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Temperature and moisture modelling of rendering on light weight constructions
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
2005 (English)In: Proceedings of the 7th Nordic Symposium on Building Physics in the Nordic countries, 2005Conference paper, Published paper (Refereed)
Abstract [en]

Rendered light weight constructions have a low thermal inertia witch makes them especially sensitive towards changes in temperature. The lack of thermal inertia causes the construction to give a much quicker response to ambient temperature. Calcium cement rendering is a commonly used material for weather protection but will expand and shrink with temperature and moisture changes. When the changes occur rapidly the fast movement of the material can cause it to crack and lose its moisture-proof characteristics. To study the drying out of the rendering, the phenomena was simulated using numerical calculations. A comparative calculation model with coupled heat and moisture transfer was created to evaluate the effects of mass transport on the heat distribution. The construction studied is a so called Symphony outer wall element which is a light weight construction. The rendering layer is assumed to have been saturated after a rain period. The drying out of the construction during a five day period is then studied. The calculations performed with the first model show large variations in temperature and moisture content which may cause the rendering to crack. The results are then compared with the second calculation model with coupled mass and heat transfer calculations which takes into account the thermal inertia of the moisture and its effects on the temperature variations. The purpose of this is to try to evaluate the significance of mass transfer in temperature simulations.

Place, publisher, year, edition, pages
2005.
Keyword [en]
rendered light weight constructions, mass and heat transfer, Capillary suction
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-6814OAI: oai:DiVA.org:kth-6814DiVA: diva2:11629
Note
QC 20100906Available from: 2007-02-27 Created: 2007-02-27 Last updated: 2010-09-06Bibliographically approved
In thesis
1. Efficient production of high-rise buildings
Open this publication in new window or tab >>Efficient production of high-rise buildings
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Production of one family houses has over time developed successfully in Sweden and producers have managed to reduce the production costs and industrialize the production process. The development has however not been that successful when it comes to high-rise buildings. There are many attempts made, but no one has really managed to create a product that can persuade the market. The systems used are not flexible and cannot cope very well with variations in the design. The aim of this work has been to develop and evaluate the idea of prefabricated high-rise buildings within the outlines of a scientific research. By understanding the problems that the building sector experiences today it will be possible to identify the solutions that are needed tomorrow. The main objective has been to develop new technologies and system concepts for buildings. Concepts that are highly flexible and respect the ambitions of the architect and technologies that will facilitate a more effective building process and address relevant key issues in building physics and building construction for cost reduction and a sustainable performance. Aside from the actual production cost it is also important to consider the lifecycle cost of the building. The production cost represents only a fraction of the total lifecycle cost of a building.

A background research has been made to understand the building process and its problems, this information served for the formulation of a building concept. The work has been interdisciplinary and has not been limited to only one single point of view. Because of the nature of the method the work has resulted in new construction techniques. The initial idea of the prefabricated high-rise building has during the course of this work developed to a complete building concept. The Symphony Concept as it is called is about industrial prefabricated buildings that are assembled on site and is based on the idea of large and flat building elements with a very high degree of prefabrication. To evaluate the concept technology detailed researches have been made in different fields. The detailed researches made in this thesis regards the strength of sheet metal studs embedded in stiff insulation blocks, hazards connected with plastering on light weight constructions and fire protection of light weight constructions. The experiences from these researches are then applied in the building concept. Theory was put to practice with the construction of an experimental building called the Research Tower. The purpose of this pilot-project was primary to evaluate the construction technology and secondary to evaluate the properties of the building concept.

