Hygrothermal behaviour of prefabricated façade elements for building renovation

Since 2015, the requirements in terms of energy performance imposed by the EPBD regulations in Flanders also apply to existing buildings undergoing major renovation works. In this context, prefabricated façade components have a large potential for renovating the existing building stock in a fast and repeatable way. Depending on the building structure, the existing façade can be demolished and replaced by new elements (skeletal structure) or it can (partly) be preserved. In that case, the new elements are installed against the existing wall and typically an adaption layer, e.g. mineral wool, is used to fill the void between the new element and the existing wall. This is done for load-bearing façades or cavity walls where the inner cavity leaf is preserved. In this paper the hygrothermal behaviour of prefabricated façade elements that are placed in front of an existing wall is studied. More specifically, the paper focuses on what happens when the existing wall is humid, e.g. because it is left unprotected after the existing outer cavity leaf was demolished or when the new element is installed in front of a massive masonry wall subjected to wind driven rain. The paper focuses both on timber frame elements and on elements with integrated vacuum insulation panels, and evaluates the impact of different choices in the design on the risk of degradation of the elements.Since 2015, the requirements in terms of energy performance imposed by the EPBD regulations in Flanders also apply to existing buildings undergoing major renovation works. In this context, prefabricated façade components have a large potential for renovating the existing building stock in a fast and repeatable way. Depending on the building structure, the existing façade can be demolished and replaced by new elements (skeletal structure) or it can (partly) be preserved. In that case, the new elements are installed against the existing wall and typically an adaption layer, e.g. mineral wool, is used to fill the void between the new element and the existing wall. This is done for load-bearing façades or cavity walls where the inner cavity leaf is preserved. In this paper the hygrothermal behaviour of prefabricated façade elements that are placed in front of an existing wall is studied. More specifically, the paper focuses on what happens when the existing wall is humid, e.g. because it is left unprotected after the existing outer cavity leaf was demolished or when the new element is installed in front of a massive masonry wall subjected to wind driven rain. The paper focuses both on timber frame elements and on elements with integrated vacuum insulation panels, and evaluates the impact of different choices in the design on the risk of degradation of the elements.C