TGD L 2011 – B.5.1.2R1b – ROOF CONSTRUCTIONS, Construction R1: Tiled or slated pitched roof, ventilated roof space, insulation at ceiling level

B.5.1.2 R1(b) Insulation between and below joists Insulation is laid in one layer between the joists, protruding above them where its depth is greater, and leaving air gaps above the joists. A composite board of plasterboard with insulation backing is used for the ceiling. Installation guidelines and precautions Similar guidelines and precautions apply as for R1(a) above. Where the thermal conductivity of insulation between and below the joists is different, the material on the warm side (i.e. below the joists) should have a vapour resistance no lower than that on the cold side (i.e. between the joists). It is preferable if the insulation on the cold side is more permeable than that on the warm side (e.g. mineral wool outside with expanded polystyrene inside).

C:BCARTGDtgd LTGD%20L%20DWELLINGS%20-%202011TGD%20L%20-%20DWELLINGS%202011%20-%20APPENDIX%20B.5.1.2R1b.pdf