Investigating on the thermal performance of a glazing window coated with transparent heat insulation paint

This paper investigated the thermal performance of a glazing window coated with transparent heat insulation paint (THIP) experimentally and numerically. A special test rig, which mainly consists of two test chambers respectively covered by a normal glazing and the THIP coated glazing (THIP glazing), was set up to comparatively study the thermal insulation performance of a normal glazing and the THIP glazing in outdoor environment. The solar irradiance as well as the solar spectral irradiance distribution passing through the glazing covers were measured by two pyranometers and spectrometers, respectively. The outdoor experimental results showed that the THIP glazing could significantly reduce the transmission of solar irradiance due to its very high infrared absorption. It could reduce the penetrating solar irradiance by up to 61.48%, which is about three times than that of the normal glazing without coating film. The optical characteristics of the THIP glazing sample was tested in Laboratory. Based on the measured optical characteristics, some key thermal indexes of the THIP glazing, such as solar heat gain coefficient (SHGC), U-factor and reference heat gain at standard testing conditions, were calculated with Window program. Numerical simulation, based on EnergyPlus, was also conducted to simulate and evaluate the THIP glazing’s annual thermal performance and daylighting performance as an office room window in Hong Kong. The simulation results indicated that compared with single clear glass window, the south facing THIP glazing window could reduce the annual building energy use by 80 kWh per unit window area in Hong Kong. Such good thermal performance makes the THIP glazing be able to considerabley reduce the solar heat gain as well as building energy use in tropic and subtropic climate zones without adverse impact on the indoor thermal comfort.