The foil-like silver surface reflects light and keeps out the hot summer sun. Overhangs and exterior shading devices reduce heat and glare that can occur at certain times of the year, particularly on south and west sides. Movable exterior shades offer even more flexibility. Interior glass partitions, often called relights, allow light to flow into interior spaces while keeping out unwanted sound. Skylights bring in light from the top story of a building and are a popular retrofit option.
Clerestories are an excellent choice for buildings with flat roofs.
The vertical glass brings in low-angle light, which bounces off the slanted surface and into the space below. They are a great way to spread light throughout the interior. Light shelves are white or reflective horizontal shelves mounted along vertical windows, usually at a height of seven feet. Light falls on the shelf and bounces into the room, directing light deep into the interior, while protecting those nearest the window from glare. Lighting loads can account for about 40 percent of energy consumption in commercial buildings.