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Energy use for heating in typical British houses is taken from the following:
Heat demand for space heating per dwelling built post-1996 (kWh delivered energy) 14,600 kWh.
Ref: 40% house, Boardman B, Darby S, Killip, Hinnells M, Jardine C N, Palmer J and Sinden G, Environmental Change Institute, University of Oxford, 2005.
Average British house size 85 sq m, average newly built dwelling 76 sq m .
Ref: Unaffordable Housing, Fables and Myths, Alan W. Evans and Oliver Marc Hartwich, Policy Exchange, 2005.
14,600kWh per year divided by 85 sq m =171.76 kWh/sq m per year.
Passivhaus practice measure heat loss per sq m of usable floor area (Treated Floor Area or TFA), whereas UK practice measures the whole area of the internal envelope, including partitions. (Gross internal floor area or GIFA). As TFA is smaller than GIFA for the same building, Passivhaus energy efficiencies are more efficient if measured using GIFA.