A systemic approach to moisture problems in buildings for mould safety modelling

Abstract

Mould growth in buildings can have negative consequences on health, comfort, and durability of construction and can cause a significant problem for inhabitants. Confronted with significant uncertainty, deterministic tools supporting design have proved insufficient for decision making. A tool that addresses the probabilistic risk/reliability analysis of building performance is needed. A systemic approach provides a proper theoretical base for the analysis. Based on a qualitative fault tree analysis, structure related vulnerabilities to moisture problems have been classified at different levels of the building construction: whole structure, component or material. A general model for evaluating the reliability of structures with respect to mould safety and based on the concept of systemic analysis is applied to moisture problems in buildings using a probabilistic limit state approach.An example of a risk analysis of mould germination on the inner surface of a wooden roof panel in a cold attic is calculated using the proposed methodology. The surface's relative humidity (given certain surface temperature interval) is chosen as a performance aspect. The performance criteria for mould germination on wood are also treated as a random variables. The probability of mould germination is evaluated for different attic floor constructions in which changes to the construction were introduced on the material or component level. The application of the probabilistic model of mould germination makes comparisons of alternative cold attic constructions possible. Uncertainties coupled to the proposed methodology are discussed.