Using lightweight cement composite and photocatalytic coating to reduce cooling energy consumption of buildings

Solar reflectance and thermal conductivity are two main factors which affect the heat transfer through opaque building envelope and cooling energy consumption of buildings in tropical countries and other regions in summer season. Effects of a lightweight cement composite (LCC) with hollow cenospheres and a photocatalytic coating with titanium dioxide (TiO2) on the thermal conductivity and solar reflectance were investigated. Individual and combined effects of the LCC and photocatalytic coating on the heat gain and surface temperatures of panel specimens exposed to simulated sunlight were evaluated under controlled experimental conditions in comparison to a conventional concrete of similar 28-day compressive strength. The LCC has a thermal conductivity of 0.39 W/m.K, 80% lower than that of the concrete (1.98 W/m.K). The photocatalytic coating increases the solar reflectance of the LCC specimen from 0.41 to 0.78 without significant effect on the thermal conductivity. The LCC and photocatalytic coating reduce the heat gain in 9 h exposure to simulated sunlight by 33% and 54%, respectively, while their combination reduces the heat gain by 69%. The inner surface temperature of the specimens is reduced by 3.7 degrees C, 4.3 degrees C, and 8.0 degrees C after 9 h exposure to simulated sunlight due to the use of LCC, photocatalytic coating, and their combination. The results indicate that the energy consumption for cooling building interior can be reduced significantly by the use of the LCC, photocatalytic coating, or a combination of these. (C) 2017 Elsevier Ltd. All rights reserved.