Climbing temperatures means greater expenditure to cool homes. Here is an easy way to cool your house even in the peak of summer at a minimal cost.

Anil K Rajvanshi, who lives in the hot and dry region of Phaltan, Maharashtra, designed and built the house and its cooling system in 1984.

The house has 16-inch thick stonewalls and a green shade net on the roof. The roof surface is covered with jute gunny sacks which are sprinkled with water either once or twice a day.

This simple system cools the house effectively. The evaporating water from the soaked gunny sacks cools the roof and the ceiling fan inside the room drives the cool air down.

The green shade net does not allow direct sunlight to heat the gunny sacks, so together with the evaporating water, they remain cool throughout the day and night.

The 16-inch thick walls have a thermal lag of about 10-12 hours, and thus allow the heat to come inside the house through the walls only late at night.

Thus, when the outside temperatures have been 40-45 degrees Celsius, his house has remained cool with temperatures around 28-30 degrees Celsius inside.

This simple rooftop cooling system is a very effective air-conditioning system. He says that this system is one-tenth of the cost of a regular electric AC system.

In addition, the capital cost of this system, including the shade net and gunny sacks, is only Rs 250 per square meter.

This system works best in areas that have dry summers. With high humidity conditions, the roof evaporation will be less and hence cooling will drop.