A simple calculation makes it possible to determine the maximum rate of heat loss from a basement and the total basement heat loss over the heating season. Tile procedure assumes that variation of basement heat loss during the year is a significant factor in the house heat balance; and it utilizes analytical as well as experimental data to develop a set of factors that are then used in the calculation of basement heat loss. This paper is a compilation of the pertinent sections of a publication describing in detail several studies undertaken by the Division of Building Research of the National Research Council of Canada on basement heat loss.