In 2015, in Horlachen near Sempach, an approximately 250-year-old agricultural building was converted and energetically upgraded with HAGA’s insulating aerogel render, so that it can be used today as a residential building. The building is built of a dry-stone wall of variable thickness, which is about 70 cm thick in the lower section and about 40 cm thick in the upper. As part of the renovation, the wall had to be partially fixed with new mortar, in order to achieve a higer stability. The u-value of this construction before renovation can be estimated to be about 2 W/(m²·K). A restoration base render was applied on the cleaned wall, followed by approximately 70 mm of HAGATHERM aerogel render, finished with a 1 mm thick top coat. Thus, the new wall reaches a mean u-value of approximately 0.35 W/(m²·K). Again, with the use of aerogel the character of the building is preserved while it can be repurposed with appropriate thermal comfort.