Concrete sandwich element design in terms of Passive Housing recommendations and moisture safety

Abstract: In this thesis project a concrete sandwich wall element of 250 mm insulation of Kooltherm has been resulted to have U-values and ψ-values closer to the passive housing recommendations. However, by using 180 mm thick insulation, no significant difference in the annual energy consumption is observed. Using a metal sheet in the window connection and small concrete brackets, low thermal bridge values are achieved. Low thermal bridge coefficient values were also observed with thick insulation in the foundation and the roof structure, although, it is impossible to achieve values below 0,01 W/mK in the corner connections. Airtightness of the building envelope is more important than the thickness of the wall in the energy consumption simulations. Therefore, the thermal bridging and the U-values of the wall are, in most cases, dependent on the thickness of the element. No conclusions on the structural reliability of the solutions can be extracted from this thesis project. In order to conclude the statements above, this thesis project has been focused on the evaluation and design of a concrete sandwich wall panel. The design of the wall element, including its reinforcement and connectors, while achieving values according to passive housing regulations, is the initial goal of this project. Subsequently, connections between the building components and the wall element are analyzed and designed through several simulations according to the passive housing regulations respectively. Simulation tests took place in Sweco Structures AB offices with the valuable contribution of experts. An existing building project was used and evaluated in order to present the simulation results in a more realistic manner. Several insulation materials have been tested for the thermal and moisture reliability. Using the existing building as a base for information, energy simulations generated the energy consumption results in order to compare different wall thicknesses, and thermal bridging effects. This project is inspired by the needs of building sustainability and efficiency, which has become a significant part of the worldwide effort on reducing the energy consumption on the planet. Regulations regarding building technology have been completely changed and adjusted in the passive housing design. Particular effort has been put on the commercial and multi-residential buildings, in which the energy consumption is usually higher than in small family houses. Concrete sandwich wall panels have been introduced in the building market as an alternative and more efficient way of constructing. Prefabrication has been proved to be less time consuming, although issues on the thermal behavior appear in this kind of structure. The evaluation of the thermal efficiency of the concrete sandwich wall elements has been a significant issue in the civil engineering society and research.