Hygrothermal behaviour of timber-framed exterior walls adjacent to wet rooms : A comparative study of different waterproofing membranes

Abstract

This study analysed the hygrothermal behaviour of timber-framed exterior walls adjacent to wet rooms exposed to critical Finnish climatic conditions. It examined the impact of water vapour transported by diffusion from a wet room into the wall structure. The first part of the thesis outlines the background needed for the above mentioned topic. Information about energy efficiency, insulation and moisture standards are given. An experimental and a calculational analysis were done to compare the results. The experimental analysis was done, using a weather simulation chamber to simulate specific climate conditions. During the experimental phase sensors were tracking the humidity and temperature at relevant positions inside the wall structure. The calculational part was done in two parts. The first part concerned heat conduction and the second one dealt with diffusive moisture transfer in porous material. The following are the main results of this thesis: •In Finnish climatic conditions timber-framed walls can be exposed to a very high level of diffusive vapour transport from the inside-out. •The moisture performance of a timber-framed external wall depends especially on the water vapour resistance of the materials used. •In case of localized moisture leaks, water can easily penetrate into the wall structure and cause damages to the wall structure in the longer term.