After a 14-month closure, the Town of Manchester has renovated Buckley Elementary School on Vernon Street into the first Net-Zero-Energy K-12 school in Connecticut! Buckley reopened to students in September 2022, and if you went to the open house, you know it is bright and beautiful! The town of Mansfeld has also recently completed an NZE school. But what does it mean to be Net-Zero-Energy? Every building needs energy for comfort and safety, so how can a building even be zero-energy? And what does that “net” part mean?
The meaning of 'Net-Zero-Energy'
Net-Zero-Energy or Zero-Net-Energy is a new trend in building design and renovation that is saving millions of dollars in energy costs in our region and around the world. By generating renewable electricity, these buildings operate with no carbon emissions. But if modern buildings must consume some energy to be safe and comfortable, to be zero-energy they will have to generate as much energy as they use. Solar panels are the most common way to add energy generation to a building, but there is a limit to how many panels can ft on a building's roof and how much power they can make. The output of solar panels varies every day because of cloud cover and the time of year, which determine how intensely the sun shines on us here in Connecticut. Fortunately, with current technology our typical 2 or 3-story buildings have enough roof area to generate the power they need, at least on an annual basis.
At our mid-northern latitude, Buckley's panels generate the most solar power in the summer months when the sun is high in the sky during long days. Its fat roof is almost facing the sun directly then. But our schools (and homes) need the most energy in the winter for heating and lighting when the sunlight is weak, so our power company, Eversource, is crucial in accepting the energy from our solar panels and distributing energy when we need it.
Buckley doesn't have any batteries to store their excess energy, so it “sells” it back to Eversource who just delivers it to neighbors around the school who do need the power right then. Buckley's electric meter turns backwards at those times and the school is credited with the power it supplied to the electric grid. When Buckley's 391 kilowatts of solar panels can't make enough electricity to heat and light the building, the school uses those credits it has built up all summer to buy electricity back from the grid. It's just like a savings account! On the bright, sunny days, Buckley School puts its extra power “in the bank” so that it will have it for the short and cloudy days. In an average year, the debits and credits cancel out to a net of zero for the whole year.
Heating and cooling with electricity
How does Buckley heat itself on those cold winter days with electricity? Isn't electricity too expensive to use for heat? The answer is yes and no. It is too expensive if you do it the old-fashioned way by heating wires as your electric stove does. But if you use a heat pump, you can “pump” heat from a lower temperature source like the outside air or the earth around the school and use electricity to move 3 to 5 times as much heat as you could make by using it to make wires glow red-hot. That is what Buckley School does. It has 60 wells under the playing felds and circulates water down those wells to the ground which is always about 50°F. The heat pumps in the classroom fan-units extract the heat in the water and can pump up that temperature to about 120°F so it can be used to heat the building (recall that when you compress a gas it gets hotter). It moves heat, as air-conditioners have done for years, but it's reversible and can move heat into or out of the building. No fuel has to be purchased since Buckley makes all the electricity it needs annually to run the heat pumps, lights, etc.
Can any building become Net-Zero-Energy with heat pumps and solar panels?
Did Buckley become net-zero-energy just by taking out the boilers and installing heat pumps and solar panels? No, it wasn't that easy, or we would all be doing it! The design team who took on this challenge did a lot of analysis first. For one thing, the purpose of the renovation was to update the building with all the modern facilities that were included in our previous three school renovations (Highland Park, Waddell, and Verplanck), as well as add 4 classrooms. The roof available for solar panels was limited, so the designers calculated how much energy the planned school would use and how much energy the new solar system could generate and looked for practical ways to make those two numbers the same.
Architects and engineers who design buildings commonly use computer models to calculate energy needs, even for houses. This major renovation allowed them to easily add features like energy-saving windows, sealing air leaks, effcient lighting, and insulation, and balanced these critical changes with making a comfortable, functional space to learn. Eventually our design team found a combination of features and systems that the computer simulation predicted would balance energy production with needs and ft within the fnancial budget. The computer models said they would have to cut the former energy use by two-thirds to reach the net-zero-energy goal and that would require major improvements to all the surfaces enclosing the building.
Here's an example of the decisions they had to make. One often-used way to lower the energy needed in net-zero-energy buildings is to install triple-pane windows, but they are very expensive. Our designers used common double-pane windows instead, and alternated them with highly-insulating, light-transmitting panels (translucent, but not clear) to replace the old, single-pane windows. Windows lose more heat than any other part of a building enclosure, so the panels reduced heat loss, lowered costs for fewer windows, while maintaining the valuable daylighting in our classrooms. It was a triple win!
Buckley School is more than just a model for Net-Zero-Energy
The new Buckley is colorful and beautiful with more daylight and a feeling of openness, as well as all the modern features we expect. It has a ventilation system that delivers the code-approved amounts of outdoor air to every part of the building and exhausts an equal amount to keep the air fresh. But before it exhausts that air, it extracts most of the energy in it to warm up the incoming air and thereby stay within the energy budget.
