SimonD

Acoustic insulation performance

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I've been scrabbling around to find sound reduction index charts for both Rockwool acoustic insulation slabs and Knauf acoustic roll. The only manufacture I've so far found that makes easy access of this info is Thermafleece although I've found some for Rockwool commercial products. I've emailed tech support for both companies but wondered if anyone here might have the data to hand as I need to make some initial calcs for a wall and ceiling buildup.

 

Ta

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I'm not sure having the acoustic absorption for the insulation will get you far here - certainly any mineral wool at a given thickness will give similar results, thinner products will be slightly worse. The issue is that any slight difference in this value is totally swamped by the effect of the rest of the construction once installed, for example in a timber stud partition. The sound reduction across a completed partition will depend upon the construction (timber or metal studs) and the density/thickness of the plasterboard each side. Note that 'mineral fibre' is deemed to be a solution in many parts of Approved Doc E. Sheep's wool (not a mineral wool) will need an independent test certificate to show similar compliance.

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Thanks, yes, I totally agree that the complete construction plays the major role, but in terms of the mineral wool, I do need to understand its response across frequencies. Some of Rockwool's commercial range shows a remarkable performance at fairly thin thickness at only 50mm, but it's a resin bound mineral wool board, whereas the domestic product looks to be inferior. It's also interesting to note that the practical absorption coefficient for some mineral wool reduces at some frequencies even with greater thickness, so the rule about thickness doesn't always hold. But all of the mineral wool products do tend to perform best at 1k hertz upwards. The sheeps wool product does have the certificated test data for building regs part E compliance.

 

For this particular instance in the wall I'm starting by looking at using a staggered timber stud wall with resilient bar, extent of plasterboard to be determined once I know the most troublesome frequencies for the room in question. I may go double stud if necessary. Intermediate floor wise I'll have a resilient layer on top of subfloor, acoustic insulation between joists, a timber resilient layer of 50mm, which can be filled with insulation and I also have the floor height to add an additional resilient bar prior to plasterboard - not quite enough for a suspended ceiling.

 

Inside, the room will have acoustic absorption measures.

 

I have some very specific requirements to adhere to with this one 😁 One word..headache..for me that is..

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I’ve just taken delivery of Rockwool acoustic slabs for some offices that we are doing 140 acoustic roll then 100 mil slabs 

Around £25 per pack of slabs 

Rarely get asked for any other brand 

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27 minutes ago, nod said:

I’ve just taken delivery of Rockwool acoustic slabs for some offices that we are doing 140 acoustic roll then 100 mil slabs 

Around £25 per pack of slabs 

Rarely get asked for any other brand 

 

It does seem to be the goto. That's an amazing price you got there for the slabs, I can't get anywhere close to that locally. Can you add me to your account??? - about 175m2 of 100mil slabs would do me fine for the rest of the house 😁😉

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28 minutes ago, SimonD said:

whereas the domestic product looks to be inferior

Rockwool comes in different densities. The more dense it is the better at absorbing lower frequencies, according to the helpful lady at Rockwool technical. The stuff you can get in Wickes/B&Q/etc is 35kg/m3, and then if you go to more specialised suppliers you can get it at 45kg/m3, 60kg/m3, and so on. The denser stuff holds its shape better. 

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1 minute ago, SimonD said:

 

It does seem to be the goto. That's an amazing price you got there for the slabs, I can't get anywhere close to that locally. Can you add me to your account??? - about 175m2 of 100mil slabs would do me fine for the rest of the house 😁😉

😂😂

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42 minutes ago, SimonD said:

It does seem to be the goto. That's an amazing price you got there for the slabs, I can't get anywhere close to that locally. Can you add me to your account??? - about 175m2 of 100mil slabs would do me fine for the rest of the house 😁😉

 

Seems like you can get them for £15.40 + VAT per pack here

 

https://insulationwholesale.co.uk/rockwool-rwa45-acoustic-insulation-slab-in-100mm-2-88m2-pack/

 

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The acoustic absorption of all mineral wool products will tail off at lower frequencies (less than 600Hz?). Denser and/or thicker product will have a slightly better low frequency performance but as above this will be lost in the noise (pun intended) of the rest of the construction. Someone on here linked to an excellent report (Canadian?) a few weeks ago that covered 100s of stud partition options. Not sure how to search for it.

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1 hour ago, ADLIan said:

The acoustic absorption of all mineral wool products will tail off at lower frequencies (less than 600Hz?). Denser and/or thicker product will have a slightly better low frequency performance but as above this will be lost in the noise (pun intended) of the rest of the construction. Someone on here linked to an excellent report (Canadian?) a few weeks ago that covered 100s of stud partition options. Not sure how to search for it.

 

Found it, thanks. Link published courtesy of @MortarThePoint on this thread https://forum.buildhub.org.uk/topic/21504-partitions-timbers-studs-vs-metal-c-studs/page/2/

 

Very interesting. Looks like my initial sketched estimates for staggered stud wall with resilient bars are not far off, just looks like I'll need to double up with acoustic plasterboard each side for what the Canadians show and refer to as a possible STC 60 - 62. Then look at any low frequencies.

 

I'm aware of the lower frequency issue. It would be much more helpful if manufacturers could give Rw + Ctr figures to account for how the buildup deals with low frequency sounds as well instead of just Rw.

 

Do I assume correctly that by noise of the rest of the construction, you're referring to the room acoustics as opposed to transmitted noise? If so, it's always been beyond me to understand how some focus is put into dealing with noise transmission through walls and floors and nothing is done about the acoustics in the room. For me, the first priority is to deal with room acoustics, then transmission. If I can successfully deal with the room noise, the walls will have less work to do and the rooms will all be more comfortable. I'm always flabbergasted by the number of expensive develoments I've visited to find that noise in some rooms can become deafening with only a few people in there, especially kitchen/dinners.

 

I haven't done any acoustics work for almost 13 years and realised all my old reference books on the subject are right at the back of the storage unit, so hoping that I might be able to find the up to date info I need online now  🤞

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4 hours ago, James Newport said:

Rockwool comes in different densities. The more dense it is the better at absorbing lower frequencies, according to the helpful lady at Rockwool technical. The stuff you can get in Wickes/B&Q/etc is 35kg/m3, and then if you go to more specialised suppliers you can get it at 45kg/m3, 60kg/m3, and so on. The denser stuff holds its shape better. 

 

Thanks, it's handy to know. It would be so helpful if the information was easily available on their website 😏

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