Relationship between Environmental Conditions and Algal Growth on the Exterior Walls of the Ninna-ji Temple, Kyoto

Abstract

We can find that many building facades are discoloured black and/or green. Some previous studies showed that the soiling of building facades is caused by the growth of airborne algae. The algal growth is strongly influenced by the water supply, including the rain, the condensation, and high humidity. However, the influence of the other environmental factors, such as the solar radiation, the temperature, and the wind on the algal growth, has not been investigated yet. The relationship between the algal growth and the environmental factors on the building facades which the algae grow for long term has not been investigated. Therefore, we quantified the relationship between the algal growth and the environmental factors based on the field survey on the algal growth in Kyoto City and the measurement on the building facades at Kusyo Myojin Shrine, Ninnna-ji Temple in Kyoto, Japan. Kusyo Myojin Shrine was constructed from 1641 to 1647. Some parts of the roof, walls and the painting were repaired from 2004 to 2006. However, the building facades have already been colored black by the algal growth. To investigate the cause of the soiling by the algal growth, the ambient conditions, and surface temperature and humidity of walls were has measured since 2011. The soiling state of the walls was investigated by the L* values and the photographs of the walls. As a result, the order of the L* values of the wall surfaces agreed well with the darkness of the photographs. We concluded that the algal growth and death on the wall surface were affected by the surface temperature of the wall.