Building performance simulation (BPS) is a powerful technique to predict the performance of a design proposal. It is extensively used towards the end of the design process to, for example, prove code compliance. However, its potential to provide design guidance early in the design process is rarely exploited. That is although decisions taken during conceptual design have a disproportionate impact on the final building performance, relative to time and effort consumed (Domeschek et al, 1994). To intensify the use of BPS early is to extend its capabilities. One issue to be addressed is the building performance uncertainty due to a wide range of plausible (uncertain) design decisions. A case study was conducted to evaluate the use and potentia...