Volume 43, Issue 2 - February 2008

Some Assembly Required  
 Interest in Unitized Curtainwall 
Continues to Rise

by Megan Headley

Unitized curtainwall isn’t necessarily new to the glazing community, but over the last few years, its use has increased noticeably. 

According to Larry Long, president of Oldcastle Glass Engineered Walls in Dallas, unitized systems are a new “old” trend—they have actually been around for a long time. 

“It’s funny; unitized systems have been around for a long, long time. They’re coming back into vogue in a big way,” says Long. “They go all the way back to the 1960s. Unitized systems were the way curtainwall used to be installed when it first originated.” 

Those systems weren’t quite as complex as what’s available today: “They were very simplistic, almost like you would do a window if you replaced it at your house,” Long says. “So we’ve come a long way. But it’s just kind of funny that … the past particularly five or six years the momentum is just growing with unitized systems.” 

Kevin Fairchild, Norcross, Ga.-based Kawneer’s product manager, adds, “We’ve been offering the systems for several years. I’ve personally just noticed an increase over the past couple of years and it seems to be climbing steadily.” 

“I would say around the nation 90 percent of our projects on the exterior side are all unitized, pre-glazed projects,” says Brian Clark, vice president and division manager of Trainor Glass in Dallas. 

He noted that some divisions have been doing unitized system for longer—notably, the Florida division, which focuses on hurricane-impact walls. Today these systems are being found across the country in a variety of building types as advantages for building owners and glazing contractors are being discovered. Kelly Portz, marketing director of Architectural Wall Systems Co. in West Des Moines, Iowa, says it’s because these systems have been around for years. “I think we are seeing the unitized system become more widely accepted simply because it’s been around for awhile and the industry has had more exposure to it and therefore feels comfortable using this approach.” Jon Sternchos, owner of Enterprise Architectural Sales Inc. in New York, says cost has helped promote interest in these systems. “In the past year-and-a-half or two years there was a push to value-engineer from a curtainwall to a window wall and because of market prices it swung the other way,” he says. Sternchos, who does a great deal of work in New York, notes that unitized systems are “being drawn prominently in a lot of these condos, especially in New York City.” However, these systems are moving from metropolitan high rises to applications across the country. “Unitized systems have always been the wall of choice for the world’s high-rise buildings because on a large scale the costs are less,” Portz says. “Today unitized systems are competitive on three-story buildings and up.”

“Once limited to major metropolitan markets as a labor cost-cutting strategy, unitized curtainwalls are finding broader application across the United States, as glazing contractors and design professionals get more familiar with performance and logistical benefits,” says Steve Fronek, vice president of Wausau Window and Wall Systems in Wausau, Wis. “New thermal barrier unitized framing systems, used in conjunction with high-performance, low-E insulating glass, sunshades and light shelves, can be designed to meet stringent energy codes and sustainable design goals in all climate zones.”

For different reasons, the architectural community and glazing contractors are gaining interest in these systems. Brian Harrington, director of sales and marketing of Architectural Glazing Technologies (AGT) in Waterboro, Maine, says, “There is a lot of interest in what unitized curtainwall is all about and I think a lot of people, from architects through glazing contractors, are looking to understand where unitized curtainwall makes sense and what the options are—how do you size it based on performance requirements, based on geography, windload and whatever. There is a lot of interest in the product and in learning how to design a building with it.”

Speaking of Spec’ing
The architectural community and glazing contractors both have reasons for being interested in these systems.

“It’s really the design that’s pushing [unitized systems],” says Sternchos. “The architects, with the impetus of the ownership.” He adds that unitized systems can provide the open vistas so desired by architects. “If it’s a rental building you wouldn’t use a curtainwall just because of the costs associated with it,” says Sternchos. “If it’s a condo and you’re getting higher prices … people want full-glass looks.” 

However, glazing contractors are also steering projects toward unitized systems. “Sometimes it comes through design in one way and the glazing contractor will say, ‘Hey we think it would better in this application to use a unitized product,’” Harrington says. “It has so many benefits for the glazing contractor, in terms of reducing the amount of time and associated labor that it makes a lot of sense for them too.” “Right on the front end there can be a lot of influence or a preexisting bias by the architect or owner or the curtainwall consultant, so that may drive the glazing contractor to say, ‘Because of the way the specification is written we need to use a unitized system on this job,’” Long says. He adds, “The glazing contractor still has a huge influence on whether it’s stick-built or unitized.” 

