From ASHRAE Handbooks: 

“The most extensive studies of the influence of floor temperature on feet comfort were performed by Olesen (1977a, 1977b), who, based on his own experiments and reanalysis of the data from Nevins and Flinner (1958), Nevins et al. (1964), and Nevins and Feyerherm (1967), recorded the following results. For floors occupied by people with bare feet (in swimming halls, gymnasiums, dressing rooms, bathrooms, and bedrooms), flooring material is important. Ranges for some typical floor materials are as follows: 

Textiles (rugs) 70 to 82˚F
Pine floor 72.5 to 82˚F
Oak floor 76 to 82˚F
Hard linoleum 75 to 82˚F
Concrete 79 to 83˚F 

To save energy, flooring materials with a low contact coefficient (cork, wood, carpets), radiant heated floors, or floor heating systems can be used to eliminate the desire for higher ambient temperatures caused by cold feet. These recommendations should also be followed in schools, where children often play directly on the floor. For floors occupied by people with normal indoor footwear, flooring material is insignificant. Olesen (1977b) found an optimal temperature of 77˚F for sedentary and 73.5˚F for standing or walking persons. At the optimal temperature, 6% of the occupants felt warm or cold discomfort in the feet. Figure 10 shows the relationship between floor temperature and percentage of dissatisfied, combining data from experiments with seated and standing subjects. In all experiments, the subjects were in thermal neutrality; thus, the percentage of dissatisfied is only related to the discomfort due to cold or warm feet. No significant difference in floor temperature was preferred by females and males.”