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Wall buildup & resonance question
http://www.johnlsayers.com/phpBB2/viewtopic.php?f=2&t=21862
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Author:  buckotouring [ Sat Jan 26, 2019 1:37 am ]
Post subject:  Wall buildup & resonance question

Hello folks.

Wonderful resource here, every day a school day! I'm hoping to answer a question regarding my studio build. It's a two-room setup in an existing shed/outbuilding. Control room to be 3.6m x 5.1m and Live Room to be 6.1m x 5.1m. The sloped ceiling in both rooms will run from 2.4m at one end to 2.7m at the other. Here's a quick cross section of the wall and ceiling buildup:

Image

My question is this: Is the RWA45 (45kg/m3) in the walls going to dampen the resonance of the PIR Foam insulation (I can't find density info on this) and the plasterboard, or will this build-up cause me headaches down the line/turn my rooms into giant horrid-sounding floor toms??

The reason for this buildup, by the way, is because of U-values. If I wanted to hit the thermal insulation target with just RWA45, I would need almost 200mm, and my studs are only 100mm deep. I know that PIR has no useful acoustical properties, but in this situation, its use is purely thermal and space-saving. But will it do me any harm acoustically? My hope is that because it's rather light, that sound will pass right through it. However, this could also mean that the plasterboard has little dampening applied to it.

I'd love to hear some opinions on this, especially if anyone has any experience using a room with similar walls (insulated plasterboard fixed to battens etc.)

Many thanks in advance, and let me know if you need more detail.

R

Author:  Soundman2020 [ Sat Jan 26, 2019 3:24 am ]
Post subject:  Re: Wall buildup & resonance question

Quote:
I would need almost 200mm, and my studs are only 100mm deep.
Yet you show an empty cavity labeled "220 mm ventilated air gap", which would be just the right size to put an extra 200mm of insulation in that wall... :) Why do you not want to use that air gap for insulation?

- Stuart -

Author:  buckotouring [ Mon Feb 11, 2019 7:19 am ]
Post subject:  Re: Wall buildup & resonance question

Stuart, thanks for the reply.

Quote:
Why do you not want to use that air gap for insulation?


I did consider this, but shied away for two reasons -
1. Cost. 200mm RWA45 would cost a full €1000 more than my design in the image above, and
2. With the insulation protruding into the cavity 100mm beyond the studs, keeping it all in place would be a challenge, particularly considering RWA45 only come is 100mm thickness maximum. I can't find impaling clips that long...

Author:  buckotouring [ Tue Feb 19, 2019 5:47 am ]
Post subject:  Re: Wall buildup & resonance question

Anyone any more thoughts on this? Hoping to get my insulation order in this week...

TIA

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