TGD L 2011 – 1.3.2.4 – Fabric insulation

1.3.2.4 The maximum area-weighted average U-value for doors, windows and rooflights of 1.6 W/m2K given in Table 1 applies when the combined area of external door, window and rooflight openings equals 25% of floor area. However, both the permitted combined area of external door, window and rooflight openings and the maximum area-weighted average U-value of these elements may be varied as set out in Table 2. The area of openings should not be reduced below that required for the provision of adequate daylight. BS 8206: Part 2: 2008 Code of Practice for daylight and CIBSE Lighting Guide LG 10 gives advice on adequate daylight provision.

C:BCARTGDtgd LTGD%20L%20DWELLINGS%20-%202011TGD%20L%20-%20DWELLINGS%202011%20-%20SECTION%201%20Table%202.pdf