i have now fully boarded the loft floor and am about to start on the "walls" my question is do i ned to actually insulate between the rafters or can i staple a breathable membrane across and plasterboard straight on to that? the reason i ask is that the rafters are very old and only the thinnest insulation would be able to leave the 50mm void for ventilation. my idea was to leave them as they are without insulation on the basis that the membrane followed by plasterboard would be enough of Insulator and would also allow me to install halogen downlighters (spots).