Insulate loft room

[bunters1976]

Advice would be massively apprciated.

Our loft room was built in the 1930s with the house. It is not insulated at all with plaster on the roof joists.

I would like this all removed and it insulated properly before being remastered.

What is the correct way to do this and what materials should I use?

Any advice would be appreciated.

Thanks

 

[oldbutnotdead]

Depends on what headroom you have. The usual is (depth of rafters - 50mm) of PIR between the joists (need to maintain 50mm air gap under the tiles/slates/felt) , then add another x mm of PIR below the joists so the total PIR thickness is about 150mm (ish- U value target in Part L is 0.16 or 0.18) then plasterboard and skim.

If you have loads of headroom them a greater thickness of rockwool is much cheaper and easier to fit (use battens to make the rafter depth greater so you can stick 250mm of rockwool in the gap, plasterboard and skim

Or a combination of the 2.

 

[bunters1976]

Hi.

Thanks. Started this. 1 further question if I may please... Do I need a vapour layer or anything between the pir and the plasterboard? If so what would you suggest? Thanks

 

[oldbutnotdead]

Foil tape on the joints between the PIR sheets and that's your vapour barrier.

 

[bunters1976]

Great thank you