What is Hydronic Radiant Heating?

B. Turner

A hydronic radiant heating system relies on hot water to heat a room or home. These systems include a central boiler, which heats the water, as well as a series of pipes that transfer the water to different parts of the building. Hydronic radiant heating serves as a popular alternative to traditional forced-air heating systems, which rely on a central furnace and duct network to distribute warm air.

Concrete is typically used in conjunction with a radiant heating system.
Concrete is typically used in conjunction with a radiant heating system.

The hydronic heating process starts at the boiler, which can be powered by electricity or gas. A pump in the boiler sends the water through a manifold, which distributes the water to sets of piping below the floors of the home. As the hot water reaches the pipes, heat energy radiates upwards into each room. As the water cools down, it travels back to the boiler for reheating, and new hot water travels into the pipes. The average hydronic radiant heating can be controlled using a standard thermostat, similar to those used to operate a furnace.

Hydronic radiant heating systems are often broken down into different zones so that homeowners can decide to heat only a portion of the home. By breaking the system down this way, users are able to heat only a single room as needed, rather than the entire house. Each zone generally has its own thermostat or control panel.

Hard copper pipes may be used in these systems, though plastic pipes have become more common in many regions. Known as “pex” piping, these tubes are buried into concrete floors for protection. In homes with wooden floors, the pipes may be enclosed within modular flooring panels. These panels include special grooves that are specially designed to accommodate hydronic radiant heating pipes.

Hydronic heating systems are highly energy efficient, resulting in low operating costs compared to traditional forced-air systems. Radiant heat also is comfortable for occupants, with a floor that's warm underfoot. Compared to forced-air heating, hydronic radiant heating creates very even heat with few drafts.

One drawback to these systems is that they tend to require a substantial upfront investment. They also tend to be fairly inefficient in small spaces, and are better suited to large rooms or an entire home. Like all radiant heat systems, hydronic underfloor piping takes time to warm up, and also tends to cool down slowly when the thermostat is adjusted. In rooms where users would prefer more rapid temperature adjustments, forced-air heating may be a better choice.

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