Since the beginning of time, man has utilized natural daylight as his main source of illumination. Using light from the sun saves energy over using artificial light. It is particularly beneficial because it is generally cooler per lumen than artificial light. Dynamic daylighting designs not only save energy by using less electricity for lighting, but also reduce internal heat loads which lowers the amount of air conditioning used.
When designing for better daylighting, there is something new under the sun
Daylighting designs have evolved a long way. According to Wes Brooker, marketing manager at
Nucor Fabricated Products, Eufaula, Ala., during the middle ages, large churches used daylighting so services would not be held in the dark. In the 1800s, train stations used daylighting and were not even aware of it. Candles and oil lamps were not capable of distributing the necessary light, so large windows on the walls and clerestory roofs captured and distributed the light. Sawtooth roofs having a series of ridges with dual pitches was another daylight strategy used for industrial buildings before the supplement or replacement of electric light. Due to our ever-evolving world, technology evolves and daylighting designs do too.
But green building codes evolve too, and more and more they are specifying the need for improved daylighting designs in buildings. “These codes are having a direct effect on the overall design of buildings,” says Mark Weaver, technical support manager at Palram Americas, Kutztown, Pa. “Architects are being forced to design their structures with more daylighting to stay in compliance with the various green building codes.”
Building owners and occupants also are demanding better interior environments. “Good building design, including daylighting, has a positive impact on occupant comfort and productivity,” says Justin Willett, energy analyst, Butler Manufacturing, Kansas City, Mo. “For commercial developers, incorporating daylighting into their buildings can.
A light to the sky
Skylights are light-transmitting fenestration first used in ancient Roman architecture. Despite their longevity, according to Brooker, conventional skylights often do a poor job of dispersing the sun’s rays, and cause hot spots, glare, UV damage and uncontrolled heat.
Brooker suggests to completely diffuse incoming sunlight, prismatic skylights should be part of daylighting designs. “They refract the light into microlight beams, spreading the sun’s bright, natural light throughout the space,” he says. “This reduces the sun’s intensity without compromising daylighting effectiveness. Prismatic skylights also maintain variable light transmission (VLT) for more years of light compared to other products. Prismatic skylights have a minimum of 4,000 tiny prisms per square foot of glazing layer.” Prismatic skylights provide 100 percent diffusion and transmit 35 percent more light than conventional skylights while producing:
- No hot spots
- No glare
- No UV damage to merchandise or furnishings
Their high-performance design has no moving parts and catches up to 20 percent more light at low angles with a mere fraction of the aperture area than traditional daylighting technologies. “This translates into more efficient building envelopes and minimal impact on building structural design,” says Neall Digert, Ph.D., MIES, vice president of product enterprise, Solatube International Inc., Vista, Calif. “Smaller optically advanced apertures mean that, in many cases, advanced optical daylighting collection systems can be integrated into a building without causing any impact on structural design or layout, easily fitting within typical spacing of structural elements.” Advanced optical light-guide technologies allow daylight to be efficiently and effectively ducted within the building’s interior, transporting daylight from rooftop collectors to deep, internal occupied spaces. “This allows daylight to be applied to nearly any space within a building, regardless of its adjacency to the building’s exterior,” Digert says. “They can also be specified such that they can be reconfigured over time to not only change how daylight is applied to a space, but also where it is applied. This means the daylighting system can be reconfigured to address changing occupant needs and/or evolving building design and use.”Orientation
One of the oldest and time-honored daylighting designs is building orientation with windows facing south; nothing next-generation here. But building owners are not always in control of which direction their buildings will face.
When orientation cannot be controlled or a significant amount of glass is needed in hotter climate zones, designing with electrochromic (EC) glass can help allow more glass without energy penalty, and can control daylight quality, even in low-angle sun. “The challenge for daylighting designs is to let enough light into the building while still controlling for glare and for heat,” says Helen Sanders, vice president of technical business development, SAGE Electrochromics Inc., Faribault, Minn. “EC glazing allows the solar heat gain to be modulated and the glare to be controlled all in one device. Also, EC glazing is now available with multiple, individually controllable segments (zones) within one pane, so that architects can have their large floor-to-ceiling glass panes with no mullions, yet can control separate sections independently to optimize glare control, daylight admission, energy admission and color rendering without loss of view.”
Building orientation is usually not a problem when daylighting with skylights. New skylight technologies can locate their collection apertures on the building’s roof plane, so they can be easily applied to a building, regardless of the building’s façade orientation. In addition to skylights, Robert W. Farber, CEO of Carbondale, Pa.-based Quality Perforating Inc., says another important building component is nontraditional perforated metal panels that allow for new daylighting designs while spanning multistory areas with fewer panels. Fabian Kremkus, AIA, LEED GA, design principal at CO Architects in Los Angeles, feels expanded metal technology is becoming more important in daylighting, allowing for metal panel design that balances the design idea with shading and daylighting requirements. “Custom perforation, folding and cutting are being done on the manufacturing end, which offers new design opportunities and better façade integration,” he says.
Lighting controls
Daylighting is more than just building components and orientation. Architects’ new daylighting designs incorporate energy-efficient lighting and daylightresponsive lighting control systems. Next-generation motion and photoelectric sensor technology is allowing this to happen. “Five to seven years ago, lighting controls had 300 control zones for any given sensor,” says Willett. “Now, there are 1,400 to 1,500 control zones per sensor capable of detecting light, heat and motion. In conjunction with controls, LED fixtures can dim once the light threshold has been reached. And when daylighting is integrated with a lighting controls system, it can reduce lighting costs by up to 70 percent-which provides a return on investment in an average of three to five years.”
Lighting controls which automatically dim the lights when there is sufficient daylight are a key part of providing energy performance in daylighting designs. “These continuously dimming controls with an ‘off’ step are essential for optimizing energy performance and occupant comfort/acceptance,” says Sanders. “[Studies] have shown that the performance of continuously dimming controls is far superior to stepped dimming with no ‘off’ state. Wireless sensors (light, occupancy) and control are increasing the adoption rate of this technology, in addition to the increased requirement for lighting controls in more spaces through the baseline energy codes.”
A dynamic daylighting system implementing lighting controls integrated directly with artificial lighting is Intelasun by Lake Forest, Ill.-based CPI Daylighting Inc. With it, light sensors can be set so that a minimum light value will be achieved. “Artificial lighting can be programmed to only come on when that particular light level is not attainable through the sole use of natural light,” says Yossi Vinograd, president of CPI Daylighting. “It balances the amount of natural light that enters a space. It gauges the sun’s position in the sky, and then dynamically manages the desired sunlight, solar heat and sunshading inside the space.”
Manufacturers are continually creating innovative ways like Intelasun to seamlessly introduce daylighting into unique building designs. With so many options, designers will continue to meet the code requirements for daylighting while designing structures which are aesthetically pleasing and energy efficient.