Most of the 25 tons of CO2 emissions each American is responsible for each year come from the home. Here are some easy ways to get that number down in a hurry without rebuilding. Open a window instead of running the AC. Adjust the thermostat a couple of degrees higher in the summer and lower in the winter. Caulk and weatherstrip all your doors and windows. Insulate your walls and ceilings. Use the dishwasher only when it's full. Install low-flow showerheads. Wash your clothes in warm or cold water. Turn down the thermostat on the water heater. At the end of the year, don't be surprised if your house feels lighter. It just lost 4,000 lbs. of carbon dioxide.