Interest in the heating industry concerning the effect of air density on heat transfer has been renewed in recent years. In 1964, ASHRAE sponsored a symposium on this subject with emphasis on the significant effect of operation at high altitude above sea level on equipment performance. During the same year, an ASHRAE Committee on Fuel Consumption reported that from some field data, the heat loss of houses appeared to be dependent on altitude as shown in Table 1.1.

Since it is vitally important to know the heat loss of a building before sizing the heating equipment to be installed the Institute of Boiler and Radiator Manufacturers under a cooperative research agreement with the University of Illinois decided to determine experimentally the effect of air density on the heat transmission coefficients of air films and some common materials currently used in building construction.