Scientists at the University of Technology Sydney have developed a coating which keeps roofs significantly cooler than the ambient air temperature, even under the most intense summer conditions.

Dr Angus Gentle and Emeritus Professor Geoff Smith reported that a roof with a “coated polymer stack” – a combination of specially chosen polyesters on a silver layer – remained  11ºC degrees or more colder than an existing state-of-the-art white roof nearby. The coating does this because it absorbs only 3% of incident sunlight while simultaneously strongly radiating heat at infrared wavelengths that are not absorbed by the atmosphere.

Professor Smith said that the surface maintained its high performance in all conditions. “Extensive dew formation is inevitable for a super cool roof and dew drops precipitate dirt. This roof site, being 25 metres above a busy city transit road, was a stern test. Results show that excellent thermal performance can be maintained.”

The materials used for the demonstration are available commercially and potentially suited to use on basic roofing.

The researchers believe that the development has major implications for reducing the heat load in urban areas and consequently cutting energy use and greenhouse gas emissions.