We are remodeling a beach house in the San Juan Islands and there is a Navy Jet base down a couple of islands - but they fly over here frequently.

The new addition is ICF but the original building is un-insulated CMU. The guest cottage will be wood framed.

We want to insulate the CMU walls for warmth AND against the noise from the Navy Jets. If we spray 3.5" of closed cell foam insulation onto the interior of the CMU walls, will this help deaden the Jet noise, or will it possibly enhance it?

I am concerned that the foam might act as a "wall speaker".

Does anybody here have experience with this situation?

This same question applies to the wood framed guest cottage - will the spray foam deaden the sound or enhance it?

Does anybody here have experience with this situation?

I do. Embrace the sound of freedom.

I can't imagine how adding insulation would make it louder inside the house. Keep in mind that sound is pernicious and can come in little cracks, so weatherstripping and sealing is important. I'm pretty sure the windows are big deals, too.

Closed cell spray foam is a fantastic product for thermal insulation, ie for keeping heat in or out. It is not good for controlling sound. The mid range frequencies will resonate through the spray foam, creating the illusion that the sound is amplified. I never recommend closed cell spray foam for sound control. Your best option would be dense pack cellulose in the walls and blown in the attic area, Roxul mineral wool batts or even open cell spray foam.

Consider Roxul COMFORTBOARD IS against the CMU wall and then drywall, Green Glue and then another layer of drywall. But I haven't checked the actual performance.

Posted By jonr on 21 Oct 2013 08:55 PM
Consider Roxul COMFORTBOARD IS against the CMU wall and then drywall, Green Glue and then another layer of drywall. But I haven't checked the actual performance.

Jonr, On the Roxul website, they mention that Comfortboard is for "exterior" use. Would it work gluing it to the interior CMU walls, then frame a wall and fill with chopped fiberglass insulation, then sheetrock, green glue, sheetrock?

Would we tape the first layer of sheetrock?

EPS foam is not a good sound absorber. It does not receive good STC ratings. I know it seems counterintuitive but rigid foam is a poor sound cancellation material.

The best sound control methods are:

• Decoupling of wall assemblies
• Mass

When using insulation, fiberglass or mineral wool work A LOT better in reducing sound than rigid foam. Cheap fiberglass batts do a better job than rigid foam. Roxul AFB (no R-Value) or Roxul CavityRock (R-Value) would be the best choice for sound control, in addition it can withstand temps of 2000F.

Single layer wall
5⁄8”  gypsum board
3-5⁄8” steel studs spaced 24” centers
3” (76 mm) ROXUL AFB
Sound Transmission Class = 52

Single layer wall
1⁄2”  gypsum board
3-5⁄8”  steel studs spaced 24”  centers
1-1⁄2”  ROXUL AFB
Sound Transmission Class = 46

Posted By Lbear on 21 Oct 2013 11:24 PM
EPS foam is not a good sound absorber. It does not receive good STC ratings. I know it seems counterintuitive but rigid foam is a poor sound cancellation material.

The best sound control methods are:

• Decoupling of wall assemblies
• Mass

When using insulation, fiberglass or mineral wool work A LOT better in reducing sound than rigid foam. Cheap fiberglass batts do a better job than rigid foam. Roxul AFB would be the best choice for sound control, in addition it can withstand temps of 2000F.

Single layer wall
5⁄8”  gypsum board
3-5⁄8” steel studs spaced 24” centers
3” (76 mm) ROXUL AFB
Sound Transmission Class = 52

Single layer wall
1⁄2”  gypsum board
3-5⁄8”  steel studs spaced 24”  centers
1-1⁄2”  ROXUL AFB
Sound Transmission Class = 46

Lbear, What do you mean by "mass"? Why use metal studs? Why not wood studs? Are you spacing the studs 24" so there are fewer of them to transmit sound?

We intend to have the new framing separate (not touching) from the CMU walls. Shouldn't that also help?

Posted By Roger R on 21 Oct 2013 11:56 PM


Lbear, What do you mean by "mass"? Why use metal studs? Why not wood studs? Are you spacing the studs 24" so there are fewer of them to transmit sound? We intend to have the new framing separate (not touching) from the CMU walls. Shouldn't that also help?

I was just using steel studs as an example but wood studs will work also.

By "mass" I am referring to solid concrete walls (monolithic) but CMU's (partially filled) work well also. Mass can also mean drywall (5/8" or two layers of 5/8").

Decoupling the wood framing from the CMU walls will help also.

You should have a STC rating in the 50's with that type of wall assembly.

What type of insulation are you putting between the wood studs?

Lbear, I could not find the R Value of the ROXUL AFB. Do you know it?

Lbear, I was tossing coins between spray in foam vs spray in chopped fiberglass. The spray in foam has merits, such as closing out any chance of future mold. Seems like it could be noisy though. It is also almost 3x's more expensive as chopped fiberglass. Chopped glass nees a 6" wall to almost be as warm as a 3.5" spray foam wall.

Everything I've seen shows steel studs working better than wood.

Posted By jonr on 22 Oct 2013 12:10 AM
Everything I've seen shows steel studs working better than wood.

Working better in what respect?

Posted By Roger R on 22 Oct 2013 12:03 AM
Lbear, I could not find the R Value of the ROXUL AFB. Do you know it?

I forgot you are going for sound control AND insulation. My fault.

Go with the Roxul CavityRock DD    It has an R-Value of 4.3 per inch and offers the STC ratings and fire resistance (2,000F). It's also better at keeping vermon, rot/mold and moisture out than fiberglass. The Roxul AFB is more flexible than CavityRock and for some strange reason they don't advertise the R-Value but it is rated at R 4.1 per inch.

Lbear, That product sounds pretty good. Do you know if it is strong enough to be glued directly onto the CMU and then have sheetrock glued to it? (or would we need to put up an interior stud wall , insulate between the studs and screw the sheetrock to the studs?)

Working better in what respect?

Steel studs work better than wood in terms of blocking sound.

Posted By Roger R on 22 Oct 2013 02:43 AM
Lbear, That product sounds pretty good. Do you know if it is strong enough to be glued directly onto the CMU and then have sheetrock glued to it? (or would we need to put up an interior stud wall , insulate between the studs and screw the sheetrock to the studs?)

You must go with the latter and install the studs wall. It's more labor and costs but that is the only way to do it.

I know it's after the fact but that is why ICF works better vs. CMU. With CMU you still need to frame an interior wall and then insulate it. Also with a CMU wall the entire mass is on the outside, which you don't want for thermal mass benefits.

Posted By Roger R on 22 Oct 2013 12:03 AM
Lbear, I could not find the R Value of the ROXUL AFB. Do you know it?

R4.3 per inch per ASTM C 518 test according to the spec.

edited to add:

Sorry- didn't see that it had already been answered.