Case studies of users of building environmental design decision support tools (eddst) are used to assess the tool effectiveness. This established a common denominator for architects, their clients, and even for eddts simulation specialist: the need for built in Quality Assurance. Contrary to their general reputation, designers want detailed quantitative environmental information. However, they also want to be able to trust this information. The book proposes a set of Quality Assurance (QA) procedures that would ensure that the black box of a digital simulation of building performance yields information that designers feel they can trust. The approach is an internet web service. It is a database of sources on the internet of Quality Assured performance data. Each new Quality tested eddst input file or measured performance report becomes another QA database. Each new product with Quality Assured performance data is also listed. The new SimQA web service provides a means of finding the data and keeping track of the provenance of that data: who has measured the data; what testing systems or instrumentation were used to measure; and what is the reliability estimate for the data.