Maintain Optimal Visual Environment

Coordinating daylight and electric light with an automated shading and lighting control system provides the optimal amount of light at the workplane automatically, every day. The Illuminating Engineering Society of North America (IESNA) has developed recommendations that define optimal light levels for various visual tasks. The IESNA recommends that office buildings maintain 40 foot-candles at working level in a single office, 40 foot-candles at the working level in open plan offices, and 30 foot-candles at working level in a conference room. As previously mentioned, daylight can range in intensity from a few foot-candles, on an overcast day, to over 1,000 foot-candles, so it is easy to imagine just how common it is for office spaces that receive any daylight, let alone a lot of sunny daylight, to be over-illuminated.

Save Energy

In commercial buildings, lighting typically accounts for more than 30 percent of the building's total electricity consumption. Much of this expense could be avoided by specifying an automated shading and lighting control system that would coordinate daylight and electric light. Daylight harvesting is the lighting control strategy where electric light is essentially used to supplement available daylight when necessary to provide the optimal level of illumination on the workplane. When sufficient daylight is present, electric lights are dimmed or switched off, saving energy and preventing the space from being over-lit.

Now required by building codes. Coordinating the presence of daylight and electric light is newly becoming required by national and state building codes. The standard adopted by the Department of Energy as the national energy standard for all commercial buildings in the United States is written by the American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) and is commonly referred to as ASHRAE 90.1. The latest version, ASHRAE 90.1-2010, requires specific daylighting controls for the first time since its initial publication in 1975. The 2012 International Energy Conservation Code or the 2012 IECC mandates that day lit zones shall be controlled independently from other general lighting and may be either manually or automatically operated. Title 24 is the building code for both residential and non-residential buildings in California. Title 24 2013, which is scheduled to take effect in January 2014, requires photocontrols in all interior day lit spaces with at least 120W of installed lighting power.