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It gets mighty cold in winter in Eagle River, a small community of less than 1,500 in the Northwood's region of upstate Wisconsin. Eagle River, a former Indian settlement that was founded by lumberjacks and trappers in 1853, experiences severe, dry cold in winter (the record low winter temperature is a frosty -45° F) and gets lots of snow, providing it with some of the best conditions for snowmobiling in the entire U.S.
Eagle River's northern climate requires special expertise when it comes to high performance for energy efficiency, so when the need arose to build a new high school for the community and a large surrounding area, the Northland Pines School District turned to a firm with extensive experience in designing and constructing schools in the Badger State: Hoffman LLC, located in Appleton, Wisconsin.
Hoffman provides fully integrated planning, architectural and construction management services to a variety of markets including education, senior living and healthcare. It is a participant in over 20 LEED registered projects in the Midwest, has completed five LEED registered buildings to date in Wisconsin, and Northland Pines High School, home to 600 students, is the first LEED certified school in Wisconsin. Hoffman, in business since 1892, is committed to designing and building healthy, sustainable environments through its unique project approach - Total Project Management: Vision Taken to the Power of Green (TPMg).
Northland Pines High School, which opened for the start of the 2006-2007 school year, encompasses 250,000 square feet contained within a brick two-story building that comes with an atrium "commons" area, a performance auditorium, and an extensive field house with a track and basketball courts. Hoffman completed the project for $29 million, including LEED certification-related costs and the enhanced commissioning requirement for LEED. Per square foot for all design and construction costs came in at $115 per square foot.
Hoffman selected Fredericksen Engineering of Mequon, Wisconsin to design the school's HVAC system. Hoffman and Fredericksen have worked together on many projects, and experience has taught them how to meet an owner's budget and performance expectations while squeezing out unnecessary costs. In the case of the Northland Pines High School, not only did they manage to live within the owner's budget, 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 quality indoor comfort environment. 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 variable frequency drives 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 is comprised of a 425 ton air-cooled Trane chiller and two base-mounted Taco pumps. The secondary pump is served by a variable frequency drive to allow the pump flow to match the load in the building.
While many facilities have pumps sized for the total connected load, the Taco pumps for the Northland Pines High School were sized to match the anticipated peak load only. This not only reduces installation costs, it also results in more efficient pump operation for the life of the building.
Additional installed Taco equipment includes sixteen Plus Two Multi-Purpose Valves, four suction diffusers, two CA and one PS expansion tanks, two air separators and over 100 Taco Accu-Flo balancing valves.
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 in summertime; the chiller was sized for 88°F summer conditions. Tower Mechanical Services of Oshkosh, Wisconsin handled the HVAC system installation.
The HVAC system's design and energy efficiency merited seven points under the LEED certification process (Energy & Atmosphere category).
Hoffman's design for the school, developed in close collaboration with the Northland Pines School District, utilized high ceilings and window location for harvesting daylight. The gray Low-E window glass has a low visual transmittance to control glare and a low Solar Heat Gain Coefficient to manage unwanted heat gains on the east and west windows. Because of the cold winter climate, extra insulation - Dow Cavity Mate material - 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.
Field commissioning was carried out by CDH Energy of Evansville, Wisconsin and executive commissioning by CTG Energetics of Irvine, California. Electricity use data for the first five months of operation indicate the electricity use is within seven percent of the pre-construction model estimates which estimate that electricity will be two thirds of the energy bill. Natural Gas use evaluation is currently underway as winter data becomes available.
The Northland Pines project was featured in the "CaseInPoint" section of the August 2007 edition of Engineered Systems. Click here to download a PDF of the article.