An experimental study of a thermosensitive retro-reflective wall in a hot-summer and cold-winter climate region

Buildings in hot-summer and cold-winter regions require envelopes that suppress summer solar gains while utilising beneficial winter gains. This study evaluates a thermosensitive retro-reflective wall (TRW) that changes optical state with temperature and redirects reflected solar radiation. Two reduced-scale, free-running test cells were monitored outdoors in Wuhan, China. They were identical on five faces; their south walls comprised either the TRW assembly (test cell H t ) or a conventional insulated wall (control cell H c ). During summer daytime periods, the mean indoor air temperature in H t was 0.74 °C lower than that in H c (SD = 0.28 °C; 95% CI: −1.44–−0.05 °C; p = 0.044), and the maximum simultaneous difference was 1.89 °C. At night, H t was 0.90 °C warmer (SD = 0.12 °C; 95% CI: 0.62–1.19 °C; p = 0.005), indicating slower nocturnal cooling. In winter, the 24 h mean temperature in H t exceeded that in H c by 1.36 °C (SD = 0.64 °C; 95% CI: −0.22–2.94 °C; p = 0.066). As daily solar irradiation declined from 14.13 to 5.81 MJ/m 2 , the indoor peak temperature difference decreased from 4.48 to 0.37 °C. The results indicate a season-dependent system-level response consistent with the intended optical states.