ProSoundWeb Community

Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => The Basement => Topic started by: John Hiemburg on June 14, 2021, 06:39:42 PM

Title: Spray-in insulation and acoustic absorption
Post by: John Hiemburg on June 14, 2021, 06:39:42 PM
Afternoon,


I've spent some time searching, and either this information is hard to find or I'm failing in my search.


We're building a metal building (16,000sf) to house a new sanctuary on the current church campus. Metal pre-fab. It will be exposed ceilings. The metal building mfgr recommends spray-in expanding foam insulation for its insulating properties, but I can't find any information on sound absorption for any of the available products.


I *can* find info regarding spray-in foam and sound *transmission*. In other words, there is a healthy amount of discussion about whether it is useful to stop sound from getting between rooms. This is not my concern. I just need to find some kind of data regarding absorption - I can pass that along to the acoustical consultant to design the proper amount of absorption for our room.


Am I missing a magical search term? Does anyone have any experience with this? Any other concerns or 'gotchas' with this kind of insulation that you've experienced?


Thank you!
Title: Re: Spray-in insulation and acoustic absorption
Post by: Dave Garoutte on June 14, 2021, 07:00:33 PM
Afternoon,


I've spent some time searching, and either this information is hard to find or I'm failing in my search.


We're building a metal building (16,000sf) to house a new sanctuary on the current church campus. Metal pre-fab. It will be exposed ceilings. The metal building mfgr recommends spray-in expanding foam insulation for its insulating properties, but I can't find any information on sound absorption for any of the available products.


I *can* find info regarding spray-in foam and sound *transmission*. In other words, there is a healthy amount of discussion about whether it is useful to stop sound from getting between rooms. This is not my concern. I just need to find some kind of data regarding absorption - I can pass that along to the acoustical consultant to design the proper amount of absorption for our room.


Am I missing a magical search term? Does anyone have any experience with this? Any other concerns or 'gotchas' with this kind of insulation that you've experienced?


Thank you!

The other advantage of the foam, is the irregular surface, helping break up and disperse reflections.
Title: Re: Spray-in insulation and acoustic absorption
Post by: Bob Stone on June 14, 2021, 07:35:04 PM
As far as I know, there's no spray foam that can be left uncovered on its own due to the noxious fumes if it ever catches fire. So what are they intending on putting over it?
Title: Re: Spray-in insulation and acoustic absorption
Post by: John Fruits on June 14, 2021, 11:24:53 PM
Have you asked your acoustical consultant?
Title: Re: Spray-in insulation and acoustic absorption
Post by: Erik Jerde on June 15, 2021, 12:54:29 AM
Thereís a few questions that need to be addressed.  First, like Bob noted spray foam in occupied spaces usually needs to be covered.  Iím not sure how this rule changes for commercial from residential.  When in doubt check with AHJ and mfgr specs.  Lacking a specific code citation mfgr specs win.

Second, what type of foam and to what thickness?  All my experience has been with closed cell foam but there is also open cell foam used in some situations.

Based on my experiences with closed cell foam Iíd expect it to perform like an irregular hard surface.  Fully cured closed cell is quite hard.  Of course you can dent it but I walk on 6Ē of closed cell in my attic with no worry about punching through or otherwise damaging the finished ceiling below.  Stuff is strong.  Definitely is not an absorptive surface.

Lastly, as far as the acoustician.  This is their job to figure out.  Thatís part of what youíre paying them for.  You should just be able to set out what you want the room to perform like and they should be able to figure out how to accomplish that.  Of course getting the budget to properly build the design is another thing entirely.  Hopefully youíve got a good acoustician.  I worked on a project a couple years ago where the building committee went against my advice on acoustician and now the back wall acoustic panels are reflective instead of absorptive.  Ugh.
Title: Re: Spray-in insulation and acoustic absorption
Post by: Brian Jojade on June 15, 2021, 12:59:51 AM
The spray foam should help prevent the metal structure from rattling with sound. However, as others have said, you're replacing one hard surface with another.  While the irregularities will potentially redirect some of the higher frequencies, it's not going to absorb much at all.  And if you cover it with another material, it isn't going to have that much impact in the sound within the room.
Title: Re: Spray-in insulation and acoustic absorption
Post by: Neale Watson on June 15, 2021, 06:54:24 AM
May I suggest that the term sound 'absorption' is misleading.  I'm being picky, but better to stick with the terms 'reflection' and 'transmission':

Soft or irregular surface will minimize reflection;
Soft or irregular surface on thin backing will minimize reflection and do nothing to stop transmission;
Thick and dense material will stop transmission;
Soft or irregular on top of dense material will minimize reflection and transmission;
Dense material with soft material behind it will minimize transmission, but do nothing to minimize reflection

Foam behind a panel helps if it removes air gaps, but otherwise does not 'absorb' sound.

