ECOTECT 5 is the one of the most comprehensive and innovative building analysis software packages on the market today. It features a designer-friendly 3-D modeling interface fully integrated with acoustic, thermal, lighting, solar and cost functions. Designers can even use ECOTECT to generate vital design information before the building form has even been considered. Using detailed climatic analysis, the potential impact of solar radiation, available light and even prevailing winds can be considered. The comparative analysis of simple sketch models can also help guide the decision-making process right from the start. However, ECOTECT was not meant as a final design validation tool. For maximum benefit, it should be used from the project's inception and, as the design nears completion, the ECOTECT data should be exported to more focused validation tools such as EnergyPlus and RADIANCE. Dr. Marsh will discuss his research on a program to link ECOTECT and the DOE EnergyPlus building energy simulation program.