12 minute read
Stadium Supports More Than The Team
by IdeaSoil
Fixtures Wash Out Light Puddles
LED fixtures reduce costs and eliminate poor light distribution that made it difficult for occupants to do business.
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The ArcheType X fixtures evenly illuminate the entire ceiling while delivering required footcandles to the customer and work areas. T he 1st Choice Savings & Credit Union in Lethbridge, Alberta, Canada, was designed to be a bright and inviting facility with an open lobby, high ceiling, and glass facades that allow plenty of sunlight into the building. While the architect had the best of intentions, the lobby lighting was not working for customers or employees.
One issue had to do with the physical position of the building. Because it faced north, large windows offered plenty of daylight on sunny days. That amount of light is normally welcome in a commercial space. In the Lethbridge building, however, it caused a tremendous amount of glare during prime working hours, making it difficult for staff to do their jobs. To rectify this issue, the maintenance team applied a tint to the windows.
The tinting solved the sunny-day problem but created illumination issues on overcast days. The 22 legacy 150-W indirect/direct metal-halide (MH) fixtures provided inadequate illumination for the lobby and many people visiting the facility were compelled to comment on how dark it felt. The fixtures were doing a poor job of throwing light out across the space. Instead, light would puddle on the floor and ceiling, which resulted in poor illumination levels as the teller and the customer were blocking the light from each side. Staff frequently found it difficult to perform critical tasks.
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Flexibility and light distribution made it possible to reduce the number of fi xtures from 22 metal-halide luminaires to 14 LED units.
In addition, recurrent metal-halide-fixture maintenance issues were becoming cost prohibitive and 1st Choice personnel would often wait to service the fixtures knowing that another issue was destined to come up shortly. Lamp and ballast failures were prevalent every week or two and a quick-fix upgrade to medium-base MH lamps proved to be unsuccessful when the fixture burnouts continued.
To solve the problem, the team at 1st Choice enlisted lighting-design firm Optics Lighting, Calgary, Alberta (opticslighting.com), to evaluate a number of lighting solutions. The designers concluded that LED technology would most certainly solve the maintenance issues but that performance would still be challenging due to the unique dimensions of the room and the ceiling.
It was decided to pilot the ArcheType X luminaire, manufactured by KIM Lighting, an affiliate of Hubbell Lighting Inc., City of Industry, CA (hubbell.com/kimlighting/en/). The luminaire makes it possible to precisely place light where it’s needed most with high target efficiency. In ArcheType X, LEAR (light engine adjustable ready) modules are individually controlled to provide custom light distribution. Each optical assembly accommodates 359-deg. of rotation and tilts between 0 and 70 deg. to provide a variety of lighting options.
The new lighting design at the credit union is significantly more efficient than the MH system, evenly illuminates the entire ceiling, and delivers the required footcandles to the floor/work areas. In fact, because of the adjustability of the fixtures, designers were able to reduce the number of fixtures needed to light the space from 22 to 14, while improving uniformity and efficacy. As a result, the system uses 57% less wattage than the MH lamps, which used 3,300 W. The ArcheType X fixtures operate at 1,414 W.
The improved light distribution has had a positive impact on customers and staff. Feedback from staff members indicates the system has improved working conditions and made them more effective at serving customers. Management has been pleased with the cost savings to date. In addition to using less energy, they are saving significant money on maintenance costs with fewer calls to the electrician.
According to 1st Choice CEO Jason Sentes, “It’s important that our facility reflect our brand standards, be inviting, and demonstrate a professional and trustworthy persona. With the ArcheType X we have an LED luminaire that blends in perfectly with the aesthetics of the designed space, is more energy efficient than our legacy fixtures, has decreased our need for on-going maintenance and, most importantly, improved the quality of light in the space for our members and staff. We have the best, most efficient lighting where we need it, when we need it.” CA
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Stadium Supports More Than The Team
The video board at U.S. Bank Stadium uses structural thermal breaks to keep up with the heat of the game.
U.S. Bank Stadium, Minneapolis, home of the NFL’s Minnesota Vikings, opened in 2016 seating 66,200, and wows visitors with its striking asymmetrical shape, transparent roof, acres of glass, 95-ft.-high pivoting glass doors, and enormous asymmetrical video board—a stunning departure from the current-day idiom of sports stadiums. The NFL selected the stadium as the site for Super Bowl LII in February 2018. Beyond aesthetics, the stadium’s sharp angles and slopes shed and disperse high volumes of Minneapolis’ snow, while its transparent façade provides spectacular views of the city’s skyline to visitors inside the stadium and of the action within the stadium for visitors standing outside. The city and the team wanted the stadium to foster a sense of community among residents, visitors, and football fans.
