I am finishing out a basement. The floor of the upstairs is insulated with R-11. I have lowered the ceiling downstairs to 9 feet in most of the area and to 8 feet in the area below the upstairs plumbing(to allow a crawl space to access the plumbing) The space between the floors will then be 2 feet and three feet respectively. I have studded the ceiling out and am putting up 3/8" sheetrock. Is it necessary to put insulation in the ceiling of the downstairs since the floor of the upstairs is insulated? Thanks for your help.

Welcome Howie

Usually don't insulate between heated areas. If using for sound proofing, use unfoiled insulation.

Would also think about using 1/2'' s/r. 3/8'' s/r is usually used as a backer for paneling.

Over time the 3/8 s/r may become wavy between studding.

Chuck

Thank you Chuck. I will increase the 3/8 to 1/2 per your advisement. With the insulation already in the floor of the area above and using 1/2" sheet rock on the ceiling, would you think that would be decent sound proofing between the two floors? Also... I have insulated between the studs in the exterior walls using R-13 with vapor barrier. Should the walls in the space between the two floors be insulated. Right now it is bare cinderblock. Thanks again.

All outside walls should be insulated. This will help with heating and inhibit moisture transfer. If u leave these spaces without insulation, u could get condensation.

Chuck

I can not tell from your post, but the basement floor ought to be insulated if you can, otherwise, you will loose a surprising amount of heat through the floor and you can have condensation form between the slab and any floor finish that you are putting down.

Planning on putting down floating floor with the foam underlayment.Will this qualify as inulating or should I put something down prior to that?

Hey Chuck or Leif,

If I put pink foambaord insulation on the outside walls between the two floors, does it also have to be covered with a vapor barrier or some other material? Thanks.

All outside wall insulation needs a vapor barrier on the warm side, even foam. I'd go so far as to lay foam board down on the floor, tape it and then install your floating floor.