Energetische Qualität von Gebäudehüllen in Stahl-Sandwichbauweise
- Energy performance of building envelopes using steel sandwich panels
Kuhnhenne, Markus; Feldmann, Markus (Thesis advisor)
Aachen : Publikationsserver der RWTH Aachen University (2009, 2010)
Dissertation / PhD Thesis
Aachen, Techn. Hochsch., Diss., 2009
The design of energy-efficient and sustainable buildings requires the knowledge of all relevant parameters for the energetic quality of building envelopes. So far, there is no scientific background for the determination of the energetic quality of building envelopes made of steel sandwich panels and its influence on the energy demand for buildings available. In particular the numerical values of the parameters governing the energetic quality are not known. Therefore, the energetic quality, so far, cannot be assessed and optimized and its effect on the energy demand for a building cannot be determined. This work gives a systematic analysis of the thermal protection and air-tightness of buildings to obtain the necessary parameters and their qualities for an accurate rating of the energetic quality of buildings made of steel sandwich panels. For particular reference buildings with envelopes made of steel sandwich panels the consistency of directives, design standards, test standards and declarations of producers are checked and proposals are made for improving the situation for assessments. The work focuses on the design and structural detailing of steel sandwich products and their connections that govern the formation of thermal bridges and the air-tightness. This leads to recommendations for the structural design and execution of steel sandwich structures. The analysis has shown that an accurate determination of the effects of thermal bridges caused by metallic components in the building envelope requires the use of finite element methods. The determination of the air-tightness of joints between steel components in reproducible and economic way is only possible by experimental tests. A conclusion of the systematic analysis is that the relevant criteria for the assessment of the thermal protection and air-tightness of steel sandwich panels are the local requirements of air-tightness of a joint and the minimum requirements for thermal protection. Where these local and minimum requirements are met and the thickness of the sandwich panels is greater or equal to 120 mm, the building envelopes are practically free of thermal bridges and air-tight. The longitudinal joints of steel sandwich panels should be further developed in such a way that they are air-tight not only for full fit but for a certain variation of the gap in the joint. The variation should be limited by a vertical and horizontal tolerance of equal or more than 5 mm. The product standard for steel sandwich panels EN 14509 should be completely revised as far as “heat transfer” and “air-tightness” are concerned taking the results of this work into account. In future, light weight steel buildings should be all optimized in view of heat transfer and durable air-tightness. To this end, the products and joints should be further developed to reduce thermal bridges and to tolerate imperfections of fit of joints. The atlas for structural detailing to reduce thermal bridges for steel polyurethane sandwich panels as developed in this work should be extended to all structural solutions for light weight metal buildings. The procedure presented in this work and the results obtained for steel sandwich components permit to assess the energetic quality of building envelopes made of any other light-weight metal component. Therefore, this work may be considered as a basic contribution to energy efficient and sustainable construction of any building made of light weight metal components.