Susceptibility of earth‐based construction materials to fungal proliferation: Laboratory and in situ assessment

Abstract

The impact of building materials on the environment and the health of occupants has become a priority issue. Ecological construction materials, such as earthen materials, are currently experiencing a regain of interest for both ecological and economic reasons. However, since microbial proliferation on indoor materials can induce a deterioration of the air quality in the building and lead to an increase in health risks for the occupants, the issue of indoor air quality raises questions about the utilization of earthen building materials and their possible susceptibility to fungal development. The microflora of earthen materials and its ability to grow on such supports have been little studied so far. This study focuses on the quantification of both bacterial and fungal microflora throughout the manufacturing process and the impact of extreme humidity, simulating a hydric accident, on microflora development analyzed on the surface of and inside earthen bricks. The initial microflora of these materials was dramatically reduced during the manufacturing process, especially after heat treatment for drying. The remaining microorganisms were observed to proliferate only under conditions of high humidity, in particular for earthen materials with vegetal aggregates. Moreover, in situ samplings were performed on naturally dried earthen materials used in buildings. The characterization of their microbial density revealed that it was higher than on manufactured specimens, while microbial concentration and detected taxa seemed mainly related to the room use and building history. These results provide a better understanding of microbial proliferation on these materials.