Volume 42, Issue 9 - September 2007
Take a walk outside and look up. What do you see? The sky. You could also stand in an enclosed building, look up (and all around, for that matter) and get the same effect—a connection with the outside. Thanks to developments in glazing and an increased desire for natural light and transparency the architectural community is getting a boost from these applications—especially the use of overhead glazing.
Skylights, which can use the sun to provide a natural source of both light and energy, are increasingly popular right now. Architectural design trends, commonly seen in vertical glazing, have shifted into the horizontal glazing market. “Skylights and architectural glazing designs are extremely popular in all areas of commercial construction,” says Ron Palombo, president of Acurlite, a skylight manufacturer based in Berwick, Pa. “[Applications include] schools, hospitals, commercial corporate buildings and state and federal buildings, as well as resort and institutional projects.” Manufacturers and installers also agree that the overhead glazing market has evolved in recent years. Some of these changes, like others that have affected the architectural glazing industry, stem from increasing demands for aesthetics and performance.
“[The changes] in overhead glazing are similar to those we’ve seen with vertical glazing,” says Terry Peterson, vice president of sales for Novum Structures in Menomonee Falls, Wis. “There’s a desire for increased transparency and for the structure to be as seamless as possible between the exterior and the interior.”
Rich Forsberg, who works in contract sales for Harrisburg Glass Co. in Shiremanstown, Pa., agrees. “People are trying to make a statement with their structures. They want something custom, something out of the ordinary.”
There’s more to the popularity of skylights than just transparency and aesthetics, though. Natural light and glazing performance qualities also have helped establish market demand.
“As the market becomes more knowledgeable about the benefits of natural light with respect to human performance, as well as the energy that can be saved by turning off electric lights during the day, the use of skylights will continue to grow,” says Randy Heather, standard products manager for Vistawall in Terrell, Texas.
Palombo agrees. “The amount of natural light that is introduced with a skylight dramatically reduces the need for artificial lighting inside the building,” he says.
The use of skylights, though, can also pose energy usage concerns. According to the U.S. Department of Energy’s Energy Efficiency and Renewable Energy program, horizontal skylights tend to receive maximum solar gain at the peak of the day. The daylight contribution is also high at midday and then declines during morning and afternoon hours. High-performance glazing options are available, however, to reduce these effects. Peterson says about 40 years ago energy concerns came into play and architects stopped trying to create “all-glass” buildings out of fear that heating and cooling costs would increase drastically.
“Glass moved forward technologically to address the challenges of energy issues,” Peterson says.
In addition to the high-performance coatings and warm-edge insulating technologies available, there are other energy-efficient choices.
“There are a lot more glazing options available than there were years ago—photovoltaics, translucents, polycarbonates, as well as everything in glass itself,” says Rod Kivioja, director of sales for Super Sky Products, a skylight manufacturer in Mequon, Wis. Building integrated photovoltaics, for example, are integrated into a structure and generate power, electricity and natural light (which also can earn LEED points). “The photovoltaic cells can be spaced on the glazing material and how far apart they are spaced determines how much light is allowed in,” says Kivioja.
An option with polycarbonate glazing is to incorporate an aerogel. “[Aerogels] are transparent, they still allow in light and significantly improve the performance of the polycarbonate panel,” Kivioja says. Plus, since polycarbonate is not as expensive as glass, he says these products are cost-effective. Having so many options can sometimes keep a skylight from being value-engineered out of a project.
“You can go with a simpler design, and a lot of that involves having the different glazing products, so that’s another reason for the many options,” Kivioja says.
In addition, polycarbonate is a recyclable material, which also can earn LEED points.
Reducing the amount of support, however, can pose design and installation challenges that must be taken into consideration. Peterson says while using large spans of glass for vertical applications is typical, doing so in horizontal applications can be more challenging. “The loading goes up significantly so we can only use the maximum-size glass possible,” Peterson says. “One way that we can create transparency is through the support system. We’ve seen a trend toward steel mullion systems because they are stiffer than aluminum so you can use smaller profiles to allow for more transparency.” He continues, “Also, when you bring in a tension system to support the mullion system you can make the mullion even smaller.”
