Designing energy-efficient affordable housing is especially complex because of the limited budget available for “special” features, the tight timelines imposed on the design team, and the many decision-makers whose approval is required. The thermal comfort of the residents is rarely considered, and as a result, the housing may be affordably built but often proves uncomfortable and expensive to live in. This paper presents some of the unique features of HEED, a Home Energy Efficiency Design tool, that helps address all these issues at the very beginning of the design process. It also gives the architects graphic tools that communicate to the clients, managers, and owners the potential impact of design decisions on human thermal comfort and energy costs.