A new paint that is capable of keeping homes and buildings cooler in the summer months and warmer in the winter months — thereby reducing energy use, costs and greenhouse gas emissions — has been developed by scientists from Stanford University.

According to its developers, the new paint is comprised of two layers that are applied separately. The infrared reflective bottom layer features aluminum flakes while the ultrathin, infrared transparent top layer features inorganic nanoparticles in a wide range of colors. The researchers noted that the infrared spectrum of sunlight produces almost 50% of natural heating of the planet when it is absorbed by surfaces.

Objects of different materials in various shapes, coated with the new paints. Source: Yucan Peng

To keep the heat out of homes and buildings, the new paint can be applied to roofs and exterior walls where the majority of infrared light passes through the color layer, reflects off the bottom layer and passes back out as light. In other words, it is not absorbed by the building materials as heat.

Meanwhile, the paints can be applied to interior walls to trap heat with the lower layer of the paint reflecting the infrared waves that transfer energy across space.

The team determined that roughly 80% of high mid-infrared light is reflected by the paints, thereby keeping heat inside during cold weather and outside during hot weather. Further, the color layer also reflected some near-infrared light, which reportedly enhanced a reduction in air conditioning.

In simulations of both hot and cold environments, the new paint reduced the energy used for heating by about 36% in the experiments and reduced the energy needed for cooling by almost 21%.

The team also suggests that the paints could be applied to other materials or objects like trucks and train cars used for refrigerated transportation, where cooling costs might otherwise take up a significant portion of the transportation budget.

The paint is detailed in the article, Colorful low-emissivity paints for space heating and cooling energy savings, which appears in the journal Proceedings of the National Academy of Sciences.