Technical Booklet F1 Conservation of Fuel and Power in Dwellings·Page 9
Definitions: Total useful floor area
Total useful floor area is the total area of all enclosed spaces measured to the inside face of external walls (gross floor area), with sloping surfaces measured as their area on plan, excluding non-enclosed areas such as open floors, covered ways and balconies.
"Total useful floor area" means the total area of all enclosed spaces measured to the inside face of the external walls, that is, the gross floor area, and in the case of sloping surfaces such as staircases, galleries, raked auditoria and tiered terraces shall be taken as their area on plan but shall exclude areas that are not enclosed such as open floors, covered ways and balconies.
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