Numerical and experimental studies on the energy performance of thermal mass windows

Thermal mass window is a transparent water storage envelope for improving energy efficiency of building. Currently, the embedded algorithms in all energy simulation programs disable the explicit energy simulation of building zones with thermal mass windows. The energy simulation methodology for building zones with thermal mass windows, as well as the comparative experiment for testing their energy performance, is presented in the article. For solving the inherent energy simulation problem, the integrated numerical approach based on the simplified one-dimensional nodal thermal model and the optical model was proposed. In a case study, the numerical approach was applied to an office-building zone with a typical thermal mass window to investigate its energy performance. Meanwhile, a comparative experiment on two thermal boxes with and without thermal mass windows under the identical outdoor conditions was also performed for the verification of energy performance of thermal mass windows. Both the simulation and the experimental results reveal that thermal mass windows can outperform conventional glazing in terms of thermal performance and energy efficiency. Shaded thermal mass windows in summer can produce cooling load reduction, while exposed ones in sunny winter days contribute to heating load reduction, which is beneficial for building energy saving.