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A Study in Green Science

St. Olaf College in Northfield, Minn., is one of the few educational institutions to receive a U.S. Green Building Council LEED Platinum rating for one of its buildings.

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St. Olaf College in Northfield, Minn., is one of the few educational institutions to receive a U.S. Green Building Council LEED Platinum rating for one of its buildings. The college's Regents Hall of Natural and Mathematical Sciences opened in September 2008 and is expected to reduce energy costs by 50% compared to the Minnesota Energy Code, which is based on ASHRAE 90.1-2004.

Science centers are not by design energy-efficient, due mostly to their high air-exchange requirements. The Regents Hall features an HVAC system designed with an extended-size 53,000 cfm Vision air handling system from McQuay. The system is designed not only for high air exchange, but also for low energy consumption, which helped the college earn LEED points and meet budget requirements.

“We added 190,400 sq ft of technical space, and the base energy model for the building predicted more than 10 million kWh would be consumed annually if designed and constructed just to meet the code level,” said Pete Sandberg, assistant vice president for facilities at St. Olaf College. “The aggressive design changed the model to predict 4.2 million kWh, and we actually operated the first 12 months using 2.7 million kWh.”

The science building was designed to meet LEED NC (new construction) 2.1, which requires that 52 credits be met in order to achieve Platinum certification. St. Olaf College anticipates achieving 14 out of 14 possible credits in the Sustainable Sites category; 4 of 5 for Water Efficiency; 16 of 17 for Energy and Atmosphere; 9 of 13 for Material and Resource; 12 of 15 for IAQ; and all 5 possible Innovation credits.

The $64 million building, designed by the Rochester, Minn., office of the Chicago-based architectural firm Holabird & Root not only replaces a 40-year-old science building, it is a model for interdisciplinary science education. New lessons on green living and sustainability include how the green roof impacts a waterfall collection system to reduce the cooling load. Regents Hall is also the first major science facility in the country designed for “green chemistry,” which minimizes the hazardous chemical waste from lab experiments. The labs use one half the number of fume hoods compared to the same curriculum with conventional chemistry.

In all, the building includes 26 teaching labs, 7 tiered classrooms, 11 flat-floored classrooms, 8 seminar-style rooms, 5 dedicated computer rooms, an 8,000-sq-ft science library, student-faculty research space, group study spaces, and informal gathering spaces. The science facility has an 850-ton cooling load for the entire building. Helping to reduce that load are sustainable systems such as a green roof, abundant day lighting, highly efficient use of ventilation air, and a heat recovery system to reclaim exhaust air energy.

All of these sustainable systems meant special design challenges for the HVAC system due to the high airflow requirements. “The first priority was to design the building for St. Olaf's own sustainable design guidelines, which we believe equate well to LEED Gold,” said Sandberg. “That meant high IAQ, which for a science building requires some special considerations. Fume hoods in research labs are notoriously inefficient and can discharge potential contaminants. To meet both LEED and the guidelines, which are incorporated into all contracts as a part of the owner's project requirements, priorities were energy recovery, efficient air exchange, and quiet operation.”

The air distribution system has several energy-saving features including a heat recovery loop, a cascade air system, and a low-flow variable air volume (VAV) fume hood exhaust system. The first of these features is a glycol heat recovery loop that recovers heat from the laboratory fume hood exhaust airstream. A standard water coil is located in the laboratory exhaust manifold upstream of the exhaust fans, and a similar coil is strategically located in the air handling unit. Energy is transferred from the warm exhaust air to the glycol loop and transported to the air handling unit coil, where it is used to preheat the outside air coming into the unit. If necessary, a reheat coil on the VAV boxes will reheat the air when it reaches the space. The second feature, a cascade air system, is an efficient way to provide the high air exchange rate required for the laboratories. These energy-saving benefits can be accomplished because of the design flexibility of the air handling units.

Regents Hall is divided into east and west wings joined by an atrium. The air handling unit serves the entire east wing. Five smaller Vision air handling units serve the west wing and a single, stacked unit serves the Link, which connects Regents Hall to the newly remodeled Old Music Building. Originally, nine air handlers were specified, but the McQuay unit replaced three of them, significantly reducing installed and operating costs.

The extended size Vision unit, with a coil face area of 142.5 sq ft, is built on a custom-modular platform. The McQuay Variable Dimensioning feature lets engineers specify cabinet sizes in increments of 2 in. high and 4 in. wide, making it easier to configure a short-and-wide unit for Regents Hall's high-air-volume requirement. Dual plenum fans in the unit also help reduce energy consumption as well as ensure quiet operation. The energy-saving steps taken by St. Olaf College have resulted in the college operating at one-third the predicted costs.

Source: CSE