Building facades often become black and/or green because of the airborne algae. The algal growth is mainly affected by the water supply, as well as other environmental factors also influence. In this study, we aimed to elucidate the relationship between the algal growth and environmental conditions. We carried out a field survey on the algal growth in Kyoto City. To investigate the factors that algal growth on the wall under the eaves, we calculated wall surface temperature and humidity considering the coupled heat and moisture transfer, and showed a possible relationship between algal death and high temperature and low humidity.
