Climatic information has been used to optimize passive heating and cooling in both the design of new structures and the retrofitting of existing structures. This paper reports on two specific projects. The first, a residence known as the Nacogdoches Houses, a passive solar and energy conscious dewlling, is discussed from initial design concept through construction and the first year of operation. The second, a passive retrofit of an 18 year old residence in Houston, is discussed from a historical viewpoint; origj original design and load profiles, reasons for choosing the building for passive retrofit, and limitations of site and structure. The retrofitting sequence and the respective results are presented, and data are reviewed from two years of operation. For each dwelling, the results and conclusions on both passive heating and cooling are specifically discussed.