TGD L 2008 – B.6.1.2W1b – WALL COnSTRUCTIOnS, W1: Cavity walls, insulation in cavity, cavity retained (partial fill)

B.6.1.2 W1(b): As W1(a) except with insulation partly in cavity and partly as internal lining. If composite boards of plasterboard backed with insulation (of similar conductivity to that used in the cavity) are used internally. Table B9 and B10 can be taken as applying to the total insulation thickness (cavity plus internal). If internal insulation is placed between timber studs, total insulation thickness will be slightly higher due to the bridging effect of the studs. Table B11 applies in this case. Lower U-values, or reduced insulation thickness, can be achieved by using insulating concrete blockwork (rather than dense concrete) between the cavity and internal insulation. Insulation partly in cavity and partly as internal lining helps minimise thermal bridging. Internal insulation limits thermal bridging at floor and roof junctions, whereas cavity insulation minimises thermal bridging at separating walls and internal fixtures. Installation guidelines and precautions Installation of insulation in the cavity should follow the guidelines given above for construction W1(a) (partial-fill cavity insulation), and installation of the internal lining should follow the guidelines given below for construction W4 (hollow-block).

C:BCARTGDtgd LTGD%20L%20NON%20DWELLINGS%20-%202008TGD%20L%20-%20NON%20DWELLINGS%202008%20-%20APPENDIX%20B%20Table%20B9.pdf