Multiscale study on thermal insulating effect of a hollow silica-coated polycarbonate window for residential buildings

To support the sustainable development of housing in a low-carbon society, this paper presents a multiscale simulation that connects material development at microscale, structural design of components at mesoscale, and evaluation of thermal insulation of the entire house at macroscale. The aim is the quantification of the correlation between local materials research and global goals. As one of important challenges, the constructed multiscale simulation was applied to a novel polycarbonate (PC) window whose surface is coated with scratch resistant resin containing hollow silica (HS) nanoparticles. The proposed PC window is one of the promising heat-insulated windows that is lightweight, has excellent light transmission, and is low in cost. The microscopic composite structure of HS particles dispersed in resin and the mesoscopic laminated structure of windows were analyzed, and the thermal insulating effect on an model room was clarified. In particular, the effects of thickness and HS content of coating layer were analyzed for the design of the window. HS particles reduced the thermal conductivity of the resin coating layer to 0.038 W/(m⋅K) or less with 3 wt%, and they also reduced the thermal conductivity of the single-glazing PC window to 0.167 W/(m⋅K) with 4 μm surface coating. Additionally, an evaluation experiment of thermal insulation was conducted in winter using a model house. The novel PC and a conventional glass windows were experimentally and computationally compared. As results, overnight in winter, the amount of CO2 emissions that could be reduced in one room was 0.048 gCO2 per window unit area.