Thermo-responsive hydrogel-based building envelopes for building energy-saving

Abstract

Transparent windows and opaque walls/roofs are two kinds of important building envelopes that significantly affect building energy consumption. Herein, a smart window with switchable solar transmittance and a wall/roof with dynamic solar absorptivity are proposed and fabricated by introducing the hydrogel that can modulate optical properties based on temperature stimulus. Optical measurement shows that the smart window can change its spectral transmittance at the solar radiation band between 0 (hot state) to 0.78 (cold state), while the solar absorptivity of the smart wall/roof varies between 0.29 (hot state) to 0.95 (cold state), exhibiting potential for self-adaptive thermal management for buildings. The experimental demonstration proves that the proposed smart window and wall/roof can reduce the indoor air temperature by 2.3 °C and 7.5 °C. In addition, building energy consumption is predicted, which reveals that energy consumption can be reduced by 10.79 %–34.28 % after the implementation of the smart window and wall/roof in buildings at Phoenix, Singapore, Nairobi, Cairo, and Hong Kong, indicating the proposed temperature-responsive spectrum modulation strategy for the window and wall/roof contributes to building energy saving.