double up on rigid fiberglass?

S

sproutrecording

New member
what is more effective? one sheet of 2" rigid fiberglass with a 2" airspace from the wall, or 4" (two 2" sheets) of rigid fiberglass against the wall? i've completed the room treatment in our studio, and we ended up having about 15 sheets of 2" rigid fiberglass leftover. the majority of the treatments are broadband absorbers: 1x4 frames, with 2" thick of insulation and then about 2" air then the wall.. would it be beneficial to put a second sheet of insulation behind the first sheet on these units? It would double the thickness of the insulation, but take away the air-space. What would this do to the bandwidth and the amount of absorption?
 
sproutrecording said:
what is more effective? one sheet of 2" rigid fiberglass with a 2" airspace from the wall, or 4" (two 2" sheets) of rigid fiberglass against the wall?
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Four inches is better, but only a little. Since air is free, 2+2 is usually recommended.

> What would this do to the bandwidth and the amount of absorption? <

See the section Optimizing the air gap in my Acoustics FAQ:

http://www.ethanwiner.com/acoustics.html

--Ethan
 
so for now, i'm going to go with 4" and no air-space. partly to optimize the material we do have, and partly to hide all those extra pieces of unwrapped 703. down the road it looks like i'll have to re-build a lot of the frames with 1x6 or 1x8's. Thanks Ethan!
 
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