beginning basement insulation
I will be installing insulation in a finished basement. I lie in NJ. No water in basement. Here’s how I plan to proceed. Please let me know what you think.
Rim joist will get 1" foam board (Owens Corning Foamular F-250 Tongue and Groove Foam) adhered with construction adhesive and spray foamed around edges.
Walls will NOT get a drylock or any other sealant. 1" foam boards (Owens Corning Foamular F-250 Tongue and Groove Foam) will be adhered with construction adhesive. On one wall(as shown in pic) framing is only 1/2" from wall therefore each board will be cut and placed in between each stud and then spray foamed behind stud to fill in vertical gap. On all other walls where boards will butt up against each other, I will use tape to seal. Spray foam will fill any gaps at bottom and top plate and around fire stops.
Any suggestions for specific adheisive?? or tape??
Also, I have seen local utility companies use Polysheild with a foil faced material used in the rim joists. Foil facing interior. Is this recomended?
If anyone has any suggestions they would like to make I am all ears.
Ok so I went to HD to pick up the boards and supplies and one of the associates told me I could use duct tape to seal the joints?? Is that correct??
Yes or Tyvek tape works well.
That being said, I would still caulk/foam the joints personally.
Hi, StCrosby. You’re on the right track – using our foam boards as insulation on the interior side of the concrete block wall is a good approach.
However, I just wanted to point out one area of concern. Ideally, the foam insulation boards should be continuous and not interrupted by the studs in place. The studs interrupting the insulation will provide a “thermal bridge,” which will adversely affect the overall thermal performance of the wall, and could provide a path for water vapor transmission through the stud.
Therefore, my recommendation is to remove the existing wood frame wall and install the foam insulation boards – if possible.
For the adhesive, just be careful to use one that’s compatible with polystyrene foam insulation as some contain solvents that could attack it. Taping the joists with duct tape may not be durable enough. I’d recommend aluminum foil tape, which typically has good adhesion and is vapor impermeable.
Once the wall has been reframed, then you can install un-faced fiberglass insulation.
Insulating the rim joist with a foam sheathing product is a great idea, but that will only pass most fire codes if it has some type of thermal barrier covering it – un-faced R-13 or greater fiberglass insulation will meet this requirement. One more thing – be sure that the top of the foam insulation on your concrete block wall transitions to a horizontal piece of foam insulation that then covers the sill plate and meets with the foam insulation at the rim joist with all of the joints being sealed. This will provide a continuous air, vapor and thermal barrier from the basement floor to the top of the rim joist.
Hope this helps. Just let me know if you have any other questions.
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