Sound-deadening effects of insulation

[Charlie_Powell]

Hi,
I live in a fairly modern 3 level semi-detached dormer. The house is built in an exposed location on already higher ground, and the gable seems to be hit by the wind hard. I am sleeping on the middle floor for a few reasons, but one is the loudness of wind noises on the top floor. The top floor has a badly installed air-tightness membrane that is non-continuous. At some stage, I wish to open up the plasterboard to make the membrane as continuous as possible, as the home doesn't hold the heat adequately. When we do this, we may replace some of the PIR slabs inserted between the rafts as I don't think they were done well. Would replacing them with rock wool or the firm but flexible cellulose fibre blocks offer a denser insulation choice and, thus, a more quieter upstairs?

 

[oldbutnotdead]

The rockwool or similar stuff is a better sound reducer than pir but is less efficient as a thermal layer- you'd need 150mm of the rockwool etc to replace 100mm of properly installed pir. Which might be a problem between rafters cos of eaves ventilation.

 

[JohnD]

But remember that CWI is often only about 50mm of minrral wool, and you will have better than that.

The wool is better for blocking draughts as you can stuff it tightly into gaps with no precision cutting or foaming needed.