Under rafter insulation

[tvrjohn]

Ok for my loft conversion i need to insulate under the rafters, multifoil insulation is the most space effiecient and represents 200 thk insulation.

Is it still necessary to fit additional rigid insulation celotex/kingspan between the rafters first ?
Can i use rockwool type ?

Thanks

 

[noseall]

Ok for my loft conversion i need to insulate under the rafters, multifoil insulation is the most space effiecient and represents 200 thk insulation.

Is it still necessary to fit additional rigid insulation celotex/kingspan between the rafters first ?

Yes.

 

[freddiemercurystwin]

I have never seen any meaningful advantage to using the multifoils as you need a 25 gap above and below and as mentioned it only complies when used in addition to a rigid insulation between the rafters.