Supporting the unconventionally large (3,000 sq. ft.) and heavy video board in its sub-zero exterior environment, are
Standing 53-ft.-high at its left corner, the trapezoidal-shaped external video board complements U.S. Bank Stadium’s irregular shape and acres of glass. Installing structural thermal breaks where each support penetrates the insulated building envelope minimizes heat loss through its cantilevered steel-support structure.
Inset. Schöck Isokorb Type S22 structural thermal break is a load-bearing thermal-insulation element for steel structures consisting of insulation foam held under compression with bolted stainless-steel rods between two end plates.
structural-steel tubes cantilevered from the steel framework within the heated building envelope, requiring an inventive engineering solution on the part of HKS Inc., Dallas (hksinc.com), the project’s architectural firm, and engineering firm Thornton Tomasetti, New York (thorntontomasetti.com). They needed to prevent the structure from forming condensation and rust on the warm interior side of the insulated building envelope. Structural thermal breaks provided the answer.
The video board sits 150 ft. above grade on the exterior of the western prow and displays game schedules, ads, upcoming concerts, and other events in extremely high resolution. The behemoth board weighs 45,000 lb. and measures 80 ft. across its top but only 48 ft. across the bottom, with the left side at 53 ft. high and the right at 45 1/2 ft., fitting neatly within the stadium’s extremities.
Thornton Tomasetti engineers were charged with devising a plan for the board’s installation and overseeing the process. “The geometry was extremely complex,” said Greg Litterick, senior associate at the firm. “We had to determine how to precisely adjust the structural supports and attach the video board so that it would integrate seamlessly with the wall.”
Adding to the challenge was the thermal conductivity of the structural steel that supports the board. The board connects to an exterior metal panel, behind which sits an array of metal studs with an insulated waterproofing barrier—all surrounded by a steel superstructure. The high thermal conductivity of steel increases thermal bridging between the sub-zero temperatures of Minnesota winters and the heated interior of the supporting steelwork. “It was imperative to prevent cold exterior steel from touching warm interior steel and causing a thermal bridge,” said Eric Grusenmeyer, project engineer.
Creating a thermal break between the exterior and interior sides of each steel cantilever is an Isokorb structural thermal break (STB) installed precisely where each support penetrates the insulated building envelope. Schöck North America, Princeton, NJ (schock-na.com), supplied the Type S22 STBs. Each module is constructed with stainless-steel bolts and a rectangular HSS within a 3 1/8-in.-thick block of HCFC-free polystyrene foam insulation. The insulation reduces the transmission of heat and cold, thus minimizing thermal bridging between the cold exterior and warm interior sides of the bolted assembly.
The same approximate width as the insulated building wall, an STB is a fabricated assembly that creates a structural insulated break between the exterior portion of a structural penetration and the interior structure that supports it to minimize thermal conductivity between the two masses while optimizing load-bearing capacity. The STBs are equipped with flanges and bolts for fastening to flanged rectangular steel tubes on the interior side and on the exterior side to opposing flanged steel tubes supporting the massive video board.
The video board’s rectangular support tubes cantilever at the building envelope to support the load of the board, which is bolstered by horizontal and vertical girts to provide additional support. The installation entailed 34 building-envelope penetrations, each by a 6 x 4-in. steel tube. The tubes serve as outriggers that cantilever from the building structure in a grid pattern spaced approximately 9-ft. vertically and 8- to 17-ft. horizontally. Each tube is divided into two opposing flanged sections fastened on opposite sides of the STBs.
The resulting assembly reduces heat loss through the penetration by as much as 50%, reducing heat energy costs, carbon emissions, and heating-system capacity require
ments accordingly. Most importantly for the video-board application, the STBs prevent the interior side of the supports from becoming cold, reaching dew point, and forming condensation that would rust, compromising the structure and incurring ongoing maintenance costs.
According to Lance Evans, principal and senior vice president for HKS, “Our design had to address severe Minnesota weather conditions. Outside temperatures can dip to 20 degrees or more below zero, while the stadium has to maintain a comfortable temperature for the people inside. Preventing thermal bridging was essential to ensuring the integrity and performance of the stadium structure. STBs provided an effective barrier to accomplish that.”
Thermal bridging was mitigated by supporting the 3,000-sq.-ft. steel video signboard using cantilevered steel tubes, insulated from the building’s interior steel support structure using structural thermal breaks.
“The bolted steel plates can handle the significant structural stresses involved in securing the video board to the building,” engineer Eric Grusenmeyer explained. “They are specifically designed for this kind of application.” CA
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EDITORS’ CHOICE
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