Depends on how cold you want the floor. We've done floors below 20 deg F....but that was for an ice skating surface. Seriously though, what is your application?
I have an installation in progress where we will be using the radiant floor piping for both heating and cooling for an atrium. The water temperature in cooling mode is reset to remain above the space dewpoint to avoid condensation on the floor. The benefit to the floor system is that the required temperature difference between the ambient and the floor does not need to be great since the surface area of the radiant panel is large. In my application the intent is to offset the solar load in the atrium. (The project should be complete in a year)