Hydronic Radiant System Piping

In-floor piping is usually used for hydronic systems in newly constructed homes. The PEX piping can be installed either in a concrete floor (with adequate insulation underneath), or fastened onto a wooden floor and covered with Gypcrete, a lightweight concrete product. Installation in Gypcrete allows heating to be done with a lower water output temperature, which raises the efficiency of the system.

Underfloor piping is usually used for retrofit hydronic systems, when it is too costly to pour all-new Gypcrete floors. PEX piping is fastened below a plywood floor (usually in an unfinished basement, where the joists are easily accessible), and then each floor joist space is insulated so the heat will move through the plywood into the living space above it. Heat moves more slowly through underfloor piping than in-floor piping, so additional heat delivery is required below certain temperatures.

Hydronic convecting radiators (baseboard radiators)* transfer heat by moving air through fins attached to piping that the heated water flows through. In a retrofit situation, this type of heat distributor is the easiest to install, but it requires the use of a high temperature water-to-water geothermal heat pump, which is much more expensive.

Traditional cast-iron hot-water or steam radiators cannot be used with geothermal heat pump hydronic radiant heat systems.

*Although they are called “radiators”, they transfer most heat by convection, not radiation.