Design of a Passive Cooling Clay Roof Tile

This paper details the design of a passive cooling clay roof tile that is sustainable and ideal for hot and arid regions. The roofing tile experimented in this research is made of clay and coated with three layers of paint containing TiO2, CaCO3, and BaSO4. The atmosphere does not re-absorb the outgoing infrared radiation from the roof surfaces paved with coated clay roof tiles. It gets reflected and emitted directly to outer space through the atmospheric window (8–13 μm). This phenomenon cools the roof surface and, thereby, cools the internal temperature of the building. Results of the experimental study indicate that compared to a plain non-coated clay tile, the average surface temperature cooling from the sustainability-focused clay roof tile is 10.8 ºC. Using the state of Arizona, U.S.A., as an example, results show that the sub-ambient radiative cooling is at 5.6 ºC. For a household with an average roofing area of 2,200 square feet, this translates to a savings of $3.9 per day in energy bills during hot summer months, amounting to a 52% reduction in their monthly energy bills. Furthermore, for every 100,000 households, the coated clay tiles reduce the demand for the energy grid by 13.1%.