Space heating, air-conditioning and refrigeration accounts for over 30% of the total energy use in the U.S. ASHRAE Standard 90P, ENERGY CONSERVATION IN NEW BUILDING DESIGN, sets forth requirements for the design of all types of new buildings, covering their exterior envelopes and selection of their HVAC, service water heating, electrical distribution and illuminating systems and equipment for efficient use of energy. This paper reviews the current status, content, and implications of the proposed energy standard and reports some experience with its use