Daylight-Based Controls

What isn't there to like about sunshine? We like sunny days over cloudy, rainy, dreary days. It's a proven fact that humans have more energy and feel better about themselves when the sun is out. There is a reason, after all, why the suicide rate is so high in cloudy, rainy Seattle, for instance. There are other reasons to like daylight, especially as it pertains to buildings: sunlight makes for a better scene (key in retail applications), it saves energy and operating costs, and it is said to reduce our impact on the planet.

Studies do show that shoppers linger longer and buy more in naturally lit environments, students do better on tests, and office workers are more productive and absent less. And, of course, energy costs keep skyrocketing. In fact, energy costs are surpassing salaries and benefits as the number one cost to businesses. So, it makes sense for daylighting technology to flourish, right? And to be effective, daylighting needs good controls.

"Controls are the key component for both lighting and daylighting and they have come a long way in just the past couple of years of making the transition from lighting to daylighting more seamless," says Earl Houston, ceo, Ciralight.

The good, no bad and no ugly

Good daylighting is the result of an integrated design process, which includes the building design, installation of the right materials and controls that make the system work. According to the Energy Center of Wisconsin, good daylighting design can include elements such as concepts of lighting power density, illuminance levels, contrast ratios, window-to-wall ratios, ceiling to skylight area percentages, and reduction in glare. Good daylighting principles can vary among geographics, building design and climate. It is a mix of art and science.

But what makes good daylighting? From the controls sense, it is the ability to save energy costs and provide the right amount of light during the day—as noted seamless light. With that, there are four basic types of controls:

1. Schedule-based.
2. Occupancy-based.
3. Personal control.
4. Daylight-based control/harvesting.

The objective of the daylight-based controls is to turn off lights in areas with abundant daylight or dim the artificial lights as natural light increases, says Eddie Hickerson, staff marketing specialist, lighting controls, Square D. In the end, energy is saved.

"Savings can be 20 percent of 30 percent via occupancy sensors, for instance, so savings can be significant," Hickerson notes. He adds the savings can even reach 80 percent.

"Savings from lighting controls can be determined pretty quickly," Hickerson adds. "Lighting controls should be an area in which contractors and building owners can be more creative and take liberties in looking for opportunities to save."

Houston adds that overall energy savings can range anywhere from 15 percent at the minimum to better than 40 percent. Houston also notes that with his company's SunTracker system, the return on investment often is in the months and, in fact, the ROI in some cases has been too quick for businesses to enjoy rebates and other energy-saving tax incentives.

The benefits of daylighting also extend beyond just lower lighting costs, it also can cut HVAC costs as well. Termed cool daylighting, it takes a holistic approach to the entire building, and aimed at reducing the cooling load of the building. The cooling load primarily is a function of internal heat gain from lights, equipment, people and sunlight. Daylighting reduces the need for electric lighting, which lowers the heat produced by electric lights.

When incorporating high performance glazing and exterior shading recommended for a comprehensive cool daylighting design, it also minimizes heat gain from the sun through the envelope. It is said these overall reduced loads often result in a reduction in the size of the cooling system.

The environmental and monetary benefits are many. For instance Wal Mart has been installing daylighting systems in its stores. For just one store, it is estimated there is a estimated cut of 618,000 pounds of carbon dioxide, 1,800 pounds of nitrogen oxides and 1,100 pounds of sulfur dioxide from being produced at power plants.

Contractor's role

Houston says electrical contractors can play a significant role in the daylighting realm. One role is integrating artificial and daylight systems.

Hickerson concurs. He adds, "A huge opportunity exists for contractors to sell real value-added products to a project."

And those benefits ultimately help the building owner. Hickerson says that for every $1 reduction in operating cost $10 is added to the buildings's value.

"Good contractors work with and do understand what to do in regard to energy efficiency and selling daylighting technology," Houston explains. And, as the concept of daylighting grows, the role of contractors will grow as well. "Daylighting will be run by sensors," he adds. "Photocells, computerization, photovoltaic technology, all of that will require the expertise of the contractor."

Photocell placement is key, correct system configuration and the coordination of controls and systems are all vital to attaining the most effective and cost-savings daylighting system.

"Daylighting systems are highly visible and they are something the building owner and the electrical contractor can show off," Hickerson contends. "People will take notice."