In order to study energy usage in residential buildings and to experimentally verify computer programs that have been written for calculating heating and cooling. loads and energy requirements in buildings, the National Bureau of Standards (NBS) purchased a factory-produced four-bedroom house. During 1972 and 1973, it was installed and tested in a high-bay environmental laboratory of approximately 2000 m3 (70,000 ft3) in volume, under simulated summer and winter conditions. Refs 1 and 2 give the details of that test program. During the latter part of 1974 and the first part of 1975, the house was relocated at a site on the NBS grounds in Gaithersburg, Maryland, and a solar heating and cooling system was added to the house. Ref 3 gives a complete and detailed description of the design and construction of the system. The purpose of this paper is to present the results of the first series of cooling tests conducted during the summer of 1975. Additional technical papers and/or reports will describe test results for the winter of 1975-1976.