The Kohlerhaus, a building dating back to the 14th century, was renovated to accommodate 10 apartments with the high standards of comfort and efficiency. The historical research carried out by the architect revealed the rich past of the building, that served as priest house, hotel or guest house. The retrofit of the building included external insulation the wall with reed mats, new replica windows and new building services (radiating heating and mechanical ventilation).
The Kohlerhaus has a long history, which begins in the 14th century. In 1784 it was rebuilt as priest's house and got its present size. In 1803 Mr. Koll (later Kohler) bought the house by auction. In 1980 a partial renovation was done in order to get livable one flat in the first floor. A fundamental restoration began in 2010, which was initially intended to give the house back its early 20th century appearance. In the course of the work, the remains of the old core came to light and slowly the history of the house became visible through building and archive research. The architect wanted to discover how the house looked like in 1784 and then bring the house back to his original aspect.
The elements that are worthy of preservation are the external walls and some windows.
In the first floor radiators with an oil boiler were installed with the renovation of 1980. In the rest of the house there were no building services.
Aim of retrofit:
The main aim of the retrofit was to get the building livable. The initial aim was also to maintain the original aspect of the building that was thought to be the one of 1925 (there is a postcard with a photo of the building).
The stone wall was insulated from the outside and from the inside with reed insulation. On the outside 12 cm of reed insulation and on the inside 2 cm with clay plaster were installed. Only in the ground floor wall heating system is installed. The architect chose to use reed insulation for its compatibility with the existing wall: reed mat is a natural material and according to the architect this is a way to respect the existing wall. The facade is plastered to restore the external aspect to the original aspect.
U-value (pre-intervention) [W/m2K]: 2,0 W/m²K
U-value (post-intervention) [W/m2K]: 0,33 W/m²K
The existing box type windows had been already replaced in the last years. The architect wanted to have an energy efficient replica of the original box type windows. The windows have been replaced with an energy efficient replica. The new external window consist of a single glazing with the original form of the frame and it is without sealing. The new internal window consists of a double glazing with a new frame and is sealed.
Existing window U-value Glass [W/m2K]: 3,0
New window U-value Glass[W/m2K]: 1,2
Existing window U-value Frame [W/m2K]: 2,0
New window U-value Frame [W/m2K]: 1,8
The building is connected to the local district heating system. In the ground floor, a wall heating system is installed while radiators are installed in the other building stocks, using the existing niches under the windows. The radiators were installed in the existing niches under the windows. In the ground floor there isn't any niche, thus there a wall heating system was built.
30 ventilation units were installed. They provide supply air and they take extract air directly in each room where they are installed, so a connection with pipes between the rooms is not needed. The devices are installed in the sleeping rooms and in the living rooms. The ambient air and exhaust air vents are integrated in the window embrasure.
The domestic hot water is provided with the district heating.
Energy performance certificate: The building has the Klima House certification.
More information can be found here.