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First, double-check that you are plotting output variables correctly: Is Zn001:FLR001 really the floor surface for WEST ZONE?

If so, then mean radiant temperature (MRT) can be calculated in different ways. It seems that the output variable in your image is from a Zone object's calculations for MRT. This approach uses a surface area × emissivity weighted average of the zone inside surface temperatures. Another option would be to set Mean Radiant Temperature Calculation Type and Surface Name/Angle Factor List Name input fields in the People object for WEST ZONE in order to account for specific placement of occupants within the zone. Then, you want to add the Zone Thermal Comfort Mean Radiant Temperature output variable to the IDF and run a new simulation to generate that new MRT output variable.

Some things that might be causing this large temperature difference between radiant floor inside face temperature and zone air temperature:

• Other wall, window, and ceiling surfaces in the WEST ZONE are much hotter than the radiant floor surface
• Other wall, window, and ceiling surfaces in the WEST ZONE have much more surface area than the radiant floor surface
• The thermal absorptance of the inside material layer of the radiant floor surface is too low, reducing it's radiant heat transfer potential