This paper summarizes the results of numerous building energy analysis and design tool evaluation exercises carried out under lEA Task VIII: Passive and Hybrid Solar Low Energy Buildings. These exercises have included: Empirical validation of detailed simulations using passive solar test room data from Canada, Switzerland and the U.S. Code to code comparison of detailed simulations for severa¡ passive solar system types in Copenhagen and Denver. Comparison of simplified design tool performance predíction to detailed simulation prediction for realístic passive solar buildíngs (direct gain, storage wall and sunspace), light and heavy weight construction, in Ibree climates (Denver, Geneva and Copenhagen). Comparison of simplified design tool performance prediction to detailed simulation performance prediction for simplified (shoebox) passive solar test cases in three climates (Denver, Geneva and Copenhagen). Evalualion of the capability and userfriendliness of resídential energy design tools. Development of 28 benchmark test cases for simplifíed design tool evaluation, based on Ihe resuits of six detailed simulations.