Rockwool for wall insulation - what type?

[Weebles]

It's a minefield of choice.  Advice please.

Looking to insulate MBC timber frame internal stud walls before plasterboarding and trying to get ahead of myself with ordering stuff in.

Rockwool seems like a popular choice but there are lots of versions.

Any preferences out there? (the comparison function on the Rockwool website is playing up)

Stud walls have a 90mm void.  I read on here in another thread about not compressing acoustic products.  Would a 75mm thick product do the job?

 

 

[Oz07]

used rwa myself before. Ideally you want something that doesn't fit tightly into the space. So if 4" void get 3" or 2" insulation. Suppose it is whatever local suppliers stock 

[A_L]

Knauf Omnifit comes in 90mm, claimed to be suitable for acoustic insulation but lower density than the Rockwools you have posted, so have to double check performance.

 

https://www.knaufinsulation.co.uk/products/earthwool-omnifit-slab

[Moonshine]

Am I right in thinking you are specing just internal walls to meet Rw 40 dB?

 

Are you looking for this as a minimum or going over and above?

 

Based on the rockwool with 38×75 timber studs at 600mm centres and 1 layer 12.5mm acoustic rated plasterboard (11 kg/m²) each side and Insulation of a minimum of 50mm of ROCKWOOL FLEXI, this will give you 40 dB.

 

It's interesting because British gypsium indicate you can achieve the 40 dB with 65mm of apr1200 which is 12kg/m3 density, and wallboard.

 

For myself I would be looking not to use batts but rolls of mineral / glass wool or polyester and filling the cavity as much as possible without compression. Bearing in mind that once you get some fluffy stuff in the cavity of decent density the greatest gains you are going to get are increase density of boards, double boarding, resilient bars, or independent studs.

 

In this case with known studs if you really want to increase the acoustics in key areas use mineral wool rolls and increase density of boards or double board.

Edited October 13, 2018 by mike m
Error in thickness

[Moonshine]

Have a look at build up 4 in the attachment, Rw 41 dB in the table