Written by: Kevin Franz, AIA, BECxP, CxA+BE, LEED AP BD+C, CSI, CDT
Metl-Span’s Specification Development Representative
When it comes to thermal and moisture protection, there are a wide array of variables to consider when selecting the optimal building envelope product: the climate, how the building will be used, and energy consumption based on those conditions. Insulated metal panels (IMPs) deliver a single solution for thermal and moisture protection without the chance for failures presented with traditional build up methods that require multiple trades’ involvement. In addition, IMPs deliver long-lasting durability and unmatched aesthetic options to the marketplace for compelling building exteriors.
Delivering on all Fronts: IMPs for Protection & Aesthetics
Meeting Demand for High Performing Exteriors
Think about a new manufacturing facility in the exurbs, a high-rise apartment tower in a bustling city, or an office complex in the suburbs. The team responsible for bringing any building to life faces increased pressure to deliver on energy efficiency and design innovation. Construction professionals today must consider a wide array of variables when selecting the optimal building envelope product: The climate in the region, how the building will be used, how it will consume energy based on all these conditions, and how it will look in the environment.
Two major factors affect thermal performance: The conductivity of the building’s steel framing and steel studs, and the failure of the multi-component air barrier systems that create air leaks through insulation. When materials make contact through steel and studs, conduction and thermal bridging occur. In addition, in traditional construction, stopping air leaks and thermal breaks requires a multi-component building envelope with additional crews for installation. Combined, these factors can reduce thermal performance by up to 50 percent. If water, air, or vapor can penetrate the building control layers, it will adversely impact building performance.
Insulated metal panels solve these coordination and thermal performance concerns by preventing the forces of Mother Nature from penetrating the wall in the first place. Considering these project variables, IMPs deliver the optimal single solution for thermal and moisture protection without the chance of failures presented with multiple trades’ involvement in traditional build-up methods using single-skin panels. The ability of IMPs to drive long-term thermal and moisture performance is matched by the aesthetic options available in the marketplace to design a compelling building exterior in an all-in-one system.
A System, Not A Skin
Insulated metal panels are factory manufactured as an all-in-one system, designed to deliver a water, vapor, air, and thermal barrier in a single product. When fastened and sealed correctly, the panel system is impermeable to the elements. IMPs feature concealed fasteners that protect joints from the elements and ensure multiple layers of protection to stop air and moisture from entering the building.
The single-component system includes advanced panel joinery, a rigid closed-cell insulation core, and a G-90 galvanized or AZ-50 Al/Zn coated steel face and liner with 70% PVDF fluoropolymer coating. Given these components, this IMP system creates a superior wall with clear benefits and eliminates the five-step, multi-component rainscreen of traditional exteriors.
For safety and efficiency, the IMP system delivers a strong and lightweight building envelope solution that reduces the weight compared to brick, precast, or tilt-up concrete by at least 10 to 25 times per foot. With footings and structural supports decreased, costs are reduced, and safety – for both construction workers and for building occupants – is enhanced.
Most importantly for thermal performance, the front steel skin and the back steel skin of an IMP do not touch, providing a continuous thermal barrier. With an IMP, the steel is adhered to closed-cell polyurethane or polyisocyanurate that does not allow conduction inside the panel, eliminating thermal bridging. IMPs are symmetrical and deliver a perfect wall that works in all climates and seasons.
Specifying an IMP replaces all other components for installing the building envelope. Rigid insulation, batt insulation, sheathing, and weather barriers do not have to be installed by separate trade crews on additional days of work, saving money, weather exposure, and crew time on site. The single solution of installing IMPs means faster wall coverage and faster project completion. In fact, a team of four IMP installers can install 5,000 square feet of panels in eight hours. In addition, the tested system provides thermal and moisture protection that building owners can count on enduring for the lifetime of the building.
Critical Color Choices: Reducing Thermal Bowing
When evaluating construction materials, particularly those that will withstand extreme temperature changes, it is important to understand how they will react to the environment. The expansion and contraction of metal when exposed to thermal stress can cause a slight bend toward the warmer side, known as thermal bowing. This bow can be visually apparent due to the restraining action of the clips and fasteners and can cause damage to the building envelope.
Darker colors absorb more heat energy, which increases thermal bowing. Knowing the exterior panel color, temperature of the interior of the building based on end use, panel type, structural support framing, and design loads allow building engineers to calculate the amount of thermal bow that is within acceptable limits. These same limits are used to determine allowable panel spans.
Although thermal bow is not a limiting factor for commercial and industrial applications of IMPs, it is a key consideration for cold storage due to the large temperature differential between the interior and exterior panel faces. To reduce the unnecessary heat gain on the exterior along with the thermal bow, cold storage facilities generally specify white or light-colored panels.
Building for Aesthetics & Durability
Architects who specify metal panels as exterior cladding can choose from a wide variety of configurations, textures, and colors whether they choose IMPs or single-skin panels. With IMPs, they maintain design freedom to build creatively while capitalizing on all the performance benefits available.
