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 requirements for the wall to fulfil, but do not specify which physical solution to be chosen. The first managing director of the institute, Øyvind Birkeland (1910-2004), won international recognition for his efforts in the development of performancebased requirements as a foundation for building codes. Preliminary findings from a case study of process induced building defects suggest that the adoption of a performance-based building code has indeed led to a positive change in quality (Mehus et al., 2005). However, even if the amended PBA appears to be contributing towards improved quality of construction, defects, flaws, and premature damage are still flourishing in new construction. Furthermore, design of details crucial to durability and service life of buildings is often omitted or they are improvised on site (Stenstad et al., 2005). The transition from a prescriptive to a performance-based code has strengthened the demand for supporting standards and design guidelines. The Building Research Design Sheets in the SINTEF Building Research Series comply with the performance-based requirements in the building code, and are an important reference to “pre-accepted” solutions in the technical regulations. The principal objective of the design sheets is to adapt experience and results from practice and research in such a way that they can be of practical benefit to the construction industry. The main purpose is to provide guidelines, solutions and recommendations that encourage high quality in the planning, design and construction of buildings. The series consists of 816 design sheets, the first sheets being published in 1958. It is the most used planning and design tool amongst Norwegian architects and engineers and is found on nearly all construction sites. The design sheets are continuously being updated to comply with the building code and experience-based knowledge. An analysis of climate differentiated design recommendations in the Building Research Series and technical approvals issued by SINTEF Building and Infrastructure illustrates the challenge at hand (Almås, 2005). The analysis clearly reveals the need for suitable time-series of climate data for the development of climate indices allowing for geographically dependent building envelope design guidelines. All 816 Building Research Design Sheets and the 241 Technical Approvals issued by the institute at the time of investigation were examined. In a great many incidents it is necessary to advise against the use of a given technical solution or material combination, simply because the local climate conditions are too harsh for the particular solution to obtain its expected lifetime or to harsh to avoid defects within a reasonable level of reliability. Evidently, rough qualitative descriptions of the climate, such as “wind exposed areas”, “cold areas”, “harsh climates”, “areas with high driving rain impact” or “exposed areas along the coast” are not appropriate as a foundation for climate adaptation with a necessary level of reliability. Instead, limit values with respect to the climatic loads that have to be taken account of must be clarified and expressed as a function of climate properties and material- or performance properties, together with national maps of climate zones for different purposes (see e.g. Figure 3). Such approaches to climate adaptation could to a large degree “replace” vanishing local craftsmanship knowledge on climatic conditions. 8
<strong>Lisø</strong>, K.R./ Building envelope performance in harsh climates: Methods for geographically dependent design Figure 3. Driving rain map for Norway (for the normal period 1961-1990). The map presents annual driving rain amounts (illustrated with colour scale) from the main wind direction (indicated with arrows) that gives the highest driving rain amounts at each observing station. The map provides driving rain exposure on the wall in mm/yr. Driving rain amounts are shown for every 10-degree sector for the cities of Oslo, Bergen, Trondheim and Tromsø. Topographic effects are not considered in the development of the map, some locations may therefore be more or less protected than the map expresses. The map is developed in cooperation with the Norwegian Meteorological institute, according to the new method given in Paper XI. The technical solutions presented in the Building Research Series are in general meant to have a reliability level suitable for all parts of the country. Standard technical solutions for all types of climate are in some cases appropriate (e.g. weather-protective flashings, see Paper VI). But, in most cases, climate differentiated performance requirements and solutions provide the highest level of reliability. This realization constitutes the starting point for the presented work. Climate data are also important in measurements and simulations of the energy performance of buildings. A main challenge for the construction industry is the following up of the Directive on the Energy Performance of Buildings (EPBD) (2002/91/EC). The Directive introduces a more holistic view on the energy performance of buildings, and a mandatory energy performance certificate for all buildings being constructed, sold or rented out. The construction industry has to be actively involved in the implementation of the Directive to meet the overall goal of promoting the improvement of energy performance. More efficient use of energy in the built environment is essential to reach political goals within Norway and the 9
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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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Lisø PhD Dissertation Manuscript - NTNU

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