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Emerging Technologies Could Mean Cool Options for Spandrel
By Ellen Rogers
When it comes to glassy facades, the spandrel area isn’t always the coolest feature. In fact, it’s usually quite the opposite. According to glass consultant and technical expert, Bill Lingnell, the spandrel area can get extremely hot. From his own measurements, he’s seen it as hot as 244 degrees. And on many projects, Lingnell points out the spandrel area can take up a significant portion of the façade.
“It can be an estimated 30 to 40% of the wall system when we consider floor-to-floor distances of roughly 12 to 13 feet and vision area windows nominally 7 to 8 feet tall,” he says.
So what if, instead of just holding on to that heat, the spandrel area became a more functional part of the building? It’s a question that several in the industry are pondering. Technologies that offer such potential are being developed, but are in their infancy. While the option is there, it could take some time before it reaches market acceptance.
Understanding Spandrel
For many multi-story buildings, spandrel glass has an important role to play. It’s there to hide the sections between floors where building components are held. Unlike the transparent vision glass portions of the facade, spandrel glass is opaque and typically coated with either a silicone-based paint or ceramic frit. It is commonly tempered or
heat-strengthened monolithic float glass. Insulating glass is also an option. The goal is to create an aesthetic that blends seamlessly with the vision glass.
While spandrel glass has an important job, it isn’t necessarily an architects’ first priority in the specs.
“They have to have [spandrel] to fill in areas between floors or columns or areas that they do not want people to see [i.e., vents, wires, slab ends and mechanical equipment],” says Lingnell.
Nathan McKenna, marketing and innovation manager with Vitro Architectural Glazing in Pittsburgh, says he does see architects putting a lot of thought into their spandrel selections.
“A lot of architects do put time into it with custom colors, for example,” he says. “Some just want the standard … but it’s on a project-to-project basis.”
Functional Options
Since the purpose of spandrel is to hide what’s behind it, the glass itself doesn’t always add to the building’s overall energy performance. In many cases, the cavity area is even filled with insulation to improve energy performance. The spandrel can encompass up to 40% of the façade on some projects. That’s led several industry experts to explore opportunities that could make spandrel more functional.
“It would be interesting to target what can be placed in that cavity to make a building more energy efficient,” says Lingnell.
David Greusel, principal with Convergence Design in Kansas City, Mo., says while what most architects want is for the spandrel to look like the vision glass it’s above or below to create the illusion of an all-glass building, “that’s somewhat impossible because the vision glass has very different properties of reflectance and transmission, but that’s the goal …” he says, adding that there are opportunities to improve on spandrel glass, beyond just making it look more like the vision glass. “Energy performance is a big one. It would be great if the spandrel glass itself had better thermal performance.”
Vitro, recently introduced Solarvolt, its building integrated photovoltaic (BIPV) glass modules that can be used in a variety of building and façade applications, potentially replacing conventional building components such as wall cladding.
“We want the whole building to be more functional—spandrel, vision, roof,” says McKenna. “Spandrel is a non-vision application so it’s perfect for electrical generation without impeding the vision or sight lines. The aesthetics would be a little different, but [spandrel] is an ideal place to put it because it won’t obstruct views.”
To fully gain market acceptance, McKenna says these products must first get into the building codes, “and someone has to want to have the electricity-generating cells in there … It has the look of traditional glass, but with wiring.”
Keeping Clear
Ubiquitous Energy in Redwood City, Calif., is another company taking strides toward improving a building’s energy performance through glazing. The company is about a decade old and has engineered transparent solar cells to selectively transmit visible light, while absorbing and converting invisible ultraviolet and infrared light into electricity. As David Maikowski, director of channel development, explains, “instead of reflecting infrared away we take it in and convert it to energy … it looks like solar control low-E, but also acts as a transparent energy collector.”
The company currently is preparing to make the products commercially available, with building facades being one of their focus areas. Maikowski says that like traditional transparent glass, his company’s product could also be opacified and used in the spandrel area.
Maikowski says his company’s intent is to give architects an energy-generating solution with completely homogenous reflective color for the façade, without sacrificing the amount of glass used, for both the vision and the spandrel area. He says while spandrel is fi ne aesthetically, there are opportunities to make it functional, such as generating electricity. This type of technology, he says, creates an opportunity to have 25 to 30% of the glazing area as an active energy footprint of the building.
Alternative Solutions
BIPV and other solar-power façade products will have to overcome a number of challenges. Nick Bagatelos, chairperson of Bagatelos Architectural Glass Systems in Sacramento, Calif., has done a lot of research into BIPV and other solar technologies. His company also operates in a net-zero facility, which includes roof top photovoltaics.
“If you have a roof top solar array on an industrial building you can get to net zero pretty easily,” says Bagatelos, explaining that it’s more difficult to gain the same benefits from a vertical installation.
Alan Kinder, East Coast regional architectural manager, with Guardian Glass North America of Auburn Hills, Mich., agrees that there are some challenges with PV in vertical installations.
“One is the cost vs. the benefit analysis. How expensive is it and how much energy does it return?” he questions. “Also, with vertical installations PV technology should be considered on locations that get the maximum exposure to sunlight so that it provides the best return on investment.”
He continues, “Remember, in any glazing application, there’s a difference in center of glass and total system performance data. You want to be cognizant of the total system modeling for any of your glazing—not just the center-of-glass performance for the spandrel panel itself. Incorporating spandrel panels does provide the ability to add insulation to boost R-value.”
Instead of opting to fill the spandrel with BIPV, Bagatelos would rather find more opportunities to increase the amount of vision glass used.
“A product like vacuum insulating glass (VIG) offers the possibility of shifting to less or even no spandrel. With VIG, glaziers can create U-Value performance equal to opaque walls with fully transparent fenestration,” he says. “They [architects] will always choose glass over materials like stucco, but glass performs poorly so their designs are always challenged by poor glass performance, and glass area is usually reduced or turned to spandrel to achieve performance. When the industry improves the performance of double pane glass … the built environment can have more vision glass and less spandrel.”
In order to increase performance in typical applications, the spandrel area can be filled with insulation, or there’s a shadow box, which consists of vision glass on the building exterior and an opaque infill on the interior side. These additions can add to the overall cost, and could be eliminated by going to a VIG, which puts it at a more competitive price point. “And it really opens the possibilities to have full transparency and dramatically better performance.”
And for projects where there is still a need for a spandrel area, there’s a solution.
“Just place a spandrel coating on the VIG,” says Bagatelos. “It’s a similar solution, but with higher performance.”
Moving Forward
As building codes demand increasingly high performance, the glazing industry has responded, offering more efficient products. While most of these have been for the vision area, opportunities exist to also improve the spandrel area. The question is, how do we get there?
Kinder says the next steps for the future involve moving beyond the typical.
“We’re finding that advanced analysis and more modeling tools are becoming increasingly important for everyone in the supply chain. It’s always a matter of cost vs. benefit, and the cost isn’t always just the installation cost, but also the payback cost,” he says. “People want glass. They want to put glass on the façade and they don’t want to reduce the glazing.”
Looking at the advances glass has seen, Maikowski adds, “We have to find ways to keep up with the game in the codes and Europe is even more aggressive… the industry has to find ways to be innovative, whether that’s through BIPV or transparent PV, triple thin glazing or VIG … we’ve got to find a way to increase [performance] beyond passive low-E,” he says. “The opportunity is there, but it takes a leap of faith. Codes drove the adoption of low-E before and I think they will with new technologies, as well.”
Ellen Rogers is the editor of USGlass magazine. She can be reached at erogers@glass.com.
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