Willow Creek Elementary School
(79,000 sq. ft. insulated walls; 31,000 sq. ft solid walls; 28,000 sq. ft 8” hollowcore plank)
Structural Precast Elements:
• Solid walls
• Hollowcore plank
Architectural Precast Elements:
Owners saw better value in precast
The two-story, 108,000 sq. ft. Willow Creek Elementary School was built in response to increased enrollments at the elementary school level. Fleetwood Area School District in Eastern Pennsylvania sought energy-efficient building materials that didn’t compromise durability or aesthetics. The district was interested in a green building solution with performance benefits to replace an existing and outdated block-and brick structure. The school opened for the 2009-2010 academic year, and features 44 classrooms, a cafeteria, gymnasium, library, computer labs, art and music classrooms for an estimated 700 students.
Willow Creek was built in proximity to other Fleetwood facilities, and takes the place of an older block and brick structure. The $22.1 million school was designed by AEM Architects, Inc., which also designed the nearby Tilden Elementary Center in Hamburg, Pa., which was completed in 2007. Both schools implemented the use of CarbonCast® High Performance Insulated Wall Panels. According to AEM project architect Justin H. Istenes, the insulated wall panels were chosen for the school because “precast is built to last, and “the owners were satisfied they were getting better value with precast insulated wall panels.”
Thermal efficiency is key to performance
Thermally efficient CarbonCast® High Performance Insulated Wall Panels used for the façade provide an R-value of 16. The panels incorporate three inches of extruded polystyrene (XPS) foam as continuous insulation (c.i.) sandwiched between the 3” exterior and 4” interior concrete wythes. C-GRID® carbon fiber grid was used as a shear connector between the two wythes. The high-strength carbon fiber grid helps the panels offer full composite action while its negligible thermal conductivity prevents thermal transfer through the panel to cut energy costs.
“These concrete mass walls provide continuous insulation because the wythe connectors minimize potential energy loss. Traditional [building] methods require refreshing sooner. Voids and cracks of traditional block and brick make it less efficient over time,” said project architect Justin H. Istenes of AEM Architects, Inc.
Use of steel in the building is limited to locations that required a thin column and to the 250-seat large group instruction area, a dual-use space that’s used daily, with a cafeteria and roll-out seating for 750. The design also preserved usable floor space for students because load-bearing panels eliminated the need for perimeter columns on construction of 44 regular and specialty classrooms, a gymnasium and library. In addition to the precast façade, floors are precast slab on grade and hollowcore plank on the second floor. The roof is TPO on steel deck over steel joists.
Aesthetically, thin brick masonry is offset by buff-pigmented precast with cut reveals on the panel faces and a light sandblast finish. Similarly, off-white block paint on the interior provides the learning environment with a sense of sophistication.
Composite loadbearing precast façade
The exterior loadbearing precast walls are fully structurally composite, meaning that the interior and exterior wythes act together to resist gravity, lateral and seismic forces. The design enabled the walls to be thinner than other systems, preserving usable floor space for occupants. The precast facade was panelized to 14’ widths to minimize the number of joints and to optimize shipping efficiency.
Interior walls are also structural precast which according to Istenes allowed the project to flow more smoothly during erection rather than having steel and block make up the structure on the building’s interior. Conduit for exterior lighting and fixtures was cast into the interior wythe of the panels for aesthetics and durability over time.
“[With precast,] everyone was forced to think about what they’re doing,” says Istenes. “On block projects contractors often will rush in before everyone has put their heads together, then they’re working on top of each other. This project was efficient and organized. Once the panels were in place we had little masonry work.” Istenes also notes that the project timeframe with its late fall and winter construction schedule would have been a challenge with block and brick.
Use of steel in the building is limited to locations that required a thin column and to the 250-seat large group instruction area, a dual-use space that’s used daily, with a cafeteria and roll-out seating for 750. In addition to the precast façade, floors are precast slab on grade and hollowcore plank on the second floor. The roof is TPO on steel deck over steel joists.
Though the project could have qualified for LEED or other green rating systems, the owner was interested in achieving the performance benefits of green building techniques without pursuing formal certifications.
Look of cut stone accents, amplifies masonry façade
The design of the school is simple in nature providing an academic schoolhouse feel with a positive sophistication. The main visual field is made up of masonry-clad insulated precast walls with strong buff-colored lintels and sills framing the windows and a buff square medallion centered over each window. The masonry is a reddish-gray thin brick from Glen-Gery in a running bond pattern with rake joints.
The façade is broken up by buff-pigmented insulated precast wall stair towers and accents on the library, large group instruction and office areas. Cut stone-like reveals on the panel faces (22” on center vertically and horizontally), bring a classic element that creates contrast while conveying substance. The finish is a light sandblast.
Back surfaces of the insulated panels were trowel-finished “… with a smoothness that almost looks like gypsum board,” says Istenes. The walls were painted with off-white block paint and are the exposed surfaces of the classrooms and halls.