okay, i'm buying tommorrow. please help!

[PAPAYAMON]

okay... i have nonsupporting walls. i am starting with a surface of drywall. i drop back from this and put up the 2nd wall.

so this is what i start with :




i'm planning on buying fiberglass.... am i better off with



or with




???


i can move the inner wall where ever i want. i can use 2 layers of r 13, or one layer of r 15 or even unfaced r 30. i'm planning on using the pink stuff and making one big buy of all materials (about $5,000) at home depot in the morning.

it's time to decide .

[PAPAYAMON]

of course, it's considerably cheaper to go with the 2nd option .... solid insulation. but is it going to make a significant difference to go with the 1st option (2 layers of insulation)?

i apologize up front for my crappy drawings! .

[avare]

There is no significant difference in acoustic peformance between the 2. Build which you prefer.

Andre

[PAPAYAMON]

so let's say 1 choose 1 layer of either R 15 or R 30. if i choose the r 30, then i have to have 9 inches in the space between the drywall? is it going to matter which i choose in a significant way? (as we've previously discussed, i'm using the unfaced r-30 on the inside for absorption, though that's a different issue. here i'm just trying to get the best performance from isolation within my walls).

my first inclination (usually wrong) is to stuff the 9 inches of unfaced r-30 in a six inch cavity . heck, i could just build the second wall an inch from the first and use 3 inch r-11 in the cavities. i guess i'm groping for the best thickness of this wall and its insulation.

[avare]

Originally Posted by PAPAYAMON

so let's say 1 choose 1 layer of either R 15 or R 30. if i choose the r 30, then i have to have 9 inches in the space between the drywall? is it going to matter which i choose in a significant way? (as we've previously discussed, i'm using the unfaced r-30 on the inside for absorption, though that's a different issue. here i'm just trying to get the best performance from isolation within my walls).

my first inclination (usually wrong) is to stuff the 9 inches of unfaced r-30 in a six inch cavity . heck, i could just build the second wall an inch from the first and use 3 inch r-11 in the cavities. i guess i'm groping for the best thickness of this wall and its insulation.

As Rod would start, with all due respect, what is your thinking? You posted a clear question with great drawings, that include a definite gap braking any continuous connection between the walls by insulation. This is the right way to do it. No bridging between the walls.

Why are asking about compressing and forming bridges between the layers, after your 2 good ideas were vetted?

Respectfully,
Andre

[PAPAYAMON]

Originally Posted by avare

As Rod would start, with all due respect, what is your thinking? You posted a clear question with great drawings, that include a definite gap braking any continuous connection between the walls by insulation. This is the right way to do it. No bridging between the walls.

Why are asking about compressing and forming bridges between the layers, after your 2 good ideas were vetted?

Respectfully,
Andre

let's forget bridging. i would have guessed you'd shoot that down, and i'm not going to do it....

it is going to matter if i make the wall 6 inches thick with r-15 or 3 1/2 thick with r-11? these walls, by the way, are 28 long x 10 feet high. how much more am i going to get out of a thicker wall? either way, the studs will be 3 1/2 inches thick.

[DrFrankencopter]

Originally Posted by PAPAYAMON

let's forget bridging. i would have guessed you'd shoot that down, and i'm not going to do it....

it is going to matter if i make the wall 6 inches thick with r-15 or 3 1/2 thick with r-11? these walls, by the way, are 28 long x 10 feet high. how much more am i going to get out of a thicker wall? either way, the studs will be 3 1/2 inches thick.

The thicker the wall, the better the low frequency transmission loss will be. If keeping low frequency sounds in & out of your studio matters, then go for the thicker wall.

Cheers

Kris

[PAPAYAMON]

yeah, i'm going with the 6 inches and the r-15, and i'll keep the insulation from touching the outside drywall.. so no coupling.

if i don't get enough isolation, then i'm going to have to green glue the inside and put up another layer of drywall :(.

[DanDan]

Isover UK had a page which showed test results comparing different densities and thickness of insulation in the gap of the stud wall. The page has vanished!
They concluded that there was no advantage to denser fibre and that a full fill was a bit superior to leaving a gap.
Light fibre needs to be supported on wire or netting or such so that it doesn't gradually sag and compress at the bottom. The difference between touching the sides lightly and bridging is not clear to me, sounds like a guess.
Given that and the fact that other research has come to different conclusions I wouldn't sweat this and would base my choice on available materials.


DD

[PAPAYAMON]

well, it's done . that has a major leap forward for me. now to take delivery of all the materials next week. all future posts in my photo diary thread. check it out .

and i did go with the 6 inch insulation .