Uniquely Unitized

by Jonathan McGaha | October 2, 2016 12:00 am

The ins and outs of unitized panel fabrication and installation

As architects embrace more complex and technical designs, fabricators and installers still need to win the bid, which means controlling costs. How do you simplify the fabrication and installation of sophisticated metal facades without losing the design intent?

To save both money and time in the field installing metal wall panels on large projects, fabricators are moving toward creating unitized systems in their shops. These modular, unitized systems combine a number of smaller metal wall panels into a larger system that can be installed by less people in less time on-site. The unitized systems are assembled off-site with all of the different building envelope components, including insulation, sheathing and weather barriers. This process has its advantages for fabricators and installers including maximizing quality while minimizing field labor and speeding the construction process.

 

The Right Project

Unitizing metal wall panels doesn’t make sense for all projects. According to D. Scott Bourdo, CEO at Kovach Building Enclosures[1], Chandler, Ariz., the decision to unitize the panels depends on the geometry of the building. “Does it have a disproportionate amount of inside and outside corners? Is it complex? Is it cut up? Does it have a ton of balconies?”

In general, modular, unitized systems lend themselves to high-rises and mid-rises with more consistent façades and long runs of panels. On the other hand, a building that has a lot of corners, balconies, architectural or structural elements coming out of it and interfering with the façade lends itself to more traditional construction methods.

“When looking at a project to determine if modular assemblies would be more profitable than smaller individual panels, the driving force is typically based off of installation,” says Tyler Bruton, PE, SE, product development and technical specialist at Austell, Ga.-based MillerClapperton[2]. “It is more efficient to install a larger assembly composed of multiple panels than it is to install the smaller panels individually.”

While the pattern of the metal wall panels on the building façade doesn’t usually make a difference in whether or not the unitized method of fabrication and installation will work, sometimes a simpler pattern is easier to work with. Dean Stuewe, project manager at MG McGrath Inc.[3], Maplewood, Minn., notes that a façade with simpler geometry decreases the need for field dimensioning and better enables the use of standardized sizes and shapes for shipping and installation. “More typicality and repetition provides economies of scale that help increase efficiencies and decrease durations,” he says.

“Projects with tight panel tolerances (or narrow joints), are not as good candidates for unitization as those with normal or wide joints because you have to deal with the structure you’re attaching to and narrow joints don’t have as much flexibility,” explains Stuewe. “Conversely, projects with tighter structural tolerances are better candidates for unitization.”

Bruton agrees, saying a simple joint layout is more desirable. “The more complex the wall panel pattern, the more of a probability that the modular units are going to require individual fabrication drawings and instructions,” he says. “When you unitize smaller panels in a shop, the fabricator has a much easier time maintaining joint alignment due to the controlled environment in which the panels are being constructed.”

 

A Controlled Environment

There are several benefits of using a unitized fabrication and installation process. “A unitized fabrication process reduces the lead times for field installation of panels, which increasing quality, safety and productivity by being able to perform more tasks in the shop versus in the field, at the job site,” says Stuewe.

“There is more fabrication on the front side than a typical project, but it is in a controlled environment and fabricated in advance of when the project schedule requires it,” explains Matt Rechkemmer, regional sales manager at Cedar Rapids, Iowa-based Metal Design Systems Inc. (MDSI)[4]. “If problems or discrepancies are found, they can be corrected in a timely fashion.”

By assembling the metal wall panels in a controlled shop environment the performance of the unitized system is as good or better than a hand set panel system. The fabricator is able to do performance testing on the unit as a whole in the shop, before the panels are ever installed on a building.

Bourdo says Kovach prefers to do as much fabrication as possible in the shop before taking the finished product into the field. While working on a project, the team creates in-house mock-ups that allow them to assemble the system and test for water intrusion, air and pullout values. “Because the panels are fabricated in a controlled environment, we don’t have to worry about dust, wind or rain affecting the parts and pieces as they’re assembled,” he says. “Typically shop labor is more competitive than having a field installer assemble every part and piece. And, if there’s little tweaks that need to be made, it’s much easier on a larger scale to do it in a shop environment than in the field, since you have the equipment and everything you need available to you.”

When building the mock-ups in shop, Kovach tests every 10 to 15 panels for water intrusion. If there’s a problem in between those 10 and 15 panels, Bourdo says they will go back and figure out what is going on and correct it right away. “It allows us to have the confidence that once we’re out in the field and installing, everything is already weathertight.” And, one of the advantages of doing the fabrication and installation this way, he adds, is that the building owner only has one warranty to deal with. If there’s a problem, they call Kovach.

 

Time and Cost Savings

The time and cost savings of doing unitized fabrication extends into the field where less installers are required to be on-site to install the panels. And, because the installers are installing less panels even though the modules are larger, it takes less time to complete the installation. The main difference in how panels are installed is in the equipment required on-site for the installation. When panels are installed by hand, a man lift, boom lift or swing stage is needed. With the larger and heavier unitized modules, a crane is usually needed for installation.

On the Cedar Rapids Public Library, Rechkemmer says MDSI fabricated more than 1,500 individual panels, but only 500 modular units needed to be installed. For the World Market Center in Las Vegas, which Kovach completed in 2003, the 10-foot-wide by 16-foot-tall units, which consisted of framing, DensGlass sheathing, waterproofing and a 4-mm composite panel were installed on the façade with a crane.

For the renovation of Edens Quad dormitory at Duke University in Durham, N.C., MillerClapperton had three months over summer break to complete all of the project work. Dwain Barter, project director at MillerClapperton, says the unitized fabrication process saved time in the field, since it would have taken six weeks to install the more than 800, 4-inch by 6-inch panels individually. Instead, they turned the 800 panels into 20 larger units and were able to do the entire install of this scope of work in a week.

 

Challenges

Installation contractors are trying to stay as competitive as they can in today’s market, and Rechkemmer says that means finding more ways to be faster and more efficient. Using a unitized fabrication and installation process means construction schedules can continue to be aggressive, and the highly engineered systems allow installation contractors to meet the demands of current and future projects, he adds.

One of the challenges of the unitized process includes getting all involved parties on board. Since unitizing has a longer design timeline, Rechkemmer says it requires early involvement with the architect or designer to ensure accuracy.

According to Stuewe, challenges include getting stakeholders to understand the fundamentals of relying on drawings and models instead of having the field dimensions, and holding required tolerances combined with shipping challenges and constraints.

Even though Kovach has been unitizing panels since as 2003, Bourdo says the demand has increased over in recent years. “I think that folks are looking at more modular construction in general, whether that means a modular restroom, modular floors or an exterior façade,” he says. “We’re seeing products being assembled in a controlled environment and then when they’re brought out into the field, it takes heavier duty equipment, but less actual field trades to install the work.”

*Photo credit for Cedar Rapids Public Library: Main Street Studios

Source URL: https://www.metalarchitecture.com/articles/uniquely-unitized/

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