Why Architects Love Insulated Metal Panels  

Photo courtesy of Nucor Insulated Panel Group

For the exterior skin of the new Children’s Hospital building in Atlanta, the project team massed the patient towers with sleek glass curtain walls and insulated metal panels (IMPs), incorporating curved corners and undulating awnings to blend with the site and aesthetics of the existing campus buildings.

Delivering tight, energy-efficient roofing and wall panels, excellent thermal performance, and fire protection with great aesthetics, insulated metal panels are a highly effective, all-in-one solution. Architects are taking notice, and IMPs of all shapes and colors are actively finding their way into a wide range of applications from sports complexes to schools to multifamily buildings. In addition to their role as an air, water, and vapor barrier and thermal insulator, IMPs are also fire resistant, act as an acoustic barrier, and provide snow load resistance. The panels also protect against insect and rodent infiltration. To create this high-performance material, two metal sheets are injected with foam in the middle. Through a chemical reaction, the foam expands and binds to the metal, creating a full interior cavity. The resulting composite system is a solid panel delivering exceptionally high thermal performance. In addition, IMPs can function as a barrier backup system.

As a comprehensive, turnkey solution, IMPs streamline the design and construction process and significantly reduce the number of trades and labor involved in installing a wall and/or roofing system. “As a prefabricated unified system, combined with fewer trade requirements and simplified logistics, this makes IMPs exceptionally efficient to construct with,” confirms Jeffrey Jean, design director, associate, CGL Architects, Toronto. “By integrating multiple functions into one streamlined assembly, IMPs free up valuable time that would otherwise be spent coordinating the details of a built-up system—allowing more focus on realizing the design vision.”

A typical IMP barrier backup wall system requires just five components: interior gypsum, a stud wall, IMPs, hat channels, and rainscreen panels. This means that one installer can attach the panels directly to the framing. Compared to a traditional rain screen wall assembly, those required components jump up to nine with the addition of a vapor retarder, air/water barrier, rigid insulation, sub framing, and exterior gypsum. IMPs are also pressure equalized, so they support the “perfect” wall assembly in one single component.

From a construction standpoint, there are fewer field-installed components, fewer trades required for installation, faster dry-in times, and a shorter construction cycle. The pre-assembled, lightweight modules arrive on site, ready for erection. IMPs can be installed at an average of 5,000 square feet of panels per day.

For installation, the IMPs come with panel clips, fasteners, sealants, secondary sub framing, and, in some cases, above sheathing ventilation shims. “In general, we specify IMPs because they achieve a unique balance of performance, constructability, design flexibility, and cost efficiency,” relates Jean. “They enable us to realize projects that can be architecturally bold, technically robust, and delivered on accelerated timelines — qualities our clients highly value.”

IMPs Versatility Produces Creative Designs

Once upon a time, IMPs were essentially limited to cold storage, industrial, and manufacturing facilities. But with the advent of sleeker designs, enhanced aesthetics, and a plethora of designs, shapes, textures, colors, special effects, and more, the panels broke into the majority of commercial markets. This includes recreational, government, schools, office, healthcare, retail, and more.

Photo Courtesy of Met-Con

The Populous-designed Amway Center, home of the NBA’s Orlando Magic, has seven concourses that offer about 875,000 square feet of space, nearly three times the size of the old arena. The exterior features IMPs and a glass curtain wall, along with a graphics display.

The outstanding energy efficiency performance of IMPs makes them an ideal option for data centers, one of the fastest-growing construction markets in North America.  Essentially, any building owner, organization, or municipality interested in an energy-efficient, thermally insulated building offering lightweight construction, durability, affordability, and timely installation will seriously consider IMPs for their walls and roofs. “Our work spans a diverse range of market sectors in all parts of the country. IMPs offer design solutions for many sectors and project types because of their versatility in addressing sustainability, energy efficiency, durability, fire resistance, and the ability to customize them for shape/form and color,” reports Brett Ewing, principal, AIA, NCARB, Cuningham, Las Vegas.

