The Passive House design features precast slabs and other sustainable materials to deliver an energy saving solution for the college
Higher Education is at the forefront of fostering the next generation of environmental stewards. None more so than Wheaton College with the first passive house residence hall in Massachusetts. Pine Hall Student Residence was designed and built for top energy performance and certified by the Passive House Institute United States (PHIUS).
Designed with a structural steel frame, precast concrete hollowcore plank and a brick façade, Pine Hall is both solid and resilient. The four-story structure is 47,500 SF, with 178 beds and includes a laundry room, a kitchen, a multi-purpose room and student lounges.
Precast Concrete and Girder Slab
Oldcastle Infrastructure manufactured the 8” thick x 48”wide precast concrete plank covering the first three levels and the roof. The hollowcore system on Girder Slab D beams complemented the linear double-loaded corridor style building that spanned grade changes that resulted in 4 stories for the southern portion.
The inherent resiliency of precast concrete construction was seen in a variety of features in this residence hall. The hard, smooth finish of the underside of the precast hollowcore plank was left exposed in lieu of suspended ceilings. Precast concrete slabs enabled longer spans while also providing excellent fire resistance and resistance to floor vibrations.
To achieve this high level of performance Pine Hall the team used airtight construction methods, including high-performing walls (R-32), roofing materials (R-50), and triple glazed windows. It also optimized exterior shading and employed high-efficiency heating, cooling and lighting systems.
According to Rob Blanchard, LEED AP BD+C, Project Executive with Construction Manager Commodore Builders: “Passive House has very rigid air infiltration requirements, it is as tight as a refrigerator with windows”. During construction and before any interior work was begun we sealed any openings and “pressurized the building to determine if there were any air leakages, which is critical,” he explains.
The precast hollowcore plank helped limit air leakage between floors. “The two inch topping on the plank really sealed the floor to floor spaces,” describes Blanchard. With the building being so tight, we wanted to ensure the proper exchange of air in each zone.
Wheaton College was satisfied with the appearance of the underside of the plank and it was left exposed. That eliminated their original plan for additional finishes. With skim coat and thicker paint the slabs provided a low maintenance ceiling.
The open cells in the plank were used to run low voltage wiring for ceiling fixtures and Wi-Fi. Every room has their own wireless access point (WAP) to meet the high demand of multiple devices. Wheaton College is meeting student expectations that wireless internet should be free, fast and everywhere. Precast hollowcore also contributed to improved sound attenuation which contributes to the comfort livability of student residence halls.
Fall Semester Deadline
Precast plank allowed for fast installation allowing Pine Hall to open in time for the fall 2019 semester after an aggressive construction schedule. In order to facilitate meeting the tight schedule, the building utilized prefabricated hollowcore which was assembled on site.
Oldcastle Infrastructure helped keep the schedule moving in order to meet the drop dead date for student move-in. “They erected plank for the entire four floors in under 30 days. That allowed other trades to follow behind and complete the structure early,” recalls Blanchard. We wanted to make sure the steel and precast went up according to schedule. That allowed us to do the façade immediately following. The great thing about plank was we didn’t need shoring nor did we have to wait for concrete to set up. After the topping slab was applied other trades were working on those floors.
There is considerable coordination among the design and construction team reviewing the stringent requirements for PHIUS certification. An independent consultant who reports back to PHI with the building’s scores on energy consumption is an important part of the rating process. Working from the original whole building energy model, the evaluation takes into account any design changes along the way and modifies the calculations. The model takes into consideration any new parameters throughout the design and construction phase.
With his prior experience on a passive house, Blanchard believes that once you get past the steep learning curve it is not that difficult. Unlike LEED, the primary goal is to meet the energy numbers. That prerequisite is monitored by independent third party “raters” who inspect the building throughout construction.
“We were doing air infiltration tests throughout stages of building and ultimately were below the target requirement of 2746 cfm50 (Cubic Feet per Minute at 50 Pascals) for air leakage characteristics,” says Blanchard. “If you don’t hit the designated numbers you won’t be considered a Passive House.”
Despite the rigorous requirements, Blanchard estimates only a 3% premium over traditional construction. “I think we will definitely see more PHIUS construction systems in the Northeast. The comfort level of these types of buildings is incredible. The quiet environment and consistent climate control as well as the energy efficiency is off the charts,” predicts Blanchard.
With the envelope, windows, and HVAC systems all meeting PHIUS criteria, Wheaton College expects Pine Hall to be 70% more energy-efficient than buildings that meet the state code. With those savings it should only take ten years for them to recoup the small premium for the PHIUS design and construction.