– By Sharon Thatcher –
Metal roofing systems already provide benefits attractive to consumers looking for efficiency and sustainability, but if you have a customer who wants to step it up a notch to achieve LEED or net-zero, nothing can help you get there faster than insulated metal panel.
While IMP for walls is a familiar breed, not so well known is IMP for roofs. Growth may be small, but it’s a segment of the industry worth knowing.
One good place to start is the IMP Council of the Metal Construction Association. The Council was created about 18 years ago by a coalition of manufacturers who wanted to provide more visibility to a niche, non-traditional product, and to keep ahead of any legislative actions that might hinder further development; after all, IMPs contain petroleum-based products, which, even when highly regulated, some people love to hate.
Today, the Council consists of the handful of prime players in the IMP field. One of its most recent accomplishments is the October release of an Environmental Product Declaration created through the work of Centria, Kingspan, Metl-Span and MBCI. The Declaration can be found and downloaded from the MCA website metalconstruction.org). As well, each company has its own EPD.
Co-chairs of the Council are Doug Pickens, vice president of marketing for Metl-Span, and Ronald E. Park, manager of Rigid Systems Sales and Strategic Marketing, Insulation Business Group, Bayer Material Science LLC. Also weighing in for this article are Brad Johnson, vice president of MBCI’s EcoFICIENT insulated metal panel product line, and Andrew F. Williams P.E., director of codes and standards for the MCA.
According to Pickens, IMPs have been around since the mid- to late-1950s, and in its current form since the mid- to late-1960s. The most growth has been seen in the last two to three years in wall panels.
At just 7.5 million square feet a year in sales for IMP roofing, the size of the market is “minuscule” compared to single skin roofing, but Pickens believes that will change. “The market for walls is growing very, very quickly, and I think at some point it will spill over [to roofs],” he said.
The growth will be customer-driven as more people demand thermal efficient buildings.
“First and foremost IMP is perceived as a sustainable product,” Pickens said. “When they survey architects on the issue of sustainability, the No. 1 factor is thermal efficiency, and these panels are highly thermal efficient.”
What can hold back the progress are reluctant roofers who fear the unknown, yet Pickens contends that “a guy who has experience with trapezoidal roof panels, or panels with clips, or structural single skin would not have a problem putting these up.”
That’s not to over simplify the process, however. “Some of the biggest misconceptions are the amount of manpower required, the type of equipment best suited for installation and the complexity and expertise required from an erector,” said MBCI’s Brad Johnson, noting that labor can be greatly reduced with the use of proper equipment, such as vacuum lifts.
To get a more precise idea on what type of equipment is necessary, Pickens suggested that roofers, “check with their manufacturer on the variety of lifting methods that are peculiar to their product. For example, Metl-Span would provide instructions for lifting a standing seam insulated panel that are a little bit different than what might be used for lifting a batten seam IMP.”
Manufacturers are typically more than willing to offer instructions and answer questions about installation as they arise.
Although insulated metal panels don’t vary much between wall and roof, there are some differences in how they are installed. “Our typical hidden fasten wall panel will have a double tongue and groove whereas the roof panels have a single tongue and groove,” Brad Johnson said.
Installation equipment for walls and roofs can also vary. “Typically there are more options for the wall panels depending on the size and length of the panels. The installer will typically be able to install more squares per day of wall panels than roof panels,” Johnson said.
There are some installation differences that roofers should heed. “They need to be very aware of the tolerances for the secondary steel, the purlins, because they’re fairly tight compared to single skin,” Doug Pickens said.
“Also one of the most common questions is how do you handle expansion and contraction since IMP roofs don’t use a slotted clip,” he said. “Insulated metal panels are a composite sandwich with the metal skins chemically bonded to the core, so there is no significant differential expansion between the interior and exterior faces of the panel. The panels are positively fastened to the roof purlins and the expansion of the panel is equally divided among the individual spans as thermal bow rather than linear expansion, which eliminates the need for slotted clips.”
Johnson said: “The substrate must be checked and monitored continuously to ensure the substrate is in proper plane for the panels. The IMP roof panel is a fixed roof system and will experience thermal bow between the purlins as opposed to single skin that are designed to allow for expansion and contraction in the panel.
“It is also of high importance to assure full engagement of vapor seal in the panel joint for the IMPs,” he said.
Because panels are factory made with a liner, insulation, structural deck and weatherproof membrane as one element, they are installed in a single step as opposed to traditional structural metal roofing systems that are installed in separate steps.
Given proper training and equipment, Pickens said that virtually three times more square footage of IMP roof panels can be installed as compared to a 24-inch wide trapezoidal, leg single skin roof system. For single skin metal roof panels, the average square footage installed a day is about 3,500, whereas with IMP as much as 10,000-12,000 square feet can be put into place.
Because of the faster installation by experienced crews, IMP is not as expensive as one might think. “In some cases the cost of materials, the base materials, can be very comparable. We may be a little more expensive, but IMP roofs go up very quickly, so a lot of the savings and what makes them truly comparable in price (except in typical shade and shelter structures), is in the labor portion. So it will be more expensive on the material side but considerably less on the labor side,” Pickens said.
The big reward
The big reward with IMP is the thermal efficiency, averaging R-7.0 to 7.2 per inch as compared to R-5.6 per inch for unfaced urethane board stock.
“Offering both a solid roof covering and energy efficiency, IMP panels are a way to address two specific concerns with a single product,” MCA spokesman Andy Williams said.
Longevity is yet another reward. “Today’s built-up roof systems need regular maintenance and replacement,” Ronald Park of Rigid Systems said. “With increasing focus on sustainable buildings, an IMP roof can last several decades with minimal repair costs.”
Change is difficult, however, and IMP roofs still have a long way to go to become a conventional option. Will it change? Park is optimistic.
“The North American market has been a long standing brick and concrete market,” he said. But “…new regulations in concert with a desire for progressive architectural design have allowed IMPs to begin getting noticed for their flexibility and function in building architecture.”