Architectural Record BE - Building Enclosure

The Ins and Outs of IMPs

Armed with the various design options offered by insulating metal panels, together with some best practices for project coordination and installation, architects will be best equipped to deliver successful IMP wall and roofing projects
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Sponsored by Metal Construction Association, IMP Funders Group

Project Team Best Practices

In order to ensure a successful IMP design and installation, like any building project, building team communication and coordination is key, as is leveraging the manufacturers’ expertise.

Regarding the latter, Haugh describes the optimal scenario as having these experts on board early, where they can provide input on constructability and detailing specific to the product. "An integrated design project delivery method facilitates this well," he says.

Similarly, Ray Elking, preconstruction director, McCarthy Building Companies, St. Louis, points out, "Especially for complex projects, it is always beneficial for the designer, contractor, and manufacturer to collaborate closely to make sure everyone understands what the goals are and what can be achieved."

For example, by involving the manufacturer early in the process, all the flashing, sealant, and vapor barrier detailing can be part of the bid drawings.

As noted, there are numerous IMP options for metal panel finishes, configurations, sizes, and styles. "There are no shortcuts to becoming an expert quickly on these intricate topics," cautions Robertson. But if the architect chooses to engage the IMP manufacturer early on, then it can provide the guidance required to make the right decisions and get the best value for the project team's time, money, and resources.

She adds that taking a design-assist approach is ideal for exterior facades but will only work if there is a pool of qualified subcontractors to choose from. Qualified IMP installers are normally trained and certified by the manufacturer to execute proper procedures and details for a weathertight envelope.

On the other hand, if the building team does not spend the time seeking out qualified and experienced IMP installers, it may end up with a situation where the product’s features and economies of scale are not fully realized.

“Some installers are not confident in their ability to sufficiently deal with moisture infiltration at the IMPs’ openings and joints,” explains Jon Heinert, AIA, principal, Wheeler Kearns Architects, Chicago. “We have experienced issues with installers not willing to provide a warranty for the systems as engineered, unless a secondary weather barrier material is installed under the panel that is separately flashed to openings and penetrations.”

While manufacturers acknowledge that some special cases may justify a redundant and separate barrier system behind IMPs, most IMPs are designed to form a very effective air and water barrier through the use of factory-installed gaskets or non-curing sealants, along with properly detailed conditions at openings and other areas critical to water entry.

“Every IMP project that has ever been installed has openings and penetrations that have been properly flashed, sealed, and present no long-term warranty issues,” insures Kim Harrell, national sales manager, All Weather Insulated Panels, Vacaville, California.

Sharing a positive experience working closely with the architect and an IMP manufacturer for a large sports team franchise project, Sage Lehr, engineering manager of the St. Louis-based contractor IWR North America, specializing in the building enclosure, relates that it was ideal working with the project team in reviewing and modifying details prior to submitting drawings. With this approach, it was easy to resolve detail issues, keep the architect’s design intact, and meet the thermal values required for the zone 6 application.

“Running thermal models helped in making these changes, and having the engineering support of a large IMP manufacturer made it easier to get things executed on the frontend. The whole job was executed smoothly from paper to installation,” she reports.

Emphasizing this point once again, Hooper stresses the advantage of possessing a strong understanding of the manufacturer’s capabilities and limitations, as well as the correct application of the product. “In addition, communicating with the manufacturer and following the correct protocol ensures that the materials will be produced correctly and when needed to support the project schedule,” he says.

IMP facade to complement Central New York Film Hub’s cutting-edge studio and soundstage

Photo courtesy of Metl-Span

Seeking a contemporary aesthetic, QPK Design specified a high-performance, modern IMP facade to complement Central New York Film Hub’s cutting-edge studio and soundstage.

Another key piece of advice offered by those who have designed and installed successful IMP projects is the importance of educating architects about the details of the IMP installation process.

“The more that architects understand about the correct application and limitations of IMPs, the more likely we are to ensure more successful IMP installations,” assures Hooper.

Similarly, Haugh explains that in order to get the details right, the architect needs to understand how the panels will be installed. For example, tolerances for panel installation are key where it connects to steel, joins concrete, or butts up to storefront systems or other building elements. “As with any material, understanding how it goes together can prevent an architect from including design elements that don’t work in the field,” he says.

Because each IMP has its own unique features—for example, the place where the panels attach to secondary supports will vary from manufacturer to manufacturer—it’s important that the architect has a good understanding of the spacing of the supports, the size of the panels, and their attachment points.

For the subcontractor, it’s important that the inevitable thermal bowing—when the exterior skin bows up slightly between purlins/joists—is taken into account as part of the bidding and installation process. This sometimes means that crews in the field have to rotate panels to expose the cooler side to the sun so that the panels can flatten out before installation.

Furthermore, IMP manufacturers offer varying choices in color, panel sizing, and thickness, for example, so architects should know their options.

Generally speaking, Robertson’s personal philosophy is that architects truly need to understand the properties of any materials they are specifying. And in the case of IMPs, knowing the product’s properties and limitations will significantly increase the chances of a successful project.

“Unfortunately, a common money saver is to use a thinner metal panel gauge, but depending on the size and orientation of the panels, this could cause oil canning,” she warns. Oil canning is visible waviness in the flat areas of metal roofing and metal wall panels. Similarly, architects might specify alternate metal panels, but depending on the panel size and orientation, this may compromise the design or quality of the installation.