In addition to many shapes and widths, special custom colors and finishes, advanced fabrication technology supports the creation of curved panels and unique geometric patterns. Panels can be smooth or textured in a variety of styles, including striated, micro-ribbed, fluted, smooth, grooved, or embossed. Breaking it down:

• Striated lends additional strength to the steel and enables the panels to be manufactured at longer lengths.
• Fluted is an ideal profile for heavy industrial applications.
• Micro ribbed offers strength to the steel while lending an aesthetic appearance of a smooth finish. Up close, the micro ribs are visible, but from a distance, it presents a flat look.
• Embossing is the process of surfacing texture on metal coils through flattening wavy coils and eliminating the mirror effect of smooth finishes. It. Directional embossing produces linear lines along the length of the coil, and non-directional embossing can be applied to create a uniform pattern.

Additional design features include joint reveal widths, formed corner panels, end folds and treatments, heavier gauge flat facings, and integrated windows and louver systems. This long list of design options and flexibility empowers designers to create imaginative and functional designs to make a bold, colorful statement, match an organization’s brand, present a high-tech, innovative statement, and/or blend with surrounding architecture and style.

Architects can design graceful curves producing flowing sight lines, bold colors, and sharp corners that capture the eye, and complementary designs with other facade materials. “The old standard of brick facade designs has disappeared from our firm’s vocabulary because IMPs offer the same self-assurance of long-lasting quality while introducing flexibility in forms and colors in a watertight envelope.  We are using IMPs in large volume structures as well as large, repetitive single-story structures,” relates Jeffrey L. Bennett, AIA, project manager, architect THA Architects Engineers, Flint, Michigan. Sharing a list of applications where Holly & Smith considers specifying IMPs, Principal and Design Director Pierre E. Theriot, AIA, states the following:

• Buildings where thermal envelope performance is important, like schools, military, healthcare facilities, labs, industrial buildings, and gymnasiums.
• Projects with tight schedules when the building needs to be enclosed as soon as possible to reduce exposure and accelerate interior work.
• Sites with space or logistical constraints, or difficult access, where prefabricated panels reduce staging, scaffolding, and complexity.
• Facades where design expression matters and architects seek custom colors, patterns, dynamic shapes, and/or integration with glazing, varying orientation, or size.
• Harsh climates or regions with high energy cost, such as hot/humid climates with large cooling loads, or places with storms for protection against wind and water intrusion.

“We are currently using the system for commercial personal locker storage facilities – the simplicity of the material has allowed us to focus on innovating the envelope design for what is normally a very functional and utilitarian building type,” says Jean. “We have also used the system for retail, light industrial, and warehouse buildings. Other buildings where implementing them would make sense are big box buildings and supermarkets. We see them frequently used on these projects, health care buildings, distribution centers, data farms, transport rest areas, and sports and recreation facilities.”

Photo courtesy of Norbec

IMPs played a key role in the construction of the Écoparc Saint-Bruno near Montreal. Their efficient insulation, durability, and high-quality finish helped create a robust and energy-efficient envelope. Their modern design, with a grey exterior and a bright interior, integrates perfectly with the project’s architecture. 

The panels are typically available in 22, 24, and 26 gauge and integrate well with customized windows, louvers, and sunshade systems. A relatively new feature is accent fins. The fins are essentially aluminum extrusions that integrate into the vertical or horizontal reveals of the IMPs.

The systems come in various panel insulation values, span lengths, and load/span capabilities. As an exterior wall, they are often applied as the primary exterior finish. The panels can also be clad with other materials, such as brick veneer.

The most common metal substrate for the IMP face is G90 galvanized steel or aluminum-zinc coated steel, though some custom panels are made from stainless steel or aluminum. On the interior, a typical finish is a standard polyester 0.8 mm—including the primer—in a light-reflective and easy-to-maintain color.

The Finish Line

IMPs are produced with a number of finish options, including silicone-modified polyester (SMP), fluoropolymer (PVDF), and polyvinyl chloride (PVC). SMP is commonly used as a one-coating exterior finish and offers excellent film integrity, weather protection, stain, and chalk resistance. It’s available in high and medium gloss finishes and is an overall good value for the investment. With certain colors, solar reflective pigments contribute to reducing heat transmission and optimizing energy efficiencies. PVDF is a resin-based system providing a smooth, hard coating. Noteworthy traits include color retention, durability, corrosion, chemical, and UV resistance. PVC is commonly used for interior applications. It offers high scratch resistance, high corrosion resistance, color retention, and durability.

