Computer-aided simulations are commonly used topredict building enclosure performance. Withoutinformed guidance, however, they may produceinaccurate or misleading results that lead to performancefailures. This paper explores common shortcomings andchallenges associated with simulation of buildingenclosure assemblies through review of a broad range ofsoftware and simulation scenarios. Topics discussedinclude quantitative and qualitative simulationconstraints, reliability of inputs, significance andintegration of project-specific data, and interpretation ofresults.