Radiant & Hydronics

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AHR Expo 2026 made it clear that hybrid systems are no longer an emerging idea; they are the answer to the ongoing balancing act of meeting decarbonization goals while remaining realistic about the grid's capacity for electrification. Manufacturers emphasized systems that combine electric technologies, gas-fired equipment, and advanced controls.

In hydronic systems, the circuit usually passes through the boiler, which adds heat. When using a block heater and the boiler is off, it dissipates heat from the circuit. This heat loss must be considered when measuring the circuit's true "net" heating output.

Figure 1 shows the piping layout for an actual installation. It uses two boilers, fired in stages, to supply three areas of a building. One of those areas is sub-divided into three zones. The other two areas are handled by individual zone circulators. The "primary circulator" operates whenever any load circuit is on. All circulators are fixed speed. There's a partially closed ball valve at the end of the "primary loop."

Modern hydronic systems benefit from wider temperature drops, energy scavenging, and careful integration with domestic hot water.

A case study of a ThermaCEILing radiant system in a Connecticut home.

Single-stage non-modulating heat sources in zoned distribution systems often face short cycling, particularly with low thermal mass. When few zones are active, they struggle to dissipate generated heat quickly, causing temperature build-up and potential shutdown of the heat pump based on internal limits, with varied restart behavior depending on controls.

Can you speculate why heat delivery in zone 3 was insufficient before the helper pump? How could the piping system be improved, considering the wasted length of PEX-AL-PEX tubing from the manifolds to the floor panels in figure 2?

WarmlyYours reported strong third-quarter momentum, driven by a surge in Great Lakes radiant heating sales and steady gains across key product lines, signaling renewed stability in the broader housing and remodeling markets.

Last month, we reviewed the basics injection mixing. It’s a method for controlling water temperatures by regulating the flow of heated water “injected” into a circulating distribution system, while simultaneously removing an equal flow of cooler water from that distribution system. Any method that controls the rate of injection flow also controls the rate of heat transfer into the distribution system.