Novel coating to keep buildings cool without air-conditioning

Air-conditioning can account for more than 40% of the domestic energy consumption, and contributes to greenhouse emissions by making use of chemical refrigerants such as chlorofluorocarbons and halogenated chlorofluorocarbons. Global temperatures, however, keep rising, and the situation becomes more unbearable in the presence of humidity. At 80% relative humidity, temperatures of 32C can be perceived as 45C.

A group in the National University of Singapore, led by Assistant Professor Tan Swee Ching, has created a coating that absorbs moisture reducing relative humidity by 20% in seven minutes, leading to a decrease in perceived temperature of 7-9 degrees C.

The coating is based on a common compound (zinc oxide) and consists of two layers: a moisture-absorbing hydrogel and a water-digesting material which allows the hydrogel to continue absorbing water vapour from the air indefinitely. Applying the coating on at least one wall will be enough to keep a room cool without the use of air-conditioning, improving comfort levels in humid days and without requiring any energy input.

The new material is piloted in the first months of 2019 at indoor locations in Singapore, before entering production. Further research is directed for the additional use of the hydrogel as a potential emergency power source.