insulating for sound


Old 09-16-01, 04:44 PM
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I would like to know what type of insulating material would be best for the inside walls and floors for sound protection? For example, would I get better sound protection from putting R-19 in a 2x4 wall or am I just wasting money?
Any input would be helpful.

Steve Karson
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Old 09-18-01, 03:31 PM
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It isn't a good idea to put a 5 1/2 batt in a 3 1/2 space. You would have endless drywall prolems. Fiber glass is not that great for sound reduction anyway. Most sound is transfered thru studs and joists.

I don't have any sites to go to here in front of me, but, Enter "wall sound control" and see what you get.
Old 09-19-01, 12:15 PM
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Thank you for the helpfull info.
Old 09-26-01, 09:42 AM
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R-11 unfaced fiberglass is all u need.... make sure there is no light showing through anywhere prior to installing drywall..
Old 09-26-01, 09:46 AM
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Had to post an additioal reply after reading ribysis reply..

Although using R-11 by no means is a sound proofing, it does make a significant reduction in sound transfer. If I were building a new home I would install R-11 fiberglass sound batts around all baths, bedrooms, laundry rooms , it actually does make a noticable difference.

Good Luck
Old 09-26-01, 10:53 AM
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Thanks for the info. So if I understand you correctly, I only need R-11 not R-13, Is that correct? I also have one more question, Does it matter if I use kraft faced batts for the inside walls? I have some extra left over from the outside walls and I would like to use it up if I can.
Old 09-26-01, 04:18 PM
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Go back and read "rbisys's" reply. Stuffing an R-19 into a 2X4 wall won't do you a bit of good. Stick with eith the R-11 or R-13. These are intended to be used in a 2X4 wall. But most of the sound transmission will occur thru the studs. What you need to do is build the wall so that the studs you put the sheetrock on on one side (say the bathroom) are not the same studs you put the sheetrock on on the other side (say a bedroom).

Use a 2X6 for the top and bottom plates, and 2X4's for the studs. Lay the studs out 8" O.C., with the even numbered studs on the bathroom side, and the odd numbered studs on the bedroom side. Now you have no solid wood connection between the two sides, other than the top and bottom plates. You will have very little sound transmission through that wall. Weave insulation between the studs, and you will have even less. Go to the extreme and build 2 parallel 2X4 walls between the rooms, with an inch space between them, insulate them with R-11 or R-13 fiberglass batts, and your sound transmissiom will be virtually nothing.
Old 09-26-01, 04:47 PM
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Thank you for taking the time to explain the proper way to build a soundproof wall.
All of my walls are already built so unfotunately, that won't work for me. I'm going to finish the insulation this weekend and start drywall next week, so basically I was not asking again if I should use R-19 in a 2x4 wall rather if there was any difference ( besides increased cost ) between R-11 and R-13 and if it made any difference if I used up the extra kraft faced batts from the outside walls in the inside walls. I would think that he kraft faced batts wouldn't matter in an inside wall because both sides of the wall would be heated/cooled and there shouldn't be any condensation problems. I guess , since I'm new at building a house, I just wanted to make sure I wasn't making a dumb mistake.
Thanks again for your feedback.
Old 09-26-01, 11:42 PM
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you can use kraft faced material if you like on an interior wall....

If you have r-13 left over use it up...

I helped my friend insulate his interior walls on a new built, we actually used r-13 kraft..the reason for the r-13 over r-11 was not for additional sound control, but because r-13 batt is a little more rigid and seems to be easier to install. We also used kraft because he had professional drywallers coming in to install the sheet rock and we figured that if an unfaced batt fell down prior to the sheetrock being installed that the drywall installers would probably not replace it...

I worked for many years for a (extremely reputable)fiberglass insulation contracting firm and have found that to be true from field experience..

Now back to the argument over whether or not it is worth installing glass batts for sound purposes...

A double wall is always best...but not very practicle in todays construction... fiberglass does not create a sound proof wall by any means... However it does make a noticabe difference... And the cost to install yourself is very minimal... approx 20 to 25 cents a sq.ft.

Good luck

Old 09-27-01, 09:35 AM
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Thanks for clearing up those last few questions that I had, also thanks for the tip on the R-13 being more ridgid. Gotta go now and finish my project.
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