Much of the difficulty in architectural design is in integrating and making explicit theknowledge of the many converging disciplines (engineering, sociology, ergonomicsand psychology, to name a few), the building requirements from many viewpoints,and to model the complex system interactions. The many roles of the architect simplycompound this. This paper describes a system currently under development: a 3D design medium and intelligent analysis tool, to help elicit and make explicit theserequirements. The building model is used to encapsulate information throughout thebuilding lifecycle, from inception and master planning to construction and 'lived-in' use. From the tight relationship between material behaviour of the model, functionalanalysis and visual feedback, the aim is to help in the resolution of functional needs,so that the building meets not only the aims of the architect, but the needs of theinhabitants, users and environment.