New building surface material has successfully decreased summer ambient temperatures and increased peak winter temperatures.
New intelligent building materials developed at UNSW adjust the optical properties used in conventional heat mitigation materials to change the amount of heat reflected and emitted based on the air’s temperature.
The materials were designed by Scientia Professor Mattheos Santamouris, Anita Lawrence Chair in High Performance Architecture at the School of Built Environment, University of New South Wales Arts, Design and Architecture. The technology could be used worldwide in buildings to help better protect from them the elements, he says.
“It is modulated according to the weather conditions, so it is ideal for cities that have issues with overheating in summer, but also have heating requirements during the winter.”
Conventional cooling materials used to help mitigate urban overheating during warmer periods are not always suitable for cities that have heating requirements in the winter. Further, because they reflect light, they can generate glare and can therefore only be used in specific locations – usually roofs.
Santamouris and his team added new layers to conventional super-cooling materials to help modify their solar reflectance and emissivity during colder periods without compromising the cooling efficiency. The first layer is composed of a ‘phase change’ material that uses traditional metal oxides to modulate the reflectivity and emissivity during the seasons. A second fluorescent layer then increases the cooling capacity of the material.
“We have integrated a new layer into the materials, which changes the reflectivity and emissivity as a function of the ambient temperature. We have also decreased the reflectivity of the materials to decrease glare by integrating another new layer that increases heat loss through fluorescence.”
Fluorescent materials absorb solar radiation but immediately re-emit it as fluorescent radiation at a lower wavelength, explains a UNSW media release. Because the material can emit more than it absorbs, it compensates for the reflectivity loss and can be used without causing glare. The result is a material that, during the summer, has a surface temperature below the ambient temperature, providing cooling to the building, and then is much above the average temperature during winter, providing heating.
Santamouris says that in a recent study his team was able to overcome the cooling issue, decrease the peak summer ambient temperature by up to five degrees Celsius and increase the peak winter temperature by 1.5 degrees.
And, as the new materials rely less on reflectivity, they can also be used on any level of a building without glare causing issues.
According to UNSW, extreme urban heat is the most documented climate change phenomenon, affecting more than 450 cities worldwide. Higher urban temperatures increase energy consumption for cooling and have adverse impacts on health.
Santamouris says the material is durable, non-toxic and will be affordable when produced at scale.