Investigation of Building Materials Containing Algae-Prone Properties: Perspectives for Sustainable Façade Design

Abstract

During the last decades, research has been concerned with the topic of microbial colonisation of building components. Algae are in focus of investigations, as they occur worldwide and are conspicuous for the intense colouring of their photopigments. As a successful model of evolution, these autotrophic microorganisms can adapt quickly to new and extreme living conditions. It is therefore no surprise that algae have recognised and conquered the large areas of façades for themselves. As water is the most important basic prerequisite for biological life, building physics countermeasures focused on preventing condensation on façades – not only on external thermal insulation composite systems (ETICS). Architects and building planners are called upon to avoid algae infestation through constructive measures and the combination of suitable building materials as the visual aesthetics and long-term serviceability of building façades must be maintained. Investigations into the influence of coating formulations have so far primarily focused on binder systems, biocides, constructive and hygrothermal properties. Research on the algal susceptibility due to magnesium-containing fillers is not to be found, but these regularly constitute a large proportion of final coatings on building surfaces. The present work investigates the role of magnesium-containing fillers in the process of algal colonization of façade coatings. The effect of in-situ generated protons on the development of algal biofilms in the outdoor weathering experiment was investigated as a possible defence strategy by water-activated filler composition. Architectural engineering not only takes place on a large scale but begins on the micro scale of functional fillers, whose creative design has the potential to solve problems on a bigger scale. Understanding the mechanisms can help to avoid causes rather than fighting symptoms of algal colonization with organic biocides and high environmental risks.Practical measurement methods are needed that can be used in the laboratory and on site. The results achieved in this PhD thesis are based on the development of a novel application of the mobile fluorescence measurement system. The focus of current research is no longer only on control, but also on targeted establishment of algal biofilms on building surfaces. Recognizing that algae contribute to CO2 sequestration and climate control, the development of bio- receptive façades gained in research importance. Less complex and reliable methods for the detection of algal biofilms are required to reveal influencing factors in all cases that can be considered for more sustainable future façade design.