Businesses across America have been called upon to create more energy efficient profiles. For retailers, many of the solutions available are too complicated, too one-sided, or just too expensive to pursue. Wind energy, for example, requires converting a mechanical energy into an electrical energy. High-priced photovoltaic cells use the light of the sun to create energy, but in the conversion process, efficiencies are lost.
There is a solution that seems tailor-made for retailers: daylighting. In the words of Grant Grable, vice president of sales and marketing for high-performance prismatic skylight maker Sunoptics, there is no greater efficiency than turning off the lights. And in retail spaces, where it’s been documented that as much as 40% of total energy usage is lighting, daylighting is a perfect solution.
Optimal applications
Also known as toplighting, daylighting refers to the method of maximizing the amount of light brought into a building with 100% diffusion, eliminating hotspots, glare, or UV damage to the interior of a space. Daylighting is also often compatible with previously installed lighting controls to maintain the same level of light in a building at all times.The optimal application of daylighting in the retail space is a location with high open ceilings. By removing drop ceilings, retailers are finding more opportunities to disperse and diffuse natural light.
Inside of any of the retail giants Sunoptics works with, be it Walmart, Best Buy, Lowe’s, or Home Depot, one 30-square-foot skylight can cover anywhere from 800 to 1,000 square feet with enough light to decrease electric light usage by approximately 3,000 hours per year. One of the greatest success stories in this regard comes from Walmart, which has installed Sunoptics prismatic skylights in more than 2,500 of its locations around the world.
Rather than installing skylights into its existing store designs, which is an option, Walmart designed new locations to bring in enough light to allow electric lights to be turned off for longer periods. At the end of the final design phase, the company considered changing up its Energy Star design and instead locating the skylights in a more varied fashion.
The project architect talked the company out of changing the original design, and the company found energy savings it was looking for. In 2008’s The Retail Green Agenda: Sustainable Practices for Retailers and Shopping Centers from the International Council of Shopping Centers, Charles Zimmerman, Walmart’s vice president of prototype and new format development, estimated the annual energy savings would be $100,000 per store.
While looking for the energy savings, the company was pleasantly surprised with another benefit Grable said many retailers don’t consider: sales in the daylit side of the store had increased. “Walmart thought it was a fluke and that it couldn’t just be from the daylighting,” he said. Walmart completely flipped the store and had the same positive correlation with increased sales in the product located in the skylit part of the store. “Human eyes are designed for natural light,” said Grable. “We can handle more of it, and we see everything in full color. Because daylighting uses natural light, retailers are paying more attention to daylighting as an energy-saving technique and an opportunity to increase sales.”
From the cold, come light
In 2003, the California Energy Commission released a report entitled “Daylight and Retail Sales,” which examined the relationship between average monthly sales levels and the presence of daylight in daylit stores. Between 1999 and 2001, the retailer used for the study opened the doors of 73 of its California locations, 24 of which had daylight illumination primarily from diffusing skylights.In addition to an increase in average monthly sales, daylit stores had a small increase in the number of transactions per month. Even more surprising, the study found the profit from increased sales associated with daylight far surpassed that of the energy efficiencies found from using skylights.
At the time, the estimated whole-building energy savings average was $.24 per square foot, with up to $.66 per square foot possible with an updated design. The benefits from increased sales surpassed these figures by at least 10 times.
For those who think stores located outside Southern California can’t benefit from daylighting, think again. In June 2008, the Department of Energy (DOE) released a report entitled “Commercial Building Toplighting: Energy Saving Potential and Potential Paths Forward.” Although the report showed a difference in total results, the benefits of daylighting came through in various climates.
One of the biggest concerns for retailers using skylights is the potential of heat loss in the cold weather. Using Burlington, Vt. as its coldest example, the study found a low level of heat loss. The same held true for studies done in the hottest climate sample, which was Phoenix, Ariz.
The report states: “The warmer cities tend to provide better savings because they have greater solar insolation that allows a greater reduction in lighting energy usage for a given skylight to floor ratio (SFR). Heating and cooling losses are second-order effects at low SFRs…even in the coldest climate modeled, the heating losses do not become significant until unreasonably high SFRs are selected.”
Efficient illumination
This may be news to many retailers out there, but for Sunoptics, which has been in business since 1978 and has installed more than 500,000 prismatic skylights, the push to become energy efficient highlights a message the company has been sending out for years: daylighting and using skylights with lighting controls is the most cost-effective option out there for building owners, especially in the retail environment.
“Many retailers are promoting their sustainable footprint in the market, and many are going for LEED certification these days,” said Grable. Such is the case with Best Buy, which became a Sunoptics client in February 2008. Skylights have become an integral part of the company’s environmental program. As an active member in the US Green Building Council’s pilot program for volume certification, the skylights give Best Buy the ability to develop LEED-certified stores. Dwayne Shmel, project development manager, said the retailer had looked at daylight harvesting technologies that required a tremendous amount of complicated redesign to install.
“The active solar tracking skylight solution required some design work, and we had a couple of units installed in a store,” said Shmel. “Prior to rolling this out into our new store program, we took a step back and asked ourselves if we were making this more complicated than it needed to be.”
Shmel contacted Walmart’s Zimmerman, who is also a member of the Retailer Energy Alliance, a group sponsored by the DOE. Zimmerman indicated that Walmart used the passive prismatic system of Sunoptics, and Shmel called Grable to find out the specifics.
“There is a rule of thumb that anything that has a moving part is subject to repair and maintenance,” said Shmel. “We did not want to introduce any additional lifestyle cost into our daylight harvesting program.”
And although a lighting expert had informed Best Buy that a solar tracking skylight would outperform a passive unit, the company was looking for uniformity among its buildings, hoping to find a solution that would fit into the company’s market-based growth strategy rather than having to design a growth strategy around where the skylights would be most effective.
Because passive units don’t need direct sunlight and work in overcast and partly cloudy situations, the Sunoptics system was the best fit. To date, Best Buy has approximately 47 stores with skylights and another 28 projects in the works. As an added bonus, the prismatic skylights complement the new ceramic metal halide lighting system the company had recently installed.
The way the system is now set up, daylit locations have threshold set points on when the dimmable lights turn on and off. There are probably six to eight hours a day during the summer where the lights in those locations can be off completely and still meet Best Buy’s design standard of a minimum of 55 foot-candles.
“If you look at the most efficient way to illuminate the inside of a space, it’s taking the roof off and letting the natural light in,” said Shmel. “We continue to look at other alternative energy strategies, but for us, the simplest way to save energy is to just let the sunshine in.”
For Sunoptics’ Grable, the energy benefits are an added bonus to a platform that enhances a retailer’s sales. “If you can maximize the visible light, utilize controls, and provide 100% diffusion of the natural light, you can have the most cost-effective solar option that will not only save energy but will also out-perform solar applications while providing an increase to sales, something that no other renewable energy technology can do,” he said.
“Lighting is key in retail, which is why daylighting is an opportunity to not only enhance the look of the store, but also save energy in the process.”
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