Domestic Heat Loss Calculation

Heat Transfer

• Heat loss is simply the transfer of heat from a warmer object, such as a house or other building, to the colder air surrounding it. The greater the difference in temperature between two, the greater the transfer of heat. If the outside environment is the same temperature as the building, no heat loss will occur.

U-Value

• A material's u-value is its conductance, the degree to which it will lose heat during an internal/external heat inequality. This number is the reciprocal of its r-value, the measurement of the material's thermal resistance. A house built of materials with low u-values will have a lower degree of heat loss than one composed of high u-value materials.

Flat Surface Heat Loss Calculations

• A flat surface will lose heat at a steady rate, dependent on its material makeup, size and temperature. The hourly heat loss in BTUs can be calculated by multiplying the u-value, surface area and temperature difference of a material, divided by the thickness in inches. Complex objects such as houses are made up of several surface materials and must use numerous such calculations, one for each type of material involved.

BTUs to Watts

• The above calculation returns the surface heat loss in BTUs per hour. If the data is required in watts, this calculation must be altered. A single watt is measured at 3.412 BTUs. The original calculation, then, must multiply the thickness by 3.412 and divide the three original multiplied factors by the product of the equation.