Assessment of mould growth on coated wood - methods and application
L Ross Gobakken, C M Whist, O Høibø, P J Hovde, E Larnøy
Discolouring fungi reduce the service life of coated wooden claddings in façades and increase the total cost of ownership due to shorter maintenance intervals. The project “Enhanced service life on coated wooden facades” has as its main objective to develop new methods for early prediction of durability and longer aesthetic service life of coated wooden cladding related to consumer needs and new building and environmental regulations. Different methods for mould growth assessment on the surface of coated wood exposed outdoors will be looked in to and Quantitative Real-Time Polymerase Chain Reaction (QRT-PCR) and Fourier Transform Infrared Spectroscopy (FTIR) will be developed as tools for objective quantification. In this paper four methods for assessment of mould growth on the surface of coated wood are presented; visual assessment, digital image analysis, QRT-PCR and FTIR, and the application of the different methods are discussed. Further, a comparative study was done using visual assessment and digital image analysis when measuring mould growth coverage on coated wood. 7 coatings with different typology and fungicide were tested according to EN927-3 outdoors for 2 years at Sogn test station, Oslo, Norway. Results obtained from visual assessment by using the rating scale in EN927-3 and a chosen algorithm for digital image processing was compared and the methods showed conformity. Alkyd modified acrylic coatings were found to perform significantly better than pure acrylic and modified alkyd coatings.