This International Standard provides the framework for a design process for single-family residential and small commercial buildings, characterized by the “energy consumption ratio” as the key criterion. The design process, or design guidelines explaining the design process, is prepared by suppliers of the design guidelines for designers of buildings as a whole system, building envelopes or building equipment, all of which are deeply related to the energy performance of buildings. Designers play the most important role in the wide propagation of energy-saving technologies because they often make the final decisions on whether energy-saving technologies should be adopted or not, and which energy-saving technologies should be adopted in actual building projects. This International Standard specifies a framework of the design process for energy-saving single-family residential and small commercial buildings, with the energy consumption ratio as the key criterion. It is intended to assist in the development of design guidelines for practitioners who design energy-related parts of buildings.