The Building Code of Australia (BCA) 5 star benchmark substantially rewards passive solar design and makes it difficult for non-passive solar designs to be approved in Perth. This study shows that winter heating loads are substantially reduced in passive solar designed houses, but external wall material is not a significant factor. On the other hand, a reduction of summertime air conditioning use is dominated by internal thermal mass more than by passive solar design strategies. The application of heating and cooling caps are not recommended as part of a regulatory mechanism, because they may adversely affect on passive solar design in some Perth houses and may eliminate some houses that otherwise perform well in the summertime. The BCA works with passive solar design to identify minimum thermal performance standards that apply to all dwellings and is the appropriate national approach to regulating residential energy efficiency standards. Passive solar design is recommended as the path beyond minimum BCA standards to deliver best practice in the future. (C) 2008 Elsevier Ltd. All rights reserved.