9781422276907

■ ■ Installing solar systems on roofs is just one way of using renewable energy.

Words to Understand

carbon dioxide: A colorless, odorless gas that is naturally present in the earth’s atmosphere. It is an important part of plant growth on earth, but if too much is released because of the burning of fossil fuels such as coal and oil, it can cause global warming and major damage to the environment. geothermal power: Energy that is created by harvesting heat that exists below the earth. retrofit: To add a component or system to a building that it did not have when it was constructed. solar energy: Energy that is produced by harvesting the heat and energy of the sun. sustainability: In the construction industry, an emphasis on building practices that save energy or reduce energy output, that use building materials from renewable resources such as wood and stone that can also be recycled or reused, and that incorporate other environmental- ly-friendly practices.