Reported in ACS’ Nano Letters, a team lead by Fuqiang Wang has developed a cost-effective energy-efficient coating that mimics a desert chameleon.  Without using additional energy, this material can keep building warm in the winter and cool in the summer. 
 
The Namaqua chameleon of southwest Africa alters its coloring to regulate body temperature in changing weather conditions. In hot temperatures it reflects sunlight to stay cool and turns a dark brown when they cool down to absorb heat. This is a unique ability that if implemented in buildings, structures would not be restricted to keeping buildings either cool or warm as current paints and tiles do now. 
 
The team mixed thermochromic microcapsules, specialized microparticles, and binders to form a suspension which was then brushed or sprayed onto metal surfaces. The coated surface began changing color from dark to light grey when heated to 69 degrees Fahrenheit. Reaching 86 degrees (F.) causes the light-colored film to reflect up to 93% solar radiation. When heated above 175 degrees for an entire day, coated materials showed no signs of damage. 
 
The coating was then tested on miniature buildings throughout all four seasons alongside regular white paint, blue steel tiles, and a passive radiative cooling paint. Testing resulted in the new coating being slightly warmer than the passive radiative cooling system in the winter. Both however, maintained similar temperatures in warmer weather. During autumn and spring, the chameleon coating was the only system that adapted to widely fluctuating temperatures occurring throughout the day. In the summer the coating was significantly cooler than the steel tiles and white paint. 
 
According to the researchers, this color-changing system is easy and inexpensive to manufacture while saving energy for regions that experience varying seasons.