ABSTRACT
The term daylight usually means any kind of light produced by the sun which reaches the earth directly or indirectly (Steffy, 2008). As described by the IES Lighting Handbook “Daylighting involves the delivery and distribution of light from the sun and sky to a building interior to provide ambient and/or task lighting to meet the visual and biological needs of the occupants” (DiLaura et al., 2011). Reinhart (2014) defined daylighting as the “controlled use of natural light in and around buildings”. He also described it as “the process by which direct sunlight and diffused daylight are reflected, scattered, admitted and/or blocked to achieve a desired lighting effect”. Daylighting can also be defined as the range of brightness and color composition for our vision, it gives us orientation in time and space, and it is a precondition for our perception and evaluation of the built environment (Mueller, 2013). In addition to visual comfort and performance, daylighting can contribute greatly to improving the sustainability level of buildings. It helps to replace artificial lighting by natural lighting; which results in saving a great deal of electricity consumption for lighting due to smaller lighting loads and also for cooling due to smaller cooling loads as a result of reducing internal heat gains caused by electric lighting fixtures.
