Purdue University engineers have developed what they describe as the whitest paint on record, a formulation designed to cool buildings by reflecting sunlight and reducing the need for air conditioning. Professor Xiulin Ruan and his team covered around 1,000 square feet of roof with the paint, which could theoretically provide 10 kilowatts of cooling power.
The Purdue whitest paint reflects up to 98.1% of sunlight, improving on the team’s earlier formulation, which reflected 95.5%. Researchers compare its visible-light performance with Vantablack, one of the blackest known materials. Typical commercial heat-rejecting paints reflect only around 80% to 90% of sunlight.
The paint’s cooling ability comes from its high concentration of barium sulfate and a carefully selected range of particle sizes. Together, these properties allow the paint to scatter a broader spectrum of sunlight. However, researchers noted that excessive particle concentration could make the paint more likely to crack or peel.
Outdoor tests showed the paint could keep surfaces around 19°F below ambient temperature at night and about 8°F below surrounding temperatures under strong midday sunlight. Even at an ambient temperature of 43°F, the painted surface was 18°F cooler.
The technology follows six years of research, during which the team tested more than 100 materials. Its manufacturing is compatible with standard commercial paint production, while patent applications have been filed through the Purdue Research Foundation.