“An architect who understands the properties of the materials will be better suited to guide the client and team to make the optimal decision about how an alternate will affect the project,” she says.

IMP Bidding

Once IMPs are selected for a building, it’s time for the contractors and subcontractors to bid on the project. To ensure that this process moves along smoothly, it is important that the scope is well defined. This begins with determining that the material specified is appropriate for the application. For example, is the span of steel being requested going to work for the application?

“Making sure that what is specified aligns with what the architect and owner are looking for ensures the project is set up for success from the start,” explains Elking.

At this point in the project, input from a qualified installer is key to ensure that the correct application of material from any of the specified manufacturers is being utilized.

Hooper adds that in many cases, specifications are written in such a way that they not only indicate the required product configuration but also the method of panel fabrication required from the manufacturer. “In these situations, installers that are not proactive in guiding the specification early in the process can face an uphill battle trying to utilize the product that is the best for both the application and the end user.”

This involves fully grasping the building structure design so that installers can best determine the tolerances for the metal panels. “This detailing can swing the number,” cautions Robertson.

Assisting contractors and installers with this process, software programs to manage drawings and take-off materials can be very useful.

“As we get revised drawings, the program we use allows us to do overlays so we can quickly see the changes. We can mark up details, save, and use the markups for any questions we may have,” explains Lehr.

The program also enables contractors to take off linear feet of flashing or extrusions as well as the square footage of the panels needed.

In terms of the general installation, contractors must be aware of the size and location of the laydown area, the weight and length of the panels, and what equipment can be used to set up the panels. Contractors should study the drawings and schedule in order to determine if other structures or landscaping might become problematic during installation, adds Lehr.

Unloading and Storing IMPs

When the construction phase of an IMP project commences, contractors will find the product protected with wood bundles or packaged in plastic shrink wrap.

When unloading, Lehr recommends using a minimum of four Nylon band slings, at least 4 inches wide, around the entire bundle/crate in a vertical position. To prevent the panels from shifting of sliding during the pick, the load must be safely balanced. For panels longer than 20 feet, IWR uses a spreader bar to maintain an even position of the slings. The use of cable or rope as a sling is not recommended, as this type of force concentration can damage the profiles metal edges of the panels.

If the panels are being unloaded to an elevated structure, the number of panels should be considered. “Panel lengths also need to be considered to make sure that excessive loads are not concentrated in a limited area of the bundle that would increase the likelihood of damage to the materials,” adds Hooper.

It is also important to review the specific loads with the engineer of record to ensure that the elevated structure can safely support the concentrated load.

Another important aspect of this process is inspecting the panels for damage. Panels should be shipped covered and free of moisture and road grime, and if any damage or shortages are obvious, this should be noted on the driver’s delivery papers, instructs Lehr.

“After unloading, if you have shortages or damaged product that were concealed during the delivery, it’s important to take pictures of the issue prior to removing it from the packaging,” she says. “We also suggest letting your customer service representative from the panel manufacturer know of the issues, sending them the pictures, and a claim will need to be filed.”

For some contractors, such as DPR Construction, it is not standard practice to store materials, as this added step means double handling and added labor, and it poses a greater risk of damage to the stored materials. Furthermore, if procuring materials with ample time to spare, that means the project team is not taking advantage of the preconstruction/design time to maximize the design and value of the building.

the Land Remediation headquarters in Waterford, New York, had more than 13,300 square feet of 3-inch-thick IMPs

Photo courtesy of Metl-Span

Looking for a practical, long-lasting, and efficient exterior, the Land Remediation headquarters in Waterford, New York, had more than 13,300 square feet of 3-inch-thick IMPs installed in its new facility.

That said, many contractors either have to or choose to store the product, in which case, the first precaution is ensuring that the panels stay dry, as the finish can be damaged by what’s called wet storage stains. This will initially present as a white powder, eventually delaminating the paint, and finally appearing as red rust.

“If the panels have wet storage corrosion, your finish warranty will typically be void,” cautions Lehr.

In the case where the panels are exposed to water, they should be unbundled and elevated off the ground, with a slight pitch, so the water can easily shed. Furthermore, the bundles should not be stacked more than two bundles high.

“Cover the materials loosely with tarps allowing for good air circulation,” she adds. “Tightly covered bundles can promote a ‘humidity chamber,’ with temperatures exceeding the surrounding air temperature. This condition with moisture trapped in the bundle can cause bacterial and chemical damage—wet stain/white rust—to the finish.”

When storing fire-resistant panels, extra care must be taken, as this product is not made with a foam core like regular IMPs, but rather a mineral wool core. Although the fibers themselves do not absorb water, moisture can wick between the fibers and take a long time to dry out.

“Mineral fiber panels that are left exposed to the weather on the ground will absorb water and provide a great medium for airborne seeds to germinate and ultimately render the material useless,” cautions Hooper.

To avoid this, “rapid installation with limited staging time will cover the exposed edges of the core and allow moisture that does enter the core to easily drain via gravity without degrading the panels,” he says.

Ideally, building teams should utilize just-in-time delivery with a robust tarping of the materials while they await imminent installation. If the panels need to be stored for an extended period of time, then they should be kept in a controlled environment free from moisture and other corrosive environments.


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Originally published in Architectural Record