john
New Member
Posts: 9
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Rockwool
Jun 5, 2016 16:23:49 GMT
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Post by john on Jun 5, 2016 16:23:49 GMT
Apologies if this has been asked before, I've searched for an answer to this. I'd prefer to work with roxul safe n sound rather than fiberglass where possible. There is a six inch gap to be filled in the basement ceiling joists (I will then be using resilient channel and Sheetrock below). Safe n sound comes in 3 inch thickness. Is this sufficient, should I double it, or is it better to fill the entire cavity with fluffy fiberglass? Thanks, John
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Post by Rock on Jun 5, 2016 17:42:00 GMT
I believe the general advice you'll find here is for inside of walls/ceilings, fluffy is all you really need. I don't know what the reason is but I think that if rockwool does give you a slight increase in STC over fluffy, it's not enough to justify the extra cost. I believe you get the most bang per buck with more sheetrock plus decoupling (RC or double stud) rather than rockwool instead of fluffy. Compressed rockwool can be used under/over bottom/top plates respectively, to attain decoupling walls/floors/ceilings.
To increase mass and therefore STC, you can also cut strips of sheetrock to fit up in between the studs and caulk the edge seams before you install the fluffy...that is if you can't add mass on the top side of the floor above, which is often not possible but much easier if you can. Depending on the STC you're shooting for, 2 layers of sheetrock is typical attached to the RC below. Of course beware of flanking. Rod Gervais' book is a great resource for this stuff if you don't already have it or read it.
Cheers, Rock
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john
New Member
Posts: 9
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Post by john on Jun 5, 2016 18:55:40 GMT
Thanks for the reply, I think I wasn't specific enough in my question. I prefer to use rock wool, the space isn't large enough for the cost differential to make a huge impact on my budget. So I need to know if a single 3" layer of rockwool is roughly equivalent in a 6" space to filling the entire space with the fluffy stuff. Thanks again.
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john
New Member
Posts: 9
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Post by john on Jun 5, 2016 19:11:38 GMT
P.S. Thanks for the other info, I'm reading the Gervais book carefully now.
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Post by Ethan Winer on Jun 5, 2016 19:42:29 GMT
The general recommendation is to fill the cavity fully with insulation. So if you have 2x6 studs and a 6-inch gap, you should use insulation that's also 6 inches thick.
--Ethan
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jhbrandt
New Member
Isolation & Acoustics Design
Posts: 8
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Post by jhbrandt on Jun 9, 2016 3:45:38 GMT
The general recommendation is to fill the cavity fully with insulation. So if you have 2x6 studs and a 6-inch gap, you should use insulation that's also 6 inches thick. --Ethan To add to Ethan's comment: Rock wool, due to it's density does NOT add any more STC!! The idea that it is denser and therefore provides MORE isolation is false and it's going all over the internet. I have a couple of papers on my resources page. The docs and calculators on my resources page are free to download. Enjoy! - and if you have any trouble or need help working my (very complicated) room mode calculator, I'll help you through it. (free) hehehe! this is NOT an ad. The document titles are: "Sound-Proofing: The Quest" and "How To Find How Much Isolation You Need" All the best! Cheers, John
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Post by octavarium on Jun 9, 2016 13:43:28 GMT
Hello jhbrandt- what does STC stand for?
Also, what are people's thoughts on OC thermafiber for bass traps? Do they work well? I see they are available in thicknesses of 6". Is that too thick?
Please forgive me if I'm derailing this thread, it's not my intention.
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