Effect of the material color on optical properties of thermochromic coatings employed in buildings

Thermochromic materials can adjust their formal reflectivity in response to changes in ambient temperature, so they offer a means of achieving seasonal thermal control and have been a reasonable choice to enhance the solar radiation heat in winter and lower the solar radiation heat in summer. To optimize thermochromic coatings to meet the application requirement on archi-tectural surface color, the effect of the material color was studied on optical properties of ther-mochromic coatings under two transition temperatures of 25 degrees C and 33 degrees C. A measurement system was designed to analyze the reflectivity spectra and solar reflectivity of thermochromic coatings in both colored and colorless phases. Experimental results show that all samples exhibited a significant increase in reflectivity from the colored phase to the colorless phase especially in the 1300 nm-1600 nm and 1900 nm-2100 nm wavelengths. The global reflectivity of the thermochromic coatings could be increased by 3.17%-10.68% under 25 degrees C and 7.22%- 18.23% under 33 degrees C. From the view of evaluating the optical properties, the purple-blue and dark-green colors are respectively the best choices for thermochromic coatings. The experimental data proposed the efficient reference for application of thermochromic materials in buildings.