Technical Booklet F2 Conservation of Fuel and Power in Buildings Other Than Dwellings·Page 59·3.62
Relaxed U-value for glazing in buildings with high internal heat gains
In buildings with high internal heat gains, a higher average U-value for windows, doors and rooflights may be used if justified by calculation, but must not exceed 2.7 W/m2.K.
In some buildings with high internal heat gains, a less demanding U-value for glazing may be an appropriate way of reducing overall CO2 emissions. Where this can be demonstrated by calculation, the average U-value for windows, doors and rooflights may be greater than the value given in Table 3.2, but should not exceed 2.7 W/m2.K.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet F2 - Conservation of Fuel and Power in Buildings Other Than Dwellings.pdf