No membrane bare tiles

[c stewart]

Hi I’m working on our new house which has a very old loft conversion , no membrane between the tiles and the plasterboard . We are going to Insert kingspan into the gap between tiles and plasterboard where we can . Any reason this is a bad idea … see photos any advice welcome

 

[oldbutnotdead]

Looking at the depth of the rafters you won't have room to put a useful thickness of insulation in and maintain ventilation under the tiles (vital to prevent battens and rafters rotting).
Better off fixing 100mm PIR boards to the rafter faces and then taping and boarding over, lot easier as well

 

[datarebal]

Take a look at Superfoil.