Few radiant floor heating systems could benefit from using emission plates.

   Radiant thermostats are very sensitive, as the temperature goes up during the day it shuts the radiant off. In the evenings when the temperature drops one degree below the comfort setting the radiant system is turned on. It only needs to "ramp-up one degree to satisfy the thermostat.
   By using the 3/4" pex staple from Peter Mangone Inc. on 1/2" pex, on 8" centers, with 120 to 130 degree water, and using 500 ft. loops, I have designed thousands of radiant systems in the last twenty years (many in Alaska) that are quite, affordable and efficient, with nothing more than staples.

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.

Answer: There is still no overall change in the efficiency of the radiant system. They are talking about percentage of change in the speed of heat transfer. A very sensitive thermostat (one degree differential) causes short cycles of heat input to the bottom of the floor and a nearly constant out put to the heated area. As the testing shows, an air gap does improve spreading the heat output. I have found that using a very small air gap (1/8") allows a rapid response, an even output without streaking and more than twenty Btu's per Sq. Ft. Radiant systems are rarely allowed to cool down and seldom need to have high rates of increased transfer output, in that case plates or floor contact would increase the response time. If the thermostat has a one degree differential, the system never needs a rapid increase of temperature. The bottom line is that the staple up system that I design with, does maintain the one degree differential and it does have the same efficiency as other systems including Plated, grooved subfloor or Gypsum. Any change of efficiency must answer the question of where did the heat go? The only place you can loose efficiency is through the envelope or out the chimney.
   It has not been proven that setback thermostats save energy with radiant floor systems so the speed of recovery is not a factor in radiant floor heating systems. One factor that could save energy with today's modulating/condensing boilers is the return water temperatures, I design with 120 degree supply water temperatures which is 10 degrees lower than the plate systems use. Another thing I design with is 500 Ft. loops, this is one thing that few designers use. 500' loops do return lower water temperatures to the heater which does significantly increase efficiency and as I have proven in over at least 5,000 system designs does work well. A more even heat output is best for hardwood floors and is more comfortable on tile.
   This study did not show any loss of efficiency. I have found that a very small gap (1/8") works best. Plates can cause streaking in heat output. A more even heat output is best for hardwood floors and is more comfortable on tile.
Comparing a 2" air gap is not fair in a comparison as is the unrealistic 4 gpm, a 1/2" radiant loop normally flows at less than 1 gpm. High flow rates gives high return water temperatures and causes short cycling which greatly decreases the efficiency of the heater.