Desk lamp on each desk that each person can turn on and off at will. If nobody ever turns on their desk lamps, add a very low level of ambient light with widel

Desk lamp on each desk that each person can turn on and off at will. If nobody ever turns on their desk lamps, add a very low level of ambient light with widely spaced ceiling lamps or torchieres using bulbs that mimic 40-watt incandescents in both brightness and spectrum. You want just enough light that people aren't tripping over every backpack or dropped pen on the floor. Avoid fluorescents like the plague. The spectrum and frequency (fluorescents actually flicker at a frequency high enough that our brains smooth it out before interpreting the signal - but doing so is taxing on the brain) both contribute to headaches and fatigue. Anyone who wants more light than the ambient can and should use their personal desk lamps. Meanwhile, leave your windows unshaded so employees can take advantage of as much natural light as the season allows - it's important for mental health and circadian rhythms.