Experimental and Numerical Investigation of Mould Growth Risk on Wooden Load-Bearing Structure in Hemp-lime Concrete Facades

Abstract

The need for reducing the environmental impact of the production of building materials has accelerated the emergence of new types of bio-based façade systems. Some of these systems are claimed to have hygro-thermal properties that eliminate the need for a dedicated air and/or vapour barrier as a part of the façade buildup. This paper presents a risk assessment of moisture-related deterioration of the wooden load-bearing structure in an existing hemp-lime concrete building façade system constructed without a dedicated air or vapour barrier in Aarhus, Denmark. Destructive investigation found no mould on structure. The façade was then modelled in WUFI 2D and calibrated using time series data from field measurements of temperature and relative humidity internally in the construction and in its surroundings. The calibrated WUFI model was used to simulate the annual moisture cycle using different initial conditions and weather data. The simulation output was analysed for the risk of mould growth at the wooden load-bearing structure using the Mould Growth Index. Results indicate that the initial moisture content of materials, the position of the wood structure, and the season of construction completion is important to consider to minimise risk of mould growth in the build-up.