ENERGY SIGNATURE MODELS FOR COMMERCIAL BUILDINGS - TEST WITH MEASURED DATA AND INTERPRETATION

The purpose of this paper is twofold: to see if the application of the energy signature model PRISM to commercial buildings can be improved by adding occupancy as a variable, and to examine what one can learn from the individual parameters that have been identified. Using occupancy rate as proxy for the operating mode of the building and its HVAC system, the model is generalized by doubling the number of parameters and distinguishing two types of day, occupied and unoccupied. This approach is tested with measured consumption data for some fifty commercial buildings. The results show that occupancy data can bring appreciable improvement in the accuracy of the model. However, the interpretation of the individual parameters, such as slope and balance point temperature, should be undertaken with great caution. Due to various biases the discrepancy between the parameters identified by an energy signature model and the true values can differ by far more than the standard errors indicated by the regression. Such biases are particularly important in commercial buildings, as we demonstrate with several examples.