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Our vision of a world where buildings generate more energy than they consume challenges us to look beyond and, in some cases, beneath the surface. In our quest for a sustainable future, we’re helping clients tap the heat beneath our feet for reliable, eco-friendly heating and cooling solutions.
Geothermal energy is generated by the ongoing decay of natural elements in the earth’s core, a reaction that has been producing heat continuously for more than four billion years. This heat offers a powerful option as a consistent source of energy for the construction industry to reduce its environmental impact while maximizing safe, cost-effective heating and cooling practices.
Drilling: The Basics
While seasonal temperatures above ground can swing to extremes, not far below the earth’s surface, the ground remains at a relatively constant temperature year-round: 40°-70°F. Rock and soil below a building act as a heat sink, absorbing excess heat in summer, and as a heat source in winter when surface temperatures are lower.
Drilling technologies take advantage of the constant subsurface temperatures. The key mechanism is the heat pump connected to a system of underground high-density polyethylene pipes laid either horizontally or vertically, depending on the surface area availability and heating and cooling needs.
Geothermal heat pumps (GHPs) move heat from either a water or ground source to the structure using a closed or open loop pipe system. Pipes for water source heat pumps are submerged in a body of water, such as a lake or well, at a depth where the water will not freeze in the winter or get too hot in the summer. Refrigerant solution in the pipes absorbs or releases heat within the water source. Ground source heat pumps operate the same way, using the soil as the source for heat capture and release.
Horizontal geothermal installations are a closed-loop system that involve digging trenches a few feet deep and several hundred feet long. These GHPs extract heat stored near the surface and transfer it into a building for heating, and reverse the process to expel heat into the ground for cooling. Vertical systems are another closed-loop variety that require specialized drilling to depths ranging from 100 to 500 feet. U-bend pipe loops inserted in the ground are grouted to promote heat transfer and protect the deep earth environment.
Open-loop systems are categorized as direct use and district heating systems and geothermal power plants. In direct use and district heating systems, hot water from springs or reservoirs is pumped through a network of pipes to transfer heat to individual or multiple buildings. Geothermal power plants rely on wells drilled into the earth and dry steam or hot water piped to the surface to power a turbine that generates electricity.
Energy and Cost: The ROI
Geothermal energy exchange involves no combustion, unlike fossil fuels that release greenhouse gases when burned. The International Energy Agency estimates that new geothermal systems could provide as much as 600 terawatts of carbon-free power capacity by 2050. Considering that one terawatt hour can power the state of California for approximately a week and a half, this is a tremendous amount of energy.
While solar and wind renewable energies largely depend upon local weather conditions, geothermal systems work anytime, rain or shine, providing a continuous, uninterrupted energy supply. Because these systems eliminate the need for fuel oil or propane required by conventional heating and cooling methods, they also come with low operating costs and when properly designed and installed, can last 25-, even 50-plus years.
Whether retrofit into an existing structure or added to a new one, geothermal installations require upfront investment. Total cost and premiums vary based on project need and factors such as climate, soil quality, site size and accessibility, and excavation required. In general for commercial projects, a geothermal-supported HVAC solution may have an initial cost premium of 50-60% more than a traditional HVAC system. Rebates can help offset this premium, and improved energy efficiency will lower utility consumption, making geothermal systems a leading economical choice for longer term building ownership and operation.
Geothermal systems can deliver as much as six heating or cooling units for every unit of electricity used. Overtime, these systems can cut heating and cooling bills by 25-70%. The United States Department of Energy estimates that costs can be recouped in energy savings within five to ten years.
Tax credits can also help maximize savings. Under the Inflation Reduction Act, projects completed with geothermal pumps may qualify for a base tax credit of 6%, with eligibility for up to 30%, if projects meet specific requirements. Some situations can also quality for further credit. For example, coal-impacted communities that meet eligibility criteria may qualify for a 10% credit on top of the base 30%, with another 10% credit bonus for meeting domestic content requirements (Made in the USA).
On the local level, resources like the Database of State Incentives for Renewables & Efficiency (DSIRE) offer comprehensive information on incentives supporting renewable energy in the United States.
A Reliable and Sustainable Energy Future: The Market Forces
According to the U.S. Department of Energy, the nation’s annual renewable energy generation surpassed coal for the first time ever in 2022. Solar and wind energy are now two of the cheapest sources of electricity, and the market for geothermal solutions is growing with GHPs currently mobilized across all 50 states. Rising energy demand from households, businesses, and data centers continue to accelerate the call for clean energy development.
