Scientific American: Our homes and offices account for more than one third of all greenhouse gases emitted by human activity–the bulk of it for heating in winter and air-conditioning in summer, according to the U.N. Intergovernmental Panel on Climate Change (IPCC). Taking simple steps such as caulking windows, installing thicker insulation and double-paned windows, and using energy-efficient appliances can cut the energy used in a given building by as much as 50 percent. In fact, such energy-saving …