The Crozet Elementary expansion project took its first steps in March, as two test wells were drilled on the north side of school grounds in preparation for a new geothermal ground HVAC system. Data from the 550-foot deep test wells was used to help inform contractors bidding on the project and also to adjust design details as needed. Matt Wertman, senior project manager for the county, said it will be the first geothermal HVAC system in a county facility.
“Geothermal systems utilize the earth’s temperature for heat exchanges [i.e. heating and cooling] since the earth’s inner temperature is always constant,” said Wertman. “A heat pump cycles water through long loops of underground pipes that then transfer heat from ambient air in the building to the ground and vice versa.”
The recent testing helped to determine the soil and rock conditions and thermal conductivity at that 550-foot depth. Thermal conductivity is a measure of the capacity of the soils and rock to conduct heat, and a higher soil conductivity allows heat to be exchanged within the soil and rock faster, which in turn affects the layout of the system’s closed ground loops.
“The tests were conducted over a 48-hour period after the wells were drilled,” said Wertman. “The testing went well and the results are being used to determine if the size of the wellfield needs to be increased or decreased. We just received the final test results and are still analyzing them to make this determination.” The test wells, drilled in the area currently serving parent pickup and the gravel parking lot, won’t go to waste. They’ll be utilized as part of the final wellfield when complete, all of which will be under the planned new bus loop.
“The geothermal system will be used for a good portion of the [campus],” said Wertman, “including the new classroom addition, the new kitchen addition, and most of the existing classrooms on the back side of the school. Much of the central core of the original building, such as the offices, the library, and the cafeteria, will still utilize existing HVAC systems.” Many of the rooftop units that serve those areas have been replaced in the last five years and still have a useful life.
“A geothermal system does come with a higher up-front cost than other HVAC systems, but the annual operating costs are much lower,” said Wertman. “A good portion of the initial up-front cost was offset by the fact that we did not have to make upgrades to the current system to accommodate higher energy usage.” He estimates that, combined with savings from other design features such as the type of building envelope and window glazing being used, the county projects a savings of about $42,000 per year compared to the current building’s systems.
“Also,” said Wertman, “the projected lifespan on a closed loop system, such as the one designed for Crozet Elementary, is 50 years, whereas other comparable systems have an estimated 25-year lifespan. This, in turn, reduces the maintenance costs on the system. For Crozet, our conservative estimates showed a total of $2.2 million in operational savings over a 25-year period, with the return on investment occurring around the 7-year mark.”
The expansion project will also replace the school’s current underground fuel oil tank, which operates the building’s water boilers, with new heat pump water heaters that are tied into the geothermal wellfield. “A temporary fuel oil tank will be utilized during construction so that the old fuel tank can be removed to make room for the new kitchen addition on the northern end of the site. The new closed-loop geothermal system allows us to remove all combustion equipment from the school without making use of expensive electric boilers, which can consume large amounts of electricity.”
Heat from the earth will be transferred via the geothermal loop and then used to heat water for the sinks and kitchen through these units. It is important to note that this system is a closed-loop system, meaning that when installation is completed, the only exchange between the loop and the ground is energy in the form of heat. No water is taken from or injected into the ground.
The county is excited about this opportunity, as it aligns well with the county’s Climate Action Plan, passed by the Board of Supervisors last October, by helping to reduce fossil fuel consumption in county facilities.
The school expansion project contains other sustainability features as well. “I’ll also add that the new classroom addition is designed to be solar-ready,” said Wertman. “It won’t include new photovoltaic panels, as we knew we could not fit those into the budget, but the addition will be able to accommodate them when funding becomes available.”
Work on the project is expected to begin on time. “The design team was very pleased with the low bid that was received, and a Notice of Intent to Award was posted for Nielsen Builders, Inc. out of Harrisonburg,” said Wertman. “Construction is still anticipated to begin this May. One of our first priorities upon issuing a Notice to Proceed will be to begin drilling the remaining the wells for the geothermal HVAC system.”