The heating, ventilation and air-conditioning (HVAC) system in commercial buildings could take up to about 40% of the whole building energyconsumption. Understanding nationwide energy savings potential in buildings for different energy conservation measures (ECMs) has a great impact onincreasing the adoption rate of a variety of ECMs. The radiant floor system with a dedicated outdoor air system (DOAS) has proven to be an effectiveECM 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 buildingtypes across the U.S. This paper investigated the energy saving potentials of the radiant floor system with DOAS for 9 commercial building types in 16climate zones across the U.S. using DOE reference commercial buildings as the baselines. The baselines are ASHRAE 90.1-2010 and IECC-2012compliant. The selected nine building types are: small office, medium office, hospital, outpatient healthcare, restaurant of fast food, restaurant of dinningin, retail standalone, retail of strip mall, primary school, and secondary school. A whole building simulation program, EnergyPlus, was used for thesimulation 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 IECC-2012. The simulation study also showed that theradiant floor system is applicable to all climate zones although there are some savings variations among the different building types. The summarizednationwide 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 ifdesired. In addition, some further studies are proposed for more detailed investigation of radiant floor systems' benefits.