A small yet determined faction of school districts is boldly pursuing net-zero energy schools. Fueled by long-reaching energy modeling and life-cycled analyses, a net-zero energy school is a dramatic way to save taxpayer dollars over the building's life. Architects and administrators are creating the schools of the future in the here and now.
The working definition of a net-zero building is one that produces the same amount of energy as it consumes over a year's time. The goal is to zero out energy consumption with energy production, with the possibility of sending surplus energy back onto the grid. Net-zero can also be applied more narrowly to electrical energy usage, carbon emissions, or energy costs.
Net-zero total energy is achieved through superior building efficiency, which reduces energy demands, and on-site renewable energy to satisfy the remainder. Any school, regardless of size or location, should focus on:
- High-performance envelope
- Daylighting strategies
- High-efficiency mechanical systems
- Resourceful use of space
No amount of renewable energy can productively offset a building that continues to operate with high energy demands. The greater your energy efficiency is, the lower your need for renewables – such as solar, wind, geothermal, and biomass – will be. "Energy efficiency is really the backbone of the whole thing," says Doug Pierce, senior associate with Perkins + Will. This is particularly important as renewables have strong upfront costs and multi-year ROIs.
Doing the Math with Renewables
Designing a net-zero school comes with a steep learning curve. A site's location and building footprint create unique parameters for each project, particularly when it comes to selecting renewables. Steve Miller, K-12 education head with Perkins + Will, emphasizes, "One size does not fit all. Financing and climate vary across the country and have a dramatic impact on the viability of net-zero energy design."
Perkins + Will has been working with the Spirit Lake School District in Iowa on a net-zero electrical energy high school. The flat terrain and local weather produce significant amounts of wind, allowing the site to host two commercial-grade wind turbines since the early 1990s. While wind is perfect for the Iowan plains, not all schools have the property space to accommodate large-scale turbines.
Richardsville Elementary School in Kentucky and the Evie Garrett Dennis (EGD) E-12 campus in Colorado, which both opened in fall 2010, found that solar power was the most viable and economical option for their locations. Richardsville uses a combination of an amorphous thin-film PV system for the entire roof and an array of traditional monocrystalline panels on a parking lot structure. The EGD campus also has a rooftop array for two of its four buildings, which is ideal for Denver's 300 annual days of sunshine.
Planning the Framework
Net-zero isn't an afterthought or a flashy design element – it's a serious commitment that should be established and committed to from the onset of planning. All of your subsequent decisions will be made in compliance with this singular goal. "It's very easy to incorporate sustainable features into a building as long as you start doing so from the onset," says Bob Binder, principal with DLR Group, which worked on the EGD Campus. "Then it's born with the project, comes out of the ground with it, and lives with it for life."
Richardsville Elementary proved to be a challenge for Sherman Carter Barnhart (SCB). The firm has served as Warren County's architect for over two decades and had already helped its average school building to go from 73-kBTU annual energy use down to 28 kBTU per square foot. To make Richardsville net-zero, an additional 8 kBTU had to be shaved from the energy load.
"There were no big gains to be had from where we were; those had already been made," explains Kenny Stanfield, principal architect of the project. "We literally had to go back to the beginning and question everything we thought we knew how to do. It took hundreds of small decisions about conserving small amounts of energy to add up to what we needed."
Out of this intense evaluation came several surprising decisions. Attic space was eliminated through the use of a low-slope roof, which was needed to accommodate the PV system. This, in turn, allowed the mechanical equipment to be located in closets between classrooms. The cafeteria not only doubles as a practice gym, but is placed in the center of the building footprint to reduce the volume and space of the perimeter wall. By going wireless and storing laptop computers on carts, a planned 1,000-square-foot computer lab was discarded.
After a conversation with the local police department, it was agreed to tie the nighttime security lighting to motion sensors. As part of the daylighting strategy, a clerestory spine runs down the middle of the building, which brings light deep into the gymnasium, cafeteria, and media center. In combination with exterior and interior light shelves, sloped classroom ceilings, and tubular skylights, the artificial lighting load was reduced by 70%.
"Going green and doing a net-zero energy school isn't so much about adding things to the building – it's about taking them away," says Stanfield.
An Evolving Status
Just like fluctuating utility prices, energy demands, and renewable energy output, a net-zero status is not a fixed one. This is especially true for schools, with lower occupancy usage in the summer and on weekends. Seasonality can also affect net-zero from month to month. A school with traditional seasons will see vastly different usage and production levels than a school with a static climate and access to natural ventilation.
"It's really an evolutionary cycle, and we anticipate that net-zero buildings will move in and out of net-zero status. This may be from an addition that has increased energy demands, or an opportunity to add more renewables," says Pierce.
This is particularly true for Spirit Lake. The school achieved net-zero electrical energy in 2003 when geothermal was added to the existing turbines. But as demand for the building space grew and an addition was built, the status dropped away. As of 2010, wind supplied 54% of the high school's electricity needs.
"You record this as a snapshot in time; you can't necessarily say that every moment is net-zero. Continuity is the biggest challenge," says Miller.
The Leaders of Tomorrow
With teaching positions slashed and funding regularly downsized, a net-zero energy building may seem like a tall order. Part of the uphill battle is the attitude that school buildings should be built quickly and for as little money as possible. This leads to underperforming facilities riddled with ongoing maintenance issues and massive energy costs. Settling for a poorly performing building isn't a sustainable way to use taxpayer dollars.
"Especially in the economy that we have, where every penny needs to be accounted for and spent wisely, now is the time to say, 'There is a better way of doing this and you're going to save an enormous amount of money in the long run,'" explains Stanfield.
Pierce feels a shift in thinking and accounting is necessary for more schools to see the benefits of net-zero. Instead of focusing on first cost, total cost of ownership should be emphasized. "Schools have long-term trajectories and they are institutions that truly serve the public over an extended period of time. There's probably no single entity that benefits greater from looking at total cost of ownership than publicly owned projects," he explains.
For Stanfield, justifying net-zero also starts with the price tag. "Any building can be net-zero as long as you have a big enough pocketbook to cover your energy costs with wind or solar. But a school district can't do that. The only way that they can make net-zero make sense is that it be affordable," he says.
There's also the future impact of climate change, which is rarely accounted for. "When everyone talks about economics and the paybacks, they're actually not doing full cost accounting. The cost of global warming is not built into the cost of our energy use," points out Pierce. "The dialogue on how much a net-zero school costs would be dramatically different. Somebody has to pay for the rise in energy costs sooner or later in a big way."
Passing the Final Test
Perhaps the biggest impact a net-zero energy school has is on its occupants. A new generation is being raised where "going green" is a default attitude, not a habit to be learned. These school buildings are an ongoing lesson plan for thousands of students as they are greeted by solar panels or wind turbines on a daily basis. All-school energy reduction challenges, touchscreen kiosks, wall displays, and themed hallways complete the students' experience of attending a net-zero energy school.
"It brings that awareness of how is it being done, why it is being done, and what the results are. It teaches the students to be global, green citizens," says DLR's Binder. "A net-zero energy school really sets a culture and an understanding with the users of the learning environment, so that hopefully they'll carry that forward throughout their lives."
Jennie Morton (firstname.lastname@example.org) is assistant editor of BUILDINGS.