Introduced in 1979, low emissivity (low-e) glass uses an ultra thin metallic coating on or in the glass to reflect the sun's rays. Commercial and residential buildings use low-e glass windows to help save energy. The powerful infrared light in sunlight heats up objects such as floors and furniture inside and sidewalks and patio furniture outside. As objects cool they emit a low powered form of infrared lights. Low-e glass can reflect this form of energy. In summer this keeps your house cooler as the warmer outside heat is kept outside. In winter, heat from objects that are heated by sunlight or other inside sources is bounced back into your home to keep your home warmer. According to the US Department of Energy, windows with low-e glass cost about 10-15 percent more than traditional windows, but can reduce heat through the windows as much as 30 to 50 percent.