Single-skin panels possess another downside when it comes to aesthetics: Oil canning. The thinner panels begin to have a wavy or distorted appearance after long-term heat exposure causes them to ripple and buckle. Three environmental or production forces can cause oil canning:
- When it is hot outside, the steel expands outward. It is screwed into a fixed material, so it will be held back, and it will stretch and create waves.
- The production process applies stress to the panel. This can happen in a full feather way, making the steel longer in the middle than on the sides, causing ripples in the middle. It can also occur in the opposite, with wavy edges from being too long on the outside. Lastly, it can camber and maintain the curl of the coil.
- The memory of the steel makes the panel want to return to the original coil, and waves appear in the steel.
With an IMP, the outer steel is adhered to the foam core, making the panel thicker. The stress from the fastener that would cause surface distortion does not have an impact on the IMP because the concealed fasteners are attached to the assembly rather than the singular layer of steel. The possibility of oil canning is rare if not eliminated, and the panels maintain their appearance for the long haul.
Additionally, IMPs integrate seamlessly with windows, louvers, and roofing, delivering an unbroken exterior appearance. Specifying an IMP system means the option to select integrated windows that further eliminate thermal breaks using the same joints as the panels. These integrated windows minimize thermal conduction and deliver a fully sealed joint to guarantee weathertight performance. For contemporary new construction and for modernizing retrofit projects, IMPs offer durable aesthetics with finish options to fit the surroundings.
The Need for Sustainability
Achieving greater efficiency and sustainability on construction projects starts with a system designed to stand the test of time. IMPs address stringent codes by providing superior continuous insulation while offering desired design flexibility. With R-values up to R-70, IMPs easily meet energy codes for every North American climate zone.
The increased insulation and reduced air leakage presented by IMP assemblies can achieve significant energy savings that reach as high as 22 percent depending on the application. Regulating the four control layers – water, air, vapor, and thermal – is critical to high performance, and IMPs offer the key to success.
The airtight, watertight systems mean that aggressive heating and cooling systems are not needed to maintain comfortable interior environments. In addition, most standard color options for IMP roof panels meet or exceed Solar Reflective Index requirements to reduce Heat Island Effect. In addition, steel is the most recycled material, and more than 35 percent of IMP steel is made from recycled steel. The high thermal efficiency of IMPs further reduces the reliance on fossil fuels and contribute toward LEED credits. IMPs are a single-component solution, contributing to less waste and a reduction in transportation emissions. IMPs can also be disassembled, moved, and reused, meaning less material waste in renovations or expansions. All these qualities lend IMPs to a lower embodied carbon footprint than concrete and mineral wool.
Case in Point: Las Vegas Courthouse
In Las Vegas, Nevada, the new buildings that are constantly rising as part of the ever-changing skyline are casinos, resorts, and hotels. When the City of Las Vegas envisioned a new courthouse, the shorter two-story structure was designed to make an impression and serve the community with an attractive, sustainable facility. Visitors are greeted by walls of metal and glazing, including an entry canopy constructed with insulated metal panels.
Architects designed a courthouse that was compatible with the surrounding neighborhood and municipal buildings while also providing an attractive structure where employees would enjoy working and serving the community.
More than 21,000 square feet of 2-inch IMPs comprise the entryway of the Las Vegas Courthouse, delivering an R-value of 17.5 for the facility. The flat-profile IMPs improve the performance of the building and enhance the interior environment for staff and visitors.
The IMPs make up the canopy and the majority of the exterior walls of the building, integrating with a glass curtain wall at the entrance for a warm and inviting entryway.
“The entry canopy makes the project unique,” said Michael Romack, project manager for Sierra Metals. “We installed IMPs as a soffit, so it’s upside down with a lot of angles. Fortunately, it’s a simple system to work with.”
Choosing IMPs for a building’s facade is a sound investment, one that delivers environmentally conscious materials, construction efficiencies, energy savings, longevity, enduring aesthetics, and more. In an evolving construction market that requires sustainable, high-performing, and eye-catching building materials, IMPs offer a single component solution.
An IMP delivers a comfortable interior environment for occupants without thermal energy loss and moisture penetration, like a Thermos keeps cold water without creating condensation on the outside. The increased thermal protection and reduced air leakage delivered by an IMP ensures a protected building envelope that is sure to endure.
Founded in 1968, Metl-Span is a pioneer of insulated metal panels, providing state-of-the-art building materials to the commercial and industrial industries. Metl-Span is committed to delivering high-quality, durable, and energy-efficient solutions designed for unparalleled performance to stand the test of time with thermal and fire-rated envelope systems. Headquartered in Lewisville, Texas, with manufacturing facilities across the United States and Canada, Metl-Span is part of the Nucor Insulated Panel Group (NIPG). For more information, visit www.metlspan.com.
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