Six test buildings were extensively instrumented to measure summer space cooling loads. The buildings were one-room structures with the same floor plan and orientation. They were identical, except for the wall construction, which was as follows: insulated lightweight wood frame; uninsulated lightweight wood frame; insulated masonry with outside mass; uninsulated masonry; log; and insulated masonry with inside mass.
The buildings were exposed to summer weather conditions at the National Bureau of Standards located in Gaithersburg, MD. Tests were carried out to investigate the effect of wall mass on the space cooling energy requirements when the buildings were operated in the following fashions: fixed indoor temperature setting of 65°F (18°C), fixed indoor tempera­ture setting of 76°F (24°C), and night ventilation cooling. The purpose of the test with a fixed indoor thermostat setting of 65°F (18°C) was to simulate building performance in hotter climates.

The study conclusively demonstrated the effect of thermal mass on the summer cooling energy requirements.