This part of ISO11855 specifies the basic definitions, symbols, and a comfort criteria for radiant heating and cooling systems. The ISO11855 series is applicable to water based embedded surface heating and cooling systems in residential, commercial and industrial buildings. The methods apply to systems integrated into the wall, floor or ceiling construction without any open air gaps. It does not apply to panel systems with open air gaps which are not integrated into the building structure. The ISO11855 series also applies, as appropriate, to the use of fluids other than water as a heating or cooling medium. The ISO11855 series is not applicable for testing of systems. The methods do not apply to heated or chilled ceiling panels or beams.