Benefits and Drawbacks
The pre-assembled, pre-glazed systems are touted for the speed they lend to closing in buildings, enhanced quality control and the need for less manpower than traditional systems. However, industry professionals caution that these pre-assembled systems do present challenges to contractors. “Installation of unitized curtainwall is straightforward, but, as with any product, glazing contractors need to pay special attention to layout, handling, distribution, protection and surface preparation prior to sealing,” says Fronek. 

Load It Up
According to Larry Long, president of Oldcastle Glass Engineered Walls, some jobs are automatically specified with unitized curtainwall systems due to load requirements. “There are advantages in unitized systems in the way they handle seismic movement,” he explains. “There are advantage in the way they handle live load movement of the building structure; really that’s what forces some jobs to go unitized, because of the loading requirements.” 

Steve Fronek, vice president of Wausau Window and Wall Systems in Wausau, Wis., adds, “[They] can be designed to accommodate substantial building dynamic movement without putting undue stress on glass lites.”

He explains that the unitized curtainwall’s panelized frames usually span vertically, from floor-to-floor, which helps to accommodate dynamic movements without placing additional stress on glass, sealants or other infills. “Depending on how you frame it, it can be a benefit in wind loading …” Mike Maguire, senior designer for Architectural Glazing Technologies (AGT) in Waterboro, Maine, adds.

Brian Harrington, director of sales and marketing of AGT, elaborates, “The unitized panels come together at the stack joint. When the stack joint is positioned above the top-of-slab anchor, you get a cantilevered effect that helps to increase the stiffness of the unit, allowing it to support higher loads.”

Quality Control
Quality control frequently is cited as a benefit of unitized systems by the simple fact that the systems are assembled and glazed in a controlled shop environment. 

“Certainly the architects and consultants believe that the more that can be done in the controlled shop environment, and the less that can be done out at the jobsite, the better system you’re going to get,” Long says. 

“Factory unitized systems are entirely assembled in a controlled environment with quality controls at each assembly and seal station,” says Kelly Portz, marketing director of Architectural Wall Systems in West Des Moines, Iowa. 

“Jobsites are pretty messy, so … it’s a lot better quality when it’s in the shop, just in a controlled environment,” Kevin Fairchild, product manager of Norcross, Ga.-based Kawneer, adds.

In addition, Brian Clark, vice president and division manager of Trainor Glass in Dallas, points out that it’s easier to keep an eye on the assembly process in the shop environment. 

“It’s all done in your shop in a quality control environment, where the management team is there to watch over the products being fabricated and unitized. All your internal seals are done on a plant floor and not in the field … where there are no managers watching and there’s not really such great quality control,” he says. 

Long cautions that just because stick-built systems are built in the field doesn’t mean they are inherently going to have quality issues. “I do share that view that you can maintain the quality better in the shop,” he says, “but for a qualified glazing contractor that has got some good quality control out in the field, stick systems can be erected and perform just as [well].” 

Sealed and Delivered
 Tying in with the issue of quality control, Fronek notes that unitized curtainwall systems reduce dependence on field sealant application. 

He explains, “Field sealant application is subject to variables such as heat, cold, humidity, dust and access.  While certainly not foolproof, application under controlled factory conditions provides fewer opportunities for quality assurance issues to arise.” 

Maguire agrees that overall, structural sealant fares better when applied in a factory environment.

“You can do structural sealant in the field—and you’re forced to do it in a glass replacement application, for example—but in general it’s better to do a structural glazed sealants in the factory environment,” he says. 

Jon Sternchos, owner of Enterprise Architectural Sales Inc. in New York, agrees that more caution is exercised in the shop. 

“You’re also eliminating quite a bit of the human error possibilities … With unitized systems, you’re putting it in panel to panel and it’s all dry setting,” he says.

The lack of intervening weather conditions is better for the quality of the weatherseal as well, he says. 

“Even though it’s not a critical structural element, you can do a much better job working in an indoor, controlled environment. You get a much better, quality look to it,” Maguire says. 

On Your Mark, Get Set—
One of the biggest advantages curtainwall suppliers note is that unitized systems help glazing contractors to complete jobs more quickly than is typically possible with stick systems. 

“There may be slightly larger costs, but … you’re installing it in 15 percent of the time,” says Sternchos. 

“Installation time virtually can be cut in half using a factory-assembled, pre-glazed, unitized curtainwall system,” says Fronek. “The faster we can help close up the building’s exterior skin, the faster that building can open for business.”

