Sweating is a vital activity which keeps our body temperatures at a suitable level, even if we may not like it very much. When water evaporates off our skins, that essentially reduces the temperature of the body, thus shielding it from warming up too much on a hot day.
Researchers at ETH Zurich are trying to apply the same principle in devising a way to cool off rooftops. They have come up with a rather novel idea to do so. The idea is to use a synethetic mat along the area of the rooftop so that when it rains, the mat absorbs this water. And then, on a hot day, it releases off the water, thus reducing the temperature of a rooftop and, in turn, that of the house.
The mat is made up of a polymer called PNIPAM. This polymer is generally water-permeable, thus allowing it to soak up water. However, when the temperature of the mat rises to thirty-two degrees, it shrinks and that, in turn, releases the water stored within it.
The image posted above shows a practical demonstration of this mat’s use. In the image, two houses are heated with a lamp and their internal temperatures are compared. The house to the right is covered with PNIPAM and it is evident that it a lot less warmer than the house on the left.
Such a mat could actually find a lot of applications in building structures. Especially in very hot regions, PNIPAM can indeed be used in rooftops to keep the interiors relatively cool.