One disadvantage, though, of using a steel profile over an aluminum profile is that aluminum can be extruded to take different forms, which is not possible with steel. “With steel you’re limited to flat surfaces, so you have to develop the glazing systems to go over the steel,” Peterson says.
Increased transparency in overhead applications can also mean installation and structural challenges. “Part of this comes from the unique forms and the desire for larger openings. We get requests to have skylight space that is 140 by 140 feet, which would need about six tresses to support it and that will detract from the transparency, which is the objective—minimal steel to create [for example] a 150-foot skylight with minimal loads on the structure,” Peterson adds.
Contract glaziers and installers also need to be involved in the development of these systems.
“We need to understand just what the customer is desiring and then we need to communicate it well to the skylight manufacturer,” says Forsberg.
“Installation is affected by requiring more [labor] to lift and handle the products. Depending on the design, sometimes the units will be pre-assembled on the ground or at the factory and hoisted into place. This would require a crane or other lifting equipment to be coordinated.”
With added requirements and increasingly demanding applications, communication and a close relationship between suppliers and installers is critical.
Forsberg says he typically has questions about the skylight’s support system. “I’m concerned about how the skylight is attached and connected to the roof,” he says.
Matt Snyder, sales and marketing assistant manager for Acurlite, says his company works closely with contract glaziers to ensure a quality installation.
“In working closely with the contract glaziers and architects we can sometimes limit the size of the support members that are required by using what is called a limited thrusting skylight,” Snyder says. “This means we build the skylight rigid so that it does not generate large thrusts onto the building. You can also put the supporting steel into tension so that the supporting steel members can be smaller as well.”
“We work with the glaziers and we develop an installation plan that takes them through the process step by step on how to do everything from the scaffold to how the glass goes in,” Peterson says. “Usually there are two trades involved [with steel and glass jobs], the steelworker/ironworker and the glazier. So the glass contractors are dealing with an element that they are used to.”
Kivioja says his company employs its own installers that do about 1⁄3 of the installations. “We subcontract out the rest to companies that we have approved and they only install our systems,” Kivioja says. “We carry the warranty, and the work remains part of our package. Single source responsibility is the one thing that’s important to any owner.”
“Today there is an increased focus on safety, energy costs and the performance of the system. We are seeing a lot of projects with blast, hurricane, etc., requirements,” says Kivioja. “Over the years we’ve had our systems tested and approved for code requirements. We’ve passed the criteria and we’ve invested time and money and it’s the same with the blast designs.”
Also, while skylights that incorporate high-performance glazing can help reduce energy costs and earn a building LEED points, they can play another green role, as they are recyclable. “Since most skylights are made from aluminum, they can be made from recycled materials and that aluminum can be recycled at the end of the building’s life cycle to create another product,” says Heather.Peterson says sometimes the glazing that’s used makes earning LEED points difficult since on many jobs glass is sourced from overseas and points are allotted when the product is manufactured within 500 miles of the jobsite.
“There’s an advantage, though, with the steel profiles, as there are many steel fabricators throughout the United States,” Peterson says. “Also, like aluminum, it’s recyclable.”
“Companies must continue to evaluate and improve their products to help them achieve the highest energy rating possible,” says Palombo.
Educating the architectural community is also important. Peterson says he thinks that the current level is strong, but misconceptions about glass performance still exist. “We have to keep the message out there,” he says. And, as the issues and requirements concerning thermal efficiencies grow, Peterson says he’s not worried that it will affect the skylight market negatively. “I am confident that glass manufacturers and fabricators will respond well to these issues,” he says.
the author: Ellen Giard is the editor of USGlass magazine.