A 2003 study of office worker productivity conducted by the California Energy Commission found exposure to daylight was consistently linked with higher levels of concentration and better short-term memory. (Wall Street Journal, Oct. 19, 2004)

The U.S. Green Building Council’s Sustainable Building Technical Manual reports that worker productivity can be increased by up to 15% by implementing smart daylighting. Because salaries of building occupants far exceed the construction or operating costs of a building, any sustainable design features that positively impact productivity, however modestly, will pay back the investment over time. (Environmental Design & Construction, January 2001 and July 2002)

Pennsylvania Power & Light reported that after completing building upgrades to use more daylight, absenteeism rates dropped 25%, productivity increased 13.2% and energy costs declined 69%. The original energy payback was calculated to be a 24% annual return on investment. Once the employee productivity and reduced absenteeism were factored in, however, the actual return on investment was approximately 1,000% per year. In other terms, it was estimated that the lighting retrofit paid for itself not in the 4.1 years estimated, but in just 69 days. (Seattle Times, January 18, 2000) (Architecture Week, July 2000) (Sustainable Development International Corp. website, www.smartoffice.com, 2002)