As for color options, the sky is the limit. Architects can choose from a wide range of standard colors, ranging from neutral tones like white, gray, beige, and tan, to more vibrant hues such as red, blue, and green. There are also selections of earthy shades like sandstone, bronze, and terra cotta, plus panels can be finished with textured surfaces mimicking natural materials, including stone, wood, and brick. Metallic finish examples include silver, gold, and copper.

“By combining a single color or a variety of colors, IMPs can create a dynamic and visually interesting exterior while providing a high-performance, all-in-one assembly. Compared to a standard metal wall panel on a stud and backing, the IMP system significantly reduces the ‘oil canning’ effect inherent in traditional construction,” adds Alex Kendle, project manager, Perkins&Will, Denver.

Sustainability Star

From a sustainability perspective, the exceptionally high thermal performance values lent by IMPs cannot be understated. Compared to other insulation materials like extruded polystyrene, with an R5 value, expanded polystyrene, providing a value of R4, and mineral fiber and cellular glass at R3, IMPs deliver insulation levels of between R-7 per inch and R-8 per inch.

This means the interiors stay cooler in the summer and warmer in the winter, drawing less energy from the HVAC systems and the building’s operational carbon levels. The ability to downsize HVAC equipment contributes to decreased embodied carbon.

As the industry moves towards lower carbon levels and net-zero goals, IMPs have a large role to play. Comparing and quantifying IMP’s thermal performance and cost savings, Kieran Timberlake analyzed the environmental performance of four warehouse building envelopes through whole-building life cycle assessments (LCAs). The insight study involved the examination of four types of 150,000-square-foot warehouse facilities in Philadelphia, honing in on the structure, envelope, and interior assemblies over a period of a cradle-to-grave 60-year cycle.

The architect used its Tally LCA app on two types of IMPs, insulated concrete and tilt-up concrete, and analyzed global warming, acidification, eutrophication, smog formation, ozone depletion, and non-renewable energy demand. The IMPs registered a global warming potential (GMP) of 28 percent lower than the insulated concrete and tilt-up concrete walls. The IMPs were also 19 percent lower in smog formation as compared to the tilt-up concrete wall.

Other ways in which IMPs contribute to sustainable designs include:

• Durability and longevity. The system’s ability to withstand wear and tear, weathering, and corrosion, combined with reduced maintenance, reduces waste and cost.
• Recyclability. IMPs are made from recyclable steel and aluminum. At the end of their useful life, the materials can be recycled into new metal products.
• Lower embodied carbon. Reduced structural support and building enclosure materials contribute to decreased carbon. The quantity and weight of materials transported to the construction site are also reduced.

Another sustainable feature of IMPs is the halogen-free foam that provides the insulation properties between the metal panels. Giving off fewer emissions, the foam is healthier for the environment. UL-listed and FM approved. The red list-free material also delivers a high level of fire resistance.

Evaluating Insulating Cores

The central performance component of IMPs is the system’s insulating core. Consequently, it’s helpful for architects to understand the pros and cons of polyisocyanurate (PIR), polyurethane (PUR), mineral wool, and expanded polystyrene (EPS).

Photo courtesy of Nucor Insulated Metal Panel Group

The New York Power Authority selected IMPs for wall and roof systems to create a complete building envelope, both inside and out, with just one component. The panels offer durable thermal and moisture protection, and the mineral wool insulation cores can provide up to a 3-hour fire rating in a single panel.

The vast majority of IMPs produced today are made with PIR insulation cores. PIR rigid foam insulation is considered best in class when it comes to thermal performance with a high R-value per inch. The material achieves this with relatively thin panels offering the best cost-to-thickness insulation value. PIR is lightweight, which makes the IMP panels easier to handle and install, thereby decreasing labor time and expense.

