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Design of mineral fibre durability test based on hygrothermal loads in flat roofs

: Zirkelbach, D.; Künzel, H.M.; Bludau, C.

Türkeri, A.N.; Sengül, Özkan:
11th International Conference on Durability of Building Materials and Components, DBMC 2008. Proceedings : Istanbul, Turkey 11-14 May 2008
Istanbul: Istanbul Technical University, 2008
ISBN: 978-975-561-328-4
International Conference on Durability of Building Materials and Components (DBMC) <11, 2008, Istanbul>
Conference Paper
Fraunhofer IBP ()
mineral fiber insulation; mechanical strength; roof; durability test procedure

The durability of mineral fiber insulations depends to a large extent on coinciding temperature and humidity conditions within these materials. Existing test procedures use combinations of rather extreme temperature and humidity conditions above 60 or 70 °C and 95 to 100 % RH. However, these test conditions lead to a significant reduction of the mechanical strength of glass fiber insulation materials which cannot be observed in real life. Subject of this work is to evaluate these loads in lightweight flat roofs with mineral fiber insulation and dark roofing membranes. Therefore a test roof was built up at the field test site of the Fraunhofer IBP in Holzkirchen (alpine region of Germany, 680 m a.s.l.). The solar radiation and the night sky radiation at this altitude lead to rather extreme temperature conditions in the test roof. In order to achieve the most unfavorable humidity conditions within the insulation two liters of water per m² were inserted to the roof before closing the construction. The measured conditions in the roof serve also to validate hygrothermal simulation results which allow in a second step to "transfer" the test roof to other locations in northern and southern Europe. Thus, the most extreme temperature and moisture conditions likely to occur in the glass fiber insulation layer of light-weight flat roofs can be determined. A material test procedure for durability assessments should accelerate the normal degradation process but not make fail a solution which performs well in reality. Therefore, new test conditions are proposed which are closer to the conditions occurring in real life while still allowing the normal aging process to be accelerated. The result will be a more realistic decrease of the material strength compared to the present procedures.