Thermalboard Compared to
Radiantec Underfloor Heat Transfer Plates

Brand Names: Radiantec Do-It-Yourself Underfloor Radiant Heating Systems

Radiantec discusses several different methods of applying radiant heat on their web site however they are best known for promoting underfloor heating because it is most accessible to DIY homeowners. Thermalboard also can be installed by any knowledgeable general contractor.

These types of systems where radiant tubing, and sometimes aluminum plates, are installed below a subfloor are at the immediate performance disadvantage of having to push heat through the resistant subfloor before reaching the flooring goods. Here we will address underfloor systems with aluminum plates.

Issues to Consider


There is an enormous difference in performance of underfloor aluminum plate staple up systems and Thermalboard. Where Thermalboard needs 108F supply water temperature to meet a 20 btu/sq/ft load, an underfloor aluminum system requires 145 F!!

At these type of temperatures, high-efficiency heat sources will not condense, eliminating the energy efficient benefits of these costlier appliances. The life cycle costs for operation of an underfloor system are much higher that our Thermalboard design.


  • Response: While underfloor systems must deliver heat from under the floor through the subfloor and floor goods, Thermalboard is immediately under the floor goods resulting in much faster response time.
  • Heat Sources: We agree with Radiantec that a qualified general contractor can install the radiant panels and radiant tubing. However, only qualified plumbing, radiant and mechanical contractors should install the heat sources, pumps, piping and controls of a system.

    There are many contingent liabilities with a DYI person installing the mechanical portion of the system, not to mention code violations in many jurisdictions, and who is going to service your system in the future?

  • Applications: Underfloor plate systems are sometimes the only choice such as under existing installed hardwood floors but this is not the best choice otherwise.
  • Noise: There is a long history of underfloor aluminum plates making irritating expansion noises upon start up as the required high temperatures required hit cooler plates. Proper installation is critical and seemingly evasive. You should also use weather responsive controls to lower the supply water temperature when possible.
  • Insulation: It is critical that one installs 2” thick foam board under these systems with zero infiltration leak paths. Fiberglass batt is neither effective or durable.
  • Cost: While the aluminum plates may cost only $1 per sq ft, this type of system is very labor intensive if installed properly. If one counts the cost of labor, underfloor is not the best choice.



Performance Data. For purposes of comparison, select a given R value (resistance of radiant system and flooring goods)… lets say R-1. Follow that line down to 20 (btu/su/ft) output on the x axis and then straight down to the water temperature required to meet that load, at the bottom. The lower the temperature, the more efficient the system type.

This data is provided by the particular manufacture or from the Design Manual of Zurn Radiant, a leading manufacturer radiant tubing.

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