As architects and designers, we are continually looking for meaningful ways our projects can integrate sustainability, economic performance, technical innovation, and design aesthetics. Ground source heat exchange (GSHE) systems are an emerging technology offering significant potential, and have been successfully integrated across a variety of project scales, from existing single-family homes to large commercial developments.
Particularly in drier, cooler climate zones like Colorado, GSHE systems are increasingly being utilized as an effective and energy-efficient method of heating and cooling buildings by leveraging the stable temperature of the earth below the surface. GSHE systems offer numerous benefits, although like any new technology, they are not without a few challenges. How can we use these systems to our best advantage? And what role will they play in the future of energy conservation and sustainability in architecture?
HOW DO GSHE SYSTEMS WORK?
Deep underground, the earth’s temperature remains a consistent 50-65 degrees Fahrenheit throughout the year, no matter what the weather is doing above. GSHE systems work by harnessing these underground temperatures and using them to heat or cool a building. A series of pipes, known as a ground loop, are placed hundreds of feet below ground and filled with a water-based liquid solution that circulates through the loop, absorbing the earth’s warmth and carrying it up into a building through a heat pump. The process is reversed for cooling, with the system transferring the heat from the building to the ground. Loops can be either horizontal or vertical (deep underground) depending on available land. Because of the depth of drilling required, vertical ground loops are often more expensive than horizontal to install, but require less piping than horizontal loops due to the increased stability of temperatures further underground.
Sustainability-minded owners are increasingly opting for GSHE systems instead of traditional furnaces and air conditioners, which are expensive to operate, have a limited lifespan, and contribute to greenhouse gas emissions. Although upfront costs of installation are higher for GSHE systems than for traditional HVAC units, the long-term life-cycle operating costs are greatly reduced. Heat pumps require significantly less electricity than traditional systems and are less vulnerable to fluctuating energy prices. GSHE systems also have fewer parts and components than traditional HVAC systems, contributing to increased lifespan and lower maintenance costs. Estimates vary, but sources suggest GSHEs can save building owners between 25% and 60% on energy costs over traditional HVAC systems that rely on fossil fuels. This is because the system is not actually generating warm or cool air, but rather transferring it—increasing the efficiency over conventional systems and resulting in substantial cost savings for homeowners over time, especially as energy prices continue to rise.
SOLUTIONS FOR A WIDE RANGE OF PROJECT TYPES
Margrit Benton’s distinctive Colonial-style brick home in Denver’s Morgan’s Historic District has been in her family for generations. Balancing a deep commitment to stewardship of the family home with a strong sense of responsibility toward sustainability and energy conservation, Margrit and her husband, Mark Nelson, opted to install a GSHE system consisting of four wells extending 400 feet beneath the earth as an alternative to traditional heating-cooling systems. They chose a GSHE system for reasons of economy, their commitment to environmental stewardship, and the systems’ reliability—providing consistently comfortable temperatures throughout the seasons.
The versatility, reliability and efficiency of GSHE systems and their potential to improve building performance without the need for fossil fuels aligns with the industry's shift toward greener building practices and is being implemented in projects at all scales, from both new and existing single-family residences like Benton and Nelson’s, to large commercial developments like the new 180,000 SF Clayworks Building B3 in Golden, Colorado.
The 12-acre former CoorsTek industrial site in Golden’s historic downtown is undergoing redevelopment by AC Development Co. as Clayworks, a new mixed-use district prioritizing health, wellness and sustainability. Currently under construction, Clayworks Building B3 will be anchored by CoorsTek’s new company headquarters. The mixed-use office and retail building incorporates a high level of sustainability measures, including green roofs and terraces, integrated photovoltaic systems, full building electrification, and adaptive reuse of portions of historic CoorsTek company buildings integrated with the contemporary new structure. The project was designed for a 32.2% reduction in embodied carbon, exceeding IECC baseline by 25%. Part of this strategy includes the installation of a GSHE system that will provide an energy-efficient and sustainable solution for heating and cooling, substantially reducing operating costs and environmental impact. The GSHE system at Building B3 is a hybrid system that works in tandem with a rooftop mechanical system that can accommodate peak loads for temperature ranges above or below a certain threshold.
