Net-Zero Schools Lead the Green Pack
More Districts Utilizing High-Efficiency HVAC Equipment to Reach Energy Goals
In August 2010, Richardsville Elementary School opened its doors to students of the Warren County Public School District in Bowling Green, Ky. The brand new, state-of-the-art $14.4 million facility features natural light, geothermal HVAC and hot water generation, an Energy Star-rated kitchen, a super-insulated building envelope, and many other green features.
But what sets the school apart is its distinction as the nation’s first-ever net-zero public school. In fact, the 82,000-square-foot building — which uses on-site solar panels to generate power — produces 108 percent of the energy it uses.
Though the school was one of a kind three years ago, it is now one of a growing number of net-zero institutions that have been popping up across the country. Meanwhile, many other schools are turning to highly efficient HVAC solutions for both new-build and retrofit projects, indicating that the once-novel concept of LEED-certified and zero-energy schools may soon become commonplace in school districts across the U.S.
At Richardsville Elementary, the HVAC system included a dedicated outdoor air system (DOAS) and geothermal water-source heat pumps. But for schools looking to improve energy efficiency and comfort without having to install underground geothermal loops, variable-refrigerant flow (VRF) ductless systems are gaining traction as a high-efficiency HVAC solution.
Chris Bellshaw, director of product marketing and engineering at Daikin AC (Americas) Inc., said Daikin’s variable-refrigerant volume (VRV) systems are popular with schools. “When we look at the high-efficiency products being used in schools, they’re going for the VRV systems along with heat recovery,” he said. “They’re going with the indoor cassette-type units because with the ductless units, you have the energy savings there.”
Bellshaw added that he’s noticed schools have been making the shift toward high-efficiency solutions for the past five years or so. “The school market is probably the most popular market from our perspective for this type of equipment,” he said. “When the school board decides to build a school, they’re basically the owners of that school, so they’re looking at sustainability, since they have to build, own, and pay for that building. They’re looking to improve the long-term costs of the school.”
For example, the Birdville Independent School District in Haltom City, Texas, replaced the HVAC system at its Shannon Learning Center with an advanced Daikin VRV system. “We’re very familiar with this technology and have been looking for an application in our district where its implementation made sense,” said Robert Frick, a senior project manager with consulting engineering firm Image Engineering, Grapevine, Texas. “Since it’s been installed, we’ve had good results with it, and we’re looking for other retrofit applications.”
Mitsubishi Electric Cooling & Heating's VRF systems are also gaining in popularity with schools across the U.S. Recently, Mitsubishi’s VRF system was installed in the net-zero George V. Leyva Middle School administration building in San Jose, Calif.
“This (Mitsubishi) system’s technology has contributed to saving us thousands of dollars this past year,” said Rob Smiley, director of operations and support services at the Evergreen School District. “And, because of its exceptional zoning capabilities, there are no more zoning wars as each office has its own temperature setting.”
Packaged Rooftop Units
For schools looking to simply replace their aging, inefficient rooftop units, several manufacturers like Carrier, Bryant, and Lennox offer high-efficiency packaged rooftop units that can easily be installed in place of an aging unit. Bill Chadwick, a senior building systems engineer at Carrier, said schools often request high-efficiency equipment for their buildings.
“Equipment that Carrier commonly sells to contractors for installation in schools includes the highly efficient rooftop units in the WeatherExpert and WeatherMaster lines,” Chadwick said. Carrier’s WeatherExpert units range from 3-23 tons and can reach an IEER of 21.
But improving energy efficiency in a building isn’t just about sticking the most efficient equipment a school can afford on the roof and hoping for good results. Other changes may have to be made, too.
“It is important to examine a number of factors using an integrated approach to lowering the building’s overall energy needs, such as architectural massing features, daylighting possibilities, and the electrical efficiency of all powered items,” he said. “Carrier recognizes that every building is unique and offers a variety of system solutions to meet the individual needs of its customers and their buildings.”
Vaughan Smith, national sales manager at Bard Mfg. Co., agreed that school officials are increasingly taking ventilation and energy efficiency into consideration when installing or upgrading their HVAC equipment. That’s what makes Bard’s through-the-wall products so enticing to schools, he said.
“We’re especially friendly for the retrofit project. Schools require units to heat and cool the classroom, and they also require a huge amount of ventilation, which can be a whole separate system,” Smith explained. “We can eliminate the need for additional ductwork by keeping all the work below the ceiling. We’re also able to offer the owner energy recovery.”
Bard’s demand-based approach to heating and cooling educational facilities effectively turns each classroom into its own individually controlled zone, where the unit only operates when the room is occupied. Additionally, the unit brings fresh air into each room only as needed, sometimes using an energy recovery wheel, which can improve IAQ and boost student performance while minimizing energy loss.
“Our equipment is geared to handle the classroom space,” Smith said. “We find that in school districts that measure the energy usage for their schools throughout the year, schools with our equipment consistently rank among the most energy efficient because they don’t have large systems that are running at part load all throughout the year.”
Smith said their geothermal products are also increasing in popularity. Bard’s Q/Tec geothermal heat pump unit was recently used in several McLean County Unit District No. 5 schools in central Illinois to decrease utility costs by 40 percent while also decreasing installation costs by 50 percent.
Carrier has also provided many geothermal heat pumps to schools, both for their superior efficiency and ability to share energy between heating and cooling zones.
“Induction beam systems are an increasingly popular choice to further reduce energy consumption while maintaining superior IAQ,” said Chadwick.
Chadwick added that some schools are also finding ways to store thermal energy as a load-leveling tactic in order to reduce the overall system capacity and peak-load energy needs. “One method is solar heating the entering outdoor ventilation air before it gets to the HVAC equipment, reducing the heating requirement,” he explained.
Smith added that the HVAC system is only going to operate at optimal efficiency if the staff understands how to properly use and maintain it. “Sometimes, districts will get top-of-the-line technologically advanced systems, but their maintenance staff won’t be able to use it,” he said. “What we do is simplify the complexity of the ventilation system.”
Just as high-efficiency equipment has become increasingly popular in schools over the past few years, energy auditing is also increasing in popularity. Some manufacturers, including Carrier, Mitsubishi, and others offer energy auditing services to schools in order to show how much energy the school is using and what changes operators could make to improve energy efficiency.
According to Mitsubishi Electric, sales representatives will work with a school's officials to orchestrate an initial energy audit. Then, subsequent energy modeling predicts how the Mitsubishi Electric systems will perform in the building.
Carrier also offers a K-12 energy assessment program, which it designed “to assist school districts as they face unprecedented challenges in their efforts to create healthy, high-quality learning environments while making fiscally responsible decisions for their community,” said Mark Rabbia, product business manager of commercial packaged rooftops and split systems at Carrier.
“Carrier’s goal is to aid administrators and school boards by identifying and remediating energy drains on campuses using cost-effective options and solutions,” Rabbia continued. “During the assessment, experts from Carrier’s energy services operations place a specific focus on lighting and mechanical systems, including the HVAC equipment, where the majority of the building’s energy use is concentrated.”
The most important goal of the school’s HVAC system is, of course, to keep students and staff healthy and comfortable, Rabbia said, adding, “Upgrading a school’s HVAC system to be more efficient has a positive impact on student performance, as well as the school’s operating costs.”
Contractors can find more ways to improve energy efficiency in schools and other buildings in ASHRAE’s Advanced Energy Design Guide, which provides the tools needed to achieve a 50 percent energy savings over buildings that meet minimum ASHRAE Standard 90.1-2004 requirements. To download the ASHRAE guide, click here.
Publication date: 8/5/2013