Assessing the error from failure to account for urban microclimate in computer simulation of building energy performance

The paper examines the importance of using site-specific data in computer simulation of building energy performance. The CAT (Canyon Air Temperature) computer model, which is designed to predict site-specific air temperature in an urban street canyon for extended periods on the basis of data from a reference station exposed to the same meso-scale weather, was used to provide modified input to a series of Ener-Win simulations of the energy performance of a hypothetical office building. The simulations show that, depending on the urban configuration represented by the aspect ratio of the street canyon, the modification to air temperature in many locations may be too large to neglect if the simulation is to be used for realistic design decision making.