“Hot” Green Topics - Articles That Highlight Green Initiatives
Day Lighting
Supplement or reduce artificial lighting use with day light.
Here are some considerations to make best use of day lighting in an existing facility:
- Factor the orientation of the building/site. Urban/rural; high-rise/low-rise will impact the amount of day light available. In general the quality of northern light is consistently cool, and clear; eastern light is warm, bright and clear; southern light is mostly available year-round; and western light can be strong and hazy.
- Different kinds of spaces require different light levels. IESNA recommends 50 foot-candles at the desktop level for regular office work in North America.
- Locate activities according to light and comfort requirements.
- Allow individual control of window treatment.
- Access control by minimizing window obstruction such as furniture.
- Use light emitting, translucent furnishing materials near windows.
- Avoid west facing zones which are least desirable for comfort and cooling
- Light interior finish colors are desirable. Avoid dark colors and high glare surfaces.
- Keep reflected view of bright windows off of computer screens.
- Filter light with blinds and open weave shades which are the best materials to control the amount of daylight.
- Integrate task lighting to reduce overhead ambient light needs
- Integrate direct/indirect lighting fixtures and reflective ceiling for even spatial distribution and avoid glare.
- Digital photos sensors, switching, and dimming controls balance light level requirements.
- Occupancy control sensors respond to movement or object surface temperature.
- Timers are a cost effective device for peak-period use.
- Consider using an energy consultant to provide a cost/benefit model to select best methods and means.
- Educate users on how to use the system. Manual harvesting is more difficult to achieve in a mid-size to large company. It can be difficult to get end-users to remember to turn off the lights.
Successful day lighting is a science and an art. It is the balance of light/contrast; shade/glare; heat gain/loss; synchronized with the position of the sun as it changes day-to-day. Natural day light can be visually stimulating. It is pleasant to occupants and increases productivity, performance, and minimizes absenteeism. Used effectively it reduces energy/operating costs and eases burden of HVAC cooling by reducing load with fewer fixtures on demand.
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