BECOP: A New Metric for Measuring the Energy Performance of the Building Envelope

Thermal properties of the building envelope (BE) prescribed by codes and standards do not provide a consistent and comprehensive measure of its performance. Qualitative comparative analysis employed by the codes to assess energy savings is deterrent to technology development as the potential energy savings are never realized. A new metric, referred to as the building envelope coefficient of performance (BECOP), is proposed, which compares the BE performance to an ideal system. BECOP, which is invariant to calculation methods and applicable to all building types and climate zones, is a comprehensive metric for assessing the thermal performance of building envelopes while accounting for the various building characteristics. The sensitivity and range of BECOP were assessed for Canadian climate and construction methods. Using case studies, BECOP results revealed that current practices and regulations pertaining to the building envelope are inconsistent and fail to provide any measure of efficiency. It was also found that current building envelope technologies are not energy efficient. A max BECOP value of 35% is obtained for the best building envelope technology, revealing inefficiencies and energy saving potentials.