Underfloor Radiant Heat Systems

Radiantmax Underfloor Packages are designed for the installation of a radiant heat system under the subfloor. We include all the parts necessary to install a complete system, including Radiantmax aluminum heat transfer plates and Astro-Foil reflective insulation.

Don't be fooled by our competitors who try and sell larger diameter tubing systems with one tube per bay. They cost less but they just don't work well.

We use 1/2" BPEX tubing on 8" centers, and we highly recommend using aluminum plates. They increase heat transfer by over 30% which means lower water temperatures and lower heating bills! Insulation is also very important. We recommend adding insulation under the Astro-Foil to create a large R-Value differential between the material below the radiant tubing and the floor goods above the system.

Underfloor Packages
• UFP2: Underfloor Radiant Heat Package up to 380 Square Feet
• UFP3: Underfloor Radiant Heat Package up to 560 Square Feet
• UFP4: Underfloor Radiant Heat Package up to 750 Square Feet
• UFP5: Underfloor Radiant Heat Package up to 945 Square Feet
• UFP6: Underfloor Radiant Heat Package up to 1130 Square Feet

Call for larger area pricing!

Every Package Includes:
• 1/2” BPEX Tubing
• Copper Manifold Set
• Split Ring Hanger Brackets
• Tubing Cutter
• Aluminum Plates
• Reflective Insulation
• Instructions
• Tubing Diagram

Aluminum Heat Transfer Plates are installed between the floor joists to provide heat transfer across the bottom of the plywood. The 1/2" BPEX tubing fits into round channels formed into the aluminum. This heat transfer increases the amount of heat delivered by the tubing to the floor and helps keep the temperatures across the floor more evenly distributed. The plates can be stapled to the plywood using an electric stapler. Space should be left between the end of the plates to allow expansion of the aluminum. We recommend the use of aluminum heat transfer plates as part of an underfloor radiant system along with Astro-Foil insulation.

How do aluminum heat-transfer plates and insulation placement affect the heat output and recovery time of staple-up radiant floor heating systems?
A recent ASHRAE-funded study conducted at Kansas State University—and described in the Radiant Panel Association Newsletter, Radiant Panel Report—evaluated the performance of four different configurations of tubing and insulation, two of which used aluminum heat-transfer plates and two of which did not. One of the plate-equipped systems and one of those without plates were insulated with rigid foam insulation pressed tightly against the underside of the tubing; in the remaining two, the insulation was suspended beneath the tubing, leaving a 2" air gap. All four assemblies used identical 1/2-inch hydronic tubing stapled to the underside of the subfloor at 9 inches on-center.

The researchers found that when 140° water was circulated through the systems at 4 gpm, the plate-equipped test assemblies increased heat transfer to the living space by between 160% and 172%, compared to the systems without plates. The placement of the insulation accounted for that relatively minor variation in Btu output, with the closely insulated tubing transferring more heat than the tubing with the air gap did. (Because the study noted only average surface temperature, however, it's possible that the air-gapped insulation produced more uniform floor-surface temperatures.)

On the other hand, the insulation placement had a much more pronounced effect on the recovery times of the test systems. In test systems without aluminum heat-transfer plates, a 2" air gap beneath the tubing resulted in a 235% increase in ramp-up time, the time needed for the system to reach a steady-state heat output. Further information on ASHRAE Research Project 1036, "Develop Simplified Methodology to Determine Heat Transfer Design Impacts Associated with Common Installation Alternatives for Radiant Conduit," is available from ASHRAE.

Floor Output at 140°F Inlet Temperature: Output in Btu/hr/sq. ft
No plates, 5/8" air gap		23.5
No plates, 2" air gap		26.2
Plates, 2" air gap		42.0
Plates, 5/8" air gap		46.3
Average test results at steady state with a 140°F inlet water temperature.

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