HVAC

This case study summarizes a University of Pennsylvania pilot study of costs and energy savings from implementing demand control ventilation solutions in the Vernon and Shirley Hill Pavilion vivarium and the Carolyn Hoff Lynch Life Sciences facility.

The University of Pennsylvania is a world-class research institution with a campus of 135 buildings totaling approximately 13 million square feet of space. In 2007, University President Dr. Amy Gutmann became one of the inaugural signatories of the American University and College Presidents’ Climate Commitment (ACUPCC), publicly committing Penn to reduce their CO₂ footprint. Penn’s pledge included a call for a 5% reduction in carbon emissions in year one of their plan and an 18% reduction by year five.

To achieve these aggressive energy reduction goals, the university assembled a comprehensive team representing every constituent department, even including student input. As sustainability and facility managers worked to consider the best energy saving ideas, they recognized the need to involve the occupants of the facilities from the beginning of the process.

It is widely understood that buildings consume the vast majority of energy and therefore dominate the carbon footprint of a college campus; facilities often represent 70-80% of the total CO₂ production across their institutions. Laboratory facilities are just as easily recognized as the “energy hogs” amongst all buildings. The University of Pennsylvania is representative of this situation: 25% of Penn’s facilities are dedicated to laboratory and research while producing 40% of their carbon emissions. To make significant reductions in energy use, the university knew they would need to investigate ways to reduce energy in the laboratory and research facilities.

The Evolution of Energy Reduction in Laboratories
Energy conservation efforts in laboratories are not new, but they do require a careful balance between the requirements for a particular research facility and the associated energy expenditure needed to deliver those requirements. As in other facilities, lighting alternatives provide a path to lower energy use, as does the reduction of plug load by removing unnecessary research equipment and introducing more Energy Star rated equipment. Reducing fume hood density to better reflect actual usage can also reduce energy demand in these facilities. Above all of these efforts, however, one item remains as the most significant consumer of energy: operating laboratories with high air change rates using 100% outside air.

The enabling step toward airside energy savings in labs is to design and build these facilities with variable air volume systems or retrofit them to be able to adjust air change rates while maintaining proper pressurization balance. If plug load and hood density issues have been addressed, the primary driver of air change rates becomes air provided for general dilution in the research or laboratory areas.

Choosing the Right Air Change Rates: You should not have to choose
Constant volume facilities have traditionally been operated at high air change rates ranging from 6-12 ACH in labs and 10-20 ACH in vivariums. The adage “the solution to pollution is dilution,” although widely recognized, is factually incorrect; the real solution to pollution is source control. Environmental Health and Safety personnel have understood this, implementing thoughtful chemical control and storage procedures in labs, and developing bedding and cage cleaning routines that help lower the airborne pollutants in animal holding areas.

So what is the right dilution air change rate? The simple answer is there is no one single number that is best for the changing conditions of a lab or vivarium. When laboratory conditions are clean (studies have suggested that most labs are clean 98% of the time) air change rates of 2-4 ACH are quite adequate. If there is an event that requires dilution, 10-12 ACH has been proven to be optimal rates for cleansing a room. Constantly running at 10 air changes would unnecessarily waste energy as clean air is being replaced with clean air most of the time; reducing the air change rates to a constant 6 ACH would save some energy but would not provide adequate volume when dilution air is really needed. Ideally, air change rates should be adjusted dynamically to reflect the actual needs of the space.