In 1956 the first solar energy assisted heat pump commercial office building in the world was completed and occupied by Bridgers and Paxton Consulting Engineers, Inc., designers, owners and since that time occupiers of the Solar Building, Albuquerque, New Mexico. Performance data were collected during the 1956-57 winter heating season and reported (Ref. 1). At that time, fossil fuels were so plentiful and at such low cost that the system was not economically viable. After a few years of operation the solar portion of the system was deactivated.

With the renewed interest in solar energy and the lack of actual performance data from solar energy systems, in April 1974 the U.S. National Science Foundation awarded a grant to The Pennsylvania State University to conduct a field evaluation of the Solar Building. As field-collected data were obtained and analyzed, various aspects of the project were presented in many publications and at several seminars and conferences.

It is relatively easy to measure system performance over a long period of time. As will be discussed subsequently, hour-by-hour computer simulation and correlation with field collected data is an altogether different problem. Reference 3 discusses the myriad of problems in field-evaluating a building solar energy system comprised of several thermostatically controlled zones. One objective of the project described in this paper was to computer-model the building and system and attempt to correlate the simulation with field collected data.