Multi-coloured paints that beat the heat

Could this paint cool buildings and reduce our reliance on air conditioning systems?

Spotted: Climate change is set to increase maximum temperatures across the world. At the same time, increasing demand for traditional air conditioning further contributes to greenhouse gas emissions, creating a catch-22 situation. The race is therefore on to develop passive cooling techniques, and a research team at the University of Maryland, led by Liangbing Hu, have made a significant contribution through a novel coating that cools any building it’s applied to.  

The microporous coating is made up of finely ground glass particles that act as a binder, combined with aluminium oxide particles, which scatter sunlight and improve the coating’s manufacturability. 

The composition of the material enables it to combat the heat in two ways. First, it reflects away up to 99 per cent of incoming solar radiation, preventing a building from absorbing heat in the first place. At the same time, it also emits heat in the form of infrared radiation, dispelling it into space through a process known as radiative cooling.  

The University of Maryland researchers are not the only ones to experiment with radiative cooling, but making coatings that are both practical to manufacture and sufficiently robust to withstand long-term weathering has proved challenging. This new coating, however, is scalable while also being strong and resilient enough to be applied to bricks, tiles, and metal. 

To commercialise the technology, the researchers created a company called Ceracool. This spinoff has further optimised the coating, applying it in the form of paints that dry at ambient temperatures and reduce temperatures inside a building by between 3 and 10 degrees Celsius.

White paint has long been deployed as a cooling technique, but Ceracool’s paints come in several colours, providing greater flexibility. These coloured paints not only reflect light better than standard equivalents of the same colour – they are also more reflective than standard acrylic white paint.

The paints are resistant to dirt, UV radiation, and even flames, and are easily wiped clean if contaminated.

Written By: Matthew Hempstead