While design costs, choices, and designs vary, most energy-efficient houses have certain fundamental elements: a well-built and tightly sealed thermal envelope; regulated ventilation; correctly sized, high-efficiency heating and cooling systems; and energy-efficient doors, windows, and appliances. Energy-efficient homes also tend to be cheaper than traditional houses. Here are five more ways that energy-efficient homes are better for the environment: they use less water; produce less carbon dioxide (CO2); offer greater security by preventing overheating and freezing-over of pipes; and last but not least, they can reduce our dependence on foreign oil. If you're planning on building a new home, it makes sense to look at building codes and standards as well as environmental issues such as energy efficiency, green building techniques, water conservation, waste reduction, etc..