Buildings consume 39 per cent of all energy in the economy, more than industry (33%) and transportation (28%). Residential buildings consume 21 per cent while commercial buildings consume 18%. And in both residential and commercial buildings, heating and air conditioning are the single biggest sources of energy consumption at 39% and 32% respectively. “An outrageous amount of energy is used to heat and cool buildings, shopping centres, hotels, office buildings, your house,” he said. “And it’s not just for a couple of months, but for eight months of the year.” By shifting to a “19 to 25 world” — no higher that 19 degrees in winter, and no lower than 25 degrees in summer — Australian businesses could save $100 million and 300,000 tonnes of carbon every year.