Scientists at Stanford University have invented paint that can keep buildings and homes insulated year-round, significantly reducing energy usage, costs, and greenhouse gas emissions.
 
Unlike current low-emissivity paints, the ones founded at Stanford comes in a wide range of colors and have two layers applied separately. One is an infrared reflective bottom layer that uses aluminum flakes and an ultrathin, the other is an infrared reflective bottom layer that using inorganic nanoparticles. The infrared spectrum of sunlight causes 49% of natural heating of the planet when absorbed by surfaces. 
 
In experiments the new paints reduced energy usage for heating by about 36% using artificial, cold conditions. Energy needed for cooling was reduced by almost 21% in artificially warm environments. Used on exterior walls and roofs, over the course of a year, simulations showed a typical mid-rise apartment building across different climate zones within the US reduced total heating, air conditioning, and ventilation energy use by 7.4%.
 
“How to reduce heat exchange between human living and workspaces and their surroundings is getting more attention, and new materials for enhancing insulation – like low-emissivity films for windows – are in demand,” said Yi Cui, the study’s senior author and professor of materials science and engineering, and photo science at SLAC National Accelerator Laboratory.
 
The insulative paint can be applied to either exterior or interior surfaces. Up to 80% of high mid-infrared light is reflected by the paint and the color layer also reflects some near-infrared light.
 
Researchers tested the paints in white, red, blue, green, yellow, dark gray, orange, and purple and were 10 times better than conventional paints in the same colors at reflecting high mid-infrared light.
 
The paints can also be applied to trucks and train cars used for refrigerated transportation. 
 
When tested in various situations, both layers proved water-repellant to enhance stability in humid climates and surfaces can be easily cleaned with a wet cloth or water flushing. Performance and aesthetic of the paint was not diminished after one week of continuous exposure to high temperature (176 degrees F.), low temperature (-320.5 degrees F.), and high and low acidic environments.
 
“Both layers can be sprayed onto absorbed surfaces of various shapes and materials providing an extra thermal barrier in many situations,” said Yucan Peng, co-author of the study and postdoctoral scholar at Stamford’s Geballe Laboratory for Advanced Materials. 
 
The study has been published in the journal Proceedings of the National Academy of Sciences.