In commercial buildings, mounting evidence about the inter-relationship of health and occupant productivity to a building’s IEQ is significant. One of the key systems that comprise good IEQ is daylighting.

The use of natural light in buildings has been addressed by building professionals since at least the first century BC, the time when 'De Architectura' was written by the Roman Architect, Vitruvius. In those days daylighting had to be thoughtfully considered since fire and oil lamps were the only means of artificial lighting.
We know that exposure to natural light is very important to human health. Daylighting helps us maintain our natural bio-rhythms which results in greater well-being. Too much darkness has resulted in a health disorder referred to as SAD (Seasonal Affective Disorder). Too much artificial light has other negative health implications.
The goal of daylighting is the transparency it provides to the natural rhythms of the day, connecting us to the great outdoors — to nature. When given the choice, 75% of people prefer to work in daylit areas. And, we perform better with natural lighting. Effective daylighting combines and balances natural light with artificial light. Synergized daylighting strategies have been shown to reduce energy usage approximately 50 to 80%.
Two main window types used to achieve daylighting are toplighting and sidelighting:
• Toplighting can include roof monitors, skylights and light tubes.
• Sidelighting

Natural light and outdoor connection influences interior walls and finishes, occupant locations and window placement — all of which should complement one another. Energy usage can be reduced through window selection, placement and glazings, sun control devices, and lighting systems and controls.

For commercial properties, LEED™ Credits are available for Daylighting.
To be eligible for LEED EQ credit number 8, Daylight & Views, a connection to outdoor environment (1 point) and daylighting (1 point) is required. Daylighting is required in 75% of task-occupied space and views are required for 90% of regularly occupied rooms.