Loft Insulation

[stevebamford]

Hi all - so sorry to ask this as there are a zillion topics on loft insulation (and yes I have looked!) but can anyone shed some light on the below.

I have a large side loft in a victorian house, currently with no insulation. 4" joists. Currently boarded

Currently planning to take up existing floor, screw on 2 by 2 cross-battens and floor with 8' by 2' T&G chipboard

Am reluctant to add in thicker cross-battens due to weight issues.

But this only gives me 150mm of insulation.

The question is, what can i put in there to match the current standard. I understand its 270mm rockwool - but I guess that some insulation is better than others so if i spend a bit more I could get the same insulation value for less thickness

Any ideas ?

ta

Steve

 

[JohnD]

150mm is still pretty good

you get diminishing returns with extra thickness

the rigid foam slabs have more insulating power than the fibreglass quilt

one method I heard about but have never used, is to put rigid slabs like kingspan over the roof timbers, and lay your flooring over that. It is essential that all short-end joints in the flooring have timber under the foam under the joints, otherwise use trimmers or noggins or something as the foam slabs are not reliable to carry weight.