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Insulating my basement

3K views 9 replies 6 participants last post by  Winchester 
#1 ·
I have a question on how to insulate my basement.

1. whats existing.... house was built 4 yrs ago. Unfinished basement ( This is what I am doing now). they put in by code for Omaha Nebraska 1 inch thermax foam insulation with foild on both sides. I framed the walls 2 X 4.
I have day windows on about 1/2 the house. Meaning that only 3 foot up of the foundation is covered with dirt.... A lot of the foundation is exposed.

2. I bought R-15 FACED insulation. I am at the point of insulation. I am using R-15 vice R-13 Cuz I want to max this out.

3. My question.... Will the Faced insulation be too much? since there is foil on the 1 inch foam thermax? I dont want to get mildew/mold.

Thanks Guys/Gals
 
#3 ·
If you are going to peel off a face, do it to the existing foam board.
Otherwise, I would put up my r-15 with the kraft face toward the living space, then put plastic sheeting over the studs before drywall.
You will want your vapor barrier to be pretty tight to avoid any condensation on the foam.
Don't peel the face on the new r-15 insulation, your vapor barrier needs to be at the living space, not in the middle of the wall. The humidity that the vapor barrier is stopping comes from the living space, the cold where it condenses comes from outside.
 
#4 ·
You say this is 2x4 construction? Do they make R-15 in fiberglass batts that fit in the cavity of a 2x4 wall? Or are you going to let it expand outward a bit? I was under the impression that R-13 was the highest (in fiberglass batts) you could go to still fit inside the 3.5" cavity. Always thought that compressing insulation only negatively effected the R value.
 
#7 ·
The foil is used to reflect radiant heat back into the living space as well as a fire retardant!
The ideal solution would be remove the thermax! Frame the walls, observing fire block requirements. Insulate between the studs, with unfaced insulation. Then fasten the thermax to the studs. Then, cover the thermax with drywall!
 
#8 ·
As per the OP, it was done for code for an unfinished basement and doubtfully to reflect heat back into the living space. I would not remove the thermax. It was either bonded with an adhesive and/or fastened, it's already in place, paid for, sealed (or should be along all seems) and not to mention, the OP said he already framed the walls (hopefully at least 1" from the thermax). Take back the faced fiberglass or remove the facing and friction fit IMO.
 
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