Exterior wall insulation? That usually means rigid foam and furring strips — although occasionally, it means mineral wool insulation and furring strips.
But there are other options. Two new products offer builders new ways to keep their wall sheathing warm.
InSoFast panels — rectangles of expanded polystyrene (EPS) foam with embedded plastic “studs” that hold drywall screws — have been around for years. The product was developed as a quick and convenient way for homeowners to insulate the interior of basement walls. The company’s original product (the InSoFast UX 2.0 panel) is 2 inches thick and rated at R-8.5.
InSoFast is now promoting a thicker panel, the InSoFast EX 2.5 panel, for use on the exterior of wall sheathing. (In many ways, the InSoFast EX 2.5 panels resemble the Quad-Lock R-etro system. For more on Quad-Lock R-etro, see my review in the fourth issue of GBA’s Insider magazine. GBA also lists the Quad-Lock R-etro system in our Green Products Guide.)
Each InSoFast EX 2.5 panel measures 24 inches by 48 inches by 2 1/2 inches thick. The EPS has a density of 1.25 pounds per cubic foot. The panels have tongue-and-groove joints around the perimeter that are described as “self-flashing.” While these joints are designed to shed water, the foam panels have not been approved for use as a water-resistive barrier (WRB), so builders will still need to install a layer of housewrap or asphalt felt to protect the wall sheathing.
The new 2 1/2-inch-thick panels have several features that differ from the original 2-inch panels designed for interior use:
While the interior panels only have to support gypsum drywall, the new exterior panels have to be strong enough to support siding. According to InSoFast president Ed Scherrer, the plastic “studs” are strong enough for this purpose, and are capable of supporting fiber-cement siding or even stone veneer.
Anyone who intends to…