On solution to avoid catastrophic climate change is as easy as painting buildings. It’s known that white pain has benefits for cooling cities and on individual buildings it can reduce the use of air conditioning. This has led to a wider adoption of white paint on buildings, and more research into making a more reflective white paint. Prof Xiulin Ruan at Purdue University in the US alongside a team of researchers has created the most reflective white paint ever!
The new paint was revealed in a report in the journal ACS Applied Materials & Interfaces. Three factors are responsible for the paintâ€™s cooling performance. First, barium sulphate was used as the pigment which, unlike conventional titanium dioxide pigment, does not absorb UV light. Second, a high concentration of pigment was used â€“ 60%.
Third, the pigment particles were of varied size. The amount of light scattered by a particle depends on its size, so using a range scatters more of the light spectrum from the sun. Ruanâ€™s lab had assessed more than 100 different materials and tested about 50 formulations for each of the most promising. Their previous whitest paint used calcium carbonate â€“ chalk â€“ and reflected 95.5% sunlight.
During summer heat air conditioners are used extensively and this can increased energy consumption can be crippling. Black outs occur in the summer thanks to people cooling their homes and workplaces – but these power issues can be avoided. By simply painting roofs white it can help cool buildings and lower energy bills. Painting multiple roofs white can a really positive effect on a large area.
They found that urban expansion alone could increase summer temperatures by up to 6Â°F in some areas in addition to greenhouse gas-induced warming by 2100. The Mid-Atlantic and Midwest seeing the biggest overall summer temperature increases.
In all areas, white roofs could completely offset the combined increase in temperatures, and if deployed across the entire megapolitan area, could actually reduce summer temperatures compared to the 1990-2010 average.
The benefits of cool roofs were particularly prominent for the urban areas stretching from Washington, D.C. to New York, Chicago and Detroit, and Californiaâ€™s Central Valley.
Cooler summertime temperatures could reduce demand for air conditioning, which could both save money and reduce the chances of electricity grid blackouts.
A computer simulation of the urban environment has proven that in theory white paint on rooftops can significantly cool cities – thus saving energy in the summer that would be used for air conditioning.
Cities are particularly vulnerable to climate change because they are warmer than outlying rural areas. Asphalt roads, tar roofs, and other artificial surfaces absorb heat from the Sun, creating an urban heat island effect that can raise temperatures on average by 2-5 degrees Fahrenheit (about 1-3 degrees Celsius) or more compared to rural areas. White roofs would reflect some of that heat back into space and cool temperatures, much as wearing a white shirt on a sunny day can be cooler than wearing a dark shirt.
The study team used a newly developed computer model to simulate the amount of solar radiation that is absorbed or reflected by urban surfaces. The model simulations, which provide scientists with an idealized view of different types of cities around the world, indicate that, if every roof were entirely painted white, the urban heat island effect could be reduced by 33 percent. This would cool the world’s cities by an average of about 0.7 degrees F, with the cooling influence particularly pronounced during the day, especially in summer.