Lisø PhD Dissertation Manuscript - NTNU

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A possible objection to the presented method could be that the index does not include the effects of wind. The moistening of e.g. a façade material is of course dependent on geographic orientation and wind conditions. But, in the end, the relative potential of a climate to promote frost decay or frost damage is basically guided by the two climate parameters included here, namely freezing events and rainfall. 6. The way forward In Norway, about 100 stations cover the normal period, and have well enough observational programs to be used. Another 100 stations have long series that, though partly outside the normal period, can be coupled to the normal period. The next step may be to look at shorter series of a choice of stations that have a more frequent observational program. During the last 3-10 years, automatically recorded hourly values of temperature and precipitation at some 30-40 stations exist, but the quality of the hourly precipitation data has to be analysed. It is of interest to look at those data to find out whether improved climate indices may be compiled. An important goal of future work is to further develop the index to provide quantitative information on the connection between climatic exposure in different regions and durability of different porous, mineral building materials (as indicated in this paper). This work will also include analyses of the influence of frost period lengths on the assessment of frost damage risk mapping. Field investigations and laboratory testing of different materials are needed for validation and further improvement of the index. An important issue to be addressed is the connection between frost resistance and suction rate, especially of interest for clay bricks. Research to address these issues are currently in progress as part of NBI’s research & development programme “Climate 2000” [19], along with several other approaches in the pursuit of design tools using climate data and strategies for risk management of climate change impacts [20]. This is particularly important with respect to the preparation of additional Norwegian appendices to international standards associated with the various types of climatic impact. The “robustness” of the Norwegian building stock will also be addressed as part of the programme, including the development of methods for classifying different climatic parameters (based on historic weather data and scenarios for future climate development under global warming) and their impact on building enclosure performance. The index can be used as a tool for assessment of changes in decay rates due to climate change under global warming incorporating data from regional- and local-level climate change scenarios. 7. Conclusions Frost resistance of brick, concrete and rendering mortar is tested according to internationally standardised methods. Test methods are given for different countries (dividing countries in far too coarse national-level climate zones), but there exists no classification of local- or regional level climate zones for frost durability assessment purposes. Frost decay assessment methods are also needed in the planning and design of high-performance building enclosures. A relative potential of frost decay or frost damage of mineral materials exposed to a given climate can be expressed using a simple index incorporating information about number of freezing events and 4-day rainfall sums prior to freezing events for the different months of the year, based on multi-year records of daily air temperatures and rainfall data. The principal advantages with the presented method are that the results are based on long-term series of climate data that are readily available. The method will be used as a foundation for the further development of a frost decay exposure Page 10 of 13
index to characterize both climates and material properties for geographically dependent frost damage risk assessments. The proposed climate index is to be justified in the future in relation with building defects observations in different climates. Acknowledgements This paper has been written within the ongoing NBI research & development programme “Climate 2000 – Building constructions in a more severe climate” (2000-2006), Strategic Institute Project “Impact of climate change on the built environment”. The authors gratefully acknowledge all our construction industry partners and the Research Council of Norway. References [1] Lisø K.R., Kvande T., Thue J.V. The robustness of the Norwegian building stock - A review of process induced building defects. In: Jòhannesson G. editor. Proceedings of the 7th Symposium on Building Physics in the Nordic Countries. Reykjavik: the Icelandic Building Research Institute, 2005. p. 1195-1202. [2] Scheffer T.C. A climate index for estimating potential for decay in wood structures above ground. Forest Product Journal 1971;21(10):25-31. [3] Cornick S., Dalgliesh W.A. A moisture index to characterize climates for building envelope design. Journal of Thermal Envelope and Building Science 2003;27(2):151-178. [4] Djebbar D., Mukhopadhyaya P., Kumaran M.K. Retrofit strategies for a high-rise wall system and analysis of their hygrothermal effects. In: Haupl P., Roloff J. editors. Proceedings of the 11 th Symposium for Building Physics, Dresden, Germany, 2002. p. 738- 746. [5] Hoppestad S. Slagregn i Norge (Driving rain in Norway, in Norwegian). NBI Report 13. Oslo: Norwegian Building Research Institute, 1955. [6] Rydock J.P., Lisø K.R., Førland E.J., Nore K., Thue J.V. A driving rain exposure index for Norway. Building and Environment 2004;40(11):1450-1458. [7] Norwegian Standard NS-EN 771-1:2003 Specification for masonry units - Part 1: Clay masonry units. Standards Norway, Oslo. [8] Norwegian Standard NS-EN 539-2:1998 Clay roofing tiles for discontinuous laying - Determination of physical characteristics - Part 2: Test for frost resistance. Standards Norway, Oslo. [9] Norwegian Standard NS-EN 1304:2005 Clay roofing tiles and fittings - Product definitions and specifications. Standards Norway, Oslo. [10] Geving S., Thue J.V. Fukt i bygninger (Moisture in buildings, in Norwegian). NBI Handbook 50. Oslo: Norwegian Building Research Institute, 2002. [11] Jacobsen S. Scaling and cracking in unsealed freeze/thaw testing of Portland cement and silica fume concretes, Dissertation 1995:101, Trondheim: The Norwegian Institute of Science and Technology, 1995. [12] Fagerlund G. Studies of the destruction mechanism at freezing of porous materials. Paper presented at Foundation Francaise d’Études Nordiques, the 6th international congress on problems raised by frost action. In: Report 1. Stockholm: Swedish Cement and Concrete Research Institute at the Institute of Technology, 1976. [13] Neville A.M. Properties of concrete. ISBN 0-582-23070-5. Harlow: Longman, 1995. [14] Powers T.C. Resistance to weathering – freezing and thawing. ASTM Special Technical Publication No. 169:182-187. West Conshohocken: ASTM International, 1956. [15] Marchand J., Sellevold E.J., Pigeon M. The deicer salt scaling deterioration of concrete – an overview, ACI SP 1994;145:1-46. [16] Fagerlund G. Samband mellom porositet och materials mekaniska egenskaper (Relations between porosity and mechanical properties of materials, in Swedish). Dissertation, Report 26, Lund: The Lund Institute of Technology, 1972. Page 11 of 13
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Building envelope performance asses
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BUILDING RESEARCH &INFORMATION (200
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LisÖ et al. on how to cope with an
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LisÖ et al. the exposure to contin
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LisÖ et al. business premises. The
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LisÖ et al. construction industry
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Research in Building Physics, Carme
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4 CLIMATE CHANGE SCENARIOS FOR NORW
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with large amounts of precipitation
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will most likely be worse, even wit
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Graves, H.M. & Phillipson, M.C. 200
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766 Nordvik and Lisø The topic of
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768 Nordvik and Lisø into the futu
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770 Nordvik and Lisø climate chang
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772 Nordvik and Lisø 0 Â Â = p d
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774 Nordvik and Lisø probably to a
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BUILDING RESEARCH &INFORMATION (200
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cost of repairing process-induced b
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change in quality (Mehus et al., 20
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on the impacts of different climati
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different strategies: risk-based, p
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Learning from experience - an analy
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An important aspect of the programm
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Concrete walls 32 % LECA masonry 10
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construction industry, and academic
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Page 105 and 106: Acknowledgements This paper was wri
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Page 183: References [1] Standards Norway. De
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