Integrated building envelope performance evaluation method towards nearly zero energy buildings based on operation data

The thermal transmittance plays a decisive role in building energy efficiency design, which determined by standard in-situ measurement are obviously not equivalent to the practical building load level. There is still a lack of post-evaluation method that can separately evaluate the energy saving effect provided by integrated building envelope, especially for the nearly-zero energy building (NZEB) whose thermal inertia cannot be neglected. This paper proposed a model-based integrated building envelope performance evaluation method, which contains a reverse parameters identification and a forward load calculation. The data-driven lumped-parameter model represented by resistance–capacitance network (RC-model) reflects the integrated envelope performance, and four different model structures were designed for different treatment of thermal mass were compared. The applicability of the selected 7R6C model in the simulation of NZEB is demonstrated by the accuracy verification, sensitivity analysis of initial values of temperature node and uncertainty assessment of internal heat gain. A renovation case achieved an annual heating demand assessment result of 14.0 kWh/(m2·a) under typical annual meteorological data, which is lower than the limit value of a NZEB in cold region of 15.0 kWh/(m2·a). The evaluation results show that the envelope renovation meets the requirements of energy efficiency design. On the way to low-carbon buildings, the corresponding post-evaluation method needs to be gradually improved.