ISO 18566-1:2017 specifies the design, test conditions and methods for the determination of the cooling and heating capacity and control of radiant heating and cooling panels with an open air gap. This document applies to all types of prefabricated radiant panels that are part of the room periphery such as ceiling, walls and floor. ISO 18566-1:2017 is applicable to water-based heating and cooling panel systems (free hanging) in residential, commercial and industrial buildings. The methods apply to systems mounted to the wall, floor or ceiling construction with an open air gap. ISO 18566-1:2017 does not cover panels embedded into ceiling, wall or floor structures and hybrid (combined thermal radiation and forced-convection) ceiling panels. ISO 18566-1:2017 specifies the definition, symbols, comfort criteria, technical specifications and requirements of ceiling mounted radiant panels.