Mattress Foam (NOT memory) in stud wall as sound insulation - sensible?

[axt]

I have a stud wall currently open on one side, bathroom / airing cupboard etc to bedroom. It will have tile backer / MR Plasterboard soon. I also have some large chunks of foam from several mattresses (not memory foam topper, the large support material yellow coloured Polyurethane (?) foam). It's easy to cut with a carving knife and I can easily fill the stud wall with foam prior to boarding.

I was wondering if this was a good idea. It had nothing before and I figured it could help acoustic transmission, and help me use up the foam. I know there are other 'proper' (expensive) materials that may be slightly different or denser foams but my question is about using mattress foam.

It's talked about online for similar such uses, and it's suggested that building insulation would be a good avenue for recycling mattress foams but my only concern is in 10 years if it decomposes and goes all sticky and rots due to lack of air, like a foam lined flightcase opened for the first time in a decade, with flakey sticky foam all over your mixer desk? Though does this even matter?

I also have lots of Jobolite Polystyrene board I could use, but figured the much higher density of the mattress Foam would help?

Any thoughts?

 

[endecotp]

How does it behave in a fire?

Does it have any effect on PVC cables, as polystyrene does?

 

[axt]

It was from very good name brand mattresses so should be pretty good in a fire (as in, not very flammable, not a great fuel!) it was just a cotton cover over the foam when on the mattress also, no fiberglass covers etc. Probably on a par with all the wood that will be around it! No PVC cables on the walls where this will be (or I will cut a large clearance out for cables / channel it)...

 

[^woody^]

Mad idea.

Furniture foam is not a sound insulator.

Furniture foam is flammable and can combust at certain temperatures without flame contact. It burns with dense toxic smoke too.

You will invalidate any home insurance.

 

[Ivor Windybottom]

Take a chunk into the garden with a blowtorch. See what happens.

But it sounds like you already have a long list of doubts anyway.

 

[axt]

Yes I am thinking of seeing how flammable it is for interest sake, considering how hot they are on furniture flammability these days I would hope it is fairly inert.

I would have though it would do something positive for sound transmission, my main worry would be it outgassing in the wall and reacting with the plasterboard/ tile backer.

With hardiboard backer board and tiles though I would suspect the sounds from a shower would be attenuated fairly well anyway, so might just consign the foam to packaging department! Shipped an old crt TV using some before and it was superb.

 

[alligatorlizard]

Mattress foam won't do much for sound insulation. You really need something like rockwool or some type of fibreglass.

 

[SFK]

Rockwool Sound Insulation Slab - 50 x 400 x 1200mm | Wickes.co.uk

Rockwool Sound Insulation Slab - 50 x 400 x 1200mm

www.wickes.co.uk

 

[axt]

I do also have lots of rolls of loft insulation / rock wool but just hate the stuff, like devils candyfloss. I am surprised mattress Foam would be so bad at sound insulation Vs rock wool as they both seem equally dense?

Someone I was talking to today was on about drilling small holes once board up (at the top of each noggin void) and filling with sand, apparently that is also a thing?

 

[axt]

Rockwool Sound Insulation Slab - 50 x 400 x 1200mm | Wickes.co.uk

Rockwool Sound Insulation Slab - 50 x 400 x 1200mm

www.wickes.co.uk

That does look pretty much bob on, I have to say...

 

[SFK]

It's not just the density.
That rock wool I posted is full of solid rock fibres.
Each has to vibrate as the sound passes through.
That vibration reduces the energy or rather the sound volume.

Loft insulation makes air voids to reduce temperature movement.But it is less good than the dense rockwool at sound absorption.

I also used with the above sound absorption plasterboard, and red fire plasterboard when I ran out of money. Both are high density.

Knauf Tapered Edge Sound Panel - 12.5 x 1200 x 2400mm | Wickes.co.uk

Knauf Tapered Edge Sound Panel - 12.5 x 1200 x 2400mm

www.wickes.co.uk

And note that unfortunately no sound reducing product will work as well as you want - to reduce sound it is always best to reduce at the source of the noise.

 

[SFK]

Also , do you know about stepping the wood studs so the each side of the wall plasterboard is on its own stud?
It reduces sound vibrations passing though plasterboard, through stud and into plasterboard on other side by always having a small gap on one side of the stud.

See this image..

Building Soundproof Walls - Fine Homebuilding

In this Q & A, builder Mike Guertin discusses how he approaches soundproofing walls. There are several different methods and some have more bang for the buck. Learn how to soundproof walls by minimize sound bridges, seal penetrations, and fill wall cavities with acoustical insulation.

www.finehomebuilding.com

 

[phatboy]

Also , do you know about stepping the wood studs so the each side of the wall plasterboard is on its own stud?
It reduces sound vibrations passing though plasterboard, through stud and into plasterboard on other side by always having a small gap on one side of the stud.

See this image..

Building Soundproof Walls - Fine Homebuilding

In this Q & A, builder Mike Guertin discusses how he approaches soundproofing walls. There are several different methods and some have more bang for the buck. Learn how to soundproof walls by minimize sound bridges, seal penetrations, and fill wall cavities with acoustical insulation.

www.finehomebuilding.com

Metal stud is even better - the sound insulation is almost continuous, and it goes up faster

 

[Deluks]

Staggered stud and dense rockwool is the way to go. Forget about sand, it will get everywhere, use extra plasterboard if you want more mass.

 

[^woody^]

Fill with sand? LOL & WTF

It will be out of the bottom by time it takes to boil an egg. Hang on, that gives me a not-so-whacky idea.