The discomfort index presented here quantifies the thermal discomfort associated with the design and operation of residential buildings during the heating season. Discomfort under steady-state conditions is estimated from the squared difference between the actual temperature and a preferred temperature (which is assumed to vary with clothing and activity levels). A penalty is also assessed for transient discomfort effects. The index allows calibration for individual preferences.

The proposed index is similar to the currently used Predicted Percentage of Dissatisfied, but is simpler and better suited to simulations of residential environments. Simulations can integrate the index over a heating season along with energy use to estimate the overall thermal performance of a building. These two complementary aspects of performance can be combined into an overall index, by using thermostat settings as an indicator of the relative weights that people assign to comfort and energy use.