I'm build a loft conversion and the builder I have in is putting the 120mm insulation in between the joists. He said that this is still a warm roof because he has put a 25m sheet of insulation above the joists - is this correct?
I understand that normally for warm roof it should be the 120mm insulation on top, not in between the joists.
Will this now cause any evaporation problems and so on down the line?
I have attached a basic drawing of this..