Regulating top albedo and bottom emissivity of concrete roof tiles for reducing building heat gains

In Southern China concrete tile roof is widely used as double-skin roof to shield sunlight directly on the roof deck. Colony of dust and algae rapidly reduces the albedo of the tile's top after construction, increasing the heat gain of the interior building during summer months. Here we show a simple retrofit strategy by decreasing the tile's bottom emissivity and increasing the tile's top albedo simultaneously. A building cell housed for concrete tiles with different tile's top albedo and with different tile's bottom emissivity is built to monitor the temperatures of the roof at different elevations. The temperatures observed at the roof tile and at the roof deck indicate that both decreasing the tile's bottom emissivity and increasing the tile's top albedo can effectively decrease the roof deck temperature and reduce the heat gain of the building. We speculate that increasing the tile's top albedo and decreasing the tile's bottom emissivity should be done simultaneously to retrofit concrete tile roofs for reducing the heat gains of buildings in summer months. (C) 2017 Published by Elsevier B.V.