The early design model for prediction of energy and cost performance of building design options

In order to encourage the use of computer modelling in building environmental analysis, it is necessary to provide a model developed from the designer's point of view. Detailed simulation models require a high degree of expertise and familiarity, further, there is also a need for detailed information not available in the early stages of the design process. Simplified models play an important role in the early stages of a design to achieve an integrated design: firstly, they are easy to use and, secondly, they require information easily available at the start of a design. In the Early Design Model (EDM) the solar gain utilisation factor has been determined as a continuous function of thermal mass. The differences between the annual energy predictions of EDM and SERI-RES ranges from 0.1% to 4.6% for time constants ranging from 378 to 2.52 hours. The differences between the two sets of predictions on monthly basis ranges from m 3.6% to m 6.48% (EDM's predictions being larger) during the heating season, and from +2.86% to a maximum of +51% (EDM's predictions being smaller) in the remaining part of the year. In addition to energy predictions, EDM incorporates a facility which gives cost indications.