Why will a white roof keep your house cooler in summer than will a black roof?

Why will a white roof keep your house cooler in summer than will a black roof?

PROF WAQAR HUSSAIN

         

         White colours repel heat rays. Therefore white roof absorbs comparatively less heat and reflects the heat outward. But the black roof absorbs the heat and does not reflect it. Hence the house with a white roof is cooler.

          White painted roofs had been in vogue since ancient times in places like Greece. Such roofs are designed to reflect more sunlight and absorb less heat than a standard roof. These are made of a highly reflective type of white paint, a white sheet covering, white cement, highly reflective white tiles, white pebbles or white foam. Even one can white wash the roof with lime water, Ca (OH) _2. Such roofs maintain lower roof temperatures. When standard or dark roofs touch temperatures of 150°F; cool roofs, under the same conditions, stay at 50°F.It means the white reflecting covering are cooler three times than the normal roofs.