Other massive materials, such as brick and stone, also store the sun's heat and add mass to a building's interior. The stone walls of the canyon itself demonstrate how massive materials store heat. The rock walls remain warm on cool nights after the sun has warmed them on sunny days. During the summer, the walls are cool in the morning after the previous day's heat was released during the night. Lighting The primary source of light in the visitor center is daylight, which enters through the clerestory and other windows.
Overhangs shade the south-facing windows from direct sunlight during the summer.
This design maximizes the amount of daylighting entering the space while minimizing glare and heat from direct sunlight. When there is not enough daylight, the building's energy management computer adjusts electric light levels to provide only the amount of additional light required. Natural Ventilation Reducing the solar heat gain in the summer significantly lowers the building's cooling load, so the building can often be kept cool solely through natural ventilation. A natural stack effect induces air movement through the building when the clerestory windows are open. The building's energy management computer automatically opens these windows when cooling is needed.