Damage-free energetic window renovation in old and listed buildings

The maintenance and renovation of existing windows depends above all on the durability and usability of the renovation measure and the energy standard achieved. The aim of the research project is to make the energetic refurbishment of sustainable existing windows safer and thus preserve historic windows, prevent damage, promote energetic refurbishment and increase the market share of specialized window manufactures. This ist achieved by the targeted research of the essential paramaters U-values of window pane combinations, air exchange conditions and the hygrothermal conditions resulting from this in the course of the year. Detailed measurements of the refurbished windows in the historic building Old Cooperage, housing the Fraunhofer-Center Benediktbeuern, generated the necessary data on energetic and hygrothermal behavior of the refurbished window solution. With additional measurement campaigns of airtightness with tracer gas method the real air exchange behavior of the cavity of the box-type window could be determined. Hygrothermal calculations with software WUFI Plus are carried out to investigate the effects of different refurbishmend variants on a box-type window. Based on the measured values, a box-type window model is created to caclulate the local climate in the cavity as a function of the flow conditions, U-values and the indoor and outdoor climate. The general effect of changed tightness on the humidity conditions in the cavity can thus be confirmed. The simulation of the effects of different U-values of the window levels on the humidity conditions in the cavity result in better understanding how to refurbish and preserve historic windows into damage free low energy box-type windows.