Walnuttown Elementary School
Location: Fleetwood, Pa.

Type of Precast: CarbonCast® High Performance Insulated Wall Panels, Solid Walls, Hollowcore Plank

Size: 108,000 sq. ft. (79,000 insulated walls; 31,000 solid walls; 28,000 8” Hollowcore plank)

Architect: AEM Architects, Inc.
Engineer: Multani Associates, Inc., Reading, Pa.
General Contractor:
Wohlsen Construction Co.
Owner: Fleetwood Area School District

  • Walnuttown Elementary School
  • Walnuttown Elementary School
  • Willow Grove Elementary
Entrance

Quick Points

  1. Insulated wall panels provide thermally efficient building envelope
  2. Wythe connectors provide fully structurally composite resistance for loadbearing conditions
  3. Look of “positive sophistication” through thin brick and light sandblast finishes
  4. CarbonCast facade made under an agreement with AltusGroup, Inc.

Contents

Summary
Owners saw better value in precast

Green Goals
Thermal efficiency key to performance

Structure
Fully composite loadbearing precast facade

Aesthetics
Look of cut stone accents, amplifies masonry facade

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.  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.

The $22.1 million school was designed by AEM Architects, Inc., which also designed the nearby Tilden Elementary Center in Hamburg, Pa. with CarbonCast High Performance Insulated Wall Panels. The Tilden school was completed in 2007.

Willow Creek was built in proximity to other Fleetwood facilities, and takes the place of an older block and brick structure. According to AEM project architect Justin H. Istenes, the insulated wall panels were chosen for the school because “precast is built to last. The owners toured High’s Denver plant and the Tilden school while it was under construction, and were satisfied they were getting better value with precast insulated wall panels.”

Thermal efficiency key to performance

Three inches of rigid extruded polystyrene (XPS) foam sandwiched between the 3” exterior wythe and 4” interior wythe provide a composite R-value of 16. The wythes are connected by low thermal conductivity C-GRID® shear trusses. “R-value isn’t a perfect indication of energy efficiency because of thermal bridging,” says project architect Istenes. “These concrete mass walls provide continuous insulation because the wythe connectors minimize potential energy loss.”

“Traditional [building] methods require refreshing sooner, says Istenes. “Voids and cracks of traditional block and brick make it less efficient over time.”

Thermal performance of the precast facade is enhanced by a high-efficiency SouthWall glazing system that is Krypton-filled and includes a thin layer of HeatMirror film suspended between two air spaces to reflect the solar energy in the summer and absorb it in the winter. The glazing provides a u-value of .11 (R-value of 9). The project also included advanced HVAC controls for measurement and verification of system performance.

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.

Composite loadbearing precast facade

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 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 facade, floors are precast slab on grade and Hollowcore plank on the second floor. The roof is TPO on steel deck over steel joists.

Look of cut stone accents, amplifies masonry facade

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 facade 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. 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.

 

CarbonCast is a registered trademark of AltusGroup, Inc. C-GRID is a registered trademark of Chomarat N.A. LEED is a registered trademark of the US Green Building Council.