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As the building industry pivots toward electrification, decarbonization, and high-efficiency infrastructure, radiant heating and cooling professionals stand at the forefront of a major shift. At this year’s AHR Expo in Orlando, FL, Greg Cunniff, a HVAC Systems Consultant at Egg Geo, delivered a forward-thinking presentation titled Future of BEST – Net the Energy with Community Thermal Energy Networks, highlighting how hydronic systems, especially radiant, are central to the next generation of building energy infrastructure.

Cunniff introduced a model of scalable, interconnected energy systems called Thermal Energy Networks (TENs). These networks leverage the strengths of radiant systems—low operating temperatures, exceptional comfort, and hydronic efficiency—by combining them with technologies like heat pumps, waste heat recovery, and intelligent control.

Understanding thermal energy networks (TENs)

Thermal Energy Networks are district-style systems that connect multiple buildings with diverse energy needs into a shared thermal infrastructure. Instead of each building operating an independent heating and cooling system, TENs allow for energy to be transferred between buildings based on their individual loads. For example, a commercial building with a cooling demand during the day can share waste heat with an adjacent residential building needing space heating at the same time.

These networks operate through single pipe ambient temperature loops, which move low-grade thermal energy efficiently throughout a community. Hydronic radiant systems are an ideal match for this approach because they operate effectively at the moderate water temperatures typically used in TENs. This synergy allows radiant systems to serve as both heat sources and heat sinks within the broader thermal network.

The role of BEST in early-stage system modeling

A major challenge in planning complex energy systems like TENs is accurately estimating energy performance and cost in the early design phases. Traditional modeling software is often cumbersome, requiring dozens of input screens and extensive engineering time. To solve this, Cunniff introduced updates to the BEST (Building Energy System Tool) software platform.

BEST allows engineers and planners to model system performance using only five input screens, delivering quick, data-driven comparisons of different HVAC system types. It uses hourly weather data and bin calculation methods to strike a balance between accuracy and speed. BEST can now also account for features such as district energy pricing and interconnected building loads. Future versions of the software will also account for waste heat recovery.

By integrating with HS2 (Hydronic System Solutions) software, BEST offers a visual planning environment. Designers can map thermal networks over actual city layouts, define system boundaries, and visually model loop routing and load balancing across multiple buildings. This makes early-stage conversations with stakeholders more productive and actionable.

Real-world TEN applications

To ground his concepts in practical application, Cunniff shared real-world examples of TENs in action. One highlighted project involved the Penn South Towers in New York City, which face a significant winter heating demand. Nearby, the Tishman Speyer Post Office redevelopment generates excess cooling load during the same season. By connecting these buildings with a shared thermal loop, each property reduces its reliance on traditional heating and cooling equipment. This synergy results in lower energy costs and dramatically improved system efficiency.

Another example involved a mixed-use urban neighborhood with residential, institutional, and commercial buildings. The natural diversity of load profiles across the buildings allowed the thermal energy network to remain well balanced, reducing peak demands and leveraging radiant distribution throughout the district.

Wastewater energy transfer (WET) as a heat source

Cunniff also explored the use of Wastewater Energy Transfer, or WET, as a renewable and often untapped energy source. Most buildings discard significant amounts of heated water through showers, dishwashers, laundry systems, and sinks. This wastewater carries usable thermal energy that can be captured and redirected into the building's heating system or a larger TEN.

One case study discussed in the presentation involved Village East Towers in Manhattan, a mid-century high-rise complex of over 430 families. A NYSERDA-funded study explored how WET could be applied in this context. Using an above-ground PIRANHA unit, the system successfully recovered heat from wastewater streams, feeding it back into the building’s hydronic network. Despite infrastructure challenges such as aging piping and persistent leaks, the study demonstrated that even in retrofit conditions, wastewater heat recovery could contribute significantly to system performance.

Radiant systems, with their low-temperature supply requirements, are well matched to WET output temperatures, making this a promising integration pathway for both new and existing projects.

Image courtesy of IAPMO and Egg Geo

Integrated piping systems: A simplified approach

An important innovation presented by Cunniff was the Integrated Piping System (IPS), designed to simplify the distribution of heating, cooling, and domestic water services. Traditional buildings often require multiple parallel pipes—sometimes up to seven—for HVAC and water distribution. IPS consolidates these into one or two primary circuits using circulator pumps rather than valves, reducing complexity and cost.   

In an IPS setup, each terminal device—whether a radiant floor loop or fan coil unit—connects independently to the main loop using a dedicated circuit. On/off or variable-speed circulators manage flow to each zone, eliminating the need for balancing valves or mixing controls. This configuration allows for individual zone control while keeping the overall system hydraulically simple and self-balancing.

Radiant systems stand to benefit immensely from IPS, particularly in projects where mechanical space is limited or labor costs are high. Installers see reduced installation time, manufacturers can support integrated solutions, and building owners enjoy simplified maintenance and long-term reliability.

The central role of heat recovery

Cunniff emphasized that heat recovery is not a supplementary feature in modern hydronic systems—it is a foundational strategy. Whether within a single building or across a multi-building TEN, rejected heat from one zone should be seen as a resource for another. Advanced heat pump systems make this possible by using refrigeration circuits and buffer tanks to capture and redistribute thermal energy.

For example, when a cooling system removes heat from an occupied space, that energy can be redirected to a domestic hot water tank or another area requiring space heating. Radiant systems integrated into such networks can both receive and reject heat, serving as intelligent energy hubs within a building’s infrastructure.

Cunniff explained that in some applications, over 75 percent of building thermal loads can be met through internal heat recovery and network balancing, drastically reducing reliance on external energy sources and backup boilers.

How radiant professionals can prepare

In the final portion of his presentation, Cunniff encouraged radiant heating professionals to adapt their strategies to align with this evolving landscape. He suggested that radiant system designs should focus on low-temperature operation and integration with single pipe ambient loop systems. This means rethinking zoning methods, shifting toward circulator-based flow control, and adopting modeling tools like BEST to support early-stage design validation.

Image courtesy of IAPMO and Egg Geo

Contractors should begin familiarizing themselves with wastewater energy recovery equipment and strategies for incorporating them into radiant loops. Distributors and manufacturers should focus on offering circulator pumps, manifolds, and tubing solutions that are optimized for integration with shared energy networks. Design professionals are encouraged to specify components that operate efficiently at moderate temperatures and can accommodate both heating and cooling loads.

Image courtesy of IAPMO and Egg Geo

Ultimately, this shift toward integration requires a broader view—one that sees each radiant system not as a standalone application, but as part of a dynamic, interconnected energy ecosystem.

A smarter future for radiant systems

Greg Cunniff’s AHR 2025 presentation made it clear that the radiant heating and cooling industry is at a pivotal moment. As buildings and cities seek sustainable and scalable heating solutions, Thermal Energy Networks, Integrated Piping Systems, and advanced heat recovery strategies will define the next generation of mechanical design.

Image courtesy of IAPMO and Egg Geo

Radiant professionals are well-positioned to lead in this transition. With systems that already operate efficiently at lower temperatures and offer unmatched comfort and control, radiant technologies can serve as the backbone of these future-ready solutions.

The key will be in how the industry adapts—through smarter design, tighter integration, and a willingness to participate in the broader conversation about energy sharing, resilience, and carbon reduction. With the right tools, strategies, and mindset, the radiant sector can move beyond standalone performance and into a role as a primary player in community-scale energy solutions.