Thermal performance of double-layer black tile roof in winter

Black tile roofs (BTR) are a traditional roof construction in Southern China. As heat insulation and waterproofing are insufficient in single-layer roofs, more climate-adapted double-layer tile roofs are used to replace them. Although providing remarkable heat insulation in summer, winter thermal performances of the double-layer BTR are unclear. Experimental comparisons of thermal performances of single-layer and double-layer BTRs showed that the indoor temperature of the single-layer BTR was 5°C higher than that of the double-layer BTR in the daytime, but 2℃ lower in the night-time. Compared with the single-layer BTR, the heat gain of the double-layer BTR was reduced by 85%, and a 55% heat loss reduction was achieved. The overall thermal resistance of the double-layer BTR was ten times higher. When considering the effects of ventilation in the air channel, the unventilated double-layer BTR reduced heat loss during the night-time, but there was no obvious difference in heat gain.