Buttock responses to contact with finishing materials over the ONDOL floor heating system in Korea

The ONDOL is a conventional floor heating system in Korea. Eight healthy college students volunteered as the subjects to investigate the buttock responses to contact with 10 types of the ONDOL covering materials: mortar, plywood, artificial marble, PVC, rubber foam, tempered glass, steel, insulation mortar, carpet, and aluminum. The temperature of water supply flowing into the floor coil underneath the floor surface was altered from 15 to 40 °C at 5 °C intervals. Floor surface temperature, skin temperature including buttock and subjective thermal sensation were monitored. The study revealed that the lower the contact coefficient of covering material, the more stable the temperature fluctuations in the floor surface and the buttock skin were. The floor finishing material should be chosen by the heat flux based on the heating load, and the friendship to human body. Using regression analysis, the neutral temperature of the buttock was determined at 32.6 °C.