Volume 48, Issue 11- November 2013
Is Two Better Than One?
Will Double-Skin Façades Make It as the Next Big Thing? by Ellen Rogers
The concept is so simple; glass wall plus glass wall equals double-skin façade. But looks can be deceiving. A double-skin façade is not as simple as all that. These structures utilize two layers of glass, typically an outer layer and inner layer. The glass can be composed of insulating and/or laminated units, but there are an added number of complexities and components when compared with single skins. Most notable is the cavity space between the walls, which may range from several inches to several feet wide. The wider the space, the more complex the structure.
Creating such a structure requires careful planning, design, communication among all parties involved and, above all, an owner willing to provide the financial backing to build it. Still, interest is growing. Everyone, it seems, is talking about double-skin façades—even though only a few exist in the United States. As with so many other glazing developments, the genesis of double-skin facades is rooted in Europe. It’s only been in recent years that a handful have even been built here. The resulting benefits are enticing: double-skin facades, at just a glance, are eye-catching; beyond looks, energy performance is abundant—but they may not be right for everyone, everywhere.
Double-skin facades are big business in many European countries—and rightfully so. There, electricity costs are roughly double those of the United States, and energy codes are more stringent than here.
Roberto Bicchiarelli is the senior vice president/general manager – south for Permasteelisa North America Corp.’s Miami location. Bicchiarelli began with the company at its Italian headquarters before he moved to the U.S. He also has a master’s degree in architecture. He says he had studied many of these systems, which are very common in Northern Europe, especially in Germany and Denmark.
“When Gartner [a German façade company] became a part of Permasteelisa in 2001, I had a chance to visit and see the projects they had done and they had a large portfolio of double walls built, most in Germany,” says Bicchiarelli. “It’s true that these are fairly new for the U.S. and are more common in Europe, and even in Asia, because of the climate situation. If you look at the codes in the various states single skins [with high-performance glazing systems will work] almost everywhere. If you look at [the U.S.] geographically, the northeast, the northern areas where it’s cold … those areas, though, are where double walls [would be most appropriate]. In other areas where there is a more moderate climate, it’s not as worth it from a thermal standpoint, but perhaps they are used for acoustical reasons. Double skins can provide a tremendous improvement in acoustics [compared to single skins], which is also good.”
Kevin Cole, director of engineering and design with Harmon Inc. of Bloomington, Minn., says his company also has had experience working on double-skin facades and agrees that the application type is substantially more prevalent in Europe than in the U.S. He believes this is due primarily to two points.
“In Europe construction [projects] are typically more energy aware/efficient and also there they have a tendency to construct buildings less concerned about first cost and more concerned with the life of a building,” says Cole. “Buildings don’t change hands as much in Europe.” He explains that commercial property owners in the U.S. often have shorter life spans with a building, “so they are not as excited about making large capital expenditures for a double-skin wall when they will turn around and sell the building.”
Cole points to another reason that the drive toward double-skins has been Cole points to another reason that the drive toward double-skins has been slower in the U.S.
“There have been improvements in the glass that maybe were not available when Europe was doing a lot of dual walls. That may be why there are not as many here.”
With double-skin facades only in their infancy here in the U.S., few contract glaziers have been involved with their construction; though most are at least somewhat familiar with the design concept. Ed Zaucha, CEO of APG International in Glassboro, N.J., for one, says his company has researched double-skins for the purpose of future business opportunities, “but we have seen only a couple of projects in our region since,” he says. “The design is fairly sophisticated and requires the collaboration of many professionals to achieve a superior result.”
When it comes to the growing interest in double-skin facades in the U.S., the push to build increasingly high-performance projects is leading the charge. In fact, Bicchiarelli says the LEED program is playing a big part.
“There are a multitude of potential benefits to a double-skin façade depending upon the sophistication of the design,” agrees Zaucha. “Thermal performance is certainly one element, but there are many other possibilities on what can be achieved with the outer façade, such as louvered glass openings, rotating BIPVs, sun-shading, fire suppression, etc.”
There are many considerations to make the project work, however, and everyone involved must be on board.
“It makes no sense if the mechanical engineer, structural engineer, building manager, etc. are not participating in the design and development,” says Bicchiarelli. “You don’t [get] the best [results] if you don’t [unite] the other systems in the building. This is a more demanding approach compared to traditional building, and there is not one person [making the decisions] … it’s about working in tune.”
He continues, “This is a different way to build the building, a more intelligent way. There are always building information modeling requirements, building management system requirements; there is always integration with the mechanical, electrical systems, etc.”
