I'm shortly going to be insulating a the upstairs of my dormer. The rafter sizes on the roof are only 6 x 2's, which doesn't leave me a great amount of dept for insulation(150mm). I'm going to be insulating between the rafters with a rigid insulation board like xtratherm/kingspan etc. Someone has advised me that if a breather memebrane if used on the roof then the recommended 50mm air space between the breather and insulation is not needed. Does anyone know if this is true, or should the airspace still be left even with a breather membrane?
thanks,
dj01
thanks,
dj01