A team of UNSW researchers have created a range of smart building materials to regulate temperature throughout the year.
The materials adjust the optical properties used in conventional heat attenuating materials to change the amount of heat they reflect and emit based on the temperature in the air.
The new materials were designed by Scientia Professor Mat Santamouris, Anita Lawrence Chair in High Performance Architecture at the School of Built Environment, UNSW Arts, Design & Architecture. He says the new materials could be used around the world in buildings to help better protect them from the elements.
“It’s a smart, smart building material that understands city temperature and is modulated based on weather conditions. It’s therefore ideal for cities that have problems with overheating in the summer, but also have heating needs in winter,” he says. .
Santamouris specializes in developing heat mitigation technologies and strategies that reduce urban temperatures in cities around the world. Extreme urban heat is the most documented climate change phenomenon affecting more than 450 cities worldwide. Higher urban temperatures significantly increase energy consumption requirements and adverse health effects, including heat-related morbidity and mortality.
His team recently tested the new generation of materials in Kolkata, India, in an international collaboration with colleagues from the University of Calcutta in India, the public University of Navarre in Spain and the University from Tsukuba in Japan. The study is the latest in their ARC Discovery Project, Fluorescent Daytime Radiative Cooling for Urban Heat Mitigation, which aims to develop cooling technologies to mitigate urban overheating and reduce cooling energy requirements in buildings.
While many cooling materials help mitigate urban overheating during the summer, these materials do not meet the needs of cities that have winter heating needs. In addition, since the materials reflect light, they can generate glare and can only be used in specific places.
“Traditional supercool materials work by having very high reflectivity and emissivity, making them ideal for cities that only require heat attenuation. However, they can cause excessive cooling in cities that also need heating during cooler periods,” says Santamouris.
“They also can’t be used on low streets or vertical facades because of glare, so they can really only be used on the roofs of tall buildings – not in walls or sidewalks.”
The Santamouris team added new layers to conventional supercooling materials to help modify their solar reflectance and emissivity during colder periods without compromising cooling efficiency. The first layer is composed of a “phase change” material, which uses transition metal oxides to modulate reflectivity and emissivity over the seasons. A second fluorescent layer then increases the cooling capacity of the material.
“We have integrated a new layer in the materials which changes the reflectivity and the emissivity according to the ambient temperature. We have also reduced the reflectivity of the materials to reduce glare by integrating [another] new layer that increases heat loss by fluorescence.
Fluorescent materials absorb solar radiation but immediately re-emit it as fluorescent radiation at a lower wavelength. Because the material can emit more than it absorbs, it compensates for the loss of reflectivity and can be used without causing glare.
The result is a material whose surface temperature is below ambient temperature in summer and then well above average temperature in winter.
“In the recent study, we were not only able to overcome the overcooling problem, but we were also able to reduce the peak summer ambient temperature by up to five degrees and increase the peak winter temperature by 1.5 degrees. .”
Because the new materials rely less on reflectivity to reduce heat, they can also be used at any level of a building.
“It’s a smart material that adapts to any climate, can be used at low intensity, can be any color and creates no glare. It is also durable, non-toxic and will be affordable if produced on a large scale,” says Santamouris.
The professor says the team will continue to test the materials in new locations around the world with a view to making the materials commercially available.