Cole agrees, and says the move toward energy conservation has played a part in whole building design, along with integrating the exterior skin with the inner-mechanics of the building.
Also speaking of the growing interest, he adds that while architects have played a role, “most of the time I think it has been an owner with interest in energy efficiency, a building with state-of-the- art design and long-term viability.”
Cole adds that in his experience the involvement with architects and other parties on a double-skin project varies company to company.
“There are some in which the architect and possibly working with a consultant and the mechanical engineer and so forth, will determine the method for the dual wall and come up with the actual criteria and development of it,” he says. “Other times a curtainwall supplier may provide that data and information.”
Zaucha agrees. “In this modern era, on any project that involves sophisticated design solutions we collaborate with specific professionals, such as engineers, university professors, researchers, architects and suppliers, throughout the globe to achieve a proper design. Only the biggest curtainwall companies can afford to have all of this expertise in-house.”
While energy performance can be significant, the savings can vary. Performance levels, for example, depend on the integration of the other systems on the building.
“The more integrated the better results you have, such as light and glare control, thermal, acoustic, occupation of indoor space,” says Bicchiarelli. “You can have your desk close to the [windows] without feeling uncomfortable. The whole experience definitely brings you to a different level. The lighting can be regulated and activated accordingly and automatically; you can control the blinds within the cavity; etc. You can have more uniform control of the temperature inside the space.”
Cole adds, though, the energy savings of a double skin are not necessarily easy to quantify.
“The pay back is long; the actual costs of the facades are typically about double that of a single-skin. It’s the potential additional costs that take it from A to B. If the exterior wall is 2 feet out you have to have a support system to hold that second façade up. If the walls are only inches apart then it’s pretty much just the cost of the two facades; the bigger the cavity the greater the cost.”
Ready to Go?
While the design may look good on paper, the client must be willing to move in that direction; and double-skin facades are not a short-term investment.
“It’s a long-term return,” says Bicchiarelli. “It’s not an investment you get back in two-three years. Double-skins require a willingness to accept new technologies, ones that are more expensive [than traditional systems], and involve a lot more integration, and not every client is willing to accept that.” He adds that the fact that these facades are more expensive than single skins is another reason not many are built here.
Education is also a barrier.
“We need to educate more people involved in this business about what means better performance and how you achieve that. There is a lot of information out there people think is correct and it’s not. [We need] more programs … training that needs to be done; more stringent codes or this will never take off because it’s expensive.” Cole adds that there is another concern.
“Does the double-skin truly have a significant enough benefit beyond that of high-performance glass to improve the thermal capabilities of the building?” he questions, saying there have been reports where double-skins have been studied in different climates to determine how much impact they will have. “In the U.S. the climatic differences will preclude whether they will be effective or not. There is an optimum situation and in other places they are not as effective. It definitely will not be the same everywhere in the U.S.”
But the interest is there. Designed by Gensler and set for completion in 2015, the Tower at PNC Plaza in Pittsburgh is such an example. The tower will feature a double-skin glass façade designed to enhance energy efficiency by reducing cooling costs and allowing natural airflow to the building. The building will also be oriented to take advantage of sunlight in workspaces, reducing the need for artificial light during the day.
The Tower at PNC Plaza is just one project; others are in the works. The Anthony J. Celebrezze Federal Building in Cleveland is undergoing a renovation, slated for a 2014-2015 completion, which will give the building a double-skin façade as well. Both projects are located in relatively cold climates, rendering a double-skin a likely good investment. Just as the experts agree, there is a place and purpose for double-skins; their success and growth will lie in this.
Double the Wall, Double the Time?
When it comes to double-skin facades, you might first think that constructing two walls will take, well, twice as long as a single-skin. Maybe, but not always. Roberto Bicchiarelli, senior vice president/general manager – south for Permasteelisa North America Corp. in Miami, says it does not necessarily take longer to build a double-skin than a single-skin façade.
“Double-skins are more demanding engineering wise and there are more components to be handled,” he says. “The overall assembly process may be a little longer because there is more to handle, but basically it can be installed at the same pace as a single skin. Most of the time these projects are design assist, so that means everyone is starting early.”
Kevin Cole, director of engineering and design with Harmon Inc. in Bloomington, Minn., adds that construction time also depends on the type of double skin. “If the cavity between the walls is 6-, 8- 10-inches you may be able to build [the facades] in the shop and hang them as one unit,” says Cole. “If you have a bigger cavity (several feet) you have to set the first system and then provide the additional structural element to support the outer wall. Next you add the outer wall. So, the projects can be twice as long or just slightly more than a single-skin.”