Originally published in Interiors & Sources

02/24/2012

Daylighting as a Cost-Effective Solution

Three solutions to maximize daylighting opportunities and minimize artificial light.

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The virtues of daylighting are well-known – better employee satisfaction, reduced absenteeism, and a more aesthetically pleasing space. But in an existing building, it’s not easy or cost-effective to put a large window in a wall that wasn’t originally designed to hold it.

Fortunately, existing buildings can still maximize sunlight use without making structural changes.

What Resources Are Available?
Your existing resources will determine the scope of what you can accomplish. Many factors will impact your decision, including:

  • Building type
  • Budget
  • Size of existing windows, roof monitors, and/or skylights
  • Building systems and controls

“Controlling the experience is the most critical aspect of incorporating daylight into a building,” says Janet Cecchettini, manager of lighting education for Juno Lighting Group by Schneider Electric. “There are pitfalls to daylighting that are not evidenced by an ROI calculation, such as glare and reflected glare, room temperature variations, and distraction due to changes in light levels.”

Assess the percentage of useful daylight entering the space to determine how it can improve. The Daylighting Pattern Guide, a free tool provided by the New Buildings Institute at patternguide.advancedbuildings.net, demonstrates the effect you can achieve with different windows and other changes.

Factors in Daylighting Savings

Daylighting’s benefits are widely recognized, but how much can it save you? Mudit Saxena, associate director for Heschong Mahone Group, says many factors can impact your savings, such as:

  • Window/skylight glazing area
  • Visible light transmittance
  • Orientation
  • Climate
  • Window head and sill height
  • Type of blinds or shades
  • Ceiling height
  • Interior furniture height
  • Wall, ceiling, and floor color
  • Lighting power density
“Variations in the pattern shows how much usable daylight you’re getting,” explains Barb Hamilton, lighting manager for the New Buildings Institute. “Your building might only get 25 to 30% useful daylight, but you could get it up to 60 or 70%.”


  1. Low-Cost Fixes
    If your building occupants are complaining about too much daylight, consider adding or changing your blinds to cut down on the light entering the space. Task lights can also address an unwanted surplus of light by allowing you to cut down on both natural and artificial light.

    “If users are complaining about eye fatigue or headaches or there’s too much daylight, adding a task light might help,” says Hamilton. “It increases the illumination on the work surface so you can turn down the other lighting further. After you look at these options, you might change luminaire parts.”

    If your budget allows, purchase plastic or glass partitions that light can penetrate when your fabric partitions are near the end of their useful life, Hamilton adds.

  2. Smart Space Usage
    In some cases, you may be able to maximize the use of entering light by rearranging space layout. Obstacles that block the path of sunlight prevent light from flowing freely throughout your space.

    “With a partition layout, the available daylight plummets as partition heights approach 72 inches,” Hamilton says. “For the price of changing out the ones that are running parallel to the windows, you could potentially increase your penetration of daylighting.”

    This change is slowly catching on with designers, says Jeff Spencer, Juno’s director of product management – commercial. The emphasis on daylighting is even changing the way some view the office itself.

    “Commercial office space is being rethought. In days gone by, being an executive meant a corner office with lots of windows,” Spencer explains. “Now executive offices are being moved to the building core to allow natural light to penetrate more deeply into the space.”

  3. Take Control
    Lighting control systems – such as daylight harvesting sensors, dimmers, and occupancy or motion sensors – will help you make the best use of your artificial lighting systems, as will switching some of your fixtures to LED or other efficient sources of light.

    “Consider the service model after you complete the project that supports your daylight harvesting system,” says Heath Martin, product manager for lighting controls at Schneider Electric. “Lamp changes should be done per the scheduled lamp life. Also, take advantage of seasonal and time savings changes by editing the footcandle set points to get the most out of ambient light.”

 

Janelle Penny (janelle.penny@buildings.com) is associate editor of BUILDINGS.

 

 

 
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