Novel Method for Assessing the Protection Lifetime of Building Coatings against Fungi

Abstract

The aim of this study was to develop a novel method for evaluating the service life of building coatings. In Stage 1, we assessed existing methods for determining the degree of fungal overgrowth on building materials (visual assessment, culture method, luminometric ATP (adenosine-5’-triphosphate) measurement, and spectrophotometric assessment of colour changes). Laboratory tests were carried out for 19 types of facade coating (mineral and silicone with/without primer, silicone paint, biocides) and 7 fungal strains (moulds Alternaria alternata, Aspergillus niger, Aureobasidium melanogenum, Cladosporium cladosporioides, Fusarium sp., Penicillium citrinum, and the yeast Rhodotorula mucilaginosa). The number of fungi on the facade coatings after 28 days of incubation was 1.7 × 105–4.6 × 105 CFUs (colony-forming units)/sample. The ATP content was 12 RLUs–30333 RLUs (relative light units). Colour change was ΔE > 5 depending on the coating type and fungal strain. A high or very high correlation was found between the ATP concentration (RLUs), colour change (ΔE), and the results of the culture method (CFUs/sample). In Stage 2, a new methodology for evaluating the protection lifetime of building coatings against fungi was developed, taking into account environmental conditions (impact of ultraviolet radiation, precipitation, presence of organic matter on the surface, quantitative and qualitative composition of bioaerosol). The developed method consists of one research cycle conducted in the laboratory, corresponding to one year under natural conditions. Preliminary verification showed the model to be compatible with long-term observations (3 years) of fungal growth on the facade coatings under real environmental conditions. The novel method could be used to design biodeterioration control and protection strategies for both new and cultural heritage buildings.