Safe to use Mineral Wool insulation along perimeter basement walls? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 05-12-2019, 09:42 AM - Thread Starter
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Safe to use Mineral Wool insulation along perimeter basement walls?

Like so many other people at the moment, I too am building a home theater in my basement. Luckily, I had my house built with a 9' ceiling for a bigger screen. I just started framing it about a month ago and read so many good things about mineral wool insulation for sound reduction. However, I might have made a big mistake. I just assumed it can be used in the stud framing around the outside walls in addition to the ceiling joists and interior walls. This is my first experience doing this kind of work and am learning as I go. I ordered tons of it:



While at Home Depot the other day I noticed the R values on all the different types of insulation and realized that my Owens Corning Thermafiber had no mention of R value anywhere on the packaging so I panicked.

I've read that it has something around R13 in value but don't know for sure. I'm in the Northern Ohio area and didn't think I needed to do a full on vapor barrier treatment of the entire perimeter:



There is already insulation to the frost line provided by the builders and I just assumed to fill the cavities with Mineral wool then drywall over that. Now I am second guessing my extremely expensive decision. Below is a video clip of the basement. Anyone able to assure me this path is ok or do I need to reevaluate my insulation plans?


Last edited by wookiegr; 05-12-2019 at 09:48 AM.
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post #2 of 8 Old 05-12-2019, 02:09 PM
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Mineral wool is fine for exterior walls, Unneeded if you are building with double damped drywall on isolated mounting. However local building codes that specify required R value and Moisture barrier should be determined as they differ by region. I'm sure you will be fine on the R rating but they may want floor to ceiling vapor barrier for finished space. If you think using mineral wool is the best strategy for sound isolation you will disappointed when your subs kick in. You have fallen prey to the marketing hype.
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post #3 of 8 Old 05-12-2019, 02:12 PM - Thread Starter
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Funny thing is. I know its useless against the subs. Im trying to keep sound OUT of theater room. Plus i plan to use 2 layers of type x 5/8 drywall on the ceiling.
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post #4 of 8 Old 05-13-2019, 09:44 PM
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I live in Wisconsin and used two trailer loads of mineral wool. On all sides, including against concrete foundation walls.
So long as you didn't add another vapor retarder in the assembly you should be fine. Once the walls get deep enough the vapor drive is typically to the inside, year round. So the damp proofing and even the concrete act as a vapor retarder against what is trying to come in. I've seen what happens when a 6mil-4mil poly sheet is placed on the basement side of studs...rot.


As for what effect it has...Big (as usual) speaks the truth. I have double studs, sealed every nook and crack, floating ceiling AND loaded with mineral wool. Heavy LFE still rumbles through. 105db - 110db inside the theater, with double doors closed no dialog or midranges gets out, just the 40hz and lower stuff (estimate).

So the mineral wool, I believe, helps dampen what gets past the drywall. So yeah, It helps. But like a lot of "sound isolating" products = a lot of hype/marketing overselling the benefit.


Good luck!
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post #5 of 8 Old 05-15-2019, 06:53 PM
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Quote:
Originally Posted by BIGmouthinDC View Post
If you think using mineral wool is the best strategy for sound isolation you will disappointed when your subs kick in. You have fallen prey to the marketing hype.
Hi Jeff -- what would you recommend instead? I thought that DD+GG, clips, and Roxul Safe & Sound was the best way to keep sound in.

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post #6 of 8 Old 05-15-2019, 07:58 PM
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Triple drywall, GG, Clips and channel and the cheapest insulation you can find, is probably cheaper but the extra mass will help with the low frequencies. Sound in a building assembly is transmitted via the physical structure not the air cavities. The mass resists vibration, the GG dampens vibration, the clips and channel keeps it from being transmitted throughout the house. Sound in the air cavity is insignificant source of sound transfer in a wall built with sound isolation strategies. So why pay a premium for over hyped insulation? Of course if you have money to burn, it won't hurt.
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post #7 of 8 Old 05-16-2019, 04:36 AM
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Quote:
Originally Posted by BIGmouthinDC View Post
Triple drywall, GG, Clips and channel and the cheapest insulation you can find, is probably cheaper but the extra mass will help with the low frequencies. Sound in a building assembly is transmitted via the physical structure not the air cavities. The mass resists vibration, the GG dampens vibration, the clips and channel keeps it from being transmitted throughout the house. Sound in the air cavity is insignificant source of sound transfer in a wall built with sound isolation strategies. So why pay a premium for over hyped insulation? Of course if you have money to burn, it won't hurt.
[Mind blown]

Are you saying that this is the best strategy against noise transmission out of the theater for all frequencies, or just the bass frequencies? [My limited knowledge thinks that if you can get the bass frequencies mitigated, all others have already been solved by that point]

I'd be a rich man if I had a nickel for every AVS theater that listed DD/GG, clips and channel PLUS Roxul. Are we going to see a paradigm shift away from sound insulation in cavities to more mass, ie triple drywall?

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post #8 of 8 Old 05-16-2019, 04:48 AM
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I would ALWAYS use insulation to mitigate resonant frequencies in every cavity. I just wouldn't pay the man for Roxul. Cheap Pink. Curve Frenzy theater in my signature, and The Beast Unleashed are two threads here that I worked on that are triple layer. You don't need it for every project. Just if you are a Bass addict and your family is not. I probably wouldn't use three layers in my personal space if I rebuilt but you asked what was the best.


If you read the original posts the thread starter isn't planning clips/and channel and double DW on the walls just the Roxul.

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