Low-Temperature Hydronic Radiant Heating…

… is considered by many to be the most comfortable, efficient, and versatile residential heating system available.

So what is it and how does it compare to the other common heating system – forced-air convection ?

Radiant heating is a process of heating objects throughout the building which then transmit their heat to all cooler objects in their line of sight (so to speak) by radiation – no air movement required. Rooms feel much more comfortable and uniform when all objects are warmed (and, thus, drawing less heat away from your body)… and forced-air convection, simply put, doesn’t do this well. The most basic examples of home radiant heating include fireplaces, woodstoves, and electric-resistance space heaters for which no other distribution system is required; however, as mentioned, they are limited to heating objects in their proximity – in their line of sight. Hydronic radiant systems have their heat sources located remotely (e.g. boilers and heat pumps in a mechanical room or basement) and transfer their heat to a water solution which is then pumped through a series of small-diameter pipes to various objects throughout the living space, for example floors, baseboard units, and radiators.

Hydronic radiant heating offers several advantages over forced-air convection:


  • Can produce a near-ideal room temperature profile – warmest at your feet, cooler at head level

  • Eliminates drafts and doesn’t dry out air
  • No noise associated with air blowing through ducts and grilles


  • Does not redistribute air-borne particles including dust, allergens, and pollutants
  • Reduces venting requirements → less potential for carbon monoxide leakage

Versatility, Adaptability:

  • Easily zoned
  • Distribution system – small diameter pipes – is less intrusive, facilitating retrofits as well as new builds
  • Choice of heat emitters: baseboard, radiator panels, and/or embedded in floor/wall/ceiling
  • Multiple loads are possible: space heating, domestic hot water, pool/spa heating, snow melt, towel warmers, garage floors
  • Embedded emitters are out of sight

Energy Efficiency:

  • Cheaper to distribute heat by pumping water than blowing air
  • Room temperature profile enables comfort at lower thermostat settings
  • Does not produce air pressure differences which can increase leakage to/from outside

Frankly, the only disadvantage versus forced-air convection is that a purely radiant system is not practical for air conditioning due to condensation considerations. Even that can be overcome by connecting one or more of the hydronic zones of a heat pump system to an air-handler and duct system or to one or more hydronic fan coils for individual room control.

Low-temperature hydronic radiant heating is a relatively new variation of radiant heating to North Americans, but has been popular in Europe for years where energy costs tend to be higher. Historically, boilers produced water between 160F and 200F for distribution to baseboard units or radiators. These high temperatures were required to deliver sufficient heat to the space that each emitter serviced and to protect the boiler from corrosion and premature failure, but they resulted in low – 80 to 85% – operating efficiencies. Modern “condensing” boilers can operate at lower temperatures, enabling efficiencies greater than 90%. Heat pumps – geothermal and air-sourced – operate at even higher efficiencies (300% or more, in many cases), but are limited to producing maximum water temperatures of 120 to 140F. While this is typically not an issue for in-floor radiant, it is for conventional baseboard and radiators. In recent years, however, a few manufacturers have addressed this limitation by designing models that are more efficient heat transmitters enabling lower source water temperatures. In fact, even hot water heaters – the kind you normally use to heat your domestic water – can be adapted as the heat source for many smaller – one- or two-room – systems.

In addition to enabling the highest energy efficiencies, low-temperature systems are even more comfortable and versatile than their higher-temperature predecessors.

With so many choices and combinations of heat sources and emitters, it’s critical that you choose a contractor with the capability to design, engineer and install a custom solution for your application.  At Lake Country Geothermal, we are perpetually training to stay abreast of new products and innovations… and we always start a project from the perspective of what our client is trying to achieve and let those objectives lead us to the combination of technologies and products that will best meet them. Contact us today to discuss your project or idea, and begin to explore the many possibilities of low-temperature hydronic radiant heating.