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White paint with high reflectance
White is the most used color in the world, not only for its symbolic connotations, which has many. From the language of architecture or painting to decoration; it is the perfect emblem of purity, neutrality, light or spaciousness, among many other aesthetic properties.
The white paint It has historically been used in the envelope of buildings and houses to combat the sweltering summer heat. Its reflective physical properties guarantee less heat absorption and, in turn, greater light reflectance.
Painting the streets white has also been shown to bring benefits to cities. And with the exponential growth of cities and climate change on our heels, we know that we must change our mentality in all areas, and, of course, the construction and architecture sector cannot be left behind.
But … What if buildings or cars were never heated by their envelope? What if we have a white paint that can keep surfaces cool? What if paint could "cool a building" enough that it doesn't need air conditioning?
Engineers at Purdue University have developed a white paint that can keep all surfaces cool, specifically, up to 18 degrees Fahrenheit (-7,778 ° C) colder than its surroundings, but without consuming energy. The "Super white paint" reflects 95.5% of sunlight and efficiently radiates infrared heat (Remember, Reflect = relative to radiation and Isolate = relative to conduction).
As a note, remember the following scheme …
According to the researchers, the paint would replace the need for air conditioning in many buildings by ensuring that the temperature of the painted surface on the building envelope did not vary - perfect for hot climates! by not absorbing almost any solar energy.
With building envelopes at lower temperatures in summer, the use of air conditioning could be reduced, and therefore, less energy consumption. Not counting, with the multiple applications that could be practiced in cities to dramatically reduce the famous "heat island". An important problem that has dire repercussions on the health of citizens.
“It is very counterintuitive, where a surface in direct sunlight is colder than the temperature reported, for example, by a local weather station for that same area. But we have shown… that it is possible! ”Said Xiulin Ruan, a professor of mechanical engineering at Purdue.
To test the efficacy of this new white paint, the Purdue researchers took images from an infrared camera comparing their product to a normal white paint on a roof. The results… Impressive!
The image from the infrared camera shows that the «cooling white paint»Developed by the researchers (left, purple) can stay cooler in direct sunlight, compared to other standard paint.
The commercial paints that we can currently buy reflect only 80% -90% of sunlight and they cannot reach temperatures lower than those of their surroundings. The new one white paint created by the researchers reflects 95.5% of sunlight and efficiently radiates infrared heat.
The researchers considered more than 100 different material combinations, narrowed them down to 10, and tested about 50 different formulations for each material. Getting a formulation made with calcium carbonate, a very abundant substance in nature commonly found in rocks and seashells.
This compound, used as a filler in paint, allowed the formulation to behave essentially the same as commercial white paint, but with greatly improved cooling properties.
Calcium carbonate hardly absorbs ultraviolet rays as a result of its atomic structure. They also have a high concentration of particles of different sizes, allowing them to disperse a greater range of wavelengths.
According to the researchers' estimates, this paint would be cheaper to produce than its commercial alternative And you could save around a dollar a day from a weatherization perspective, which would have been spent on air conditioning, for a house of approximately 100 m2.
Obviously, using less energy in homes benefits us all, from our pockets to less carbon dioxide emissions that are tangible benefits for the environment. And remember our article on tips on how to paint a wall, a long and useful article.
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