"Bren Hall" Beyond Platinum—Pushing the Envelope on Energy-Efficient HVAC Design
Brad Cochran, CPP, Inc.
Bren Hall on the University of California, Santa Barbara (UCSB) campus opened in April 2002 as the first laboratory building in the United States to receive the USGBC Platinum LEED® accreditation. In 2009, Bren Hall received a second Platinum rating as an existing building, making it the first duel LEED Platinum building in the country. To maintain its leadership in sustainable design and operation, UCSB continues to push the envelope to make the laboratory operation more efficient, safer, and more sustainable.
Recent focus has been placed on the HVAC system, both on the supply and exhaust sides. On the supply side, UCSB designed the building to be upgraded with a sensor suite that provides demand-based control of the laboratory’s air change rate. Currently, the minimum air change rates range from six to 17 air change rates per hour (ACH) with maximum air change rates of up to 36 ACH. With the sensor suite installed, the building’s air change rates can be reduced to four ACH in occupied mode and two ACH in unoccupied mode (when chemical concentrations levels within the laboratories are below established threshold values).
To fully realize the energy savings associated with the reduced air change rates, the exhaust system also needed to be updated to safely operate at these lower volume flow rates, without the need to significantly increase by-pass air requirements. Three different VAV operating strategies were investigated and their corresponding payback period and return on investment (ROI) were calculated.
The first VAV method evaluated involved simple turndown where the stack heights were increased to compensate for the reduced vertical momentum out of the exhaust stack. The second strategy involved using local wind speed and wind direction measurements to define minimum flow rates (wind responsive system). The third used in-situ monitoring of the chemical constituents within the exhaust plenum to reduce minimum flow rate requirements when the exhaust plume is essentially "clean."
The results of the analysis indicate that simple payback period of less than 12 months and five-year ROI values greater than 20 percent can be obtained with either the wind responsive system or the in-situ monitoring.
Biography:
Brad Cochran is a registered professional engineer in the State of Colorado and has nearly 20 years of experience conducting wind-tunnel and mathematical modeling studies related to laboratory exhaust design. Mr. Cochran has managed projects for such clients as Harvard Unversity, the National Institutes of Health, University of Texas Medical Center, Loyola University, Genentech, and the University of California.
Mr. Cochran is active in ASHRAE and is currently serving as the lead author of Chapter 9, Exhaust Stack Design, in the upcoming latest edition of the ASHRAE Laboratory Design Guide.
Mr. Cochran also served on the Air Movement and Control Association International, Inc. (AMCA) Induced Flow Fan CRP Committee that developed AMCA Standard 260-07, "Laboratory Methods of Testing Induced Flow Fans for Rating."
During the past decade, Mr. Cochran has focused on defining new design techniques to minimize the energy requirements for laboratory exhaust stacks. In 2005, Mr. Cochran developed the first laboratory exhaust system that used local wind data to minimize exhaust fan horsepower requirements, and in 2008 introduced the concept of monitoring chemical constituents within the exhaust manifold to reduce volume flow rates when the exhaust is essentially "clean." Both of these techniques are either in use or under development in laboratories across the country.
He has authored and presented several papers on the subject of energy efficient laboratory exhaust design for ASHRAE, Labs21, R&D Magazine, Lab Manager, LabWize, IFMA, AMCA, and the Air and Waste Management Association (AWMA).