GSHE systems are a viable option for many large commercial projects, especially those that are part of larger urban redevelopments like Clayworks, because they have enough land to accommodate the ground loops. However, one of the drawbacks of ground source heat pumps is that they are often not conducive to compact urban lots or densely developed locations. In some cases, geology can also factor into the viability of a GSHE system. Because of the intense amount of drilling required to install the pumps, they can prove cost-prohibitive at sites with exceedingly rocky, dry or hard soils. Extremely hot and humid climate zones are also less suited to GSHE systems due to higher ground temperatures, meaning the systems must work harder to cool a building. In conditions like those of Colorado, however, GSHEs can prove highly beneficial, especially for large-scale commercial buildings which typically spend a large portion of their operating budgets on heating and air conditioning. In larger projects, GSHE systems can be integrated with smart sensors and automated controls to maximize efficiency and performance while reducing overall energy consumption.
SUSTAINABILITY AND STEWARDSHIP
As Benton and Nelson discovered, utilizing GHSE systems for historic properties offers unique advantages for addressing the challenges of energy efficiency and comfort while maintaining historic integrity. The ground loop’s location underground and outside of the building allows for preservation of historic fabric that might otherwise require modifications. There is no need for visible radiators and ductwork in the interiors or mechanical units on the roof, which can detract from a building’s original appearance. Minimally invasive installation, and a reduction in visibly intrusive changes to a historic building, not only preserves a building’s historic integrity and marketability, but can also help with meeting regulatory requirements for properties like Benton’s that are designated historic landmarks. In addition, designated properties may also be eligible for historic tax credits that help offset the cost of excavation and installation.
Since many older buildings tend to have higher energy costs due to poor insulation or outdated heating and cooling systems, GSHE systems provide consistent and comfortable heating and cooling, avoiding the temperature fluctuations common with traditional heating methods which can potentially damage sensitive historical materials like wood, paint, or fabric. In addition to enhancing visual aesthetics, GSHE systems are also quieter than traditional HVAC systems, contributing to enhanced comfort for building users. Integrating geothermal systems into historic buildings ensures that these properties can meet current energy and carbon reduction requirements and contemporary desired comfort levels without sacrificing their historical integrity.
LIFE-CYCLE COST BENEFITS
Tapping into the earth’s consistent underground temperatures provides efficient and predictable heating and cooling solutions that enhance energy efficiency and reduce long-term operating costs. The lifespan of a GSHE system can range from 25-50 years for the ground loop and more than 20 years for the heat pump—a significantly longer lifespan than the average traditional furnace or air conditioning unit. These systems’ longevity further contributes to a building’s overall sustainability and reduces the need for frequent repairs or upgrades. GSHE systems also typically require minimal maintenance once installed, reducing the burden on building owners and making them an effective solution for long-term building performance.
Although the initial installation of a ground-source heat exchange system can be expensive, owners can recover this cost over time through an increase in property values and a reduction in energy bills. Tax incentives and rebates are available to help offset the upfront costs. The federal Residential Renewable Energy Tax Credit (ITC) offers homeowners a 30% tax credit on the total installed cost of ground source heat exchange systems that meet Energy Star criteria. Additionally, the Energy Efficient Home Improvement Credit offers up to $2,000 in tax credits for certain home energy efficiency upgrades, such as ground source heat pump systems.
Many government agencies also offer grants to help offset the costs of installation. The Colorado Energy Office, for example, sponsors a Geothermal Energy Grant Program “to advance the use of zero-emission, geothermal energy for electricity generation and space/water heating and cooling in homes, businesses and communities.”
CONCLUSION
Architects, builders and owners considering installing GSHE systems must ask the question, does the benefit justify the cost—not just of installation, but throughout the life of the system? The answer is not always, but in many cases, yes. As the demand for sustainable building solutions grows, ground-source heat exchange systems combined benefits of sustainability, economy and aesthetics for both single-family homes and commercial buildings. In residential settings, the energy efficiency and long-term cost savings provided by GSHEs make them a wise investment, despite the challenges of retrofitting existing homes. For newly constructed commercial buildings, the integration of ground-source heat pumps allows for energy-efficient designs that contribute to both operational cost savings and sustainability goals, while also meeting the increasing demand for LEED and other green building certifications. Eliminating the need for heating and air conditioning units to be housed within buildings allows architects and builders to experiment with innovative, more sustainable methods of construction such as slab-on-grade. GSHEs have the added benefit of reducing water consumption, as opposed to air conditioning units which consume significant amounts of water, especially in large commercial buildings.
2024 saw a rise in the number of GSHE system installations, with an expected 8.64% annual growth rate through 2028. Looking ahead, as technology improves and installation costs decrease, it is likely that ground-source heat pumps will become a standard feature in both residential and commercial construction. As technology continues to advance, increased adoption of GSHE systems will be an important step in achieving the broader goal of creating a built environment that is more sustainable, efficient, resilient and beautiful.
