After several years of success with its insulated wall panel technology, replacing conventional reinforcement with a noncorrosive, high-strength, embedded carbon-fiber grid, Lancaster, Pa.-based AltusGroup recently introduced a sandwich-style exterior spandrel panel or column cover that offers insulation properties while weighing significantly less than conventional precast concrete.
Field tested for much of the past two years by such precasters as High Concrete Group and Metromont Corp., the CarbonCast insulated architectural cladding offers weight reductions of about 40 percent compared to solid 7-in.-thick precast and is engineered to provide insulation values of R-10 or more, according to AltusGroup.
The panels feature inner and outer wythes, usually between 1.75-2 in. thick, depending on reveal depth. Sandwiching a layer of edge-to-edge foam insulation of 2.5 inches or more (depending on R-value demands) meets the requirements of ASHRAE 90.1 for continuous insulation. The thicker the insulation layer, the higher the R-value.
AltusGroup precasters are able to incorporate various architectural finishes into the cladding to create a distinct, expressive fa¡ade that will meet a variety of design needs. For example, thin brick can be used instead of full-depth brick. Simulated limestone or granite can replace extracted rock. An assortment of architectural elements such as cornices, bullnoses and reveals can also be cast into the panel face, making it unique among insulated cladding systems.
The design of CarbonCast's cladding is based closely on the successful, high-performance insulated wall panel. Whereas the wall panel is generally oriented vertically as a load-bearing panel, the cladding is meant for horizontal placement as a nonload-bearing spandrel. Nonetheless, the similarity in sandwich design means the cladding is engineered to exhibit the exceptional strength and durability benefits of its load-bearing cousin.
SCALING NEW HEIGHTS
Although the technology behind CarbonCast wall panels began life as a solution to finding lighter-weight panels for low-rise schools and commercial structures, driven by projects from High Concrete Group and Metromont, AltusGroup first developed a high-performance, fully composite precast wall panel for taller and more elaborate structures. Panels were eventually turned horizontally and made into architectural cladding.
The transitional project that turned wall panels into cladding was Georgia State's University Commons in Atlanta. The largest privately funded university housing complex in the nation, it required 8.5 acres of mass wall cladding on five buildings ranging from eight to 14 stories.
The design team opted to use the panels, because it was more economical to replace the metal stud and brick veneer system with an easy-to-install precast wall panel, finished on the exterior and ready to paint on the interior. This limited the cost and unpredictability of field labor as well as finishing materials. Setting the panels at night allowed for use of the general contractor's on-site tower crane, eliminating the need for mobilization of another crane and knocking months off the construction schedule. According to Metromont, the energy savings in the first year with the insulated wall panels was 33 percent Û more than $400,000.
The panels for the GSU job featured concrete with welded-wire reinforcement and internal pilaster (minimum 5,000 psi), along with paint-ready interior surface, an exterior with reveals and/or brick, and continuous insulation as a requirement.
Metromont also delivered CarbonCast insulated wall panels for the Proximity Hotel in Greensboro, N.C., which became the first hotel in the country to achieve LEED Platinum certification. The panels delivered R-14 to help minimize energy costs to heat and cool the building.
The panels were also the building material of choice by High Concrete for work on Cincinnati's new Fairview German Language School, which had specific visual qualifications. The yellow brick of the historic buildings in the surrounding neighborhood had to be matched, and to avoid the cost and unpredictability of conventional masonry work, 219 insulated wall panels were delivered. Modular-size thin brick was incorporated into the panels, and an acid-washed aggregate finish created different colors and textures for a traditional look consistent with the surrounding structures. The panels also resulted in improved strength and thermal performance.