To be able to find methods for production of sustainable, cost-effective and attractive high-rise buildings it is necessary to have a holistic view. A holistic concept that takes into consideration the whole building process will yield time- and cost-efficient production while it will also make it possible to achieve better quality. The detail researches shows that embedding of the sheet metal profiles in the rigid insulation blocks will increase the buckling load of the stud and that the thickness of the plastering layer and the material properties of its substrate will affect the strains in the plastering layer and the moisture stored in it. Regarding the fire protection it could be stated that the Symphony outer wall construction protected with a double layer of gypsum board can maintain segregation of the fire up to 60 min as long as the gypsum boards do not crumble. In the production of the pilot projected it could be stated that the fact that the whole building was designed by one homogenous team with information about all details, made it possible to foresee many problems. The production of elements even in the temporary experimental production facility proved to be fast and economic, even with untrained labour force and the elements could be prefabricated to a very high level with facades that are plastered before assembly.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xii, 51 p.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5563 ; 199
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-4285 (URN)978-91-7178-576-3 (ISBN)
Presentation
2007-02-27, Fys.lab., KTH, Brinellvägen 34, Stockholm, 09:00
Opponent
Supervisors
Note
QC 20101108Available from: 2007-02-27 Created: 2007-02-27 Last updated: 2010-11-08Bibliographically approved
2. Industrial Construction Methods for Cost-Effective and Sustainable Multi-Storey Buildings
Open this publication in new window or tab >>Industrial Construction Methods for Cost-Effective and Sustainable Multi-Storey Buildings
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Reduction of the cost of construction is a constant goal for the building industry. One way of reducing the construction cost of buildings is to develop building technologies that will give increased productivity. Reduced construction time at the building-site and waste of materials and resources contribute to furtherreduction of the costs. This is why the sector is developing towards more industrialized construction methods with prefabricated components. The objective of this thesis is development of industrial construction methods forcost-effective and energy-efficient construction of multi-storey buildings. It is important to highlight the difference between cheap or low-cost and cost-effective production. It is possible to produce buildings to a low-cost at the expense of decreased quality and design. Conversely, cost-effective buildings are buildings that are produced to a low cost while maintaining a high standard of design and comfort. While cost reduction efforts are often made based on a, relatively, fixed building process, this research is focused on reducing the costs by changing the building process with the help of innovative building technologies. The construction of a building is a very complex practice with a wide range of interacting processes. The hypothesis is that a holistic approach is advantageous in order to find effective construction methods. To achieve a holistic view, an interdisciplinary approach to the research is required. By approaching the development of construction methods from the point of view of the entire building process, it is possible to achieve optimizations with synergy effects and by that find solutions that are time-efficient, energy-efficient and cost-effective at the same time.

The work started by analysing the building process and the construction methods currently used in order to; discover the most common problems, gain understanding of the strengths and weaknesses in the conventional construction methods and identify the fields where the largest potential for improvements existed. Based on this analysis, a new building concept for industrial construction of multi-storey buildings is formulated called The Symphony concept. The concept involves a holistic view of the whole building process and is based on a prefabricated heavy structure that is covered with a prefabricated building envelope consisting of large, light-weight elements with a high degree of prefabrication and finished exterior surfaces. The concept required development of new types of building-elements and assembly methods. The technology was first evaluated while still on the drawing table. Some of these evaluations have been of a more detailed character and are reported in scientific papers. Thereafter an experimental building in full scale was erected in order to test the developed technology during production and assembly, while measurements and tests were performed in order to evaluate the performance of the building in operation. Based on the obtained results suggestions for improvements could be given in order to upgrade the concept further.

The economic analysis of the building process showed that the largest cost posts in the construction of dwellings are the climatic shell (24 %), the interior finishing, and the management costs. The construction of the climatic shell is optimized through the use of the Symphony elements while the management costs are reduced through the use of prefabricated elements with a high degree of prefabrication which, substantially, increase the construction speed. Results show that it is possible to reduce the construction costs with about 25 % when constructing according to the Symphony concept compared to conventional construction methods.

The construction of the large light-weight Symphony-elements was possible thanks to the CasaBona system. CasaBona is a building system which integrates the thermal insulation with the structural elements in the outer walls by embedding sheet metal profiles into stiff insulation blocks. The results show that the strength of the profile, when embedded in rigid insulation blocks, is increased between 22 % and 33 % when submitted to bending forces, and between 161 % and 210 % when submitted to compressive forces.

Simulations of the annual energy use of buildings show that the energy performance of buildings is improved with increased effective thermal mass. Increased mass is also beneficial from the acoustic point of view. However, it is important that the interior space is separated from the exterior climate with constructions that have low U-values. It could be concluded that the most beneficial design strategy is the combination of a heavy core-construction (which has a large mass and thermal inertia) and a light-weight building envelope (which yields low U-value without adding to the thickness of the outer-wall).

The construction of the experimental building made it possible to test the technology in an inexpensive yet realistic way. However, it is important to bear in mind that the information which can be gathered from an experimental building can be limited depending on the size of the building and its finishing standard. It could also be noticed that industrial construction benefits from an interdisciplinary design process since this render the increased use of prefabricated components possible.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. xiv, 15-101 p.
Series
Meddelande. Institutionen för byggvetenskap, ISSN 1651-5563 ; 08/201
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-9212 (URN)978-91-7415-122-0 (ISBN)
Public defence
2008-10-10, Salongen, KTHB, Osquars backe 31, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100906Available from: 2008-10-08 Created: 2008-10-08 Last updated: 2010-11-24Bibliographically approved

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