Cavity filling question

Hi everyone! I`m buying mineral wool for the cavity behind mi walls. I have 2 options... 1) 70mm 35Kg/M mineral wool-------17(arg$) M2 2) 50mm 60Kg/M mineral wool-------27(arg$) M2 I know the heavier the best, but I prefer save some bucks for a 3º layer of gypsumboard, so... is it very important the density of wool between my walls? since it's just for reducing resonance inside the cavity. is 70mm 35kg/m and 3 layers of gypsum ok? or shoul I use 50mm 60kg/m and 2 layers of gypsum? Thanks everyone. and again... sorry for my english I'll post some pics of my studio as soon as I can start building

JTZ wrote:

Hi everyone! I`m buying mineral wool for the cavity behind mi walls. I have 2 options... 1) 70mm 35Kg/M mineral wool-------17(arg$) M2 2) 50mm 60Kg/M mineral wool-------27(arg$) M2 I know the heavier the best, but I prefer save some bucks for a 3º layer of gypsumboard, so... is it very important the density of wool between my walls? since it's just for reducing resonance inside the cavity. is 70mm 35kg/m and 3 layers of gypsum ok? or shoul I use 50mm 60kg/m and 2 layers of gypsum? Thanks everyone. and again... sorry for my english I'll post some pics of my studio as soon as I can start building

If i understand you correct, you are putting the mineral wool inside the cavity and the gypsum as your inner wall covering? Kinda unclear... but the density of gypsum is much greater than mineral wool batts my friend, if you are just planning on putting in the mineral fiber. I don't know the exact specs, but i think just one layer of gypsum would be like 50 times heavier than any insulation material. The purpose of putting the layers of drywall, osb, or plywood between the studs is to beef up your 2 leaf (outer) for low freq. Just putting mineral wool up against traditional construction would not be enough to keep the bass levels down. THe mineral wool also can be replaced with the regular unfaced "pink" insulation which is cheaper than mineral wool...for inside the studs of your interior/exterior 2 leaf system. If you are putting gypsum in between the studs, you can go with 2 or 3 layers of it depending on the rest of the existing construction outer wall. Mine is 1.5" of stucco, which is quite thick and i'm only using a layer of OSB and gypsum. If your outer leaf is weaker, use more.

I believe he meant in the cavity, then covering with 2 or 3 layers of gypsum.

THe mineral wool also can be replaced with the regular unfaced "pink" insulation which is cheaper than mineral wool...for inside the studs of your interior/exterior 2 leaf system.

+1 Which means, of the two choices you've mentioned, go with the cheaper.