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Article_crowley.jpg

©2017 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 59, no. 7, July 2017

By Bradford Crowley, P.E., Member ASHRAE

About the Author
Bradford Crowley, P.E., is an associate principal and team leader at Ballinger in Philadelphia.

Meeting sustainability goals in a lab with 142 fume hoods is a huge challenge for design engineers. It’s an even taller order when those labs require the flexibility to change rapidly, such as from a wet lab to a dry one. Both were the case for the new Undergraduate Teaching Laboratories at Johns Hopkins University (JHU).

Designers met those goals, creating a building that used 50% less energy in 2016 compared to ASHRAE Standard 90.1-2007’s baseline. This helped the building earn LEED Platinum certification.

The teaching and research lab brings together undergraduate labs and faculty research in the biology, chemistry, neuroscience, and biophysics departments and provides a student commons area.

It was the first major construction following an initiative to reduce carbon emissions by 51% by 2025.

 

Energy Efficiency

Energy consumption in a laboratory is driven by outdoor air (OA) requirements, the heating and cooling to condition this air, and high internal heat gains from laboratory equipment. The 105,000 gross ft2 (9755 gross m2) Undergraduate Teaching Laboratories (UTL) building uses a number of technologies, strategies, and systems specifically designed to mitigate the energy impact of these drivers including:

  • Enthalpy and sensible energy recovery wheels to deliver neutral temperature ventilation air;
  • Chilled beams, radiant floor heating, and perimeter radiators;
  • Waterside economizer using air-handling unit (AHU) cooling coils (free winter cooling);
  • District energy from campus trigeneration plants;
  • High-efficiency lighting and daylighting with occupancy sensor controls;
  • High performance fume hoods;
  • Occupancy based airflow reset;
  • “Decommissioning switches” to turn off airflow to vacant labs; and
  • High performing envelope and minimal east/west glazing.

Energy use is shown in Table 1. In 2016, energy consumption of 144 kBtu per gross ft2 (1635 MJ per gross m2) was lower than the modeled design, 192 kBtu per gross ft2 (2180 MJ per gross m2), which confirmes a 50% cost savings over ASHRAE Standard 90.1-2007’s baseline of 408 kBtu per gross ft2 (4633 MJ per gross m2). The installed air-handling system (Figure 1) uses two energy recovery wheels: a 3A molecular sieve-coated media enthalpy wheel and a sensible wheel. The two wheels act to recover exhaust energy and reheat air toward a neutral temperature. This design decouples ventilation requirements from heating/cooling demands. Active chilled beams provide sensible cooling throughout the building, while perimeter radiation offsets envelope heating losses.

Because ventilation air is kept at 68°F (20°C), reheat coils are not required at supply terminals. In addition to reducing/eliminating reheat, neutral supply air allows displacement makeup air delivery system that significantly reduces ductwork. Ducted air was sized only as required to drive chilled beam cooling.

Exhaust venturi valves maintain the required exhaust flow (fume hood flow and minimum air change rate) in each laboratory. Exhausts on each floor are summed, and large floor-based supply valves introduce the balance of the floor’s makeup air (minus ducted chilled beam air) into a pressurized plenum above the corridor ceiling.

The makeup air is passively pulled through large displacement grilles, with fabric backdraft dampers that balance pressures between the plenum and labs. This air delivery concept inherently creates a low-pressure, high-volumetric offset that ensures each laboratory is negatively pressurized with respect to the corridor. It also significantly simplifies controls, improves the quality of the building design via minimizing ductwork, and eliminates dumping of cold (or reheated) air.

 

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Table 1

crowley t1.jpg

 

Figure 1

crowley f1.jpg

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