Validation of building energy simulation programs consists of a combination of empirical validation, analytical verification, and comparative analysis techniques. An analytical verification and comparative diagnostic procedure was developed to test the ability of whole-building simulation programs to model the performance of unitary space-cooling equipment that is typically modeled using manufacturer design data presented as empirically derived performance maps. This procedure is based on the International Energy Agency (IEA) building energy simulation test (BESTEST) diagnostic method and systematically tests whole-building energy simulation software by comparing results from such software to analytical solutions that were developed for the test cases. Field trials of the new procedure were conducted by researchers from nations participating in the IEA Solar Heating and Cooling (SHC) Programme Task 22, using a number of detailed hourly simulation programs from Europe and the US, including: CA-SIS, CLIM2000, ENERGYPLUS, PROMETHEUS, TRNSYSTUD, and two versions of DOE-2.1E. This article also includes discussion about simulation validation methodologies. Crown Copyright