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Next-gen paint lowers building emissions by reducing cooling and heating need

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A new kind of paint has been developed that keeps buildings cooler in the summer and warmer in the winter, thereby reducing energy costs and greenhouse gas emissions.

Space heating and cooling accounts for about 13 per cent of global energy use and about 11 per cent of greenhouse gas emissions.

The new paints, developed by Stanford University scientists, reduced the energy used for heating by about 36 per cent and for cooling by almost 21 per cent.

In simulations of a typical mid-rise apartment building in different climate zones across the US, the use of the new paint on exterior walls and roofs meant total heating, ventilation and air conditioning energy use declined 7.4 per cent over the course of a year.

“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 Yi Cui, the study’s senior author. “For both heating and air conditioning, we must reduce energy and emissions globally to meet our zero-emissions goals.”

He added: “How to reduce heat exchange between human living and work spaces and their surroundings is getting more attention, and new materials for enhanced insulation – such as low-emissivity films for windows – are in demand.”

Current low-emissivity paints usually have a metallic silver or grey colour, which limits their use aesthetically.

The newly-invented paints have two layers applied separately – an infrared reflective bottom layer using aluminium flakes and an ultra-thin, infrared transparent upper layer using inorganic nanoparticles that come in a wide range of colours.

For keeping heat out, the paint can be applied to exterior walls and roofs – infrared light from the sun passes through the colour layer of the new paints and reflects off the lower layer, passing back out as light rather than being absorbed by the building materials as heat.

To keep heat inside, the paints are applied to interior walls where the lower layer reflects the infrared waves, which transfer energy across space and are invisible to the human eye.

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

The paints could also be applied to improve energy efficiencies elsewhere, such as covering trucks and train cars used for refrigerated transportation, in which cooling costs can take up to half the transportation budget.

“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.

The researchers also evaluated how practical their paints would be in various situations.

Both layers are water-repellent, which should enhance stability in humid environments. Painted surfaces can be cleaned easily with a wet cloth or water flushing, the researchers found.

The paints’ performance and aesthetics were not diminished after continuous exposure for one week to high temperatures (80°C) and low temperatures (-195°C), as well as high-acidity and low-acidity environments.

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