HI-85-28-4 -- Determination of Thermal Time Constants in Residential Housing PDF

The thermal time constant of a house structure is directly related to tile heat capacity and mass of its construction materials and furnishings. The greater its overall heat loss, however, the more the effect of heat capacity and mass is offset. It will be shown that the thermal time constant follows an exponential decay that is proportional to the initial inside-outside temperature difference.

Twenty-five individual days of field-collected data, over a wide range of inside-outside temperatures, will be used to calculate a constant of proportionality. The test house constant was 0 .0428 with a standard deviation of 0.0091. This constant permits determination of the thermal decay of a house for any initial inside-outside temperature difference.

The thermal time constant will be utilized to show how energy savings from thermostat setback may be influenced. The impact of the length of thermostat setback period will be demonstrated.

Units: Dual