Vurdering av branntekniske egenskaper til fasadekledning av tre - Branntesting av trekledning med ulike typer behandling

This report describes 19 large-scale fire tests of wood cladding with various forms of treatment. The test setup is intended to represent a real façade, and the tests were carried out at RISE Fire Research's laboratory in Trondheim in the spring of 2021. The tests were carried out with different levels of fire exposure representing fire in smaller objects. Burner effects of 125 kW, 251 kW and 376 kW have been used in the experiments. The purpose of the project has been to investigate the fire development in these cladding products and to interpret the results in relation to the safety level of buildings with such claddings. The results of the large-scale tests have been assessed and compared with results from fire testing in small and medium scale tests of the same products. This was done to investigate if the tests in a smaller scale can predict the fire behaviour of the claddings in the large-scale test.The study is limited to investigating fire development and flame spread on the exterior surface of a façade with wooden cladding, to assess the differences between claddings with different treatments. The report also describes the regulations for exterior cladding provided in the Norwegian building regulations with guidelines, and the system for fire testing and classification of such products. Conclusions: It should be specified clearly, either in the product standard EN 14915 Solid wood panelling and cladding - Characteristics, requirements and marking, or preferably in the table of CWFT provisions, that fire classification without testing applies only to untreated wood, as long as otherwise not stated. Pre-accepted performance for all types of treated wooden exterior cladding should be considered in more detail. Today, there are probably a large number of exterior walls with wooden claddings in Norway that do not meet the criteria of fire class D-s3,d0, where this is given as a pre-accepted level of performance in the guidance to the building regulations. The SBI method is considered a good method for assessing and classifying building products' reaction to fire properties, also for exterior wood cladding. Ranking of the tested products based on results from the large-scale test is largely consistent with the ranking of the products based on results from the SBI test. The possibilities of developing a separate set of euroclasses for facades based on testing according to the SBI method should be investigated. In all large-scale experiments, it was demonstrated that the claddings' treatment had the greatest impact on the heat flux measured at different heights in the first 2 minutes of the fire. Geometry in the experimental setup had a major impact on the spread of fire in the façade when the flames reached up to the cantilevered soffit. The effect of geometric conditions may probably be greater than the effect of the surface treatment. Cladding profile and installation of the cladding, especially if the joints are tight and there are no holes in the cladding, are important factors with regard to fire spread in the façade and to cavities behind the cladding