ASHRAE Journal - September 2010 - 57

technology award case studies
ing. These AHUs use chilled water for cooling and serve zones with hot water reheat. Three exhaust fans located in an enclosed attic area serve the fume and general exhaust for the laboratories and general exhaust for the offices and other support areas. Each of these fans has a dedicated exhaust stack on the roof. The air-handling units and exhaust fans were designed to be constant volume systems, but prior to the retrofit, the AHUs and exhaust fans were retrofitted with variable speed drives used for balancing only. The zones had pneumatic controls and the central fans (air handlers and exhaust fans) were controlled by an industrial energy management and controls system (EMCS) maintained by Stanford’s EMCS group. Supplemental cooling for certain high-load spaces (primarily dry laboratories in the basement) was provided by dedicated chilled water fan coils. As with most buildings on Stanford’s campus, Stauffer I is served by central chilled water and steam from the Stanford cogeneration plant. Hot water for heating and reheat coils is provided by a steam to hot water heat exchanger. Since construction in 1960, the building has had many retrofits resulting in a complicated duct system and a lack of spare capacity on all supply and exhaust fans. Additionally, intensive users—current research included the use of nuclear magnetic resonance and molecular tweezers—required tight temperature control and low vibration. At the beginning of the design process, the building operator identified a number of additional existing operational issues. Both the supply and exhaust fans were operating at nearly full capacity. Additionally, any change in an individual laboratory layout required a full building test and rebalance. Maintaining the correct relative room pressurizations was problematic. The building operator often received thermal and acoustical complaints from occupants.
September 2010

Building at a Glance
Name: Stanford University Stauffer Building I Laboratory VAV conversion Location: Stanford, Calif.
Stauffer I

Owner: Stanford University Principal Use: Chemical Research
Stauffer II

Gross Square Footage: 28,000 Conditioned Space: 22,000 Substantial Completion/Occupancy: Retrofit completed 2007 Occupancy: 100%

Photo 1: Stauffer I lab at Stanford University.

The Design

The project was implemented in three phases: Phase 1, an assessment of the potential energy cost savings from multiple energy conserving retrofit measures; Phase 2, a detailed life-cycle cost analysis and the selection of the final package of energy efficiency measures; and Phase 3, the construction project implementing the selected measures. The Phase 1 and Phase 2 projects were conducted in 2002– 2003. Construction began in June 2006 and was completed in July 2007. The final design for the retrofit is shown in Figure 1. Based on life-cycle cost analysis and evaluation of safety and comfort impacts, the following measures were implemented in the retrofit: • Replacement of pneumatic zone controls with a direct digital control (DDC) system, which enabled supply air temperature reset in response to zone demand; • Conversion of all constant volume zones to variable air volume (VAV) zones by adding calibrated control valves to supply and exhaust ducts; • Conversion of the constant volume bypass air hoods to VAV hoods by

•

installing blank-off plates over the existing bypass pathways; Addition of occupancy sensors at the fume hoods to provide variable face velocity during hood “occupied” and “unoccupied” conditions; Reduction of total exhaust air quantity while maintaining the University Environmental Health and Safety Department’s recommended stack velocity requirements by reducing the diameter of the three main exhaust stacks (based on an estimated 30% reduction in fume exhaust through diversity observed at other laboratories on campus with VAV fume exhaust); Addition of differential pressure sensors across the supply valves, enabling dynamic reset of the supply fan duct pressure setpoint while ensuring adequate pressure for control of the supply valves; Addition of intake bypass dampers at the three exhaust fans and corresponding barometric makeup air dampers at the roof;
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ASHRAE Journal

ASHRAE Journal - September 2010

Table of Contents for the Digital Edition of ASHRAE Journal - September 2010