Performance-rating-based approach to formulate a new envelope index for commercial buildings in perspective of energy efficiency and thermal comfort

Taiwan's building envelope thermal performance assessment method (ENVLOAD) was implemented in 1995. The lack of regard for thermal comfort in ENVLOAD has caused ENVLOAD certified buildings to have indoor areas that cause thermal discomfort, which leads to an increase in the energy end-use of the building during actual operation stage. This study aims to develop a new building envelop energy performance index by simultaneously analyzing the influence of energy consumption and thermal comfort. Latin hypercube sampling method is adopted to generate various building envelope samples for building energy simulation to construct the evaluation equations. By comparing to each sample’s annual sensible cooling energy against its own baseline case, indices of performance ratings (PR) based on the dry-bulb temperature and the operative temperature control are proposed. Another aim is to establish an algorithm to convert the proposed index to the previous ENVLOAD benchmark so that the new index can be directly applied to the existing building energy conservation regulations. The study found that the standard regression coefficient of the glazing's thermal insulation property rises from 0.11 to 0.20 when the control scheme switches from dry-bulb control to operative temperature control. Suggesting that the thermal performance requirements for the openings of building envelopes are more important for the new index based on thermal comfort, and that designers need to pay more attention to the control of indoor solar radiation heat gain.