Is my house sick enough to call the doctor? A methodological approach to market house-doctoring.

States that the dependence between the energy consumption to maintain a comfortable indoor climate and the average outdoor temperature is close to being linear (at least in the absence of significant passive solar gains). Calls the slope of the graph the energy signature of the building. Such an analysis yields a powerful tool to monitor the energy consumption of a building and thereafter to evaluate the effectiveness of a set of retrofits. Suggests that the energy signature be expressed in units of hourly air change rate.