This Home Energy Brief focuses on whole-system design. The Brief covers the application of whole-system design to a building envelope, building materials, and the cost and financing of whole-system design. The Brief introduces the synergies that exist between thermal mass, windows, and other components of passive solar design. This process of working through whole-system design can be applied to other projects. As of 2012, the Home Energy Briefs have been updated and adapted to Southern California Edison’s Online Home Energy Guide.