PIR vs Rockwool?

[ashthekid]

Silly question but what's better at sound insulation for internal studwalls between rooms: Rigid PIR boards or some sort of Rockwool?

 

Only reason I ask is because I have a lot of 100mm PIR leftover on my project and rather than waste it I was considering using it up in my internal studwalls between rooms?

Would this be a silly move?

[JohnMo]

PIR has little or no sound insulation value.

[Iceverge]

Yup. 

 

It would make a minimal difference but rockwool would be better.

 

Your aim with sound transmission is to.

 

1. Have no direct airbourne path for it to travel. EG sealing the backs of sockets in stud walls, drop down acoustic seals in doors etc. 

 

2. By taking care of this sound is forced to travel directly through a structure. In this process you want the sound waves to loose as much energy as possible. Thus can be done in a couple of ways.

 

Have a very heavy structure like a concrete wall . This is also the main difference with sound block plasterboard vs normal. its weight. Ths sound waves struggle to transmit vibrations through the heavy substance.

 

the decoupling a structure at both sides so the sound is forced to transfer its energy to one plasterboard, then back to the air , then back to the air, then to the plasterboard amd finally the air in the other room. This is why a twin stud wall or a wall with resilient bars will be better than a plain one with plasterboard on both sides, effectively the sound could pass straight through the studs. 

 

Finally you can have a layer of absorbent material in the cavity of the wall to deaden the sound further like acousitc foam or rockwool. It will stop the sound bouncing around inside the wall like a drum and make things quiter at the other side. The PIR would be of little use here as it's not very heavy and it has a smooth surface so would just reflect the sound around inside the wall not deaden it.

 

Someone please correct me if I'm mistaken.

 

 

 

 

 

 

 

 

 

[ashthekid]

@Iceverge thank you that's great info and makes a lot of sense.

 

I'll scrap the PIR then and sell what I have left on Ebay or something.

 

And focus on the cavity space and plasterboard type. I plan to use 12.5mm Soundbloc(or similar) on both sides of all studwalls which will hopefully make a big difference and then 75mm or 100mm of acoustic Rockwool(or similar) in-between the studs. Every stud is 2x4 timber so should I pack it out with the max I can get in there or perhaps do just 50mm to allow for an air gap so that the "transfer of energy" changes.

[ashthekid]

Also, I may have some OSB Structural 18mm left to perhaps use on internal stud walls. Would that help in any way?

[Iceverge]

As I understand it you need to avoid packing it as it might create a bridge for sound to travel through. Maybe it was @nodsaid the thickness of mineral wool doesn't really matter, more that it acts as a sponge and an anti reflector for the sound. obviously more mass is better as it is harder to for sound to "move" but that's not it's primary function. 

 

If you could stagger the studs and create a mini twin stud wall it would help. Resilient bars would be good or acoustic strips on the studs. 

 

In terms of plasterboard, Kg/m2 is the only meaningful measurement. Soundblock at 12.5mm is probably similar to normal plasterboard at 15mm. It's just up to you what your trade off with cost Vs labour Vs space lost is. 

 

I think someone did an excellent table on here. Maybe @Ferdinand.

 

@Nickfromwales mentioned soundblock is better than normal for mounting stuff on. I don't know . I've never used the stuff. 

[Iceverge]

OSB is about 640kg/m3, similar to plasterboard. Sound block is 850kg/m3. 

 

18mm OSB should significantly help. However it's an expensive improvement unless you have no other use for it. It would be awesome for hanging stuff on. Behind plasterboard mind you. 

 

Remember too, sound will take the path of least resistance. Going over the top soundproofing a wall with a door isn't much benefit for example. Also consider floor voids and service cavity voids that run above and below stud walls. 

 

As to the PIR.  Flog it or add it somewhere else in the build. I have some PIR offcuts buried in the 400mm cellulose in the attic. 

 

 

 

[Radian]

Check out these diagrams detailing double stud wall soundproofing

[nod]

Ideally a gypliner wall and ceiling 

But a cheaper way is a coat of gypsum sound coat (Parge) will help 

[nod]

13 minutes ago, Iceverge said:

As I understand it you need to avoid packing it as it might create a bridge for sound to travel through. Maybe it was @nodsaid the thickness of mineral wool doesn't really matter, more that it acts as a sponge and an anti reflector for the sound. obviously more mass is better as it is harder to for sound to "move" but that's not it's primary function. 

 

If you could stagger the studs and create a mini twin stud wall it would help. Resilient bars would be good or acoustic strips on the studs. 

 

In terms of plasterboard, Kg/m2 is the only meaningful measurement. Soundblock at 12.5mm is probably similar to normal plasterboard at 15mm. It's just up to you what your trade off with cost Vs labour Vs space lost is. 

 

I think someone did an excellent table on here. Maybe @Ferdinand.

 

@Nickfromwales mentioned soundblock is better than normal for mounting stuff on. I don't know . I've never used the stuff. 

Correct 

Most of our jobs only spec 25 mil acoustic Even party walls 

It simply stops the sound bouncing around 

[ashthekid]

@nod Thank you

 

So a gypsum sound coat could be applied directly to the blockwork and then perhaps an 12mm timber batten and 12.5mm acoustic plasterboard on top?

I could even squeeze in a layer of 

 

Gypliner wall and ceiling isn't a viable option sadly.

 

Has anyone used the SM20 rubber panels between the wall and plasterboard? Or GenieClips? Or Tecsound 50 (2mm layer)?

 

 

 

[Thorfun]

I spoke to a Rockwool rep today and he recommended 50mm batts in my 89mm internal timber studs. Said it shouldn’t be fully filled as you risk compressing the insulation. 
 

but he’s a salesman and maybe 25mm will do as @nod says. 

[nod]

8 hours ago, Thorfun said:

I spoke to a Rockwool rep today and he recommended 50mm batts in my 89mm internal timber studs. Said it shouldn’t be fully filled as you risk compressing the insulation. 
 

but he’s a salesman and maybe 25mm will do as @nod says. 

He’s correct in stating 50 in Timber 

Timber and soundproofing don’t go hand in hand 

What you to realize is that there isn’t a comparison with timber and MF 

Even without the difference in density of the two 

When you insulate an mf stud 

There is 2 mil every 400 mil of surface area without insulation Hardly anything 

where as with timber you have no insulation on 50 mil of every 400

You just relying on 89 mil of timber 

Which allows sounds to travel through like butter 

[ruggers]

On 04/03/2022 at 22:24, ashthekid said:

@nod Thank you

 

So a gypsum sound coat could be applied directly to the blockwork and then perhaps an 12mm timber batten and 12.5mm acoustic plasterboard on top?

I could even squeeze in a layer of 

 

Gypliner wall and ceiling isn't a viable option sadly.

 

Has anyone used the SM20 rubber panels between the wall and plasterboard? Or GenieClips? Or Tecsound 50 (2mm layer)?

All of them are good examples but I'd expect the genie clip with tech sound 50 to work very well as theres less contact patches. Sound struggles to travel through different layered materials with varying thicknesses. So on double glazed windows, if you can have the inner and outer panes of glass at different thicknesses it stops the frequency travelling through so easy. The same applies to the walls when your decoupling the plasterboard with the rubber sheet or using two different types of plasterboard. You might want to also decouple the stud work from the floor walls and ceiling but it depends how far you want to go. Staggered twin stud walls work best with rockwool in both.

[cwr]

How does mounting plasterboard on resilient bars compare to the likes of SM20, genie clips or Techsound? They are certainly much cheaper.