A zero-net-energy teaching lab
The 50,000-sf New Technology and Learning Center (NTLC) for Bristol Community College (BCC) in Fall River, Mass., brings together currently disparate programs from across campus, including chemistry, biology and medical and dental education. It holds an energy-dense program, including 22 fume hoods, high plug loads and specific ventilation and lighting requirements.
Initially, a standard high-performance building served as the basis of design for the NTLC, including numerous energy-conservation measures (ECMs). It was designed to meet the statutory requirement of Massachusetts LEED Silver Plus, including a minimum of 20% energy-cost reduction, compared to the ASHRAE 90.1-2007 baseline.
While the project was on hold awaiting funding, BCC doubled-down on their commitment to achieving carbon neutrality for their entire campus operations by the year 2050, initiating plans to develop a campus-scale photovoltaic (PV) array over one of their existing parking lots. Given this new context, when the NTLC project was authorized by the state to proceed, Sasaki Architects and BR+A took a closer look at the original “high-performance” design.
Our detailed energy model of the high-performance design showed the NTLC would use approximately as much electricity as the existing campus, as well as a natural gas equivalent to the consumption of 120 homes. Given the NTLC would only be half-way through its lifespan by the year 2050, the high-performance design clearly wasn’t keeping pace with BCC’s vision.
Over the following weeks, BR+A and Sasaki made a strategic investment to develop a zero-net-energy (ZNE) design in parallel with the high-performance design. To start the process, we searched for precedent ZNE buildings. Of the seven similar projects identified, four were either in design or construction. Although laudable projects, those built appeared to fall short of their ZNE goals. Only one of the built projects, located in the mild California climate, had significant exhaust demand. So the question remained of how to achieve ZNE for an energy-dense program in a cold climate.
Beginning with a series of potential solutions, the NTLC team vetted these options through exhaustive building simulation, calculations, research and discussions with manufacturers of advanced building technologies. BR+A also performed a comprehensive plug-load study, plugging in every piece of equipment going into the new building to right-size the cooling and electrical systems. We then interviewed key staff and faculty to understand how equipment is used for each class and integrated dozens of load profiles into the energy model, based on the actual academic calendar to maximize the accuracy of the energy analysis.
Ultimately, a synergistic combination of old and new technologies was developed. The ZNE design relies on a hybrid ground-source/air-source heat pump system with expanded ground-temperature range and an advanced optimization control logic, filtered fume hoods, enthalpy wheel heat recovery, reduced minimum air change rates, central air quality monitoring, fan-coil units with EC motors, 50% lighting power density reduction, a high-performance envelope with thermally broken assemblies and a combination of manual and fully automated natural ventilation systems.
On a parallel track, BCC entered into a power-purchase agreement (PPA) to install a 3.2-MW PV array over the adjacent parking lot. This system has been sized to achieve zero-net electricity for the entire campus, including powering the NTLC. Through the PPA, not only will the array be installed at no cost to BCC, but the electricity will be provided at a lower cost/kWh than they currently pay, with no annual rate escalation.
Overall, the ZNE approach not only eliminated fossil fuel consumption, but reduced overall energy consumption by a predicted 70% compared to the original high-performance design, saving nearly $100,000 in energy cost per year. The true test of our design, however, came when the detailed line-item cost estimate was completed by the cost estimator, providing a comparison of the two designs. The result: The ZNE design came in $200,000 lower than the original high-performance design.
Beyond achieving ZNE at zero-net cost, the project was able to take advantage of nearly $750,000 in grants and incentives. This, in combination with the first energy and maintenance cost savings, results in a net present savings of nearly $2.25 million over the first 20 years of the building’s life.
As Director of Sustainable Design at BR+A Consulting Engineers, Jacob Knowles heads the NET+ sustainability consulting team. Over the past decade, he has championed the sustainability agenda for over 20 million sf of healthcare, research, commercial and institutional projects.