in 96/97 and has 7' poured concrete walls. There are pink batts in the rim joist. I plan on eventually finishing most of the basement but unlikely ill go to the perimeter so I can leave walkways around the finished space to access mechanicals, electrical panels, drain pipes, storage areas and a small workshape. I'll still be able to have a sizeable finished space in the interior section of the basement with this approach and reduces the number of ceiling adjustments I would otherwise need to make to account for pipes etc.. My plan is to use 4'x8' sheets of foil faced polysiso cut down to 7' on a table saw. The remaining 1' sections can be used for the rim jost. I was going to start with the rim joist by cutting sections slightly smaller than each opening then spray foaming the perimeter to hold it in place. After the rim joist, I was going to move onto the walls. For the walls I was planning on using a caulk/adhesive in vertical lengths along the board and then use a plastic washer and 3 1/4" tapcon screw. I will use 4 washer/screws per 4x8 sheet to hold it in place while the caulk sets up. I was going to use aluminum faced tape to seal the seams and over each washer. Does this approach sound reasonable? I keep reading myself in circles about what to use XPS, EPS, Polyiso as well as variations on many other things. I have an oil tank, oil furnace and hybrid hot water tank in the basement. Basement is very dry with no water intrusion. Here are some specific questions: 1. for glue, i was looking at loctite power grab but ive seen lots of mentions of PLA300. What should i use for foil faced polyiso attaching to poured concrete with ridges from the forms and other imperfections? 2. is aluminum face tape ok to seal the seams? 3. do i need to leave a gap or have a barrier at the bottom of each foam board between the bottom and slab? can i leave each piece a 1/2" short and spray foam that seam along the bottom? 4. does that 4 washer/tapcon with glue sound reasonable? 5. Do i need to insulate the sill plate itself or just the rim joist cavities? 6. for the rim joist that runs parallel to the floor joists, should I just glue and screw with washer lengths of rigid foam board cut to the correct height? 7. my basement stairs are against a concrete wall, how do I handle that section? just do above and below the step? 8. my electrical panel is mounted to a 4x4 piece of plywood. Just go around that area with foam board? Do i need to tape or foam the perimeter of the plywood and foam board? 9. there are 3 basement windows, do i need to do anything specific around those with respect to the foam board or just go right up and around all of them? 10. I have a regular interior door going out to the bulkhead. I was going to attach 2 pieces of foam board to the exterior side of that door in the bulkhead area. anything special i need to consider there.

I like simple and efficient. In my past career as an insulation installer I did several jobs like this. Use full height boards. From the floor to the bottom of the sub floor. For get the seam tape and glue.
Use one componet foam on the seams and floor where the board rest. This be enough to hold the board in place. The goal is to have a completely insulated wall. Since you have concrete where the snap ties were this will work better. Plus the glue probably won't stick to the aluminum face. Electrical boxes and such will have to be cut around. You can't cover every thing. Put screws in the top plate and 2 in the field, it will save time drilling the concrete. Hope this helps.

poly iso and xps styrofoam’s R-value diminishes over time.Not a good idea ! Use closed cell styrofoam.instead. You will also be able to seal joints and around electrical boxes etc with rips spray foam much easier to install! There is a new drywall you might also consider using a new type of drywall made of sulfate magnesium oxide. The drywall is ihigh impact resistant ( don’t recommend you kick or hit the wall when loosing your temper least you wanna take a trip to the hospital… LOL). Water resistant, mold and mildew resistant, it has sound proofing qualities, excellent fire resistance , is considered a green building material, carbon negative, and screws and nails in the material will not rust because of the material. Used in conjunction with steel stud framing on internal walls you don’t even need to remove the drywall should the basement get flooded!’

Posted By drclaw on 03 Jan 2024 12:15 AM
Hi everyone. I am preparing to insulate my basement walls and rim joist. I am located in southern Maine along the coast, zone 6a. I have a general plan and looking for advice/inputs and a few specific questions. My house was built in 96/97 and has 7' poured concrete walls. There are pink batts in the rim joist. I plan on eventually finishing most of the basement but unlikely ill go to the perimeter so I can leave walkways around the finished space to access mechanicals, electrical panels, drain pipes, storage areas and a small workshape. I'll still be able to have a sizeable finished space in the interior section of the basement with this approach and reduces the number of ceiling adjustments I would otherwise need to make to account for pipes etc.. My plan is to use 4'x8' sheets of foil faced polysiso cut down to 7' on a table saw. The remaining 1' sections can be used for the rim jost. I was going to start with the rim joist by cutting sections slightly smaller than each opening then spray foaming the perimeter to hold it in place. After the rim joist, I was going to move onto the walls. For the walls I was planning on using a caulk/adhesive in vertical lengths along the board and then use a plastic washer and 3 1/4" tapcon screw. I will use 4 washer/screws per 4x8 sheet to hold it in place while the caulk sets up. I was going to use aluminum faced tape to seal the seams and over each washer. Does this approach sound reasonable? I keep reading myself in circles about what to use XPS, EPS, Polyiso as well as variations on many other things. I have an oil tank, oil furnace and hybrid hot water tank in the basement. Basement is very dry with no water intrusion. Here are some specific questions: 1. for glue, i was looking at loctite power grab but ive seen lots of mentions of PLA300. What should i use for foil faced polyiso attaching to poured concrete with ridges from the forms and other imperfections? 2. is aluminum face tape ok to seal the seams? 3. do i need to leave a gap or have a barrier at the bottom of each foam board between the bottom and slab? can i leave each piece a 1/2" short and spray foam that seam along the bottom? 4. does that 4 washer/tapcon with glue sound reasonable? 5. Do i need to insulate the sill plate itself or just the rim joist cavities? 6. for the rim joist that runs parallel to the floor joists, should I just glue and screw with washer lengths of rigid foam board cut to the correct height? 7. my basement stairs are against a concrete wall, how do I handle that section? just do above and below the step? 8. my electrical panel is mounted to a 4x4 piece of plywood. Just go around that area with foam board? Do i need to tape or foam the perimeter of the plywood and foam board? 9. there are 3 basement windows, do i need to do anything specific around those with respect to the foam board or just go right up and around all of them? 10. I have a regular interior door going out to the bulkhead. I was going to attach 2 pieces of foam board to the exterior side of that door in the bulkhead area. anything special i need to consider there.

For attaching the foil-faced polyiso to your concrete, both Loctite Power Grab and PLA300 are good options. They’ll stick well, but if you want a bit more flexibility, PLA300 might be a better choice. As for the aluminum tape, it's totally fine for sealing seams as long as you press it down well and get a good bond. I’d recommend leaving a small gap at the bottom of the foam board, maybe around half an inch, and spray foaming that seam to make sure everything’s sealed tight. The 4 washers and tapcon screws with glue sounds like a good plan to keep everything in place while the adhesive sets. For insulation, it’s definitely worth insulating both the sill plate and the rim joist cavities for better energy efficiency. When you're working on the rim joist running parallel to the floor joists, just make sure the foam is cut to the right height and then glue and screw it into place. For your basement stairs, you can insulate above and below them, just make sure you’re sealing the edges so everything stays tight. When you’re around the electrical panel, just be sure not to cover any electrical components, but a little foam around the edges should be fine. For the windows, I’d suggest going right up to the frame with the foam board, but leave a little space for any trim or for expansion. As for the bulkhead door, putting foam board on the exterior side is a great idea! Just seal the edges to make sure no air gets in.