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In-wall fiberglass insulation question

I am building a small scale studio in the near future. i will be building the stud framing out of 2" x 6"'s to add a bit more space for insulation to dampen the audio from both the inside and out. I am debating if I should use R-19 or R-24 fiberglass insulation for the in wall insulation. I would have gone with spray in, but it doesn't last that well over the long run.

The building total will be 12' x 14' so space is really limited... I just figured that since I wanted to try for the best insulation from noise and heat transferI should go with the extra 2".

What do y'all recommend?


thatjeffguy Mon, 03/15/2010 - 09:36
You will get as much or more sound transmission through the studs than through the air space in between them. Sound will vibrate one wall surface, vibrate the stud, which will vibrate the opposite wall surface.
Since you have allowed for the thickness of a 2" X 6" wall, a good choice would be to build a "staggered stud" wall out of 2" X 4" studs. You alternate, or 'stagger' the studs so that the stud attached to one wall is not attached to the other. Every other stud attaches to alternating wall surfaces. This "acoustically decouples" the wall surfaces from each other. Then fill with fiberglass insulation.
A step up from that would be to construct two separate walls with an airspace between them. Takes up more space, though.
Hope this helps!

somexone75 Mon, 03/15/2010 - 16:12
That makes a really good point. Staggered would be a good start and then if I still need the extra isolation I could do the drywall, z-channel, drywall combo.

For the room inside a room structure do you think I'd be able to do a 1/4" sheet on the studs with a 1/4" z-channel and 3/8" exterior, or do you think I should go 3/8" for all?

thatjeffguy Mon, 03/15/2010 - 19:17
If you go with either a staggered wall or a double wall construction you have already addressed structural sound migration. The Z channel will not contribute that much more.
However, Mass is one factor that will reduce the ability of the wall surface to resonate with any sounds present. This is why it is often recommended to install two layers of 5/8" drywall over the studs. Anything thinner than at least one 5/8" drywall sheet would be asking for trouble.
This is my studied opinion. Others may differ with me. But in my professional studio I have employed both staggered and double wall construction with double layer of 5/8" drywall, and I have no problem with sound migration, either between rooms of to/from the outside.
Keep in mind that sound migration is only half of the challenge... you still need to treat the room for ambient reflections (reverberation). But this is a different topic.
Hope this helps, and good luck with your project!





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