“Really, for the owner the big advantage is getting occupancy faster. It’s a much faster process,” Harrington says. Long agrees. “It can be installed on a project quicker—it normally takes you a little longer initially to get there initially, but once you’re there you can cover a lot more square footage in a shorter period of time with a unitized system.” 

Even if it’s quicker to install, if it takes longer to arrive doesn’t that balance out the benefits? Not exactly, the pros say. 

Fairchild explains, “When you’re trying to construct a curtainwall with a stick system you’re basically … trying to build a grid system along the outside of a building, and then you have to come back in and fill all the glass in the building. All the other trades have to wait until you complete that before they go in to do what they have to do.”

Not so with a unitized system, which has been pre-glazed. “With a unitized system, [the glaziers] can actually start on the first floor and get that whole first floor completely glazed in—so you’ve got all the curtainwall on the first floor—and then when you go to start on the second floor and put the unitized system on there, the trades can then start on the first floor and start their work.” 

“When unitized panels can be taken from a truck to the wall in a sequential manner, it encloses the building more quickly than other more conventional approaches. This is beneficial for the project schedule and project costs and allows other trades to progress with inside work sooner,” Portz says. 

Fairchild adds, “As you’re going up enclosing the building the other trades are going up right behind you and doing their work. Really speeds up the whole project.” In addition, contractors aren’t spending a lengthy amount of time assembling custom or complex systems. 

“We can build a corner unit in-house and deliver that to the field in that way, so that the guys out in the field aren’t having to put together a corner unit, which slows them down,” Harrington says. “You get a lot of production efficiencies from unitized because really you’re basically just snapping these units together.” And Fairchild points out that the sooner the glazing contractor can get out of the field the better—less time in the field means less need for expensive field labor. 

Reduced Manpower
Performance benefits aren’t the only reason the use of these systems is picking up. “We have found, on the supply side, that a glazing contractor usually needs about 1⁄3 of the manpower on a unitized system than a stick-built system,” Long says.

 “They can get a lot less people out on the jobsite, because they’re not building. It’s already built.” Because glaziers are putting up the framing and glass together, Clark points out that only one crew is needed for unitized curtainwall systems as compared to stick-built. 

“For us, less manpower is less risk; fewer hours worked is fewer accidents, and so on. It’s a win-win,” says Clark. Using less labor in the field also becomes a big advantage for glazing contractors struggling to find qualified labor. 

“We’re finding there’s a huge labor shortage for qualified field labor and you’re finding that a lot of glazing contractor are trying to shift that labor into the shops where they have more readily available labor,” Fairchild says.

In addition, shifting the need for labor into the shops from the field can help reduce costs. “The cost of the field labor, it just continues to go up,” Long comments. “Typically, shop labor is less expensive than field labor,” Fairchild adds. “Typically, the labor rates are a lot higher for field labor as well. You’ve got higher insurance costs. There’s just a lot of things that drives those costs.” 

Too Much of a Good Thing? 
Brian Harrington, director of sales and marketing of Architectural Glazing Technologies (AGT) in Waterboro, Maine, points out one challenge that AGT has faced with unitized systems. 

“When that building structure is erected, we design the unitized curtainwall based on the dimensions of the structure that are given to us by the architect,” he says. Using high-precision CNC, the panels are produced exactly as they were defined. “What happens often is you get into the field and that building is not built with those kinds of tolerances.“

“What we tend to do, especially on the complex projects, we do a total station survey, it’s a … GPS survey of all of the key points on the building and you can create this 3-D model of what the actual building frame looks like. Then we overlay that with our curtainwall model and we can match up and say, ‘Ok, here’s where there might have to be some changes to where the anchor goes,’ or whatever it is.”

“Unitized curtainwall inherently involves more applications engineering than stick systems, hence economies can be affected by frequent discontinuities in building envelope design such as changes in sill height, soffits, parapets, corners and set-backs,” says Steve Fronek, vice president of Wausau Window and Wall Systems in Wausau, Wis. “Manufacturer involvement early in the design cycle can help sort out these issues.”

Harrington agrees that keeping in close contact to the glaziers working in the field helps the company “make sure what was designed is what comes out on the other end.” 

What An Architect Wants
Maybe these unitized systems are more useful in certain situations than stick systems, but they may not always provide the aesthetic possibilities desired by the architect. 

