This paper summarises the work of the CIBSE Example Year Task Group. Its main task has been to develop a methodology for the selection of representative weather data. This data is required as input to the various procedures available for the estimation of the energy performance of buildings and their engineering systems. As a further aid to applying a consistent set of meteorological data as input to energy calculations, the Task Group's work has extended to the preparation of a set of algorithms for calculating psychrometric properties 

Two methods for reducing weather data are assessed and compared with respect to use for heating calculations. Degree days for calendar months, utility bill periods and without weekends were calculated and compared along with temperature 'bins' of various sizes using the CIBSE Example Weather Year. Wind velocity and solar radiation are also analysed with respect to degree days. Both methods, degree days and the bin method, are found to represent the actual weather conditions adequately for use in heating calculations.

To predict the performance of a naturally ventilated building, estimates of the windinduced surface pressure distribution are needed. In urban environments, where buildings are grouped closely together, these surface pressures will be strongly influenced by the surrounding structures. In addition, the sheltering effect of the surrounding built-up environment can make it more difficult to obtain large enough pressure differences across a building necessary to produce adequate natural ventilation air flow rates.