What is Hydronic Radiant Heating?

What is Hydronic Radiant Heating?

Hydronics is the use of water as the heat-transfer agent in heating systems. Hydronic Radiant Heating is the most efficient method of heating. It is water or an antifreeze/water mix between 65F and 160F circulated in O² Barrier PEX tubing embedded in floors, driveways, walls or driveways. This type of heating system is much more efficient than forced air, and offers independent zone by zone temperature control. A Hydronic Radiant Heating system is as much as 50 percent more efficient than a forced air system. They last up to 40 years and offer independent zone by zone temperature controls. Maintenance for a hydronic system is minimal. The boiler will need an annual check-up, but most modern pumps are low maintenance using water to lubricate the parts. Your boiler or water heater will heat the water to the required temperature. A manifold will then distribute the hot water into O² Barrier PEX tubing that is embedded in the floor by a re-circulating water pump. O² Barrier PEX tubing is polyethylene tubing that’s leak-free, non-toxic, flexible and capable of handling high temperatures. You can set up multiple manifolds with multiple zones all controller by a floor sensing thermostat. This way, you can heat each area of your home independent of the others.

Hydronic Radiant Heating vs Forced Air
Hydronic Radiant Heating vs Forced Air

The types of radiant heat installations

The two main types of radiant heat installation methods are dry and wet. Dry installation is when the radiant O² Barrier PEX tubing is not embedded in some form of concrete. Wet installation is when the radiant tubing is embedded in the floor concrete slab,  in self leveling concrete (Gypcrete or similar) or dry pack concrete.

 

Dry installation method

Dry installation method, staple up with reflective plate.
Dry installation method, staple up with reflective plate.

Dry radiant heat installation methods in Canada usually involve under the plywood, between joists staple up or screw up using heat reflecting panels. This method is vastly inferior to wet install methods in performance and a major pain to install as far as the installer is concerned. After the tubing is secured to the plywood from below a reflective insulation must be installed underneath directing the heat upwards.

The advantages of the dry method are:
  • The only method that can be utilized if the floor above is not undergoing construction or renovation and the flooring cannot be removed.
  • Does not take away from the height of the room above.
  • No added expense of an overpour with gypcrete or concrete.
The drawbacks of the dry method are:
  • Cannot run loops close together, only one going and one coming between joists (if that).
  • The heat from the tubing take forever to penetrate the plywood (an insulator) and flooring above.
  • More labor intensive than staple down from above.
  • The  water running in the tubes must be is much higher, so it can penetrate above, than in wet installations and that extra heat can warp joists, heat up cold water lines sharing the joist space.
  • Since there is no thermal mass the moment the floor reaches the set temperature and heats shuts off the heat dissipates. This results in heat turning off and on must more frequently.

In general we try our best to convince our customers to get this idea out of their heads unless there is absolutely no other way of doing floor heating for a given area that they insist on. Been there, done that, we suffered and at the end the home owners were disappointed with the performance compared to the areas in their homes we did wet installations.

Wet installation method

Puck style insulation with concrete overpour
Puck style insulation with concrete overpour

 

Staple down with Gypcrete overpour
Staple down with Gypcrete overpour

 

Wire mesh on existing concrete , Gypcrete overpour
Wire mesh on existing concrete , Gypcrete overpour

 

Concrete acts as a large underfoot radiator storing and radiating the heat. Concrete has high density and low conductivity and will retain heat for a long time –> has a high thermal mass. Wood has a very high conductivity and low thermal mass. You have undoubtedly experienced how fast wooden decks or surfaces cool down once the sun sets. Large thermal mass  systems like wet installs take longer to heat up and need to run longer. Once reaching the preset temperature they hold it for a long time. To maintain temperature you just need to “trickle charge” the slab, a task modern modulating boilers can accomplish by firing at 15% of their max power resulting in extremely high efficiency operation.

 

The advantages of the wet method are:
  • The encasing material (concrete or gypcrete) thanks to its large thermal mass turns the whole floor into a large radiator.
  • Prevents creaking of upper floors.
  • With the insulation in basements and snow melts or the insulating plywood on upper floors being UNDER the tubing heat has no way to go but up where you want it.
  • Can be trickle charged resulting in high efficient operation with less on and off switching.
  • Can run at a lower temperature which is easy on the flooring material above.
  • Loop spacing is only limited by the minimum turning radius of the tubing used.

The wet by far is the most popular and most energy efficient radiant heating installation method.

The drawbacks of the wet method are:
  • Over-pouring with gypcrete on upper floors will cost extra and raise the floor by about 1″- 1.5″ depending on how level the floor is.

We are a strong proponent for the wet installation method. We can guarantee satisfaction and energy savings if there is a thermal mass.

Wet and dry btu comparison
Wet and dry BTU/h comparison. Note the loop spacing difference and heat requirements.

 

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