“No space, architecturally, is a space unless it has natural light.” This quote from 20th century architect Louis Kahn is echoed by many of today’s architectural and building design professionals. Similarly, the concept of daylighting is not new to the commercial roofing industry, but many are now realizing its numerous benefits, including energy cost savings, improved employee productivity and minimal maintenance.
Daylighting refers to the use of lighting controls to dim or turn off electric lights when photosensors detect sufficient levels of natural light indoors. There are two primary methods for achieving daylighting: toplighting installations, which include traditional skylights, monitors and sawtooths, and sidelighting, which is the use of windows.
At this year’s American Architectural Manufacturers Association (AAMA) National Summer Conference in Minneapolis, the association shared its initial green building survey results. Of the results, daylighting was ranked second in the survey as a priority among AAMA Green Building survey respondents.
Traditional Skylights vs. Daylighting
Traditional skylights and daylighting systems have both been used to help buildings bring in natural light. These systems can be used in new roofing construction and retrofit applications with all roof system types. Also, with advancements in design these systems now have an average lifespan of 20 years.
Traditional skylights have been in use for decades in commercial and residential applications. While skylights are passive lighting systems, daylighting systems are used to achieve energy savings with lighting controls, which allow the building owner to dim or turn off electric lights depending on the available daylight. The lighting control systems consist of photocells that can be used outside, below the daylighting system or inside the building. These photocells monitor levels of light and in turn control the amount of natural versus electric light being used in the building. The combination of light refraction and diffusion through prisms allows the maximum amount of light transmission with optimal light distribution into the building as compared to standard skylights. Unlike electric light sources, modern daylighting, including high-performance prismatic systems, provides full spectrum, flicker-free light. Also, compared to traditional skylights, these systems also use fewer domes and therefore fewer penetrations in the roof, allowing for a smaller chance of roof leaks, integrity problems and heat loss/gain.
The daylighting industry continues to expand with new and groundbreaking products. Light shelves, mirrored louvers and prismatic glazing are some of the innovative systems that can be used to help reduce glare, increase light levels and redirect daylight further into the room.
A new system being developed by Ciralight Global Inc. includes a mirrored assembly attached to a photovoltaic (PV) powered motor that is controlled with GPS technology. As the sun moves, so does the mirror reflecting the light downward into the building allowing for maximum usage of the sun’s light. Compared to conventional skylights, this system provides more consistent light levels for a longer duration throughout the day, generates up to four times to the light levels and has lower initial costs and ongoing expenses.
With little to no maintenance required and only a yearly cleaning recommended, daylighting systems with prolonged use during the day can achieve much of the same results as PV systems for a much lower cost. Depending on local power costs, rebates, incentives and tax credits, daylighting users could see a return on investment in one or two years versus 10 or more years for PV systems and other energy savings options including micro-turbines and solar thermal systems. Useful tools such as the Database of State Incentives for Renewables and Efficiency (www.dsireusa.org) can help you determine your local incentives.
Benefits of Daylighting
A recent study on toplighting - in this case, the combination of skylights and electric lighting controls - conducted for the U.S. Department of Energy (DOE) titled “Commercial Building Toplighting: Energy Saving Potential and Potential Paths Forward” concluded that daylighting has the potential to realize significant reductions in lighting energy consumption, but this potential has not been fully realized. The greatest opportunity exists in buildings with high, open ceilings. A study referenced in the DOE report found that toplit buildings with high ceilings and photocontrols achieved, on average, 98 percent of theoretical energy savings.
The DOE has also concluded based on modeling results that 35 percent to 55 percent of lighting energy can be saved, with minimal incremental heating and air conditioning energy consumption, by installing an economically optimum toplighting system.
Not only do daylighting systems provide outstanding energy savings benefits, but many are finding that the natural sunlight also provides benefits to people in the buildings as well. Increased retail sales, increased productivity and enhanced learning have all been cited as perceived benefits of daylighting installations.
A recent study conducted for the PIER program at the California Energy Commission found that stores with daylighting experienced as much as a six percent increase in sales. The study also examined potential benefits of daylighting including: health (circadian system); worker perception/happiness; visual clarity and color perception; and reduced eye strain (if glare free). PIER studies found a “significant and positive” increase in mental function and attention, and found that glare, common with sidelighting, had a significant negative effect.
Companies such as Wal-Mart, Lockheed Martin and Pennsylvania Power & Light have all seen the many benefits for daylighting in commercial building applications including reduced absenteeism, increased sales and increased worker productivity.
Results are even being reported in the classroom. Pacific Gas and Electric Company in California recently initiated a study which showed that students with the most daylighting in their classrooms progressed 20 percent faster on math tests and 26 percent faster on reading tests in one year than those with no daylighting.
Daylighting can be used in buildings to achieve Leadership in Energy and Environmental Design (LEED) points, and the systems also meet the requirements of the California Energy Commission’s 2009 Title 24 energy standards and other institutions that influence the market for daylighting a space properly.
Properly designed daylighting systems can play a major role in reducing America’s peak demand. According to Jon McHugh, PE, LC, and technical director with the Energy Consulting and Research firm, Heschong Mahone Group, Inc., America could reduce its peak load electrical demand by 24,000 megawatts just by daylighting existing buildings. The savings is equal to 24 1,000-megawatt nuclear power plants or 48 500-megawatt coal-fired power plants.
There is a unique opportunity for architects and building design professionals with daylighting systems. There is a science behind daylighting. Advanced daylighting systems can provide many of the energy benefits of more expensive systems, yet at fraction of the cost.