The Design and Value Engineering Challenge
The design-build team for a high rise residential project in downtown Los Angeles were hitting hurdles. The façade system for their 23-story, highly-visible hotel, predominately metal panel and glass curtain wall, was not penciling out. The owner and design-build team tasked Clark Pacific to come up with a solution that would meet the budget and high-performance needs (including continuous insulation “ci” requirements) of the project without compromising the aesthetics of their design.
Clark Pacific’s preconstruction team, working with long-time strategic glass partner, AGA (Architectural Glass and Aluminum, Livermore, CA), came up with multiple options for the design team. The solution chosen was a façade comprised of multicolored and finished Clark Composite Architectural Precast Panels (C-CAPP) that are pre-insulated and pre-glazed at the precast plant as part of the assembly and sent to the jobsite ready for interior finishing after installation. Each composite panel consists of: • 2¼” – 3” of integral three-color and multi-finish mesh-reinforced concrete skin (5500psi average compressive strength); • 2” of NCFI spray foam insulation (two-component, self-adhering polyurethane closed cell foam system with 2pcf core density provides an Rvalue of 6.8/inch, an air and vapor barrier, high STC rating and high resistance to bacterial or fungal growth); • 1.5” offset, 4” deep light gauge and tube steel engineered frame system with galvanized pins to connect the skin to the frame and provide window support; • AGA custom designed thermally broken window assembly for minimal heat/cold transmittance with anchors designed specifically for precast panels (Glass selected was high performance tinted, Low E glass, accented with custom color spandrel inserts); • Return air HVAC vents, LED lighting connections; • Joint sealants (Dow Corning® 790 and 795 for panel-to-panel and panel-to-window mullions, respectively).
Putting the System to the Test
Performance mockup tests were conducted at Construction Consulting Lab West (Ontario, CA). After standard pre-test tune ups and adjustments, industry recommended ASTM and AAMA tests were performed including air infiltration, structural wind loading to 100, 150 and 200% of design loads (70-131mph winds), cyclic static and dynamic water penetration at 12.0 psf (68.5mph wind), elastic and inelastic in-plane seismic movement up to 1.5” at the floor line for 3 cycles and vertical live load deflections. No structural damage to the mockup occurred and designs were verified. No uncontrolled water leakage occurred into the mockup under design loading and elastic movement.
Clark Pacific’s Composite Architectural Precast Panels delivered the aesthetic and budgetary goals. Pre-glazing and pre-insulation can deliver a state-of-the-art precast solution for design-build teams looking for cost-effective façade assemblies.
Mike Ryan, PE, LEED AP BD&C, Clark Pacific