The Corrected Heat Loss Formula
The corrected heat loss formula was devised in 1965 by Warren
S. Harris and Calvin H. Fitch of the University of Illinois. It takes into consideration internal heat gains, which have shown a marked increase over the past 40 to 50 years. These internal heat gains make a significant contribution to the total required heat of a house or building, a factor that makes the original 65°F heat base established some 40-odd years ago too low for making a correct estimate. Furthermore, an inside average temperature of 73°F is probably more correct than the 70°F temperature previously used.
According to Harris and Fitch, the degree-day base (for all areas except along the Pacific Coast) must be corrected by the percentage given in Table 4-7. The calculated heat loss should then be reduced by 3.5 percent for each 1000 ft. the house or building is located above sea level. If the heat loss is below 1000 Btu per degree temperature difference, the 65°F degree-day base should be further reduced to the figures given in Table 4-8.
Table 4-9 illustrates the use of the corrected heat loss formula for determining comparative fuel requirements for No. 2 oil and natural gas.