Can the paint on the outside of a house help keep the house cool in hot weather? Yes. Some types of paint reflect (to bounce back from the surface of an object) up to 80 percent of sunlight. These paints also send heat back into the air. These paints can reduce the amount of air conditioning needed to cool a house by up to 30 percent. These paints work well in hot, dry climates. But, when it’s humid, there is a lot of water vapor (water in a gas state) in the air. The water vapor prevents heat taken in by the paint from going back out into the atmosphere. These paints do not work as well in places with high humidity.
Scientists wondered how to solve this problem. They turned to the natural process of evaporative cooling. Evaporative cooling is how the human body keeps cool. When it is hot, people sweat. Sweat is mostly water. Sweat evaporates (the process by which water changes from a liquid to gas) from the surface of skin. Heat is lost. This process helps keep your body cool.
Scientists modeled this process to make a paint that holds water. The water then slowly evaporates into the atmosphere. The new paint also reflects about 90 percent of sunlight. By holding water and allowing it to evaporate, the paint sends 95 percent of heat back into the atmosphere. Overall, houses in Singapore painted with the new paint decreased their use of electricity for air conditioning by up to 40 percent!
What Do You Think? What happens when water evaporates?
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