Fred .......... read your entire website this afternoon. What a great resource!
I agree with your material expect the claim concerning no value in using the aluminum heat panels [EMISSION PLATES:
I am interested in your thoughts of the research from Kansas State: 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.