In addition to that, all the air is filtered by high-efficiency filters that can remove 90% of very fine particles down in the 2.5-micron range (about the size of a bacteria cell). To do even better in our pandemic times, the air is exposed to ultraviolet lamps to kill bacteria and viruses. The building even has its own report card: in the entry lobby there's a large screen that tells everyone how the building is operating compared to how it is supposed to, or how it did yesterday or last year. Our children are learning about energy efficiency as well as their “ABC's” and STEM.
Moving towards greater energy efficiency
Can every school or town building in the state be converted to net-zero-energy? Probably not, for as we have learned, it's not an easy task. It requires a really major building upgrade, and a suitable place to put the solar panels. You have to provide expensive-to-heat ventilation for good air quality when you update an older building, plus all the building lighting, heating and cooling, all while lowering the total energy used to what you can produce. We have to demand that our town leaders commit to doing the deep analysis needed for each existing building if we really want this low carbon future.
Do we always have to replace fossil-fueled boilers with electric heat pumps to make our buildings net-zero-energy? The answer is YES! Electricity is the only energy that can be generated on-site to supply our energy needs, and heat pumps are the only practical way to use electricity for heat. Besides, now we know that burning fossil fuels emits carbon dioxide that keeps more of the sun's heat in the atmosphere. This increase in temperature is disrupting climates all over the world, which generates massive natural disasters that damage our communities. Net-Zero-Energy buildings will reduce climate change and damage from extreme weather, which we all want!
What if enough solar panels don't fit on the roof, or it's too shady?
Many public (and private) buildings have large parking areas to accommodate our abhorrence of public transit. If there is not enough roof space, carport solar is an option and the shade is a wonderful amenity in the summer. However, the carport supports or even a ground mount structure will add costs not needed with rooftop solar. Tall office buildings have lots of interior space compared to their roof size, but fortunately our town buildings, most of which are three stories or less, will generally have enough roof space for solar panels that can power the whole building, after it has undergone a deep-energy-retrofit.
There are other options. In many other states, you can buy a share of the output of a community solar farm on someone else's property and get credits from your utility to cover the cost of the electricity bill (Shared or Community Solar). In Connecticut, though, Shared Solar projects have been extremely slow to develop. In 5 years we have built one in Bloomfeld, and their largest subscriber is a school. Clearly to make net-zero-energy possible for all types of buildings, whether they are tall or just don't have a sunny roof, we need more of these shared solar farms, but the design of our current program is more roadblock than ramp towards innovation. The permitting process so far has been very slow, and builders cannot guarantee the costs of equipment quoted in their bids while the permit review drags on for years. Solar developers have been unwilling to sign contracts with this kind of risk. Another pathway towards making our communities net-zero is purchasing sustainable power through our state marketplace at www.energizect.com. This builds demand for our utility grid to keep adding power generation from sources that do not burn fossil fuels.
Can we afford to make more town buildings Net-Zero-Energy?
Of course, the best place for solar is on your own building site. That minimizes transmission losses and the wait for approval for Shared Solar. Crucially, by reducing energy use in your building, you can make it possible for your own solar system to cover your needs. The Town of Manchester committed funding to fnd a way to renovate a 70-year-old elementary school into a net-zero-energy showplace, with another already under renovation and a third in the design phase. Their design teams have shown that our older buildings can not only be brought up to modern standards, but can far exceed them, and go all the way to net-zero-energy! Each of these schools is expected to save the town about $100,000 a year in energy costs.
The additional work to achieve a net-zero-energy Buckley School came out to 5% of the total project cost. After an incentive payment from Eversource, the cost of solar equipment to produce the needed energy added just under 7% to the cost. Since the bids came in below the original budget, the town decided to purchase the solar system at Buckley instead of leasing it, which gives us 100% of the fnancial benefts. As electric costs rise, as they did at the beginning of 2023, this self-generated power becomes more and more valuable.
If you visit the school, you probably won’t notice the solar panels on the roof unless you go to the highest spot in the parking area on the south side, but you will see the Smart Flower, a tracking solar collector that follows the sun through the sky like the sunflowers planted around it. In its industrial heyday, when Manchester was known for its production of silk, the town adopted the Mulberry Tree that fed the silkworms as the town logo. Perhaps the solar Smart Flower at Buckley School is a more accurate depiction of the town's productive future. Making an older building net-zero-energy is not easy to do, especially not in the first draft, but it will get easier with more experience. Manchester's Board of Directors bravely decided to try. Our first step towards a well-planned and stable energy future is to demand a high performance design that balances energy use with generation in every renovation, in every town in our state.
Article written by Gene DeJoannis of Hartford, CT