We present two recent test case application examples of a new high-performance insulation panel with product name SLENTITE® used as core element of a rendered internal wall insulation system. The first case study refers to the 18th-century building Alte Schäfflerei now the Fraunhofer Centre for Conservation and Energy Performance of Historic Buildings, at the monastery Benediktbeuern, southern Germany, where SLENTITE® was applied in 11/2017. The second test case was installed in 04/2019 in a heritage building situated in the historic center of Luxembourg. In Benediktbeuern, a single layer of insulation material was chosen, in Luxembourg we applied two layers of insulation. In both cases, detail work around the windows was a main task and we gained experience on product processing under real conditions. In terms of indoor room usage, the object in Benediktbeuern is used as exhibition hall with rare traffic and well controlled climate, whereas the object in Luxembourg is used as meeting room without climate control. Measured data of 20 months from the object in Benediktbeuern and first impressions of the performance in Luxembourg are discussed.

Following the European directive to reduce CO2 emissions of existing buildings by improving energy efficiency, internal insulation systems play a central role in the renovation of historically valuable buildings which cannot be insulated from the outside for reasons of monumental protection, or in cases where no additional exterior space is available. However, besides the thermal property of insulation systems, there are other relevant properties to be considered before choosing an internal insulation system, such as the hygrothermal behavior which plays a particularly important role in diffusion‐open interior insulation systems. As the internal insulation layer reduces the temperature of the existing wall during the heating season, its drying potential after rain events is considerably reduced. In addition to the effects of moisture from the outside (mainly wind driven rain), the entry of humidity from the inside through diffusion plays an important role. In the presented study, high performance insulation materials with nanostructure based on silicon dioxide and polyurethane are compared to conventional material based on wood fiber from a hygrothermal point of view by analyzing in situ measurements and simulations.