Laboratory-based investigation of the materials’ water activity and pH relative to fungal growth in internally insulated solid masonry walls

This project investigated fungal growth conditions in artificially contaminated interfaces between solid masonry and adhesive mortar for internal insulation. The project comprised several laboratory experiments: test of three fungal decontamination methods; investigation of development of fungal growth in solid masonry walls fitted with five internal insulation systems; and investigation of volatile organic compounds (VOC) diffusion through materials and whole insulation systems.

One aim was to examine whether the alkaline environment (pH > 9) in the adhesive mortars could prevent fungal growth despite the water activity (aw) in the interface exceeds the level (aw > 0.75) commonly considered critical for fungal growth. The findings indicate that do-it-yourself decontamination solutions were inadequate for removal of fungal growth, while professional solutions were successful.

However, the choice of decontamination method was of minor importance in the case of application of internal insulation with high pH adhesive mortar, as the high pH adhesive mortars were found to inactivate existing growth and prevented spore germination during the experimental period. The three tested VOCs were capable of diffusing through most of the examined products and could potentially affect the indoor air quality.