HAM and mould growth analysis of a wooden wall

Abstract

Abstract The aim of engineers is to design structures, while minimising their energy dependence and create a suitable environment for living. Some of the most important factors for maintaining the indoor environment are temperature and humidity. Unsuitable combinations of heat and moisture (HAM) could indicate a danger of mould growing. The mould’s existence influences the reliability and lifespan of a structure. Some materials, for example wood, are very sensitive to mould growth. To analyse a structure for mould growth risk it is necessary to know the values of temperature and relative humidity on the surfaces and inside of structures. There are two possibilities to acquire these quantities; taking measurements at a construction site or in a laboratory, or applying numerical solutions using an accessible programme. One such programme is Wufi, which has been developed especially for HAM analysis. An advantage of measuring at the construction site is the reality, which is not affected by numerical errors. On the other hand, numerical analysis usually needs lower costs and does not demand so much time to simulate long term periods. From the point of view of accuracy, it is suitable to verify the numerical solution with measurements. The aim of this paper is threefold. First, to analyse the risk of mould growth. Second, it presents a verification of numerically calculated data using Wufi 2D against actual measurement data acquired from a real structure, which is presented by a low-energy house located in Oulu/Finland. Third, to prove that the form of low-energy building structures do not increase mould growth risk. After carrying out the verification, the received outcomes are utilised for mould growth analysis. For an expression of reality in the numerical solution, a transient simulation was needed. The received outcomes were then used for mould growth analyses. There is a possibility to predict real mould growth risk inside the structure and on its surfaces, corresponding to the critical relation between temperature and relative humidity, which separates favourable and unfavourable areas for mould growth.