From promoting carbon-infused concrete to implementing stormwater pollution prevention plans to integrating solar arrays, Pepper’s energy solutions are answering this call. Our creative way of solving mechanical systems questions upholds our commitment to improve quality of life through the built world.
Pepper's Promise in Action: The Projects
Shaker Trace Nursery: a multi-building renovation on 16-acres owned by Great Parks of Hamilton County, Ohio. The facility is one of the largest native seed nurseries in the state, harvesting, processing, and storing native prairie and wetland seeds for habitat restoration projects. The renovation involves four enclosed structures and one shade structure that include a 200-year-old barn, greenhouse, equipment and seed-drying barns. The campus will be a Net Zero Energy facility, generating all of its energy on-site through solar panels and using geothermal heat, sourced from 20 wells at a depth of 300 feet each, to power the new facilities. Because the site is located on a former riverbed, the renovation required exceptional planning and scheduling to address complex environmental and engineering challenges.
Certifications earned acknowledge the meticulous planning and commitment to going beyond standard green building practices. These include LEED Platinum certification, the highest level of recognition from the U.S. Green Building Council; LEED Zero Energy, recognizing a source energy use balance of zero over a period of 12 months; and Pepper’s first SITES certification, given to projects that prioritize biodiversity and mitigate climate change while conserving resources, improving public health, and providing economic benefits.
Barrington’s White House: a three-story, 14,000-square-foot home built in 1898 turned elegant, high-functioning community center. The renovated structure has seven wells cored outside running 500-feet deep and circulating a mixture of water and glycol to provide heating and cooling from a 57°F base. With this and other environmentally conscious measures, the structure was the first to achieve LEED Gold status in Barrington, Illinois, and generated a 42% energy reduction.
Source: Pepper Construction, McWilliams Electric Renovate Two Chicago Landmarks | PowerForward DuPage
Lincon King Community Center: an 85,000-square-foot state-of-the-art community space for education, health, and recreation scheduled for completion in Fall 2026. Sixty geothermal boreholes drilled 500-feet deep under a parking lot, will be a perpetual thermal resource for the new center located in the Lincoln King neighborhood of Racine, Wisconsin. A safety-first mindset addressed excavation and risk mitigation early in the project, which put the right equipment in the right hands at the right time. Techniques like benching and sloping created safe platforms for workers and equipment, while proactive communication and planning helped avoid pitfalls associated with the need to restrict access to one-third of the site during construction. Combined with solar-power installations, the geothermal system will enable the facility to achieve Net Zero in one year.
Pepper Construction's Cincinnati Office: our 23,000-square-foot office building. Built approximately 110 years ago, it is now one of the oldest in the country to reach Net Zero Energy status. In addition to on-site solar power, a geothermal system of 16 wells fuels the structure’s radiant floor heating with year-round thermal efficiency.
Indiana University (IU) Health - Fort Wayne: a new five-story, 295,000 square-foot full-service hospital serving communities in Fort Wayne and northeast Indiana. Expected to open in 2027, The hospital will provide 140 beds, six operating rooms, 17 Emergency Department exam rooms, three catheterization laboratories, and four endoscopy rooms. A 300-well geothermal field beneath the property – a first of its kind in the IU Health system – will create more than $140,000 of annual operating cost savings and prevent 1,620 metric tons of carbon dioxide emissions per year, equivalent to carbon sequestered by 1,625 acres of U.S. forests in one year.
Source: Greenhouse Gas Equivalencies Calculator | US EPA
The strength behind what we do doesn’t always come from what we can see. Like any natural resource, the use of geothermal energy must be carefully managed, and with a mix of renewable technologies that includes geothermal solutions, we can bring the future of a decarbonized grid closer. Helping clients effectively unlock this underground potential for clean, continuous, resilient power is a cornerstone of a strategy that leverages the greatest opportunity for transformative change.
Thank you to the following members of the High-Performance team who contributed to this article:
Allison Biernacki, LEED AP BD+C, Project Engineer II, Pepper Construction Company of Ohio
Juanita Garcia, LEED AP BD+C, WELL AP, LFA, Project Executive, Pepper Construction Company
Calvin Young, LEED AP BD+C, NABCEP PVA, Project Executive, Pepper Construction Company of Indiana
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