Daylight harvesting systems can save you money – or they can be derailed by a handful of common problems and mistakes.
By Aaron Stern
April 26, 2012
The benefits of daylight harvesting are numerous, the technology is evolving and improving rapidly and the costs are going down. But if done wrong these systems can be self-defeating. There are some common problems that arise from overlooking some important factors:
- Defining the right sensors or the right placement of the light sensors is often a problem, says Gary Meshberg, the president of the Lighting Controls Association and the Director of Sales at Encelium Technologies. Sensor types include indoor, outdoor, and sensors with direct or indirect views to the sun. Sensor placements include open loop (facing at the window with direct sun) or closed loop (within the interior and facing reflected sun or electric light) – but any mistake with any type of sensor can throw things off. Meshberg says that common mistakes include putting a sensor directly above a suspended light fixture and flooding it with electric light, thereby giving an inaccurate measurement of ambient light. Another common mistake is not using a reference surface to calibrate a sensor – a dark desk with white paper on it can change the reflected light hitting the sensor and give false readings.
- As high tech as daylight harvesting systems can be, the biggest problem often comes when people try to keep shades the low tech tools they’ve been for so long.
“I don’t see how you can have a daylight harvesting operation with manual shades,” says Brennen Matthews, the North American specifications sales manager for lighting technology company Lutron Electronics. Matthews says that a proper daylight harvesting lighting control system has to be fully automated. He argues that employees are not going to take it upon themselves to run around and put the shades up and down manually in the right spot as the sun moves throughout the day. Shades left up lead to excessive light coming through the windows, which leads to glare and, more importantly, heat. Temperatures rise, the HVAC system kicks in to keep things cool, and just like that, you’ve defeated the entire purpose of letting in the sun in the first place.
“To me the automatic shades process is almost critical,” Matthews says.
- Educating building occupants about the technologies in use is critical. Matthews warns
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