Title: Re: Spray-in insulation and acoustic absorption
Post by: Caleb Dueck on June 15, 2021, 07:05:39 AM

Lastly, as far as the acoustician.  This is their job to figure out.  Thatís part of what youíre paying them for.  You should just be able to set out what you want the room to perform like and they should be able to figure out how to accomplish that.  Of course getting the budget to properly build the design is another thing entirely.  Hopefully youíve got a good acoustician. 

This here.
Title: Re: Spray-in insulation and acoustic absorption
Post by: Chris Hindle on June 15, 2021, 07:51:03 AM

 The metal building mfgr recommends spray-in expanding foam insulation for its insulating properties, but I can't find any information on sound absorption for any of the available products.

Is the foam to be used to fill a void between inner wall and outer wall, or just as a covering to the inner side of the only wall?
Is the manufacturer intending for an inner "finish" wall to be applied after erection of the pre-fab components?
Any metal left exposed (ceiling) WILL be an acoustical problem.
Chris.
Title: Re: Spray-in insulation and acoustic absorption
Post by: John Hiemburg on June 15, 2021, 01:13:05 PM
Thereís a few questions that need to be addressed.  First, like Bob noted spray foam in occupied spaces usually needs to be covered.  Iím not sure how this rule changes for commercial from residential.  When in doubt check with AHJ and mfgr specs.  Lacking a specific code citation mfgr specs win.

Second, what type of foam and to what thickness?  All my experience has been with closed cell foam but there is also open cell foam used in some situations.

Based on my experiences with closed cell foam Iíd expect it to perform like an irregular hard surface.  Fully cured closed cell is quite hard.  Of course you can dent it but I walk on 6Ē of closed cell in my attic with no worry about punching through or otherwise damaging the finished ceiling below.  Stuff is strong.  Definitely is not an absorptive surface.

Lastly, as far as the acoustician.  This is their job to figure out.  Thatís part of what youíre paying them for.  You should just be able to set out what you want the room to perform like and they should be able to figure out how to accomplish that.  Of course getting the budget to properly build the design is another thing entirely.  Hopefully youíve got a good acoustician.  I worked on a project a couple years ago where the building committee went against my advice on acoustician and now the back wall acoustic panels are reflective instead of absorptive.  Ugh.


Erik, et al, good points all around. I will look into the question of leaving the foam exposed - it was suggested by one foam manufacturer that it could be painted (good for me) but no mention of it needing to be covered because of fumes/etc. I'll look into it.


As for the acoustician, right on all counts. We have relationship with an excellent company in Australia that has worked on some recent projects for us, and will consult on this one as well. I would like to know and understand for myself going into it. Also at this point insulation is a sizable budget line-item so choosing spray in vs soft goods is an important decision. Having an idea if it is helping or hurting at this stage will certainly help with the math.


Thank you!
Title: Re: Spray-in insulation and acoustic absorption
Post by: Rick Earl on June 15, 2021, 03:16:51 PM
Afternoon,


I've spent some time searching, and either this information is hard to find or I'm failing in my search.


We're building a metal building (16,000sf) to house a new sanctuary on the current church campus. Metal pre-fab. It will be exposed ceilings. The metal building mfgr recommends spray-in expanding foam insulation for its insulating properties, but I can't find any information on sound absorption for any of the available products.


I *can* find info regarding spray-in foam and sound *transmission*. In other words, there is a healthy amount of discussion about whether it is useful to stop sound from getting between rooms. This is not my concern. I just need to find some kind of data regarding absorption - I can pass that along to the acoustical consultant to design the proper amount of absorption for our room.


Am I missing a magical search term? Does anyone have any experience with this? Any other concerns or 'gotchas' with this kind of insulation that you've experienced?


Thank you!

Usually I am looking for Coefficient of Absorption when looking at acoustical properties of materials.  It should give you data across different frequencies.   On issue I have had dealing with polyurethane foams is they are different, so there is no one source. I know one manufacturer had some data a few years ago, but I cannot find it.  Even from the same manufacturer, we had choices of closed or open cell, slow or fast cure.  We went with an unknown product (no my choice) we knew it was going to be covered so we decided not to worry about it for the rest of the design.  It did reduce outside noise quite a bit, I had only wished I had thought of doing before and after RT-60 measurements. 

EDIT:  Here is the article I started with - still had it bookmarked, but could not find the other related information: https://www.constructionspecifier.com/sound-deadening-with-sprayfoam-adding-unexpected-value-with-spf/ (https://www.constructionspecifier.com/sound-deadening-with-sprayfoam-adding-unexpected-value-with-spf/)