im doing an insulation job in my attic (cold roof). 110mm celotex between the rafters and 40 mm beneath. the rafters are very uneven so before plasterboarding ive take the opportunity to straighten them out with battons and spacers so the final plasterboard layer will be flat. however this means that in places the beneath the rafters layer of plasterboard will not be up against the plasterboard - there will be a small air gap. ive done what seems practical to eliminate any air ingress on the layer of insulation between the rafters (still allowing for 50mm air gap) - but will i be negating some of my insulation efforts to allow this air gap between the plasterboard and beneath the rafters layer of insulation - ie possibility of cold air getting in between the insulation
thanks