Characterizing Thermal Performance of Buildings Using Dynamic Model Identification

© 2013 ASHRAE. The energy performance of a building is, apart frominstalled systems and building usage, primarily determined by the thermal characteristics of the building envelope. An important distinction needs to be made between the theoretical building energy performance as calculated in the design phase and its actual as-built performance. Several studies have shown that these can differ rather significantly. As a first step in bridging this energy performance gap, this paper investigates the possibility of characterizing the as-built thermal performance of building envelopes using dynamic data analysis of appropriate experiments. Essentially, the investigated building is modeled as a simplified thermal system. The parameters governing the workings of the thermal system are estimated by fitting it to measured thermal performance data of the building, by means of maximum likelihood estimation. A scale model of a building serves as a case study. Identical measurement campaigns are simulated in winter and summer. Models of increasing complexity are fitted to the simulated measurement data of both campaigns. The fitted models are evaluated and compared on the basis of their log-likelihood, output residuals, and corresponding auto-correlation function and the cumulated periodogram. Using likelihood ratio tests, it is assessed whether models of larger complexity perform significantly better than smaller models. The best-performing models of different model orders are cross-validated. Hence, a model order tailored to the investigated fabric, the imposed experiment, and the weather conditions is determined.status: publishe