If you’ve ever redone a room in your home and gone to the hardware store to look for fresh paint, you know there are a lot of different shades of white on the market. It turns out that there is a new shade of white in the city, and that it can have some pretty cool (literally) climatic implications.
In a study published Thursday in ACS Applied Materials & Interfaces, researchers at Purdue University say they have now made the whitest paint on the planet. By creating the whitest paint in history, which researchers say reflects up to 98.1% of light, Purdue researchers surpass their own record, set just last fall, when they developed a paint that reflects 95.5% of sunlight.
It might seem pointless to run to get the whitest paint of all at just a couple of percentage points when many of us don’t know how to differentiate most white sample chips in Home Depot. However, when it comes to the cooling effects of white paints, these few percentages are important.
Anyone who has taken to the streets on a hot summer day knows how to wear white clothes; white reflects light, while black absorbs. But white paints currently on the market with labels like “ultra-reflective” or “highly reflective” only reflect between 80 percent and 90 percent of the light, said Xiulin Ruan, lead author of the study. This may be enough to make your kitchen look clean every day, but if we talk about cooling properties, it is less effective.
“We think 90% to 98% are not very different, but we need to think about absorbing sunlight,” Ruan said. “Our paint absorbs 1.9% of sunlight, but these commercial paints, even with reflectors, absorb 10% of sunlight, five times more than our paint. They look white, they’re pretty white , but they are not white enough, they are not able to cool down beyond the ambient temperature ”.
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Ruan said efforts to develop the whitest paint possible that could also act as refrigerants date back to the 1970s. Only Ruan’s team has been working on how to make white paints whiter for about seven years and is analyzing methods to add reflective materials to the paint to help it outperform the sun. This white paint successfully incorporates high concentrations of barium sulfate, a chemical compound used to make white cosmetics and photographic paper, with particles of different sizes spread throughout the paint.
“Sunlight has different colors, because it has different wavelengths,” Ruan explained. “We need different particle sizes to disperse each wavelength.”
The development of this type of ultra-reflective paint could change the game of how we design buildings as our world heats up more and more. There is a growing work around urban design options: changing super hot and superabsorbent asphalt roofs for reflective surfaces, for example, or building in parks or others green dots in cities literally cool the area: it can help us fight the heat of cities and other built spaces without using more energy to power air conditioners.
Ruan and his team have great insights into the potential of painting; they estimate that the use of large-scale super-reflective white paint in cities like Reno or Phoenix could save up to 80% on air conditioning costs. “If you have very hot days, our paint alone might not do the job, but on other days it could prevent you from turning on the air conditioning,” he said.
These types of climate pirates seem to be the solution to all our problems, but there are still many real world considerations that need to be erased when thinking about designing cities to overcome the heat. “To make cities more reflective, you need to be very, very, very practical,” said Hashem Akbari, a professor of engineering for the construction of professors, civilians and environmentalists at Concordia University.
Akbari noted that regular wear and tear on reflective walls or ceilings can affect the percentages of reflectivity measured in a laboratory. “Soot and dust tend to decrease the reflectivity of the surface,” he said. “If they start with a 95% reflectivity, air pollutants, drops and soot could accumulate on the surface and decrease the reflectors.”
Still, Akbari said starting now to replace the ceilings regularly, which need updating every few decades or so, with more reflective materials, regardless of the whiteness of the paint you use or the percentage it actually reflects, would be a good idea. beginning for most cities.
“If every roof that needed to be replaced could be replaced by a highly reflective roof, in a period of 10 to 30 years all roofs will be highly reflective. There is no need to push a particular technology, such as a cladding,” he said. the marketing and insulation of reflective materials as roofs are being replaced. “