Product Review from Environmental Building News
September 1, 2009
Invelope:
A Breakthrough in Exterior Commercial Wall Assemblies?
Invelope is a unique steel and foam panel installed behind brick veneer or terra cotta in metal-framed commercial buildings. The panel serves as a moisture and vapor barrier, drainage plane, and insulation while also providing a mounting system for brick veneer or terra-cotta cladding. Manufactured by Centria, Invelope is certified Cradle-to-Cradle Silver by MBDC (see
EBN Feb. 2007), using the same steel-wrapped polyisocyanurate foam construction as the company’s Formawall panels. As a backup wall, this one-piece design offers some distinct advantages over traditional assemblies.
One of the most common ways to create a commercial backup wall for steel-stud construction combines exterior drywall; an air, water, and vapor barrier; and rigid or semi-rigid insulation board. This system creates a thermal break between insulation and studs as well as a rainscreen with air space and a drainage plane that allows moisture driven behind the cladding to escape. After the backup wall is complete, masons secure anchors into the studs to support the bricks, penetrating through the insulation, barriers, and gypsum. Maintaining a weather-tight seal during installation of all the components by different trades can be a significant challenge, and once the brick is installed, air, moisture, and thermal problems are difficult to assess and remediate.
Invelope’s 32"-wide (80 cm) interlocking panels come in 12' (4 m) and 20' (6 m) lengths, and in 2" (5 cm; R-14) and 3" (8 cm; R-21) thicknesses, and, instead of using separate bolts, the panels are attached to the steel frame using masonry anchors. The tongue of the next panel then overlaps the secured panel to cover the bolt, minimizing thermal bridging and penetrations of the outer skin. This saves the masons significant time and labor. A factory-installed, low-emitting butyl sealant in the groove ensures a tight connection between the panels. To complete the air- and watertight envelope, all corners and window and door openings are flashed with peel-and-stick membranes, and panels are sealed in back against the steel studs.
If installed properly, Invelope should produce an extremely tight building envelope. The product has been used almost exclusively in the Northeast so far but should work well in any climate zone, particularly where hot summers and cold winters make placement of the vapor barrier difficult. “We have only done brick so far,” according to Invelope product manager William Hornfeck, “but the panels are designed to integrate with Shildan’s clips.” (Shildan is the U.S. importer of Moeding’s Alphaton and Longoton terra-cotta cladding.) Terra-cotta may be the best environmental choice for use with Invelope since it fires at a lower temperature than brick, is easy to replace if damaged, and does a good job of managing moisture.
Three of the eight Invelope installations so far were managed by Ted Kerrnosh, director of field operations for SFL Construction and Legacy Construction Group. Though Invelope provides training and supervision to ensure its panels are installed properly, he confessed that, as with any new system, it took some time to learn. “We first installed it in terrible conditions up 14 floors,” he said. “It was pretty awkward, but if you plan in advance with layout and details, it speeds up the process.” Kerrnosh emphasized that one of the real advantages of the system is that the components can be installed and left exposed to the elements for months at a time without ultraviolet light or moisture damaging the insulation.
He also noted that since Invelope is doing three jobs at once, it’s actually faster and less expensive to install than conventional backup walls, and becomes more cost-effective with larger jobs. Since fewer trades are necessary on the job site, he said, “We saved two months on scaffolding at almost $40,000 a month.” Initial material costs run about $4.50/ft
2 ($48/m
2), according to Hornfeck, about $0.50 more than a gypsum/barrier/insulation back-wall. Centria tried to keep initial costs down by using a thinner-gauge steel, modified foam, and primer instead of exterior top coat. But Hornfeck asserts that the durable panels are a long-term investment and should hold their insulation value better than polystyrene foams, which lose some of their R-value after installation.
The long-term performance of these panels is difficult to judge, but Richard Keleher, AIA, thinks the panels are a good approach. He has some concerns about potential thermal bridging and flashing where the window assemblies and panels connect, but if architects follow Centria’s details, “It could be an inexpensive way to build a wall.” Windows are typically the weak link in any wall assembly, however. Hornbeck acknowledges that he has received requests for R-30 walls. A four-inch-thick panel may be in the future, but those who want to improve upon the company’s current R-value should contact Centria before installing additional cavity insulation. Without a careful dew-point analysis, adding interior insulation could create condensation on the interior of the panels, potentially causing mold and air-quality problems.
– Brent Ehrlich
For more information:
Centria Services Group
Moon Township, Pennsylvania
866-279-3777
www.buildbetterwalls.com
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Photo: Alyssa Peconi, Centria Service Group
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