Polystyrene for insulation

Hi I am new to this forum but have been reading it for a while now and find it unbelieveably useful! My question is :- Is polystyrene sheets approx 2" thick any good for acoustic insulation within a stud wall, I'm building a small studio just for my own use and wondered what material would be best for both sound and heat insulation. BTW I am meaning sound isolation, I am not going to be using the room for drums mainly for monitoring and recording some live guitar. Thanks.

No. Polystyrene is closed cell insulation, fine for heat but SUCKS for sound, either inside a wall or outside. You want nearly anything that has the word "wool" in it - rockwool, mineral wool, sheep wool, fiberglass wool, rigid fiberglass, slagwool, etc - inside a wall you want UNDER 3 pounds per cubic foot density, or (metric) 48 kG/m^3. If you can't BLOW through it, throw it away... Steve

Wow I knew this was the right place to post! Thanks for the advice :-) I'll stick to the wooly stuff then, I'll also check on the density when shopping around.

If you can follow the very top link in the forum, including the part about editing your profile to include a location, we may be able to help with things like availability of materials... Steve

Thanks steve, I've just updated my profile must have missed that when signing up. I'll search the site for brand names in the UK for types/brands of insulation but if you know of any of the top of your head then please suggest away. Any help is much appreciated.

Yan, welcome -not to hijack your thread but I have another question about polystyrene, you may like to know the answer to as well. Would Polystyrene or (EPS expanded polystyrene) be a spring in construction, it's a closed cell foam so would this be a soft layer in a leaf, of a spring? I ask this because the american ingenuity domes, i was considering have pre-built panels with EPS in between concrete and gypsum wallboard.

It would be considered more of a "wimpy mass" -- i.e., a solid in the sense that air doesn't pass through it, and since it's firmly connected to the other materials and most likely not compressed the "ideal" amount so as to form a spring, it pretty much increases the thickness of the outer leaf without increasing attenuation any noticable amount. That's just a guess, of course, since there probably aren't any published specifications or tests on it in this regard. --Keith :mrgreen:

pre-built panels with EPS in between concrete and gypsum wallboard. This would be considered a single leaf of mass for isolation purposes - and Keith's comments are good; the EPS shouldn't HURT anything, but won't add any noticeable mass to the leaf. You could assume the same effectiveness as using just the concrete and gypsum as far as sound isolation is concerned, and should be really close... Steve

I would like to add. When I built my vocal booth (before knowing about this place) I used 2 layers of 3/4 inch polystyrene thinking it would be a good "insulator". It did abosultely nothing to attenuate the noise coming and going, but did turn my vocal booth into a nice ice chest for beer! I later added several layers of 5/8ths drywall so now I can keep my beer cold AND no one can hear me drinking it! Tom

but would those EPS pucks not de-couple walls like RC does?

Not much at all; they're too rigid. Pick up a piece, hold it up to your ear, and tap on the other side with a drum stick to see how much isolation you get... Steve

:roll: okay, so what you're saying is that they're useless building a rised floor too? I'mean if they flank sound that much why put'm on the floor to carry the rised floor. Or did I totally missed the point here?

No, you didn't miss the point - as simply as possible, EPS/polystyrene doesn't belong ANYWHERE in a studio... Steve

haha, yeah I figured already :) thanx steve