Using a special polymer, researchers have found a way to use rain water to cool buildings, Gizmag.com reported. Researchers from ETH Zurich used sponge-like mats made from a material known as Poly N-isopropylacrylamide (PNIPAM) to test their idea.

Using model hobby railroad houses in a test, researchers found that a house covered with their mat could save real houses 60 percent on energy use.

In practice, the mat, just 5 millimeters thick, would be placed on rooftops and collect rain water. The mats are sponge-like and collect rain water while under 89.6 degrees Fahrenheit. After exceeding 89.6 degrees, the material becomes hydrophobic and begins sweating the collected rainwater, thus cooling the structure.

Researchers suggested the technology, which is inexpensive to produce, could be well applied in tropical climates where it is both warm and there is rain. Researchers also said there are some problems to work out, such as the fact that the mats are not resistant to frost.