Does closed cell foam transmit any audio??

Hello Everyone, A quick question for everyone on closed cell foam (with a bit of background as to my project) I have read Rod's book inside out, and it's been extremely helpful. I am doing a proper room in room design with concrete floors, etc. As much "by the book" as possible. This room has one exterior wall, plus two walls which are concrete block and have neighbors on either side. One of them is an empty warehouse that is kept very cold in the winter, and the other is another manufacturer that keeps that part of the building quite cool in the winter as well. After speaking with a few reputable insulation contractors, all think that shooting those three wall (the 4th is facing into my climate controlled office area and therefore is not in need of R value insulation) with approx 1.5 inches of closed cell insulation is best (We already did it to the ceiling a while back). My question is this - as I want as much cubic volume to the space as possible, will any audio be passed through the closed cell foam if it touches the wood studs? (trying to keep them 1" off the wall which will end up "nestling" into the closed cell foam by 1/2" Thanks Brian Michigan USA

Closed cell foam is ineffective for acoustical purposes. That said, I suspect the reason the contractors are pushing this is because the structure may have a tendency to sweat and/or produce high levels of moisture which would ruin the open cell insulation and render it useless due to saturation. But it may only be simply because it is easier to use...who knows @ this point. To answer your question, yes.

Thanks xSpace The closed cell is in fact only for insulation purposes and will be applied 1.5" thick. We set the walls today, and kept a minimum of 2" from the existing block walls. If the spray in expands and touches some of the 2X4's a bit, we'll just carve it out to they aren't touching... BTW - I'll set this contractor straight on the topic and explain how in fact there IS transmission via spray in closed cell. Brian

I'm just curious here: You say you are doing a proper MSM room-in-a-room design, which means that you are going to have a lot of insulation in the wall cavity anyway (either mineral wool or fiberglass): So why do you also need closed-cell insulation in there? Wouldn't it just be better to use more of whatever insulation you were going to use in there anyway? You will lose isolation but not filling the cavity with wool. Is condensation is the issue, as xSpace suspects? Or is there another reason for needing the closed-cell, rather than using wool? Also, you say that you are building the walls inside-out, which means that there will NOT be any studs in the cavity. So why are you worried about the closed-cell touching the studs? With inside-out construction, there cannot possibly even be any studs in there!!!! Maybe you should draw a diagram of how your room will be built, and take some photos of what you have already. Something just doesn't sound right here... - Stuart -

Very good observation Stuart. To add, there was not enough information for anyone to really answer this, except with more questions but as is often the case, this project has already moved along and we are getting the "hindsight" portion of it.. For example: "This room has one exterior wall, plus two walls which are concrete block..." This line suggests that there are walls of different materials, two of concrete and one of an unknown composition on the exterior. And this line: "...with approx 1.5 inches of closed cell insulation is best (We already did it to the ceiling a while back). " Closed cell foam performs like a vapor barrier. To install a vapor barrier in the ceiling requires some thought about the existing building, the roof / ceiling design, HVAC, and where geographically a person resides for the simple reason that moving from the higher pressure to the lower pressure, usually from the warm side to the cooler side, a vapor barrier in the ceiling will keep the vapor and potential condensation on the inside of the structure. Other consideration for the concrete block are just as pertinent, has it been bonded/sealed? To simply install a spray foam directly over it is inviting problems.