Stanford Scientists Invent New Insulative Paint


A new kind of paint from Stanford University can reportedly keep buildings cooler in the summer and warmer in the winter, reducing energy use, costs and greenhouse gas emissions.

According to the researchers, while heating and cooling accounts for about 13% of global energy use and about 11% of GHG emissions, the new colorful paints were able to reduce the energy used by approximately 36% in artificial cool conditions and almost 21% in artificial warm conditions.

Additionally, in simulations of a typical mid-rise apartment building with the new paint on the exterior walls and roofs, total energy use declined 7.4% over a year. The study was published earlier this week in the journal Proceedings of the National Academy of Sciences.

“Energy and emissions from heating are forecast to continue to fall due to energy efficiency gains, but air conditioning use is rising, especially in developing economies in a warming world,” said the study’s senior author, Yi Cui, professor of materials science and engineering, of energy science and engineering, and of photon science at SLAC National Accelerator Laboratory.

“For both heating and air conditioning we must reduce energy and emissions globally to meet our zero-emissions goals,” said Cui. “How to reduce heat exchange between human living and work spaces and their surroundings is getting more attention, and new materials for enhanced insulation—like low-emissivity films for windows—are in demand.”

About the Research

Standford explains that current low-emissivity paints typically have a metallic silver or gray color, limiting use. However, the new paint has two layers applied separately, including:

  • An infrared reflective bottom layer using aluminum flakes; and
  • An ultrathin, infrared transparent upper layer using inorganic nanoparticles that comes in a wide range of colors.

The paint can reportedly be applied to exterior walls and roofs, allowing most of the sun’s infrared light to pass through the colored layer of the paint, reflect off the lower layer and pass back out as light rather than be absorbed as heat.

Alternatively, to keep heat inside, the paints would be applied to interior walls where it would reflect the infrared waves.

According to the release, up to 80% of high mid-infrared light is reflected by the paints. The color layer also reflected some near-infrared light, enhancing the reduction in air conditioning.

The research team reportedly tested their paints in white, blue, red, yellow, green, orange, purple and dark gray. They were 10 times better than conventional paints in the same colors at reflecting high mid-infrared light, the researchers say.

The scientists add that the paint has the potential to be applied to more than buildings, including trucks and train cars used for refrigerated transportation.

“Both layers can be sprayed onto assorted surfaces of various shapes and materials providing an extra thermal barrier in many different situations,” said Yucan Peng, co-lead author of the study,

For the research, the team also evaluated how practical the paints would be in various scenarios. Both layers are reportedly water-repellant, enhancing stability in humid environments, and painted surfaces can be cleaned easily with water.

Furthermore, the researchers report, the paints’ performance and aesthetics were not diminished after continuous exposure for one week to high temperature (176 degrees Fahrenheit) and low temperature (-320.5 degrees Fahrenheit), as well as high acidic and low acidic environments.

While the paint actually increased the use of air conditioning slightly in some U.S. cities, no location showed an increased total HVAC load.

“Our team continues to work on refining the paint formulations for practical applications,” said the study’s other co-lead author, Jian-Cheng Lai, a postdoctoral scholar advised by Zhenan Bao, professor of chemical engineering. “For example, water-based solutions would be more environmentally friendly than the organic solvents we used. That could facilitate the commercialization of the paints.”

Recent Energy-Saving Coatings Research

In March, scientists from Cambridge University unveiled a new plant-based coating that gets cooler when exposed to sunlight. Available in a variety of textures and iridescent colors, the material reportedly aims to keep buildings, cars and other structures cool without external power.

For the research, the team reportedly layered colorful cellulose nanocrystal materials with a white-colored material made from ethyl cellulose, producing a colorful bi-layered PDRC film. They made films with vibrant blue, green and red colors that, when placed under sunlight, were an average of nearly 40 degrees Fahrenheit cooler than the surrounding air. 

The researchers said that a square meter of the film generated over 120 watts of cooling power. Since CN films were brittle and the ethyl cellulose layer had to be plasma-treated to get good adhesion, the resulting films are described as robust and can be prepared several meters at a time in a standard manufacturing line.

Earlier this month, researchers reportedly developed new films that don’t absorb light to potentially reduce the energy needed for cooling in buildings or vehicles, while still maintaining vivid colors. The films were reportedly inspired by the nanostructures in butterfly wings and were found to have lowered the temperature of colorful objects to about 2 degrees Celsius below ambient temperatures.

The nanofilms are reportedly created by placing a disordered material, or rough frosted glass, under a multilayer material made of titanium dioxide and aluminum dioxide. They then placed the structure on a silver layer that reflects all light, consequently preventing the absorption of solar radiation and the heating associated with that absorption.

For the testing, the research team reportedly created blue, yellow and colorless films. These were placed outdoors at Shenzhen University on surfaces such as roofs, cars, cloth and cell phones throughout the day in both winter and summer weather.

Then, thermocouple sensors and infrared cameras were used to measure the temperature. The scientists reportedly found that the cooling films were about 15 C cooler than surfaces they were placed on in the winter and about 35 C cooler in the summer.


Tagged categories: Asia Pacific; Coating Materials; Coating Materials - Commercial; Coatings Technology; Coatings technology; Coatings Technology; Colleges and Universities; Color; Cool Coatings; EMEA (Europe, Middle East and Africa); Emissivity; Energy efficiency; Green coatings; Latin America; North America; Paint; Research and development; Z-Continents

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