To make informed decisions about the design, construction and operation of a building, it is necessary to predict and evaluate the impact of these decisions on the performance of the building. Each of these decisions impacts the performance of the building in a number of different and inter-related ways. Therefore, a computational environment that seeks to support this decision-making process needs to enable the prediction and evaluation of different aspects of building performance. Several stand-alone computer tools are currently available, each of which addresses a particular aspect of the building performance. The Building Design Advisor (BDA) brings these tools together and provides the data management and process control required for their integrated use, from the initial, schematic phases of building design. The output of one tool is easily used as input to another, either directly, or after appropriate manipulation to ensure compatibility, which makes the whole integrated environment more than the sum of its parts. A simple graphical user interface allows easy generation and maintenance of multiple design options, and enables the comparative evaluation of these design options with respect to multiple performance aspects. This presentation will focus on the concepts underlying the BDA software and illustrate them with examples. It includes a sequence of BDA screen shots demonstrating its use and information on current status and future directions.