Installing Rockwool acoustic insulation between floors in timber frame house

theaaao

Looking to improve sound traveling between floors in a timber framed house. I took up the floor upstairs and there is approx 400mm void between plasterboard ceiling downstairs to the stud floor upstairs. Its a newly constructed house from 2024.

Was going to put some Rockwool acoustic insulation in between the void to dampen the sound. Is there any issue with doing this and interrupting the airflow between the floors? is there a risk of condensation build up or another issue I'm not considering?

Is it enough to put rockwool between the joist, or should I also considering removing the stud floor to put a damper on on the joists before relaying the stud floor?

mike_2009

I'm doing Cellecta Screedboard 28 on top of the upstairs subfloor and 100mm acoustic insulation between the pozi joists as part of an acoustic system. If using just 100mm breathable insulation I doubt it will cause any issues (I've Pozi open web joists but I've seen new builds use I Joists and am not familiar if they will have an issue - best check with builder?).

There are lots of other systems, I didn't want to take up my subfloor but I've access underneath as I'm self building currently. Are you more worried about impact noise or general sound noise? Takes a different approach to mitigate each but both together work very well. I've to seal/treat the Screedboard before tiling / gluing flooring so that's another consideration.

theaaao

Thanks for the comment!

It’s more general sound noise travelling up from kitchen/ living area. With the current void having nothing to absorb the sound travelling up, hoping the insulation can dampened that.For example there are spotlights in the ceiling so these would be weak points already leaking sound.

I looked up the screedboard which is an interesting option, but I think it will raise the floor too much now upstairs. We’re putting carpet upstairs with thick under lay so hoping that will be sufficient to dampen sound from above.

mike_2009

if you're taking up the floor upstairs you can deal with those downlighters (fire rated I'm assuming) but a nice layer of insulation should assist with the general noise transfers and a nice carpet underlay will also help. Or noise cancelling headphones!!

Mellor

https://www.boards.ie/discussion/comment/123428307#Comment_123428307

I wouldn't assume they are fire rated downlights. Certainly wouldn't be the norm.

Carpet underlay will help with footfall noise (impact) but will do very little for general noise travelling (airbourne).
To get the best benefit form rockwool or the like you want to use a higher density. 14kg is good, 25kg/m3 better.
Ultimately the system needs mass to to sound proof. A good build up would be 2 layers of firerated plasterboard. 100mm of 14-25kg rockwool, and rubber isolation later in the floor above. Every bit helps.

mike_2009

Don't they have to be fire rated for below bedrooms? That build up you've listed is solid, very nice!