Thermalboard Compared to Underfloor Radiant Heat Transfer Plates

Common Brand Names: Radiantec
Thermalboard Compared to Gypsum Concrete Pour

Underfloor staple up systems are primarily promoted by online radiant heating supply companies serving the DIY market because the system is easy to explain and supply giving the impression of lower cost.

These types of staple up systems are rarely used by professional radiant heating companies, particularly when grappling with the design challenge of retaining existing hardwood floors in a home remodel. Professional installers also don’t use these types of systems because of the significant technical and economic downsides.

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Issues to Consider with DIY Underfloor Radiant Floor Heating Systems

Poor Performance of Staple-Up DIY Systems
Thermalboard’s high performance originates from our patented board design. Because our high heat transfer aluminum surface is right next to the floor covering, a lower supply water temperate is required. In contrast, underfloor systems are insulted by the subfloor, which means heat needs to travel through the subfloor layer before finally reaching the surface of the floor. This extra layer results in a significant cost increase, especially over the product lifetime. 

Thermalboard only requires a supply water temperature of 108°F, compared to an underfloor aluminum plate system which requires a whopping 145°F water temperature! Simple physics dictates, the higher the water temperature required to heat a space lowers the efficiency of the radiant heat system significantly.

Compare the performance chart at the bottom of the page for a typical underfloor application with aluminum plates. The underfloor performance difference compared to “above floor” solutions such as Thermalboard are enormous.

Benefits of Thermalboard Radiant Floor Heating


Cost Effective


Low Profile (5/8")


Easy Installation


Factory Direct


Free Freight


High Performance


Layout Design


Remodel Friendly


Light Weight

Thermalboard Installation
Thermalboard Installation

Thermalboard is far more cost efficient than DIY underfloor radiant heat systems

 Lower material costs, but higher installation costs for underfloor systems

While the aluminum plates may only cost $1 / sq.ft, installing this type of system properly is extremely labor intensive. It is far easier and faster to install Thermalboard on top of the subfloor rather than beneath it. It’s also more heat efficient.

Life Cycle Costs: Much higher lifetime operational costs due to higher water temperature required.

Mechanical Operational Costs: Most radiant floor systems utilize a condensing boiler or water heater. The condensing in these heaters, which generate the cost savings, occur below a 135F degree exit temperature. If the radiant system requires temperatures higher than 135F, then the actual heat source efficiency drops to about 85%.

The premium price you paid for the condensing heat source is lost and your energy bills will be higher. Underfloor systems often require water temperatures above 135F, further increasing the life cycle cost of your system. Lower temperature equals lower costs — and better comfort!

Design Performance Issues with Underfloor Systems:

  • Response Time: While underfloor plate systems deliver heat from under the floor, through the subfloor, then up through the flooring goods (hardwood, carpet, tile, etc.) Thermalboard is installed immediately under the floor, resulting in much faster response time for heat delivery.
  • Noise: There is a long history of underfloor aluminum plates making irritating expansion noises when turning on the system. These sounds occur when the required high temperatures come into contact with cooler plates. Proper installation is critical and seemingly evasive. You should also use weather responsive controls to lower the supply water temperature when employing this application to avoid high temperatures shocking the system.
  • Insulation: It is critical that one installs 2 or more inches of foam board under these systems with zero infiltration leak paths. Fiberglass batt is neither effective or durable in horizontal subfloor application. Meticulous installation that avoids “points of infiltration” is critical in lowering the already higher heat loss of these systems.

Installation Videos


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