Research on Performance of Color Reversible Coatings for Exterior Wall of Buildings

The purpose of this study is to investigate the ability to improve building envelope thermal insulation efficiency by adding thermochromic material into the outer paint coating layer. Normal white-color paint (W) is mixed with a reasonable amount of black-color reversible thermochromic material (r) and thus turns to gray-color paint (R) which can perform color-changing process. The new paint mixture (R) is then compared to the normal gray-color paint (G) and white-color paint (W) in the market in terms of reflectance and absorption under solar radiation. Also, phase-change-material (p) is added to form a new paint mixture (R + p) in order to increase the heat-insulating effect of the original paint. Three parameters including reflectance, absorption and surface temperature have been investigated to analyze thermal performance of all of the prepared paint samples. Experiments are conducted indoor with halogen light source which acts as the simulated solar infrared radiation source. Although thermal performance of the color-changing paint (R) should be revealed more realistic in the real outdoor experiments, the indoor conditions show a more convenient comparison with the achieved results with more controllable parameters. From the thermal analysis of the samples, it has been found that the color-changing paints (R) and the color-changing paint with phase-change-material (R + p) can moderately grow insulation effect to keep the indoor space cool in summer but fail to keep indoor space warm in winter. Besides, the combination of normal gray paint (G) and phase-change-material (G + p) is not recommended since it does not help either reject heat in summer or absorb heat in winter significantly.