Insulated Metal Panels for Walls and Roofs: What You Need to Know
Insulated metal panels (IMPs) have for many years been a popular building component in commercial and industrial construction. IMPs are single-element, factory-insulated manufactured composite panels consisting of a rigid urethane foam sandwiched between two sheets of coated metal, sealed at the perimeter and side laps.
IMPs are used for exterior walls, ceilings and roofs in both new and retrofit buildings, and can easily be adapted to pre-engineered metal building designs. Panels come in a variety of styles, colors and sizes to fit virtually any low-rise application including office buildings, schools, warehouses, manufacturing facilities, aircraft hangars, cold storage, data centers, and more.
IMP systems provide many of the same features found in other metal wall and roof systems and offer numerous benefits and advantages over conventional, field-assembled construction. However, it’s important to keep in mind that there are also a number of risks associated with the use of IMPs. Design and workmanship considerations for mitigating those risks can prevent water and air intrusion related to the panel assemblies.
Design and Installation Benefits
IMP systems offer design professionals the opportunity to create functional and sustainable buildings. The use of IMPs can result in lower construction costs as well as reduced energy use and maintenance costs. One of the primary design advantages of an IMP system is flexibility. Multiple wall and roof profiles, colors, finishes, accessories and trims can be integrated into any building style. Wall panels can be installed either vertically or horizontally. IMP systems easily integrate with doors, windows, louvers, and other building envelope components.
IMPs provide higher installation efficiency compared to other field-assembled products because the one-piece construction process ensures rapid completion of the wall or roof system. They are lightweight and less affected by weather conditions. Since IMPs are attached directly to the supporting structure, multiple steps needed to construct a conventional wall or roof are eliminated. This is especially beneficial on large commercial and industrial facilities such as manufacturing plants, storage, and food processing facilities, where in many installations the liner side of the panels is also used as the interior finish. Because of their durability and ease of installation, IMPs can be easily disassembled and reused for the interior or exterior walls of a new project or building expansion.
IMP roof systems provide specific benefits when compared to traditional metal roof systems. Field-assembled roofs require a separate liner panel or deck, vapor retarder, insulation board and roof panel. Properly installed factory-assembled IMPs combine all of these benefits into one package:
- Composite panels allow one-step installation, reducing labor time and costs.
- Inclusive vapor barrier/retarder eliminates risk of misapplication.
- Panels have consistent insulation values across the entire roof, with no compressed insulation points.
- Side joints feature a continuous thermal break, with no heat or cold conductivity.
- Panels can be installed in adverse weather conditions.
One of the biggest advantages of insulated metal panels compared to conventional construction is superior thermal performance due to their high insulation value. IMPs can provide greater insulation efficiency versus a field-assembled wall or roof system. The IMP foam core provides R-values ranging from 15 to 48 for wall systems and from 10 to 48 for roof systems—the primary variable being the thickness of the panel relative to the thermal value. Insulated tongue-and-groove joints at structural attachments are designed to provide continuous R-values and create a consistent thermal barrier at the building envelope. There are no areas where the insulation is compressed, which could cause a reduction in overall thermal value.
IMPs are encased in the metal faces and trim, creating a solid cladding with no gaps or voids, effectively blocking air and moisture. This protects the building envelope from moisture intrusion that could result in the degradation of building components and materials. As an additional thermal safeguard, IMPs should include a sealed fastener system that prevents gaps in the vapor, air and water barriers.
Important Quality Assurance Practices
When properly installed, IMPs do not allow water or air leakage at the seams. However, if the manufacturer’s recommended process for installing the panels is not followed with attention to detailing, problems such as water infiltration can occur.
Misunderstanding of the drainage plane of panels can lead to significant performance problems. The drainage line between two panels is often a watertight internal seal within the tongue and groove joint where the two panels meet. When penetration detailing for the “tie-in” material is located on the front face of the panels, water draining within the joint is trapped and flows to the interior of the assembly. To ensure proper water management and a complete enclosure, it is very important to pay close attention to where the water is actually draining, and design the tie-in details accordingly.
Less than acceptable embedment between panels can also result in air leakage, as shown in the image below.
Ultimately, it is important to remember that while a completed building assembly constructed from IMPs gives the impression of a unified surface, IMP systems are really many components including the panels themselves, fasteners, mending plates, flashing, sealants, etc. Each of these elements provides a potential failure point for the system, which is why the quality of the design and installation process and subsequent inspection is critical to the success of the IMP enclosure.
Below are important areas to focus on when installing IMPs. Experience has found that attention to these key details can prevent many common IMP performance issues.
- Ensure correct alignment to framing and depth.
- Thoroughly seal abandoned fastener holes with butyl sealant prior to panel installation.
- Fasteners used to secure sheet metal to integrated aluminum coping extrusion should have gasketed washers and should be cap sealed.
- Use two continuous rows of butyl sealant between the mending plate and the insulated metal panel.
- Use butyl sealant at termination mending plates.
- Bed flashings/extrusions together at the horizontal transitions.
3. Mending Plate
- Use two continuous rows of butyl sealant between the mending plate and fluid applied air barrier.
- Use one continuous 90-degree shaped mending plate at inside corners rather than two pieces.
- Shingle end laps 3” with double butyl sealant beads.
- Ensure that shims create a linear substrate for panels, in order to prevent a wavy substrate that can allow gaps.
- Use a primer before applying sealant to porous substrates.
- Seal all vertical end dams.
- Use a single piece at corners.
- Use a minimum of two fasteners per clip.
- Screw clips in between butyl sealant.
- Ensure framing is sized to fit two fasteners.
- Ensure continuous, full integration of tongue-and-groove joint through the entire panel to panel connection.
- Use double butyl sealant at the marriage bead.
- Lap the marriage bead over the vertical leg after gasket placement.
What Pie Can Do for You
As a leader in building science, Pie works with architects as they develop the specifications for IMPs. We help ensure that the materials adjacent to an IMP are congruent with best insulation practices, and that all the elements work together effectively as a system.
We also provide construction quality assurance, which includes testing for air leakage and water penetration. Our job is to ensure that contractors are performing installations per the manufacturer’s instructions so that the completed project meets the design specifications and the owner’s expectations.