Lisø PhD Dissertation Manuscript - NTNU

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<strong>Lisø</strong>, K.R./ Building envelope performance in harsh climates: Methods for geographically dependent design area. Observations are done four times daily (2400, 0600, 1200 and 1800 UTC (Coordinated Universal Time)) at the larger stations and three times daily (0600, 1200 and 1800 UTC) at the more rural stations (i.e. these latter stations do not have midnight observations). Electronic records of synoptic observations go back to at least 1957 for most stations, the data being stored in the Norwegian Meteorological Institute’s Climate archive (see www.met.no). Historically, location-specific climate data have only to a very limited extent been applied systematically for climate differentiation of the suitability of a given technical solution in a given climate. Hourly climate data necessary for full numerical modelling of the performance of building envelope elements are only available for a handful of locations in Norway. The presented dissertation focuses on methods for assessing impacts of external climatic parameters on a local scale, but with the use of daily and monthly averages of climate data. The reliability of climate indices or climate differentiated design guidelines is strongly dependent on the geographical spreading of the observing station network. The Norwegian network is not optimally distributed to fully embrace local variations, but provides a solid platform for the development of methods for geographically dependent design and guidelines on the appropriateness of different solutions in different climates. 1.4 Climate change The Intergovernmental Panel on Climate Change (IPCC) defines climate change as “a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer). Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use” (Houghton et al., 2001). The United Nations Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. Modern climate change is now dominated by human influences large enough to exceed the bounds of natural variability, the main source of global climate change being human-induced changes in atmospheric composition (Karl and Trenberth, 2003). According to Crowley (2000) “a 21 st -century global warming projection far exceeds the natural variability of the past 1000 years, and is greater than the best estimate of global temperature change for the last interglacial”. Man induced climate change can be avoided in the long term only by reducing global emissions of greenhouse gases to a small fraction of present levels within one or two centuries (Hasselmann et al., 2003). Regional changes in climate, particularly increases in temperature, have already affected several physical and biological systems in many parts of the world, for example shrinkage of glaciers, thawing of permafrost and lengthening of mid- to high-latitude growing seasons ((McCarthy et al., 2001). Measures aimed at halting global climate change through greenhouse gas mitigation options need to overcome many technical, economic, political, cultural, social, behavioural and/or institutional barriers which prevent the full exploitation of the 4
<strong>Lisø</strong>, K.R./ Building envelope performance in harsh climates: Methods for geographically dependent design technical, economic and social opportunities of these mitigation options (Metz et al., 2001). Global warming will lead to changes in the local climate in Norway in this century. Climate scenarios for Norway emanating from the project “Regional climate development under global warming” (RegClim) suggest changes in mean and extreme values of temperature, precipitation and wind. The most realistic scenarios for changes in global climate are based on Atmosphere-Ocean General Circulation Models, AOGCM’s (Houghton et al., 2001). These global climate models are “fully coupled, mathematical, computer-based models of the physics, chemistry and biology of the atmosphere, land surface, oceans and cryosphere and their interaction with each other and with the sun and other influences like e.g. volcanic eruptions” (Karl and Trenberth, 2003). The spatial resolution in the recent AOGCMs is still too coarse to enable these global climate models to reproduce the climate on regional or local scale. To deduce detailed scenarios for future climate development in different parts of Norway, both dynamic and empirical downscaling techniques are being applied on integrations with global climate models. The downscaled scenarios indicate a general increase in temperature and precipitation rates across the country (see e.g. Paper II; Benestad, 2005). Consistent with emerging global patterns, the projected temperature increases are at a maximum during the winter and at a minimum during the summer and warming rates increase from south to north and from coast to inland. Precipitation scenarios suggest increased precipitation in existing wet areas and periods, in agreement with scenarios at the global scale. Extreme amounts of precipitation will appear more often in all of Norway. The RegClim scenarios also suggest a moderate increase in wind in the southernmost areas and along the coast of Central Norway, with most of the increase manifesting itself during the autumn and winter months. The climate is a product of both ordered forcing and chaotic behaviour (Rind, 1999). Several sources of uncertainties exist related to both scenarios for global climate change, and to the effects of global warming on regional-level climate. The regional scenarios should not be considered as forecasts in an absolute sense. They offer insights into the likely range and nature of future weather scenarios. The regional scenarios for climate change are continuously being improved, increasing their reliability along with knowledge on uncertainties connected with inaccurate climate models, random climate variations and different downscaling techniques. The possible effects of climate change, and the subject of risk management, adaptation and mitigation, are now being addressed in several parts of the world. Challenges confronting the built environment in responding to the potential impacts of climate change were one of the main themes in a special issue of Building Research & Information in 2003 (Paper I; Sanders and Phillipson, 2003; Shimoda, 2003; Larsson, 2003; du Plessis et al., 2003; Mills, 2003; Hertin et al., 2003; Steemers, 2003). The amount of building defects in Norway (see Section 1.5) clearly illustrates that it is not only the extreme weather events that need to be studied as a foundation for long-term adaptation towards a changing climate. A well-functioning and reliable infrastructure is an important basis for economic growth and social development. 5
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Page 55 and 56: with large amounts of precipitation
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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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Lisø, K.R./ Building envelope perf
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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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BUILDING RESEARCH &INFORMATION (JAN
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greater variations (Lisø et al., 2
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Typical problem areas and recommend
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Figure 3b Recommended design of win
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Figure 7 Example showing the recomm
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Figure 11a Poor solution for a £as
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Acknowledgements This paper was wri
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Climate adapted design of masonry s
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2. Masonry defects in Norway 2.1. S
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Fig. 2. Example illustrations of th
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The presented results are in good a
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appropriate in a more severe type o
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screen in a two-stage weatherproofi
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INCREASED SNOW LOADS AND WIND ACTIO
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The hurricane (Beaufort number 12)
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The extensive revisions of the code
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The number of buildings investigate
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As is apparent from the values in t
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climate change is now dominated by
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TABLE 3. Summary of findings Struct
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Lisø, K.R./ Building envelope perf
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temperature of -4°C or less. See F
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Today, frost resistance of brick, c
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degree of saturation, freezing will
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accelerated frost damage or frost d
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A possible objection to the present
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[17] Dührkop H., Saretok V., Sneck
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Decay potential in wood structures
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Wood decaying fungi will only be ac
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to promote decay prevails. Two of t
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Acknowledgements This paper has bee
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(a driving rain gauge), however, is
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Fig. 1. Map of Norwayshowing the lo
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Frequency 25 20 15 10 5 0 highest p
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interesting to compare those result
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Effects of wind exposure on roof sn
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In ISO 4355 ”Bases for design of
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variety of roofs and wind exposures
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Li and Pomeroy [13] evaluated hourl
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Fig. 5. Exposure coefficients for 3
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meteorological stations are expecte
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Many of the meteorological stations
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the ground with return period of 30
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References [1] Standards Norway. De
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