A team of UNSW Sydney has developed smart new building materials that can help control the temperature throughout the seasons. The innovative design adjusts the optical properties used in conventional heat attenuating materials (building coatings) to alter the amount of heat they reflect and emit based on air temperature.
The new materials were designed by Professor Scientia Mat SantamourisAnita Lawrence High Performance Architecture Chair at the School of the Built Environment, UNSW Arts, Design and 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…so it’s ideal for cities that have problems with overheating in the summer, but have also heating needs in winter,” said Pr. dit Santamouris.
Professor Santamouris specializes in the development of 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 to 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.
Thermal comfort throughout the seasons
Although many conventional cooling materials help mitigate urban overheating during warmer periods, they are not necessarily suitable for cities with 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 operate 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 of heating during cooler periods,” says Professor Santamouris. “They also cannot be used on low streets or vertical facades because of glare, so they can really only be used on the roofs of buildings. tall buildings – not in walls or sidewalks.”
Professor Santamouris’ team added new layers to conventional supercooling materials to help alter their solar reflectance and emissivity during colder periods without compromising cooling efficiency.
The first layer is composed of a “phase change” material that 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 depending on the ambient temperature”, explains Professor Santamouris. “We have also reduced the reflectivity of the materials to reduce glare by integrating [another] new layer that increases heat loss by fluorescence.
“It’s a smart material that adapts to any climate, can be used at low intensity, can be any color and creates no glare.”
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 which, during the summer, has a surface temperature lower than the ambient temperature, ensuring the cooling of the building, then much higher than the average temperature during the winter, ensuring the heating.
“In the recent study, we were not only able to overcome the overcooling problem, but we were also able to reduce the maximum summer ambient temperature by up to five degrees and increase the maximum winter temperature by 1.5 degrees,” says Professor Santamouris.
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 all climates, can be used at low intensity, can be any color and creates no glare,” says Professor Santamouris. “It’s also durable, non-toxic and will be affordable if produced on a large scale.”
Professor Santamouris says the team will continue to test the materials in new locations around the world with a view to making the materials commercially available.
“This technology has the potential to be used in cities all over the world, which would reduce energy costs and help combat the impacts of climate change.”