I intend having all the slates re-layed on the roof of my 99 year-old house, in order to repair several leaks. There is an attic room in most of the main roof, with sloped ceilings along both sides. The rafters here are 3.5" deep, so there is only this space above the original lime ceiling plaster (which crests up through its laths) and the bottom of the 0.75" thick battens. The battens are spaced about 7" apart (for 16 x 8" slates), and the rafters about 12" apart.
Will it be adequate to lay 50mm of the the common yellow glass-fibre insulation over and above the back of the plaster laths (between the rafters), leaving about 1.5" space for the breathable membrane to dip a little. The membrane would not be stretched taut, as the roof will not be counter-battened.
Could I practicably do more than this to insulate sufficiently in this area of the roof?
Will it be adequate to lay 50mm of the the common yellow glass-fibre insulation over and above the back of the plaster laths (between the rafters), leaving about 1.5" space for the breathable membrane to dip a little. The membrane would not be stretched taut, as the roof will not be counter-battened.
Could I practicably do more than this to insulate sufficiently in this area of the roof?
