Monthly building thermal energy demand calculation procedures such as the utilisation method described in EN ISO 13790 and the monthly degree-day procedure contain parameters that reflect the variation of heating and cooling demands within a particular month. The frequency distribution of the loads is, however, neither explicit nor visible. This frequency information is important when calculating seasonal system efficiency and when apportioning load between the different fuels used in bivalent systems. This paper extracts the distributions embedded in the two procedures and examines the similarities and differences between them. It also illustrates how the distributions vary with the effective thermal capacity of the building. The report proposes appropriate areas of application for these methodologies, bearing in mind the levels of generalisation on which they are based.
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