Comparison Between Laboratory Water Permeability Tests and Wood Moisture Content in Full Scale Window Frames

摘要

The permeability of coatings was measured by water and vapour absorption and desorption according to the European standards prEN 927-4 and prEN 927-5. Several combinations of waterborne, solventborne and high solid model coatings were used as a primer or topcoat. The type of measurement had an influence on the results although the relative ranking was not much affected. The influence of coating permeability on wood moisture content was studied using full size spruce window frames in a test-house to create different outdoor and indoor climates. The wood moisture content was measured as a function of time at different depths and locations in the windows and the frames of the elements. The wood moisture content is partly influenced by the permeability of the coating but construction details, especially around end-grains had a strong influence as well. The best correlation between permeability and practical wood moisture content data was with the water absorption value. The influence of drying conditions (temperature, relative humidity) and type of pigment (colour) on laboratory water permeability has been studied for several commercial products. The permeability was influenced by application conditions and colour of the paint but the was highly dependent on the formulation of the coating.