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“Systems shall operate to permit independent and bi-directional heating and cooling for comfort and water heating …”

Chapter 17 of the 2024 Uniform Mechanical Code (UMC) focuses on a new generation of district energy systems, where energy flows easily between and among buildings. These systems operate without significant concerns about thermal losses, insulation, pressure or the high costs of central plants that provide only heating or cooling. In this model, each connected building can independently choose its HVAC and water heating systems, as they are linked to water at ground temperature. This approach avoids the need for expensive central plants or the installation of ground heat exchangers, even when such systems are applicable.

Thermal Energy Networks: A community asset

Thermal energy networks (TEN) allow public funds to cover infrastructure costs without the need for consumables, as water circulates and energy moves between buildings. In a recent article, RPA Technical Liaison John Mullen wrote, “Water has a particular talent for going with the flow, and it’s about time we started to use its full power and potential by circulating water and not wasting it. It’s a ripe opportunity for new communities to embrace what the next environmental neighborhood could do for its citizens, making waste heat an asset to a community’s energy use.

“Buildings, like people, have moods, or in the language of thermodynamics, microstates. Each zone, with its unique temperature needs, represents miniature challenges in energy management.”

By complementing rebates and individual incentives, public ownership of a district ambient temperature loop (ATL) or TEN removes the financial burden from building owners, enabling the application of technologies that further reduce both power and natural gas usage. TEN allows for both cooling or warming to be applied to decarbonization efforts. This is particularly important in addressing environmental issues associated with commercial buildings, where HVAC heat rejection contributes to global warming, and water heating increases on-site carbon consumption.

Cooling as a means to decarbonize is an effective environmental action for commercial buildings because modern piping, pumps, and equipment address these issues without requiring “extended or extreme” operation. No pilot projects or case studies are needed, as ATL systems have been in use since the 1970s. The key difference now is public ownership of a third central water system. Since TEN is a closed system, it is simpler to design and manage, as it is not subject to the complexities of individual water usage such as faucets or flushes. The TEN approach, which integrates HVAC and plumbing systems, allows the use of any water or ground heat source or sink for energy exchange. In a collaborative article by Jay Egg and Mimi Egg of Egg Geo, the duo wrote, “Geothermal heat pumps tied into building loops and TEN will eventually become as simple as installing a window air conditioner or clothes washing machine

By applying the bidirectional ATL loop concept within individual buildings, this allows our heating and cooling systems to contribute to decarbonization. Water, as the energy conduit, is a well-understood concept, leveraging existing skillsets while reducing capital expenditures and operating costs for building owners. This revenue-gathering infrastructure allows commercial building energy to be shared with neighboring residences, reducing operating costs even if only for one neighbor, some of the time. The result is energy efficiency without sacrifice — everyone uses less.

While these systems may sound futurist, the provisions in UMC help us get there. IAPMO and the Pace Energy and Climate Center at the Elisabeth Haub School of Law at Pace University (Pace) have agreed to jointly publish Chapter 17 of the UMC as a standalone document (IAPMO/UMC/Chapter 17-2024) to address the needs for enforceable safety provisions for geothermal district ambient temperature loop systems. The document “addresses the general requirements such as permitting, operating, and metering; and design requirements such as thermal resources, performance, and diversity factors.” As mentioned in the release statement, it can be viewed at: https://bit.ly/48pmzpO. Learn more at Radiantpros.org and Iapmo.org