The material’s closed-cell structure keeps out moisture, thereby protecting the longevity of thermal performance and reducing the risk of mold and mildew penetration. When exposed to fire, the panels char, forming a protective layer that acts to slow down the spread of fire, buying time for firefighters to arrive and mitigating damage to the facility.

Similar to PIR, polyurethane is lightweight and also offers high thermal insulation properties. The PUR foam is less expensive than PIR, but delivers a lower level of fire resistance.

Mineral wool brings excellent fire resistance plus strong sound absorption to an IMP. It’s made from volcanic rock and recycled slag, is resistant to moisture, mold, and mildew, and the price tag is comparable to PUR, though its thermal insulation values are lower.

The fourth option, closed-cell expanded polystyrene, is a lightweight, rigid foam insulation core with high mold and mildew resistance. The material is also easy to mold into different shapes. However, in comparison to the other options, it offers a lower R value, is less fire resistant than PIR or mineral wood, plus the material is delicate and must be handled with extra care.

Thermal Bridging

After selecting an insulating core and an IMP, a building is on track to deliver excellent energy efficiencies and performance. However, this could all be derailed if the building enclosure design fails to properly account for thermal bridging.

Defined as a bridge where heat or cold can transfer from the interior to the building exterior and vice versa, unchecked thermal bridges can be the cause of significant heat and cooling loss, wasted energy, and uncomfortable interiors. Over time, these thermal losses can lead to deteriorating building components and eventually failure.

Putting this issue into perspective, Jim D’Aloisio, P.E., LEED AP, principal, Klepper, Hagn & Hyatt, East Syracuse, N.Y., and Ivan Lee, P.Eng., M A Sc., LEED AP BD+C, WblCA AP building science engineer, Stantec, recently wrote in Structure magazine, “Without considering thermal bridging, many architects and engineers have falsely believed the building envelope has better thermal performance than it actually does. This leads to underperformance of actual versus modeled energy consumption—and failure to meet energy targets.” Heat or cold escapes through breaks in the insulation or components. Some examples include wall studs, columns extending from the interior to the exterior, window and door frames, balcony slabs extending from exterior walls, and roof-wall junctions. According to the U.K.-based research and standards organization BRE, thermal bridging can account for up to 30 percent of a building’s total heat loss, require oversized HVAC systems, and/or make the building’s HVAC system work harder and expend more energy to regulate building temperatures for occupant comfort.

Thermal bridging reduces the effectiveness of the insulation, resulting in a lower effective R-value. It can also create cold spots on interior surfaces, leading to condensation, damage from freeze-thaw cycles, mold growth, and adversely affecting indoor air quality. Designing enclosures to eliminate thermal bridges has become even more important with stricter energy codes, a great focus on sustainable design, occupant comfort, and reduced operational and embodied carbon.

The antidote to thermal bridging is continuous insulation, and energy codes allow for a higher overall R-value when continuous insulation is used. IMPs provide an uninterrupted layer of insulation across the building envelope, thereby preventing thermal bridging by breaking the connection between building elements like studs and the interior and exterior walls. This results in a low U value as the rate of heat transfer through the panel is significantly slowed.

Image courtesy of Nucor Insulated Metal Panel Group

IMPs are made from two sheets of metal sandwiched with a highly insulating core.

Enhancing the continuous insulation, IMPs also mitigate thermal bridging through:

• Minimized Penetrations. The large panel sizes and integrated fastening systems reduce the number of thermal bridges created by fasteners and joints.
• Factory-Controlled Quality. IMPs are manufactured under controlled conditions, ensuring consistent insulation thickness and performance.
• Thermal Break Design. Many IMP systems incorporate thermal breaks at panel joints, further reducing heat transfer.
• Versatility. IMPs can be used for walls, roofs, and ceilings, providing a comprehensive thermal envelope solution.

As previously noted, the IMPs deliver that high R-value with excellent thermal resistance per inch. A tight building envelope is also better ensured with the airtight construction of IMPs’ interlocking design and the reduced complexity in combining the multiple components of an exterior finish, insulation, air barrier, and vapor retarder into a single product.

