The thesis presents a comprehensive study of the moisture transfer through some coated substrates and the influence of varying environmental conditions with the objectives to procure relevant hygrothermal material properties of organic coatings and porous materials. The purpose of this work was to increase the understanding of how moisture and other environmental factors affect the moisture transport and hence the moisture accumulation of coated substrates. This was approached through a theoretical portion, an experimental investigation and a moisture performance analysis, that was further divided into six tasks presented as follows:

Determine what deterioration mechanisms are involved and what factors affect the deterioration of different coated substrates when exposed to a severe environment. Present an overview of existing critical performance criteria for the different substrates To study the theoretical formulation of water permeation in porous materials and organic coatings, and the need of quantifying their transport properties and dependency of other factors. Evaluate different measuring methods and techniques according to their accuracy in determining the necessary material properties. Conduct an experimental investigation in order to establish necessary material properties and their dependency of relative humidity and temperature, in both the hygroscopic and capillary range. Conduct an experim ental investigation in order to establish necessary material properties and their dependency of relative humidity and temperature.

• HAM: theory and modelling