blown-in cellulose???

nukmusic · Post by **nukmusic** » Sat May 24, 2003 3:14 am

added STC for my design:

Any thoughts on Blown-in cellulose, it can also be sprayed-on. I was also thinking of filling the attic(over the garage) and existing walls with it. I can rent the blower and buy the 40 sq ft bags($5) anywhere in town(blown-in). I read on several sites that per inch, it is a little better than rockwool and much, much better than the pink stuff...........is this hype? If you remember I have a standard brick vineer home garage. brick\air gap\felt paper\5/8 shranboard\2x4 studs\3/8 drywall. All I have to do is cut small holes at the top of the wall to blow it in, very easy(helped do it before), then repair the drywall holes.

The following Sound Transmission Class (STC) ratings demonstrate its effectiveness in attenuating noise. The higher the STC number, the greater the reduction in sound.
Cellulose insulated wall 44 STC
Fiberglass insulated wall 39 STC
Uninsulated wall 35 STC
[Ratings for the empty wall and the fiberglass insulated wall are from the Owens-Corning “Noise Control Design Guide”. Ratings for the cellulose insulated wall are from the Cellulose Insulation Manufacturers Association.]

I also read http://www.saecollege.de/reference_material/index.html

knightfly · Post by **knightfly** » Sat May 24, 2003 9:32 am

Do you have a link to the Cellulose site? I'd be interested to see what they say about settling and its effect on STC at the top (therefore the whole) of the wall...

Your wall construction, effectively, (since the brick is vented) is really just strandboard/studs/3/8" wallboard. If you want any more than just typical tract-house sound isolation, I would remove the inner wallboard, insulate with rockwool, put up RC, then add two layers of 5/8 firecode sheet rock.

Adding on extra studs/wallboard, etc, AFTER the original two wall surfaces, will actually WORSEN the wall performance - it's much less frustrating to just bite the bullet and pull off the thin, non-resilient-mounted wallboard and do it right.

If you blow in insulation and patch the holes, you'll be lucky to get STC 40 with that thin inner wallboard, plus (I've not tried blown-in, but) I'd still be very curious about the settling issue... Steve

nukmusic · Post by **nukmusic** » Sat May 24, 2003 4:22 pm

I have been searching for "across -the-board" spec with no luck. I was just curious and did a search on google.com for "sound proofing with cellulose" and read a few articles, and from reading I think that the spray-on is better than the blown-in type. The spray-in looking just like semi-rigid insulation when completed. I'll try to find that photo again.

Lowes has this brand: http://www.us-gf.com/SoundControl.asp?Type=C

this site also has a few small videos.........

nukmusic · Post by **nukmusic** » Sat May 24, 2003 4:24 pm

I read this too ...... http://www.soundproofing101.com/wall_cavities.htm

http://groups.yahoo.com/group/acoustics/message/1755

http://www.studioelectronics.biz/recentprojects1.html
(contruction article)

http://www.comfortech.biz/stc_info.html

AndrewMc · Post by **AndrewMc** » Sat May 24, 2003 6:18 pm

Adding on extra studs/wallboard, etc, AFTER the original two wall surfaces, will actually WORSEN the wall performance

How can that be true? The example of a double wall with drywall in the middle is a lot lower than the one without on the inner faces, which makes sense, but this is still 10 STC points higher than a single wall.

knightfly · Post by **knightfly** » Sat May 24, 2003 7:16 pm

Andrew, you caught me - I could have worded that comment much better. What I meant to say was that there was much less gain to be had by adding on in that way, than by backing up and improving (and staying with) just two centers of mass. I was comparing differences between double frame walls with the mass distributed differently. Note that in the several examples of double stud frame, that each time you get rid of an inner layer of mass, the STC improves - so there are some cases where less material = better sound performance.

You're right that a second wall improves STC some, but if you look at the comparison chart here

http://www.homer.com.au/phpBB2/viewtopi ... 86&start=0

look at the STC 40 wall example, and compare it to the STC 63 example - exactly the same materials, almost exactly the same labor, with a difference in performance of 23 dB. If you had a bitchy neighbor and only so much room, which wall would you build?

Again, sorry for the mis-statement... Steve

AndrewMc · Post by **AndrewMc** » Sat May 24, 2003 8:29 pm

I was just making sure I didn't have it wrong

because there is absolutely no question that you have probably forgotten more than I know on this subject.

One thing I've noticed after reading anything I can find over several months is that often there is conflicting info floating about - thanks for clarifying that my understanding is correct.

Here's one question - that I have seen conflicting info on. In the air gap between walls, some sources say that insulation in the air gap doesn't impact the air gap "size" and in other places I've seen the opposite. The first seems to be more logical given that insulation is not heavy - so would act like the air gap. This does raise the question of the best density of insulation to use in the air gap - I'm concluding that the pink stuff is probably just as optimal inside the wall than going the extra expense of denser insulation. What's your take on it?

knightfly · Post by **knightfly** » Sun May 25, 2003 4:01 am

Keeping in mind that I'm not a test lab, and therefore don't have first-hand experience in the actual, quantifiable differences, here's what I've found so far -

From what actual performance testing that HAS been done, USG and others seem to agree that a filling of 3 lb/cu ft density, either fiberglas or (preferably) rockwool, gives the best overall performance in a wall.

Heavier than that tends to help some with bass performance (at the expense of highs getting through) and lighter than that tends to favor high freq attenuation, at a cost of worse bass performance.

Sooo, if you're planning a Hip Hop studio, maybe 12 lb/Cu Ft stuffing, and if you're into "Power Ambience", 4 Oz/Cu Ft, or just air :=)

Serious mode back on - If your isolation requirements aren't drastic and your budget is kinda tight, I'd just use the pink stuff and make sure everything else is done perfect (caulking, fit, design) If, on the other hand, you need max isolation, I'd spring for the 3 lb/cu ft rockwool to be sure.

In my case, even living in the country on 10 acres, I have one neighbor that isn't smarter than his (large) dogs and so can't teach them to only bark when it's important, and the guy on the other side mows his (2 acre) lawn twice a day, rain or shine, with a large John Deere 3-blade rider - so for my new facility (hopefully less than two years away) I'll be using foam concrete shell with a total of probably 6 layers of inner wallboard, (part against the concrete and part on the other leaf), etc... Steve

nukmusic · Post by **nukmusic** » Mon May 26, 2003 4:17 pm

Any finally thoughts KnightFly?

knightfly · Post by **knightfly** » Mon May 26, 2003 7:21 pm

Yeah, I think it takes a REALLY big dog to weigh a ton... :=)

Seriously though, it sounds like the spray cellulose is more efficient if you can stand the mess, and the guy who put 4 glasses in a window needs to read more - I think he could have gotten better isolation with two thicker, laminated glasses.

Only thing about the Cellulose - Comfortech's chart shows 2 lb rockwool compared to 3 lb Cellulose - where was the referree during this fight?