Hi all,

I have a few quotes on the insulation and drywall for my basement and i have two different opinions on how to do it.

1 quote is for 3 layers of r18 fiberglass in the ceiling, and the other is for 2 layers of roxul in the ceiling.

both quotes are using 5/8" double drywall, channels and clips and green gue in between...

the only difference is the type and amount of layers of insulation....

i HAVE read the other posts and im still not sure. the fiberglass way is cheaper however....

please help

Go with fiberglass.

Why three layers though? How deep are your joists? For most applications a single layer of r-19 would work. The FG should not be compressed.

my joists are 16" deep.

one guy said that 2 layers of roxall is better and another said that 3 layers of fiberglass is better, as it fills the whole cavity (not compressed) 4" + 4" + 4" (4" left over)

I'm sure Ted or someone will chime in with the data, but it's my understanding that all you really need is the one layer assuming DD/GG. The incremental dB reduction is negligible given the cost of multiple layers or using mineral wool.

Cathan is exactly right. Test data shows that a ceiling cavity filled with more than simple R19 fiberglass will not see any practical improvement. Hard data.