“Some of the sight lines of the unitized system have to grow wider both horizontally and vertically in a unitized system, just the way they mate together, and so … he may want to see a 2 ½-inch sight line where unitized may have to go 3 inches,” Larry Long, president of Oldcastle Glass Engineered Walls in Dallas, says. “Sometimes it’s difficult to give the architect exactly what they want if they’re wanting to see slim lines.” 

He notes that it can also be difficult to handle very large spans. “You don’t see them used around ground floors, tall spans. You tend to see unitized systems on repetitive-type projects,” Long says.

Rising Costs
Unitized systems may be considered cost-effective in many instances—but that is not always the case. 

“It is important for contractors to understand when a unitized system is a cost and time advantage,” Kelly Portz, marketing director of Architectural Wall Systems Co. in West Des Moines, says. 

“There is a tipping point for which unitization is the most cost effective solution—but not always. It may not be ideal for every project, so it’s important to really understand what the project priorities are.” 

The framing materials in particular can raise costs. 

“I think generally they’re a little bit more expensive than a stick system because they use more aluminum,” Long says. “Stick systems, you can span two floors and you can use the aluminum more efficiently in the way it loads on the building, where unitized systems generally span floor to floor, just single span, so you end up with more pounds of aluminum per square foot in unitized systems.” 

Transportation Woes
Clearly units will vary in size depending on the project but, in general, panels come in big sizes and odd shapes. 

“An average size would be 6 feet wide by floor height, let’s say 13 feet tall. You’re normally getting between 20 or 30 units on a truck. But that’s a good average size,” Long says. 

“A typical panel is 5 feet wide by 12 to 13 feet tall,” Kevin Fairchild, product manager of Norcross, Ga.-based Kawneer, agrees. He adds, “Typically, you need more storage/warehouse space to assemble, glaze and store the units prior to shipping to the jobsite.” 

Not only are the panels big, but they often come in odd, difficult-to-ship shapes. 

“When you’re doing a stick-type job you’re just shipping little things of metal, they’re 5-inch in diameter by 24 feet long and it’s a lot easier to bundle those and ship them on a truck,” Fairchild says, “whereas these are prebuilt panels where you have to have some type of racking system to get these onto the truck and that can be difficult.” 

“It is also important to discuss the packaging required to ensure the units don’t arrive damaged,” Portz says. “If there is a mock-up test, we try to also mockup the delivery method to work out any problems ahead of time. Some units can weigh 1,500 pounds or more. It’s critical to ship unitized components with adequate protection so that upon arrival they can be installed.”

Fairchild explains that not only is transportation tricky, but so is shipping the panels in the right order. It’s usually necessary for the panels to be shipped to the jobsite in sequence. Typically there’s not a lot of room on a jobsite to store these things. So what you try to do is every morning have a shipment of these panels that are going on the building for that day. So you’ve got a lot of different shipments; there’s a lot to do with timing and coordinating on the shipments and coordinating the actual fabricating and glazing of the panels.” 

“Any type of material delivery can be challenging if not planned for correctly,” Portz says. “With regard to unitized systems the challenge is to have the panelized units ready ahead of field needs The manufacturer can make 15 panels per day and the field can set 40 per day. It is imperative that the unitized system be delivered in order of installation.” 

Site Logistics
Long points out that site access is critical for unitized systems because once the product arrives it may need to be stored. “If you use a unitized system the site logistics are a big deal. You’ve got have access to trucks to get in there at the perimeter. 

The site logistics have to agree so you can load these units off and on the building. So a lot of time the glazing contractor, right upfront, will look at the job and say either ‘Ok, we can do this out of unitized,’ or ‘There’s no way we can do this out of unitized just because we can’t get the trucks in and out of where they need to be to load it and unload it,’” Long says. Even when the panels arrive at the jobsite, scheduling and installation provides challenges. 

“The biggest logistic [challenge] that I see, that always seems to get forgotten, is the logistics of how do you get the materials to the floor, to be able to get to install,” Brian Clark, vice president and division manager of Trainor Glass in Dallas, says. 

“You’ve got to get them from your shop or your plant, wherever that is—from area A to jobsite area B—and the logistics of that, the trucking, the scheduling of crane time with the contractor to get the panels up the buildings and how do you get this panel to the building and to the floor you need to work off of, is always a logistical nightmare and always seems to get forgotten.” 

Clark advises planning well ahead. “If they can nail that down then it will help them out a whole lot more,” he says. “You really have to preplan and think ahead.” 

Megan Headley is the editor of USGlass.

USG Only Online
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