Evaluation of the dynamic energy performance gap of green buildings: Case studies in China

The green building concept originated from the need and desire for more energy efficient and environmentally friendly construction practices. With a boom in certified green buildings in recent decades, however, various stakeholders have raised concerns about the actual energy performance of such buildings. While studies have shown significant gaps between the expected and actual energy use of green buildings, the methods used in the analyses have been considered inappropriate. A dynamic approach has been suggested to quantify the discrepancy between the expected and actual energy use in green buildings. However, although the concept of the dynamic approach has been discussed in several studies, a process and methods for applying the approach in real applications are not available in the literature. This study introduces a process and methods for practicing the dynamic approach and provides five case studies of using this approach to assess the energy performance gap of green buildings. The analyses show that the dynamic performance gap of the five buildings ranges from 3.0% to 53.5%, with a median of 24.7%, and the average dynamic gap of the HVAC system is nearly two orders of magnitude greater than that of the non-HVAC system. The degraded controls of HVAC systems may be a main cause of the performance gap.