Tubular-daylighting-device technology, properly specified, makes it possible to use daylight as the primary light source in convention-center sized spaces.
By Neall Digert, Ph.D., MIES, Solatube International Inc., Vista, CA
Daylighting a convention center presents a considerable challenge, especially in high-bay structures with high ceilings. Until recently, innovative architectural design and expensive façade articulation was required to make it possible for traditional windows and skylights to deliver natural light into this type of space. Even then, significant system tradeoffs existed.
In Pittsburgh’s David L. Lawrence Convention Center, for instance, clerestory windows and ribbon skylights successfully combine to provide natural light to 75% of the exhibit space for an energy savings of 9.5 million kWh/yr.
In similar projects, with large penetrations to the building envelope, heat transfer becomes a huge concern. To maintain comfortable temperatures for convention attendees, air-conditioning units often must be activated to offset the solar heat gain.
Daylight is also a variable resource, and controlling it is difficult. Natural light transmitted through skylights and windows can create issues such as glare, hot spots, and shifting light patterns. This causes discomfort and distraction for exhibitors and booth visitors.
Being able to consistently direct daylight to the exhibit floor can also be quite difficult, if not impossible, given the high ceilings and large floor plates. Daylight can get trapped near the ceiling plane, leaving the exhibit space below with less than optimal lighting. This may force convention-center personnel to switch on electric lighting to compensate, which defeats the purpose of daylighting.
A third option
Fortunately, a third option now exists that addresses all of these issues. High-output tubular daylighting devices (TDDs)—part of the optically complex fenestration device category—use advanced optical technologies to capture, transfer, and deliver massive amounts of daylight into a high bay space without the issues commonly associated with traditional fenestration resources.
Consisting of an optical dome, a highly reflective optical light guide (tubing), and a specially designed diffuser, TDDs capture daylight at the roof level. That light then travels downward through the tubing until it exits through a diffuser and is evenly distributed throughout the exhibit space.
So how does a TDD solve typical daylighting issues?
Let’s address the space issue first. We all know that a hefty output of light is required to illuminate the expansive floor of a convention center. That’s why a TDD’s dome is so crucial.
Built-in optical-dome technologies harvest light from the diffuse sky and direct it downward into the tube. Some models use Fresnel lenses to increase input during low-light hours and bring in even more daylight than less-sophisticated models.
For extra-large convention spaces, the most advanced TDDs offer collectors that further maximize daylight capture. Their larger initial input helps achieve a greater ultimate yield with increased output consistency throughout the year.
Even with all this light coming in, getting it down to the exhibit floor 40, 80, perhaps 100 f.t below is a herculean task. The solution? Certain TDDs offer an amplifier that attaches near the bottom of the tube and redirects daylight down to the exhibit floor. This provides focused lighting with perfect color rendition that showcases products in their natural hues and makes exhibit spaces more inviting.
With some TDDs, the amplifier can be combined with the core unit and collector for a system that brings in massive amounts of light that can be precisely projected onto the exhibit floor.
In some cases, spreading light evenly throughout the space may be preferred. That is easily accomplished using special diffusers that integrate with the TDD. This reduces shadowing, hot spots, glare and shifting patterns of light, making the environment more visually comfortable for attendees.
And don’t forget about the importance of controlling ultraviolet light. Left un-checked, it will fade carpets, fabrics, furniture, and wood and plastic surfaces. If this is a concern, look for TDDs that feature domes with UV-blockers, so interiors retain their original appeal for years.
Despite its numerous benefits, sunlight does have its drawbacks. Heat is one of them. With typical windows and skylights, solar energy passes freely through the glazing. This can warm the interior to uncomfortable levels and send air conditioning units into overdrive.
When that happens, attendees are not able to enjoy the convention experience. They may become distracted, impatient, or irritated. They could even leave the event prematurely to retreat to the cool comfort of an air-conditioned hotel room.
To address this issue, some TDDs feature technologies that prevent heat-infused infrared rays from entering the building. To do this, a special proprietary material in the dome and tubing—think of it as a double barrier—dissipates heat from the system and sends it back into the atmosphere. The result is reduced solar heat gain and a more comfortable environment without overworking a building’s air conditioning system.
Whether using skylights, windows, or TDDs, one of the best reasons to consider daylighting a convention center is for the people benefits it provides.
When an exhibit area is cheerfully lit and maintains a comfortable temperature, people attending a convention find it more inviting and easer to navigate. They also tend to feel happier, are more energetic, and can concentrate for longer periods. Walking from booth to booth for hours under electric lighting, on the other hand, can drain energy and promote lethargy.
Daylighting design techniques
So how can TDDs be used to achieve specific effects?
In a convention setting, a common setup is to space units around the periphery of an exhibit hall and use Prismatic diffusers to evenly distribute the daylight on the perimeter walls for a warm, welcoming atmosphere. If some drama is desired, placing TDDs with amplifiers near walls creates an intriguing wash effect.
In the central exhibit area, TDDs with amplifiers over booths bring light down to the floor level to ensure products are optimally lit. Collectors are effective in any areas needing an extra boost of light.
When it comes to daylighting convention centers, TDDs offer many benefits. For contractors, the simple engineering and compact size of TDDs make them easy to install and maintain. This limits roof penetration liability and results in fewer warranty call-backs.
Building owners will profit from reduced energy consumption and lower maintenance costs. Brighter, more comfortable interiors that feature distinguishing TDD units will also attract additional business to a convention center by visually differentiating it from others while meeting the specific needs of meeting planners.
Architects will also experience positive results by using TDDs. Through sustainable daylighting, they’ll successfully increase energy efficiency, reduce the carbon footprint, and improve building usability. All of which aid in meeting USGBC LEED and Net Zero goals.
In the past, daylighting a convention center was a formidable task. But the recent introduction of high-output TDDs makes it a whole lot easier. The trick is to determine which benefits are most important, then do the research to find the TDDs that deliver them.
Neall Digert, Ph.D., MIES, is vice president of Product Enterprise at Solatube International Inc., Vista, CA.