Brian is right. Newer radiant systems (not the old Levittown ones) often have separate balancing valves or temperature control valves to make a specific temperature in each room floor. Parquet and tile floors last longer if the temperature is kept constant so they do not expand and contract through temperature change. Have a radiant heating contractor install or set a controller for that room that maintains a fairly steady temperature. The floor temperature will not have to be as high to heat when the rug is no longer insulating the surface. 85 or higher can make your feet and legs hurt; below 80 is comfortable.