How best to insulate the lower level from the upper level, (ceiling/floor joist bays)? Each floor is on separate zone. Lower level is on concrete slab with hot water baseboards. Like to have some sound proofing also.
Do you use faced (paper/foil) batts, unfaced and cover with plastic or not?
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Replies
Mike: This is an easy one. The purpose of foil or plastic is to provide a vapor (moisture) barrier. Unless you expect the moisture content in the upper and lower levels to be significantly different, use only unfaced batts. The exception may be below a bath, that should have a 30# bldg. felt installed between the subflorr layers and on all walls, especially at the tub/shower.
The insulation will help somewhat with sound (airborne only, not impact). You can get addtional sound control by installing double layer of 5/8" or 1/2" gypbd. on the lower level ceiling. This adds weight and reduces the ability of sound waves (essentially pressure or vibrations) to "vibrate" the construction (remember wood is lightweight construction) and transmit sound through the floor-ceiling assembly.
If you have a double layer of plywd on the upper floor, PLEASE, put 30# felt or Rosen paper between the layers. If you don't the squeaks that will eventually develop will make all the other efforts mute.
Hope this helps.
You would get more sound deadening from a denser insulation than fiberglass, like cellulose or spray foam.
Norm and Mike:
I think you are both right and wrong. The heavier material will/may some dead weight, but the looser a material the greater the sound energy absorption. Basically, you want the sound waves to bounce around inside the material and not have the material dense enough so the energy passes through. In fact, sound attenuation fiberglass batts are only 2" thick.
I think another suggestion, in lieu of the double gypbd layer, is to install 1/2" gypbd directly to the rafters, then screw fasten sound attenuation furring (light gage metal "Z" sections) perpendicular to the joists, then apply 5/8" gypbd. This leaves the lower layer floating free of the floor construction. The sound energy then is dissipated by having to "move/vibrate" the heavy layer of gypbd. Of course you'll never see it move unless you have a fireworks display indoors.
The weather is improving so I better get off this discussion and do some work.
Edited 9/17/2004 12:57 pm ET by David
Edited 9/17/2004 12:57 pm ET by David
Thanks guys. This is a remodel of a 50 yo split level so some things are not going to be changed. No plywood floors, T&G pine boards with oak and plenty of squeaks, new bath has felt under mud for tile floor, not under tub.
So I'll have to live with some noise and Ill insulate as Dave recommends. Might have to drop ceiling with hat channel perpendicular to joist which will help.