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I'm finishing my basement and adding insulation. I am insulating the ceiling joists between my basement and upstairs living room as well since the room is for a theater. So, it's for acoustic purposes rather than energy/moisture.

The guys installing the insulation didn't get the instructions very well and used faced insulation in the joist space above where my soffit is. I wanted them to use unfaced in that area, and then, if they needed to, they could use faced at the bottom of the soffit. Instead, they have faced up in the joist spaces, and then another layer of faced beneath that.

I have to redo some of it anyway, because they didn't quite fill in the space as much as I'd like, so wanted to see if that aspect of it would cause any issues while I'm at it?

I didn't figure it would since it's not really for moisture or dealing with the outside, but wanted to be sure.

FreeMan
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Kevinicus
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  • The way they deaden hi-end basements in expensive mcmansions is two layers of _thinner_ drywall with a scribble bead of _latex caulk_ between them _nailed_ to the ceiling/joists. – dandavis Mar 08 '23 at 00:04

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It will not be a problem. Condensation occurs where temperatures reach the dew point, and that's generally not going to happen in a floor cavity between conditioned spaces.

Be aware that sound insulation is mostly about mass, so fluffing layers of fiberglass as you would for thermal value won't accomplish much. Knowing this might save you some hassle.

isherwood
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It won't be worth your effort to remove the faced insulation and replace it with the unfaced type. The important issue is to completely fill in the spaces that the contractor didn't quite do. That can have major impact on the entire effectiveness of the reduction of sound. It's probably too late to mention it, but there are insulations made for acoustical use.

JACK
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You might try Styrofoam- it can be pricey but will deaden sound quite well. Sound is transmitted through vibration so stopping up any air gaps that would transmit such would help. Additional vibration is transmitted through the hard surfaces which is why studios put the soft foam on the exterior of the wall to deaden the vibration and break up the transmission of it through the hard surfaces too. If you don't want it on the exterior, a full styrofoam layer under the drywall surface - even breaking up the direct contact of the drywall to the joists may deaden sound quite significantly.

Donal of all trades
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    This doesn't really answer the question. Please see [answer] and take the [tour]. We're not a discussion forum. – isherwood Mar 07 '23 at 22:00