Describes the mathematical methods employed in the ENCORE-Canada computer program which predicts the hourly as well as the annual heating requirements of small residential-type buildings. The model includes the effects of thermal storage, internal heat gains, basement and air infiltration losses, transmission heatlosses and solar heat gains. The heating system is a thermostatically controlled oil-fired furnace with warm air distribution. Hourly solar radiation and weather data forvarious Canadian cities are used to simulate outdoor conditions.