The Northland Pines School district sought high levels of IAQ, site protection, and energy and water conservation in its new high school. A D-B approach to its HVAC design was guided by a need to balance three critical considerations: to keep an eye on first costs, to achieve energy savings, and to provide a healthy, comfortable indoor environment.

The Northland Pines School District (NPSD) in Eagle River, WI is the proud owner of the first LEED® Certified School in the Badger State. The school district, located in the state’s North Woods region, turned to Hoffman, LLC (Appleton, WI) for its extensive experience in designing and constructing sustainable schools in cold climates. Hoffman provides fully integrated planning, architectural design, and construction management services using a D-B approach.

The Northland Pines High School (NPHS) project presented numerous challenges, including a tight design and construction schedule that had to accommodate the long northern winters, plus a fixed budget set by referendum. These challenges were amplified by the need to work immediately adjacent to the existing high school building that was deconstructed in after school was out in June of 2006.

A green vision

The Hoffman D-B approach, Total Project Management: Vision Taken to the Power of Green (TPMg), provided a single project team from planning through construction and post-occupancy monitoring. The approach also provided a single responsible party in working closely with the NPSD. These were key elements in delivering a LEED Gold project at $115/sq ft on budget and on schedule.

NPHS, which opened for the 2006-2007 school year, encompasses 250,000 sq ft contained within a brick two-story building that includes an atrium commons area, an auditorium, and a field house with basketball courts and a track. Hoffman completed the project for $29 million, including LEED certification-related costs and the enhanced LEED commissioning requirements.

Hoffman recommended Fredericksen Engineering (Mequon, WI) to design the school’s HVAC system. In the case of the NPHS, not only did they manage to live within the owner’s budget, but they did so while achieving LEED Gold certification status.

Fredericksen’s design for the HVAC system was guided by a need to balance three critical considerations: to keep an eye on first costs, to achieve energy savings, and to provide a healthy, comfortable indoor environment.

The wet side

The wet side of the HVAC system consists of a hot water boiler plant and a chilled glycol cooling plant. The boiler plant pumping is configured in a primary-secondary arrangement. The system comprises eight Patterson Kelly Mod-U Fire non-condensing boilers for optimal heat recovery, two Taco FI Series base mounted pumps to serve the secondary loop, and eight Taco 1600 Series inline pumps to serve the primary hot water loop. The secondary pumps are served by VFDs to allow the pump flow to match the building’s load.

The chilled glycol plant pumping is also configured in a primary-secondary arrangement. The system comprises a 425 ton air-cooled Trane chiller and two base-mounted Taco pumps. To allow the pump flow to match the load in the building, a VFD serves the secondary pump. The pumps were sized to match the anticipated peak load only, a move intended to reduce installation costs and also produce more efficient pump operation.

Fredericksen designed the heating system for -25_F, reflecting the harsh winter conditions experienced in Eagle River. The harsh winter, however, does not preclude the need for air conditioning, and the chiller was sized for 88_ summer conditions. Tower Mechanical Services of Oshkosh, WI, installed the HVAC system, which merited seven points under the LEED certification process (Energy & Atmosphere category).

Other green measures

The design also incorporated extensive daylighting measures, and because of the cold winter climate, extra insulation was placed within the school’s walls. As part of the LEED process, over 80% of construction waste was either recycled or salvaged. Water conservation measures include use of waterless urinals and low-flow lavatories.

Electricity use data for the first five months of operation indicate the electricity use is within 7% of the pre-construction model estimates. Electricity is estimated to be two-thirds of the energy bill. Natural Gas use evaluation is currently underway as data for a complete heating season becomes available.

The lessons in sustainable design are being directly transferred to the students and teachers at the high school. Energy use data are being logged on the Johnson Controls system and provided for instructional purposes through the school’s Intranet system.

“Northland Pines High School is a great building that delivers energy efficiencies and maximum indoor comfort,” said Michael Richie, superintendent of schools. “We’re very pleased with the outcome of this LEED project. For a cold environment, its heating system delivered perfect comfort this past winter and promises us significant energy savings from one heating season to the next.”