Lisø PhD Dissertation Manuscript - NTNU

Decay potential in wood structures using climate data
Kim Robert Lisø 1, 4 , Hans Olav Hygen 2 , Tore Kvande 3, 4 and Jan Vincent Thue 4
1 SINTEF Building and Infrastructure, P.O. Box 124 Blindern, N-0314 Oslo
E-mail: kim.robert.liso@sintef.no
2 Norwegian Meteorological Institute, P.O. Box 43 Blindern, NO-0313 Oslo, Norway
E-mail: hans.olav.hygen@met.no
3 SINTEF Building and Infrastructure, Høgskoleringen 7B, N-7491 Trondheim
E-mail: tore.kvande@sintef.no
4 Department of Civil and Transport Engineering, Norwegian University of Science and Technology
(NTNU), Høgskoleringen 7A, N-7491 Trondheim
E-mail: jan.thue@bygg.ntnu.no
Abstract:
The relationship between building materials, structures and climate is complex, and there is an urgent
need for more accurate methods to assess building performance. E.g. the lifetime of wooden claddings
is strongly dependent on the local-level climatic impact. This paper presents a national map of the
potential for decay in wood structures in Norway, based on Scheffer’s climate index formula. Weather
data from 115 observing stations for the reference 30-year period 1961 – 1990 is used. The climate
index distribution allows for geographically differentiated guidelines on protective measures. Detailed
scenarios for climate change for selected locations in Norway are used to provide an indication of the
possible future development of decay rates. Climate indices allowing for quantitative assessment of
building enclosure performance may be an important element in the development of adaptation
measures to meet the future risks of climate change in different parts of the world. Established
quantified relations between climatic impact and material behaviour or building performance, can be
used as a tool for evaluation of the need for changes in functional requirements. The presented work
represents an example of a first step towards such measures. Ways to further improve the reliability of
the index are also suggested.
Keywords:
building enclosure performance, climate adaptation, climate change, climatic impact, decay risk,
Norway, wooden structures, wood decaying fungi.
Introduction
Wood has for centuries been the dominant cladding material for dwellings and smaller
buildings in Norway. The performance of a wooden cladding depends on the quality
of the wood material, the surface coating, the construction details and the climatic
impacts they are being exposed to. The design guidelines for the use of wood as
cladding material in façade systems with separate wind and rain barriers have been
unaltered for many years (Lisø et al., 2003a). The principle of two-stage tightening
(with an outer rain protection layer, a ventilated and drained space and an airtight
layer) was thoroughly studied in Norway in the 1960’s (Birkeland, 1963; Isaksen,
1966), the results still being applied. The principle is even today a highly relevant
research topic in the pursuit of high-performance building enclosures (e.g. Nore et al.,
2005). One feasible way of ensuring further development of design guidelines for the
use of wood as cladding material is to develop climate classifications or climate
exposure indices based on long-term series of climate data, allowing for climate
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