CIBSE TM59 sets out a methodology for assessing the likely internal temperatures for a domestic property. It gives input data that the energy modeller can use including the hours of occupancy; internal heat gains from equipment for bedrooms, living rooms and kitchens; and internal heat gains from occupants. There are also guidelines for determining at what internal air temperature the windows are to be opened at, as well as suggesting heat gains for hot water pipework that runs through the accommodation or through communal circulation areas, such as corridors in a block of apartments.
The guide then sets out criteria that should be met in order to demonstrate compliance and that overheating is not a risk. These criteria are in the form of hours of occupancy that the air temperature in the building exceeds a set level. Criteria are there for daytime and night time occupancy, to also ensure comfort whilst sleeping.