Insulation, Radiant and Vapor Barriers - radiant heat insulation help ?

I'm installing radiant heat under the floor in the joists, & need to know what type of insulation is required
this is the kind w/water in pex type, hung from the joists
does anyone know?
Also I forgot to mention this area is the second floor above a radiant heated slab also

Radiant floor systems are usually for the first floor.It is somewhat unusual to see it on the second floor.This is because the cool floor effect is not associated on a second floor. With this in mind, you probably don't even need insulation between the first and second floor with this application. If you really want to put some, then use either a radiant barrier or a thin type of fiberglass insulation like duct insulation. Which ever is easier for you to do. In my opinion it is not going to make that much of a difference if you insulate or not.

Though when heat radiates, it does so in every direction and your proximity to the radiant heat plays a factor, between two conditioned spaces like the first and second floors, there will be little or no heat loss. Unlike on the first floor radiant heat system.

I have been advised by 2 heat contractors that specialize in installing radiant heating systems. that you want to insulate the space below the radiant heating tubes. they specify to leave an airspace between the second floor and the insulation. Since it is radiant it radiates in all directions and you want to redirect as best you can towards the second floor. I am currently installing the same type of system in a garage with a second floor. after I install all the pex loops with deflector plates then I am going to leave appox. 2-3" airspace and insulate heavily below with fiberglass batts. some contractors have specified to put foil backed insulation panels first and then fiberglass batts. end result you want that heat to be directed up.

Yes I found that the BC building code requires me to use r12 insulation
Thanks for your help