The Sustainable Campus (Trends and Innovations)

Zero Net Energy, Zero Added Cost

Zero Net Energy college

PHOTO © EDWARD CARUSO

A Zero Net Energy (ZNE) academic lab-science building is without precedent in the Northeast, but Bristol Community College is leading the way with the completion of the John J. Sbrega Health & Science Building, designed by Sasaki Associates. ZNE means the amount of energy required annually to operate the building is equal to the energy generated onsite. This is no easy accomplishment in New England’s climate.

Bristol has committed to reaching campus-wide carbon neutrality by 2050. With ambitious goals in sight, Bristol and the Sasaki team, including BR+A and Haley & Aldrich, raised the stakes on the sustainable design of the project, aspiring to make the building not only elegant and inviting, but also a model for energy-efficient building on cold-climate campuses. In designing the building, the team uncovered ways to eliminate the use of fossil fuels, increase efficiency, and dramatically reduce demand — three critical components of ZNE design — all without increasing the budget.

1. Eliminating the use of fossil fuels. The design team cut fossil fuel use for heating and hot water through two strategies: an air/ground source heat pump and a solar hot-water system. The pump’s design permits a wider ground temperature range, reducing the number of wells needed. Coupling the ground and air source components allows for seasonal optimization by using air during more temperate seasons.

2. Generating renewable energy on-site. The second component of the design was tapping into the campus’ existing 3.2-megawatt solar array. A standard high-performance design would have used half the array’s power, but the ZNE design uses only 17 percent. The building also has a rooftop PV array that offsets some of the power usage, providing about 10 percent of anticipated demand.

3. Reducing demand. Much of the building’s energy demand was driven by its 18 fume hoods, designed to exhaust 100 percent outside air. Reducing the number of fume hoods was not programmatically feasible, so a more efficient alternative was found in filtration fume hoods. After engaging in due diligence, including a trip to a university that had installed them, Bristol agreed to adopt this relatively new technology. In so doing, the school was able to achieve several other energy conservation measures — reducing energy use by 80 percent relative to baseline and capturing dramatic cost-savings, making the ZNE approach feasible in the eyes of the college and the state.

4. The fume hood solution made a cascade of other conservations possible: a 67 percent reduction in hourly air changes and air-handling capacity; enthalpy wheel heat recovery; and decoupling cooling/heating from ventilation by using fan coil units for local cooling based on space occupancy.

These triggered a number of capital cost savings: a reduction of the lab exhaust system and associated welded stainless steel ductwork; less supply ductwork; a reduction in air handling equipment quantity and size; and decreases in floor-to-floor height and building envelope area.

Additional Strategies

A number of passive strategies also capture energy and cost savings, including implementation of a high-performance envelope by increasing R-value and decreasing thermal bridging and air leakage; expansion of the interior temperature range to 70-76°F; leveraging of natural ventilation; reduction in glass use, achieving a 22 percent window-to-wall ratio; self-shading; and 50 percent reduction in lighting power density.

The project is an achievement in creative thinking, stakeholder alignment and technological execution. However, one of its most valuable attributes is its net zero budget execution — a result of taking a holistic approach, rather than simply combining an unrelated menu of sustainable measures.

In an environment of fiscal constraint across the education sector and growing pressures to reach higher sustainability benchmarks, navigating seemingly competing forces is the linchpin of success. Analyzing both a standard, high-performance LEED Silver building and the ZNE approach, the team demonstrated that the ZNE approach would not increase the budget. In a world where effects of climate change are manifesting and all resources — including dollars — are limited, this seems the most reasonable approach.

This article originally appeared in the October 2016 issue of College Planning & Management.

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