SURVEYS show that air conditioning units, which emit greenhouse gases and contribute to global warming, consume over 50 per cent electricity in buildings in India. Brian Ford, professor of Bio-climatic architecture in University of Nottingham, says this percentage can be brought down by designing buildings that promote natural ventilation. Ford was the consultant of the Sydney Olympic stadium and the Torrent Research laboratories in Gujarat, India. In town to deliver a lecture on designs for low carbon buildings, he says, "During summer, there is tremendous consumption of energy, which can be drastically reduced through natural ventilation." How? Through passive downdraft evaporative cooling. High pressure water misting nozzles introduced through vents on the roof induce a downdraft cooling. Hot air from outside mixes with the cool misty air and the cooled air is passed through the entire building. Ford says, "This brings down energy consumption in buildings considerably. Houses are also physically and thermally buffered from external environment." The advantages? "One year after the system was installed in Torrent, the centre reportedly used 64 per cent less electricity. This significantly lowered the carbon quotient of the building," says Ford. So, how does the building material increase energy consumption? "It does. But the embodied energy (energy from building material) is only 10 per cent of the total energy consumption that arises from materials like cement and asbestos sheets. The major chunk is from electricity consumption," says Ford. Suggesting ways for conventional buildings to reduce energy consumption, Ford says: "Insulation prevents external heart from entering. Also, natural ventilation can be used at nights in summer to lower inside temperatures. If windows are kept open at night, the trapped hot air can be ventilated and keep the room cool"