Effects of water retentive ceramic roof on the urban thermal condition

Heated buildings or residence roof tops have a great importance in the formation of urban heat island. Additionally, the surrounding conditions affect their roof temperature and indoor energy use. To mitigate these effects, a water retainable ceramic tile which was developed from industrial wastes was applied as a residential roof material. Field experiments were continuously conducted for a half year with a normal slate roof.

In summer, after a 10mm of rain fall, the temperature of the ceramic roof was reduced by the latent heat of water, and was more than 20 degrees lower than that of a normal roof at maximum. From a numerical simulation results, the reduction of sensible heat transport into the atmosphere was evaluated as 40 MJ/m2 per day. Moreover, this effect continued for 5 days at least.

In winter, ceramic tiled roof temperature hardly reached below 0 degrees compared with normal roof, because of the freezing point of water. The experiment showed that 15 MJ/m2 heat loss was prevented on a clear, calm night.

It was obvious that during more severe weather conditions, greater mitigation effects were performed.