What is the best insulation for concrete block foundation wall and basement stud wall system?
My daughter has a 1954 storey and a half house with a concrete block wall foundation. I have a 1975 home with a block wall foundation. Both of us want to insuate the basement walls. She wants to spray foam the rin joists and apply 2" of foam on the walls with the stud wall being installed 1" from the block wall. However I am concerned that concrete block needs to breath, based on what I have read on this site, and that the temperature of the block will now be colder with the insulation on it and will cause damage to the block and morter. How should these walls be insulated. Is a gap required under the sill plate to let moisture out and prevent rot of sill plate ( proposed sill plate is pressure treated wood.)
Choosing the best way to Insulate the interior of a CMU or block foundation is not as simple as with poured foudations as they are only held together but the mortar between blocks, so they are not nearly as strong as a poured concrete foundation.
So right off the bat I would say if she is able to, insulating the exterior of block foundations is a much better and safer route. Insulating the interior will subject the block wall to the freeze and thaw cycles if you're in a cold climate. We are happy to help, but a lot of your questions are already answered on this page about the best way to insulate a block foundation and the risks, so read that and the links in it first and if you have more questions let us know, but also let us know where you are or what climate zone you are in as that makes a big difference.
I am in Sarnia Ontario, which is I believe zone 5. Installing insulation on the outside of my daughter,s house is not possible with a concrete driveway up to the side wall of the house and similar construction on the back of the house.