Simplified hourly method to calculate summer temperatures in dwellings

The objective of this study was to develop a method for hourly calculation of the operating temperature in order to evaluate summer comfort in dwellings to help improve building design.
A simplified method was developed on the basis of the simple hourly method of the standard ISO 13790:2008 but with further simplifications. The method is used for calculating room temperatures for all hours of a reference year. It is essential that the simplified method is able to predict the temperature in the room with the highest heat load. The heat load is influenced by the solar load, internal load, ventilation loss, heat loss and the external temperature. The numbers of hours exceeding 26 °C and 27 °C are summarised in order to compare them with the requirements for summer comfort in the Danish Building Regulations.
The simplified method was qualified by comparison with simulation results from an advanced program for thermal simulations of buildings. The results are based on one year simulations of two cases. The cases were based on a low energy dwelling of 196 m². The transmission loss for the building envelope was 3.3 W/m², not including windows and doors. The dwelling was tested in two cases, a case with an ordinary distribution of windows and a “worst” case where the window area facing south and west was increased by more than 60%.
The simplified method used Danish weather data and only needs information on transmission losses, thermal mass, surface contact, internal load, ventilation scheme and solar load.
The developed method can calculate the number of hours above a given temperature limit. The limits are a prerequisite for the development of the simplified method, and a supplementary maximum temperature limit is suggested to ensure robustness. The setting of the ventilation rate is found to be essential for the fulfilment of summer comfort. Thus it is very important to address both opening areas and ventilation rates.
The developed simplified method makes it possible to test whether or not a building design for a dwelling will prevent excess of the summer comfort limits set by the building regulations.