Cold loft insulation

[tomaszm89]

Hello,

I plan to reinsulate my cold loft. It's fully boarded with very old wool insulation between 100m joists.

For new insulation I want to include PIR boards but the question is if I can lay it in between the joists instead of the wool (for example 75mm with some space between top storey ceilling and the insulation board and between chipboard and insulation board )? Would it cause any condensation issues?

The other idea is to put new 100mm wool betweeen the joists and add 50mm insulation boards on top of that and then board the area back.

Any thoughts ?

 

[JohnD]

The other idea is to put new 100mm wool betweeen the joists and add 50mm insulation boards on top of that and then board the area back.

That is a method that used to be recommended by manufacturers. The recommendation, and how-to-do-it video on Utube, disappeared shortly after the Grenfell disaster.

At about the same time, I resolved never to use rigid foam insulation inside my house.

Not a coincidence.