Assessment and optimization of environmental regulation measures for stone carvings from the perspective of algal growth

Airborne algae cause the main damage to the value and safety of open-air stone carvings. Due to this, certain sheltering measures are currently in use in order to protect them. This study aims to analyze the inhibition of algal growth on the surface of stone carvings using the two most currently commonly used protective measures that glass covers and pavilion covers by a coupled heat-and-moisture-transfer-algal growth prediction model. The impacts of the design parameters, such as the air exchange rate of the glass cover, the solar transmittance of the glass, and the moisture permeability of the bottom of the glass cover, are also discussed. The results show that pavilion cover effectively reduces algal growth on the vertical surface of the stone, while also effectively slowing down daily temperature fluctuations on the surface of the stone, which, in turn, can mitigate damage from thermal stress. However, the occurrence of more temperature extremes on the horizontal surface are reduced, thereby accelerating algal growth on the horizontal surface. Completely sealed glass covers promote algal growth compared to open-air conditions, in addition to the risk of deterioration regarding the thermal stress on the stone. In hot and humid climates, an air exchange rate between the glass cover and the outside air of between 0.5 and 2.0 times per hour is recommended; further, considering the algae growth and thermal stress damage to the stone, a smaller glass transmittance should be selected.

Automated summary

Airborne algae are the main cause of damage to open-air stone carvings, which are currently protected by certain sheltering measures. This study analyzes the inhibition of algal growth on stone carving surfaces using glass covers and pavilion covers. The results show that pavilion covers effectively reduce algal growth on vertical surfaces and mitigate thermal stress damage, while completely sealed glass covers promote algal growth and increase the risk of thermal stress damage. An air exchange rate between the glass cover and outside air of 0.5 to 2.0 times per hour is recommended in hot and humid climates, along with a lower glass transmittance.