In 2007 the orangery of “Ansitz Kofler” (listed building dating 1749), was refurbished – both aesthetically towards historic roots and energetically to low energy building. Applying efficient insulation (internal and external – meeting preservation of monuments’ demands), windows with passive-house-standard, ventilation with heat-recovery and geothermal heat-exchanger, and avoiding thermal bridges, the design heating-demand was lowered from 450 to 30 kWh/m²a (CasaClima-Certfication A+). A pellets-boiler satisfies the remaining demand without CO2. EURAC monitors the building’s energy-consumption, indoor-comfort and hygrothermal-wall-behaviour since October 2008 with 70 sensors. The measured heating-demand is slightly higher than calculated (also due to user influence), but still at absolute low values. Indoor climate has proven comfortable with warm surfaces and without need for active summer-cooling. Finally, the monitored wall profiles confirm good hygrothermal performance.