Methods of Computations

The computations are carried out on an hour-by-hour basis. Heat transfer through walls is calculated using a conduction transfer function, with its coefficients determined for each wall/roof construction using the ‘State-Space’ method.

This procedure accounts for the time delay and amplitude decrement of the heat flux through multi-layer wall/roof constructions, and is applicable to any outdoor temperature and solar radiation hourly profile (such as hourly profiles affected by varying cloud cover and shadow effects).  

Heat storage in the building structure is accounted for by applying radiant time series factors to the radiant portion of the instantaneous heat gains thus ‘spreading’ the radiant heat gains over time in relation to the thermal capacity of the building.  

Computations of the heat gains through glazing are based on the principles of radiant heat transfer using the solar-optical properties of the glazing element, solar radiation intensities and angles, and the effects of shading.