The heating, ventilation and air-conditioning (HVAC) system in commercial buildings could take up to about 40% of the whole building energy consumption. Understanding nationwide energy savings potential in buildings for different energy conservation measures (ECMs) has a great impact on increasing the adoption rate of a variety of ECMs. The radiant floor system with a dedicated outdoor air system (DOAS) has proven to be an effective ECM for building cooling and heating, compared to the traditional HVAC system, such as variable air volume (VAV) system in some climate zones. There is a lack of study of the nationwide energy saving potentials of radiant the floor system for all climate zones and all the main commercial building types across the U.S. This paper investigated the energy saving potentials of the radiant floor system with DOAS for 9 commercial building types in 16 climate zones across the U.S. using DOE reference commercial buildings as the baselines. The baselines are ASHRAE 90.1-2010 and MCC-2012 compliant. The selected nine building types are: small office, medium office, hospital outpatient healthcare, restaurant of fast food, restaurant of dinning in, retail standalone, retail of strip mall primary school and secondary school. A whole building simulation program, EnergyPlus, was used for the simulation and the simulation results showed that the energy savings can go as high as 48% depending on the building type and the climate zone, compared to the traditional HVAC system defined in the ASHRAE 90.1-2010 and MCC-2012. The simulation study also showed that the radiant floor system is applicable to all climate zones although them are some savings variations among the different building types. The summarized nationwide energy savings in the U.S for 9 building types and 16climate zones could be used as a design or retrofit guideline for the radiant floor system if desired. In addition, some further studies are proposed for more detailed investigation of radiant floor systems' benefits.