Technical Booklet F1 Conservation of Fuel and Power in Dwellings·Page 48·3.50
Window and Roof Light Area Limits
The total area of windows, roof windows, rooflights and doors should not exceed 25% of the dwelling's total floor area unless compensating measures are implemented elsewhere.
Where a window is enlarged or a new window opening is created, the total area of windows, roof windows, rooflights and doors should not exceed 25% of the total floor area of the dwelling unless compensating measures are made elsewhere in the dwelling.
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