Determination of the Critical Moisture Level for Mould Growth on Building Materials
type: CreativeWork
description: The susceptibility to mould growth varies between building materials. The factors that most affect mould growth, the relative humidity (RH) and temperature also vary in different parts of buildings. One way of preventing the growth of mould in buildings is therefore to choose building materials that can withstand the expected conditions. It is thus crucial that data are available to allow the correct choices of materials to be made, especially information on the critical moisture level for mould growth is needed. This is the lowest RH at which mould can grow on the building material. In this work, a variety of laboratory studies on mould growth on building materials at different combinations of RH and temperature were performed. Based on the results, the critical moisture level for the tested materials were determined. This made it possible to predict the propensity for mould growth on these materials in parts of building subject to known RH and temperature. To validate these predictions, the same materials tested in the laboratory were exposed to the conditions in three crawlspaces and three attics, with varying RH and temperature, for 2½ years. Good agreement was found between the predicted and observed mould growth. A new test method for determining the critical moisture level of a material was therefore developed based on the results of these studies. It was also shown that this method will make better prediction than traditional mould resistance tests, which evaluate the resistance to mould growth in a “worst case scenario”, i.e. at relatively high RH and temperature. The RH and temperature in buildings fluctuate, as does the length of time that the critical mositure level is exceeded. A simplified approach, considering the cumulative time that conditions had exceeded this level gave sufficient information to validate the laboratory tests. Using this approach will not underestimate the risk of mould growth, but will include a margin of safety. However, it was a…
abstract: The susceptibility to mould growth varies between building materials. The factors that most affect mould growth, the relative humidity (RH) and temperature also vary in different parts of buildings. One way of preventing the growth of mould in buildings is therefore to choose building materials that can withstand the expected conditions. It is thus crucial that data are available to allow the correct choices of materials to be made, especially information on the critical moisture level for mould growth is needed. This is the lowest RH at which mould can grow on the building material. In this work, a variety of laboratory studies on mould growth on building materials at different combinations of RH and temperature were performed. Based on the results, the critical moisture level for the tested materials were determined. This made it possible to predict the propensity for mould growth on these materials in parts of building subject to known RH and temperature. To validate these predictions, the same materials tested in the laboratory were exposed to the conditions in three crawlspaces and three attics, with varying RH and temperature, for 2½ years. Good agreement was found between the predicted and observed mould growth. A new test method for determining the critical moisture level of a material was therefore developed based on the results of these studies. It was also shown that this method will make better prediction than traditional mould resistance tests, which evaluate the resistance to mould growth in a “worst case scenario”, i.e. at relatively high RH and temperature. The RH and temperature in buildings fluctuate, as does the length of time that the critical mositure level is exceeded. A simplified approach, considering the cumulative time that conditions had exceeded this level gave sufficient information to validate the laboratory tests. Using this approach will not underestimate the risk of mould growth, but will include a margin of safety. However, it was a…
author: Johansson, Pernilla
language: eng
keywords: Building Technologies, Crawl space, Fungus, Mould resistance, Wood, Building materials, Mould, Critical moisture level, Attic, Relative humidity, Cyclic conditions, Laboratory method
date published: 2014
date modified: 2026-07-24T02:59:49Z
provider: University of Lund
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Byggnadsfysik LTH, Lunds Tekniska Högskola