Girt Spacing Best Practices

Another technical aspect of IMP design and construction is calculating the spacing of the girts that attach the panels to the substructure. As opposed to purlins that anchor roof panels, girt spacing is important to protect the panels against wind uplift, help evenly distribute weight across the building, and prevent sagging. Overall, the girts are an important component of the structural cladding system.

Starting with the wind load determination, architects need to consider the risk category of the building, wind speed based on location, the building’s dimensions, surface roughness, enclosure classification, and the external pressure coefficient. Designers are strongly advised to involve an engineer with girt spacing evaluations.

There are four risk categories:

• I - Low risk on human life, i.e., a storage warehouse
• II - Not covered in other categories, i.e., manufacturing facilities
• III - Substantial economic risk to human life or risk to disruption of daily civilian life
• IV - Essential services, including police, fire, electricity, communications, etc.

Building dimensions fall under three categories:

• Low-rise - the building height is less than 60 feet or lower than the footprint of the building.
• High-rise - the building is up to 190 feet in height, or the height is higher than the building’s footprint.
• The building, essentially a skyscraper, is greater than 190 feet and requires different calculations.

The next category is surface roughness, which falls under three classifications: B,  C, and D:

• B - Urban and suburban areas, wooded areas, or terrain with numerous closely spaced obstructions, i.e., warehouses, manufacturing facilities
• C - Open terrain with scattered obstructions of heights less than 30 feet, i.e., flat open country, grasslands
• D - Flat, unobstructed areas and water surfaces

With regards to exposure classification, this is based on the openings in the buildings, which impact internal wind pressures. There are four categories:

• Open - 80% open walls (0.0 interior pressure coefficient, GCpi)
• Partially enclosed - The most stringent category, this condition is described as unevenly distributed openings around the building, with some walls containing large openings, like an aircraft hangar, where wind can engulf the building, thereby creating additional pressure on the IMPs. (0.55 GCpi)
• Partially open - Not covered by other categories (0.18 GCpi)
• Enclosed - Less than 1% of the building walls are open (0.18 GCpi)

This pressure coefficient is the difference in wind pressure in relation to the building zone, measured by GCp/GCPi. Where the external GCP considers the difference in wind pressure in relation to the building zone and effective wind area, and the internal GCPi considers the internal wind pressure imposed by the exposure classification.

On the topic of panel deflection resistance, most IMP manufacturers use ASTM E72 - Standard Test Methods of Conducting Strength Tests of Panels for Building Construction to obtain these numbers. The test involves putting the panel under pressure to identify weak points/points of breakage. Many factors impact this, including panel thickness, adhesion of the foam to steel faces, and foam properties. Some systems will offer higher rigidity, better compression ratio, and better shear strength. Another variable here is the thickness of the steel faces, i.e., gauge, surface profiles. For example, multiple span panels have a higher span distribution.

Another question is the structural element composition and the girt thickness. The thicker gauge structural elements will generally enable greater girt spacing. At the very least, it’s preferred to have some steel grid behind the panels or over the concrete structure, as a concrete surface is not entirely flat, so this can otherwise induce defects on the panel junctions.

On the topic of fastening capacity, IMP manufacturers offer different engineered fastening clips to optimize support to the structure, fit with the panel joints, and keep installation costs down. Other considerations for fasteners include panel width, quality, and matching structure thickness. For example, if there are more fasteners, the girt spacing can be larger.

With regards to the Factory Mutual standard wind load calculation, this is based on RM 1-28 Wind Design. Installations must be made in accordance with FM-approved hardware and fastening design.

The Final Word

Taken together, the superior thermal performance, tight building enclosure properties, aesthetics, fire protection, affordability, and ease and speed of installation make insulated panels and walls an excellent choice for today’s commercial, institutional, and industrial applications.

Well-known building scientist John Straube, with the Building Science Corporation, sums it up in stating, “IMPs are one of only a few types of building products that can provide an entire building enclosure in one prefabricated product.”

Barbara Horwitz-Bennett is a veteran architectural journalist who has written hundreds of CEUs and articles for various AEC publications. www.linkedin.com/in/barbarahbennett/