Rockwool advise please

[DMT]

Garage is now studded and so I need insulation; I have seen 140KG/M RW6 Rockwool (and equivalents) but this is very expensive. I have also read that the RW3 is just as good for sound proofing despite being a lower gsm, can anyone please offer some advice.

Thanks.

[johngray]

Originally Posted by DMT

Garage is now studded and so I need insulation; I have seen 140KG/M RW6 Rockwool (and equivalents) but this is very expensive. I have also read that the RW3 is just as good for sound proofing despite being a lower gsm, can anyone please offer some advice.

Thanks.

Hi DMT,

Yes you are quite right that lower densities also provide useful acoustic performance, the British Gypsum white book offers extremely helpful guidance on differing wall constructs, and the basic rules of thumb are as follows:

The mass lines of the wall provide the greatest effect to sound insulation, particularly at low frequency.
The greater the size of the void the greater the performance
Isolating the timbers from the underlying structure also improves performance.
Allowing an air void is also assistive.

Therefore assuming you are using a mass-line of plasterboard, twin skin with staggered joints is best (each sheet offset by 400mm for instance) using 100mm studs with the studwork isolated from the brick/block work and the void filled with a 50mm mineral wool absorbent, then all that remains is seal all joints and the perimiter for leakage.

Note that these comments relate to insulation only and not to absorption within the enternal condition (room).

A company with very helpful info is Siderise Insulation - www.siderise.co.uk - their 'solution' pages have alot of useful pointers.

Regards JG

[DMT]

JG,

Thanks for the reply.

I have a single bricked garage followed by a 2" airgap, hardboard and wood studding with lafarge 12.5mm db check board to go on after insulation.
I think I am going with Rockwool 67MM acoustic partition slab, pack of 9 £44.42 from Travis Perkins. I am taking the project on from here, the previous work was done by a builder but with no previous acoustic knowledge.

Material Thickness Frequency (Hz)
(mm) 125 250 500 1K 2K 4K
Acoustic Partition Slab 67 0.30 0.70 1.00 1.00 1.00 1.00

Thanks.