Considerations in Daylighting Options

We receive inquiries about energy efficiency and energy audits from clients ranging from homeowners to facility managers and everyone in between.  One of the main areas of immediate payback is analyzing current or planned lighting systems and fixtures.  Lighting makes or breaks any space and also is directly tied to the overall feeling of a space.  Too dark and it feels uninviting, too bright and it can be overwhelming.

There have been many daylighting studies done, all proving the productivity and general well being improvements of having lots of natural light.   A recent article in the January edition of  Architectural Products Magazine highlighted some notable results:

• Full daylighting enabled students to get more vitamin D than students in schools with primarily electric lighting.  These students’ had nine times less dental decay and grew nearly an inch more in height over two years.
• Daylighting has proved to increase per transaction value in retail store settings.  Customers stay in the store longer.

The most obvious way to obtain more daylighting is more windows.  However, windows are typically the weakest part of a building envelope in terms of insulation, and adding more may create a potential for greater energy consumption in heating and cooling.   To solve this problem, consider some alternatives such as:

• Light shelves
• Tubular skylights
• Channel glass
• Exterior / interior shading
• Active systems that track and direct daylight

When comparing the cost of a passive system (fixed skylight, light shelf, etc) against an active (exterior solar control, tracking skylight, etc) system it is important to include all the variables that contribute to ultimate performance.  For example, active daylighting systems can provide up to nine times more light than a passive system and spreads light more evenly over a wider area saving valuable energy costs.

In the end, the most effective daylighting scheme is going to rely on both passive and active as well as interior and exterior systems, but hopefully this post has given you some ideas for your own analysis.

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