To Add Insulation or Not?

[AlexG]

Hello All,

I've been following all the posts about basement insulation closely and also read the info from building science about moisture and what to do about it.

First of all this is in a new home with water proofing or dampening barrier and R-10 foam insulation around the outside of the foundation. My lower level is about 2 1/2 in the ground and the basement is a full 8ft basement. I'm starting to work on the family room which is on the lower level.

My question is should I bother adding rigid foam insulation in the lower level family room? If I should be adding insulation, does it matter whether I use the 1 1/2" expanded insulation (is this the styrofoam everybody here speaks of?) or the 1 1/2" extruded insulation? The expanded one has a R-6 while the extruded has a R-7.5. The cost difference is what I'm considering here.

Also, since it is not a full basement, should I still be concerned with moisture and maintain about 1/2" to 1" spacing between the insulation and the concrete block wall if I'm to add insulation?

Thanks,

Alex

[mfarver]

I'm not an expert, but I've usually found unless you are really space constrained, the easiest solution is to build a 2x4 stud wall slighty inset from the block wall (so the studs are not in direct contact with the concrete). The stud wall will be easier to run utilities in, and you can use standard fiberglass batts to insulate (which are generally cheaper than rigid insulation)

Mark

[Wgoodrich]

If you have R10 insulation mounted on the outside of the basement wall you are not required to further insulate the inside walls. If you have a part of a basement wall that is above ground that is not insulated you can glue the styrofoam right to the wall if the outside has no vapor barrier such as purging or tar on the outside. The concern is double vapor barrier trapping moisture. If not waterproofed on that part of the wall above ground then you have no vapor barrier allowing the styrofoam to be placed directly on the wall inside.

Hope this helps

Wg