Quick Points:

• Top 24 floors clad with precast panels 33% lighter in weight than conventional precast
• Innovative slab attachment; reduced size and number of columns improved floor plan
• Facade tested to perform in Category 5 hurricane conditions
• CarbonCast cladding made under license from AltusGroup, Inc.

Background
Durable, lightweight exterior for 32-story tower

Aesthetics
Colors, reveals and articulation

Performance
Face-sealed curtainwall

Durable, lightweight exterior for 32-story tower

The developer of Symphony House, a breathtaking 31-story, $125-million condominium in Philadelphia, promises residents “a provocative design that takes from the grandeur and romance of the 1920s and gives it 21st century transformation.” Coincidently, the same could be said about the building’s exterior, a majority of which features next-generation CarbonCast® Architectural Cladding manufactured by High Concrete Group that deliver a traditional aesthetic sensibility and a remarkable 33% weight reduction of precast members.

Designed by Bower Lewis Thrower Architects and constructed by a joint venture of L.F. Driscoll Co. and Intech Construction, the impressive structure rises along Philadelphia’s Avenue of the Arts. The project includes a tower with an adjacent theater and eight levels of parking. The base is clad in conventional solid precast panels, and the 24 residential floors use CarbonCast.

The weight reduction provides two benefits. First, the restrictive building site necessitated a tower crane to lift the 770 exterior panels into place. The CarbonCast panels, which use significantly less concrete than conventional panels, were easily accommodated by the crane—even at the more distant corners of the building. Second, the lower-weight panels reduced loads on the floor slab, where they were mounted, as well as on the rest of the reinforced concrete structure.

Conventional precast panels from High were used on most of the building’s podium; although CarbonCast panels could have worked, the architect opted for thick, heavy, standard panels to meet the functional impact requirements of the parking deck.

Colors, reveals and articulation

The building team had specific color and texture requirements. They wanted a textured red finish, complemented by smooth brown hued sections and trim. High was able to satisfy their exacting requirements at its all-indoor precasting facility, through the use of environmentally-friendly steel shot blasting instead of sand blasting. In addition, the seven-inch-thick cladding panels enabled very deep reveals, recessed planes and deep window recesses that helped cast the shade and shadow that enliven the facade. Alternative lightweight cladding options are too thin and would have failed this demand. 

Face-sealed curtainwall

From a performance standpoint, the precast system will provide a face-sealed curtainwall to reduce moisture risk, a preferable design over rainscreen brick veneer or liability-burdened EIFS. In addition, the insulation in CarbonCast Architectural Cladding panels mitigates the chance of condensation-related mold or mildew in the cavity wall. 

CarbonCast Architectural Cladding Panels use carbon fiber grid as secondary reinforcement in the panel face, replacing conventional steel mesh. Because carbon fiber will not corrode, CarbonCast panels use less than two inches of concrete in the panel face. Typical precast wall panels use up to six inches of concrete in the face, because extra concrete is needed to protect the steel mesh reinforcement from corrosive elements. The dramatic reduction in concrete results in panel weights up to 50 percent lighter than conventional precast and with better durability than steel-stud systems or brick cavity wall.

Another advantage is that CarbonCast Architectural Cladding panels replace concrete with insulating foam, which can deliver panels with improved R-values. Further, the factory fabrication of panels allowed erection of the entire exterior envelope in only five months.