once it gets past the ceiling to the wall plate it wouldnt be insulating the house and if thicker than the depth of the rafters would be in contact with the felt/ membrane which could wick moisture into the insulation?
I had some one pop over to look at insulation the loft as currently I only have 100mm of Insullation up there. He is method would be to use a spray foam. He said he would spray the foam right into the corners of the loft space (which will mean coveting the top of the cavity). I take it this is a no no then?
Also would spray the membrane on underside of the roof.