The discoloration of building facades due to airborne algae is observed in our surroundings. The growth conditions of these algae are not yet fully understood, and efficient measures for preventing the growth of the algae are not presently available. The objective of this study was to investigate the effects of the ambient environment and building structure on algal growth. A residential building in a cold region of Japan was surveyed. The roof was a multi-layered structure comprising a semi-transparent film, an air layer, and a layer of insulation from the outside, supported by rafters. The soiled state was visually observed by taking photographs. On the northeast (NE) and northwest (NW) roofs, several black stripes appeared 4 months after cleaning. The soiling increased in the spring and autumn. The soiling first appeared on the film backed by the rafter and then extended to the film backed by the air layer. The condensation time during the day in the rafter part was longer than that in the air-layer part. Condensation occurred during the night, but its frequency exhibited no dependence on the orientation of the roof. Algae tend to die when exposed to an environment with a temperature higher than 45°C. The NE roof had the shortest period with a surface temperature of >45°C. These measurements agreed well with the survey results, which indicated that the soiling mainly occurred on the NE and NW sides of the roofs. The time for algal growth was estimated under the assumption that algae can grow at surface temperatures ranging from 0 to 45°C, in agreement with the observed soiling. The observed soiling changes were well explained by the algal population calculated via a growth predictive model according to the algal temperature and relative humidity.

在我们周围的环境中，观察到由于浮游藻类导致的建筑立面变色。这些藻类的生长条件尚未完全了解，并且目前尚没有用于防止藻类生长的有效措施。这项研究的目的是调查周围环境和建筑结构对藻类生长的影响。对日本寒冷地区的一栋居民楼进行了调查。屋顶是多层结构，包括半透明薄膜，空气层和由r子支撑的与外界的绝缘层。通过拍照视觉观察污染状态。清洁后4个月，在东北（NE）和西北（NW）屋顶上出现了几个黑色条纹。在春季和秋季，污垢增加。污垢首先出现在由after子支撑的薄膜上，然后扩展到由空气层支撑的薄膜上。after子部分白天的冷凝时间长于空气层部分的冷凝时间。凝结发生在夜间，但其频率与屋顶的方向无关。当暴露于温度高于45°C的环境中时，藻类往往会死亡。NE屋顶的最短时间是表面温度> 45°C。这些测量结果与调查结果非常吻合，表明污垢主要发生在屋顶的东北和西北侧。藻类生长的时间是在假定藻类可以在0至45°C的表面温度下生长的前提下估算的，这与观察到的污物一致。