The project IDEA+ aims to develop an “Integrated Design Environment for Architecture”. Its goal is providing a tool for the designer-architect that can be of assistance in the early-design phases. It should provide the possibility to perform tests (like heat or cost calculations) and simple simulations in the different (early) design phases, without the need for a fully detailed design or remodelling in a different application. The test for daylighting is already in development (Geebelen, to be published). The conceptual foundation for this design environment has been laid out in a scheme in which different design phases and scales are defined, together with appropriate tests at the different levels (Neuckermans, 1992). It is a translation of the “designerly” way of thinking of the architect (Cross, 1982). This conceptual model has been translated into a “Core Object Model” (Hendricx, 2000), which defines a structured object model to describe the necessary building model. These developments form the theoretical basis for the implementation of IDEA+ (both the data structure & prototype software), which is currently in progress. The research project addresses some issues, which are at the forefront of the architectis interest while designing with CAAD. These are treated from the point of view of a practicing architect.