Another method of sustainable green building design is to incorporate means of natural ventilation and lighting into a building, and thus reduce the need for energy use. Innovative new methods of accomplishing this are solar tubes mounted on the roof of buildings that bring concentrated sunlight into buildings and often replace the need for daylight lighting within the building. Also, buildings are increasingly being built with vents on the roof that can be opened to suck the hot air out of buildings and with windows that open that can draw fresh air into buildings.