Technical Booklet F1 Conservation of Fuel and Power in Dwellings·Page 31·2.45
Roof Window and Rooflight U-Value Assessment Position
U-values for roof windows and rooflights are based on vertical position assessment; where assessed in other planes, adjustments must be made per BR 443.
The U-values for roof windows and rooflights given in this Technical Booklet are based on the U-value having been assessed with the roof window or rooflight in the vertical position. Where a unit has been assessed in a plane other than the vertical, the U-value given in this Technical Booklet should be modified by making a U-value adjustment in accordance with BR 443.
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