Natural Light in an Office Space and Building Performance (Financial Efficiency)

In the United States, the peak demand of electricity occurs during standard business hours. The price of electricity used during peak demand times is higher than the price of electricity used when the overall demand wanes. Effectively using the daylight available during those business hours not only reduces the total electricity demanded by lighting and HVAC systems, but also reduces peak demand, minimizing the use of the most expensive electricity. Saving one kilowatt-hour (kWh) of energy during daylight hours saves a building more money than saving that same kWh at midnight.

Natural Light in an Office Space and Sustainable Design

The Leadership in Energy and Environmental Design (LEEDâ„¢) rating system recognizes that incorporating natural light and views into a building can promote occupant well-being, while reducing the amount of electricity used by the lighting and HVAC systems.

LEED is a rating system sanctioned by the U.S. Green Building Council (USGBC) that provides a national standard for what constitutes a "green" building. LEED principles promote buildings that are environmentally responsible, profitable, and healthy places to work.

The rating system is composed of six categories: Sustainable Sites (SS), Water Efficiency (WE), Energy and Atmosphere (EA), Material Resources (MR), Indoor Environmental Quality (EQ), and Innovation and Design Process (ID). There are a total of 69 LEED credits available between these six categories. Twenty-six credits are required to attain the most basic level of LEED certification. Incorporating natural and electric lighting control into a project can contribute toward earning up to 22 LEED credits.

The Indoor Environmental Quality category offers up to two credits for providing building occupants with a connection to the outdoors by incorporating daylight and views into regularly occupied areas of the building. As specified in the Version 2.1 of the LEED Reference Package for New Construction & Major Renovations, to earn credit 8.1, "75 percent of all spaces occupied for critical visual tasks must achieve a minimum Daylight Factor of 2 percent, excluding all direct sunlight penetration." Credit 8.2 mandates that "occupants in 90 percent of regularly occupied spaces must have a direct line of sight to vision glazing."

The Energy and Atmosphere category offers up to 10 points for reducing the electricity consumption and costs attributed to various building systems (ASHRAE/IESNA Standard 90.1-1999 is used as the baseline). The interior lighting and HVAC systems are two of the systems considered by this credit. Using natural light to reduce a building's peak energy demand upon these two systems effectively reduces both the overall electricity use and cost.

For more information on LEED, visitwww.usgbc.org.

Adding daylight into an office space can boost building and employee performance. However, effectively incorporating natural light into an office space requires greater consideration than simply increasing glazing area. Natural light needs to be managed and controlled. The fenestration is no longer just metal and glass. Instead, it is glass, metal, and a dynamic shading component.