The purpose of this paper is to establish thermal comfort limits for the temperature of floors occupied by people with bare feet A knowledge of these limits is important when choosing flooring materials and -in the dimensioning of heated floors in bathrooms, swimming baths, gymnasiums, dressing rooms, bedrooms, etc.

Thermal comfort is defined as that condition of mind which expresses satisfaction with the thermal environment. It is a necessary condition for thermal comfort that the body as a whole is in thermal neutrality, i. e., that the person cannot say whether he would like a higher or a lower ambient temperature. The conditions for thermal neutrality have been established independent of the environmental parameters in several earlier works (Ref. 7,11,14,8). However, thermal neutrality for the body as a whole is insufficient in itself to ensure thermal comfort. It lS a further condition that the thermal influence on the body is not so nonuniform that it gives rise to local discomfort. Warm or cold discomfort of the feet can occur, for example, due to extremes of heat conduction to the floor. The present paper deals with the question of which surface temperatures floors of different materials should have in order to avoid discomfort for people with bare feet.

Until now very few investigations have been made with barefooted persons. Schedule (Ref. 15) performed an experiment with three persons, and Munro and Chrenko (Ref. 10) performed experiments with two persons. As the number of subjects was so small, it was impossible to determine floor temperature limits which, with reasonable certainty, would satisfy most people. The present paper deals with a series of experiments with 16 persons, the aim being to determine thermal comfort requirements for two characteristic flooring materials (concrete and wood). Moreover, a method is recommended for the characterization of flooring materials and for the determination of comfort requirements for other floors than those investigated. Finally, investigations are made by supplementary experiments of the influence on the comfort requirements of length of occupancy, activity, clothing, and of the general thermal state of the body.