The windows of the New Palace in Stuttgart are being refurbished and modernised into 2021.
Holzmanufaktur Rottweil, the woodworking company commissioned with the job, attaches great importance to handicraft tradition in accordance with the modern requirements of building energy efficiency. One of the style elements used in this is the Georgian bar from SWISSPACER, which has only a minor impact on the low UW value of the windows.
Stuttgart’s New Palace, which stands in the heart of the capital of Baden-Württemberg, can look back over a long history. Built in several phases starting in 1746, it was only actually completed in 1806. During aerial bombardments in the spring of 1944, the palace was almost completely destroyed by fire, with only the outer façade left standing. Since its reconstruction after the war, between 1958 and 1964, the building has been used by, amongst other things, the Baden-Württemberg state government and other government bodies.
The palace consists of two full-height floors and a half-height floor, which is formed as a mezzanine with a continuous façade or as an attic level with a steep mansard roof. The classic punctuated façade is characterised by rectangular windows, arched or pointed windows and finally round windows in the dormers. In 2019, the state of Baden-Württemberg – represented by Landesbetrieb – Vermögen und Bau Baden-Württemberg, Stuttgart office, put out a tender for the refurbishment of wooden window elements and glazing work in the Planie wing and Rosengarten wing. The project packages include the refurbishment of about 530 wooden windows, which equate to around 1,700 m2 of glazing.
The art of preservation
Holzmanufaktur Rottweil was commissioned with the works for both project packages. The company, which hails from the oldest town in Baden-Württemberg, has been engaged as a woodworking company in the areas of monument preservation, building culture and architecture for over 30 years. “We restore and repair historic fittings such as windows, doors, floors and wood panelling. Existing quality is combined with new quality, regardless of whether the work involves restorations, repairs or additions,” is how the authorised officer Adelina Bytyci-Dodolli describes the company’s philosophy.
Holzmanufaktur Rottweil, founded by the two managing directors Hermann Klos and Günther Seitz in 1988, presently employs over 100 people in the areas of carpentry, glazing, painting and administration. “As many heavily utilised windows, doors, stairs or floors have justified claims to thermal, acoustic and safety-related improvements, convincing solutions have to be found for the technical implementation,” says head of sales Karsten Braun. “If too much is changed, or changed too insensitively, the elements lose their historic legibility. Conservation and restoration does not mean standing still or some form of technical regression.”
This remark can also be applied to the basic maintenance and restoration of the wooden windows in Stuttgart’s New Palace, which Holzmanufaktur Rottweil started last year and will continue into 2021. Its task is to overhaul the wood and fittings of the historic windows. “Our tasks are manifold,” explains Karsten Braun. They involve reconciling the energy requirements for a building used as administrative offices with its heritage status.
The client therefore decided to fit the old single-glazed composite windows in the outer level with insulated glass units. The highly efficient CLIMAPLUS XTREME solar control glass from Saint-Gobain was chosen, which is extremely translucent and at the same time offers maximum transparency. “In doing so, our employees can only carry out the work on the windows from outside without any scaffolding erected in front of the façade, which represents a considerably logistical effort,” says Braun. The restoration encompasses the careful restoration and surface treatment and repair of the window frames, as well as the renewal of seals, tapes and putty bevels.
Georgian bar with a clean look
A special feature of this project is the installation of special insulating glass or solar control glass in the area of the mansard windows, all of which will be fitted with a Georgian bar. “Here, we opted for the Georgian bar from SWISSPACER,” says Karsten Braun. “We find its look appealing and the range of colours is advantageous. At the same time, all energy-related requirements are met. The client wants the edges to be installed so that they are to all intents and purposes invisible. Which is why being able to adjust the colours is also so important to us. We can also manufacture cleanly assembled corners with SWISSPACER.”
Another important criterion for the team at Holzmanufaktur Rottweil is being able to easily match the Georgian bar to the existing situation. In total, SWISSPACER has 13 different sizes of Georgian bar and a bar intersection with integrated rattle guard in its portfolio. A width of 10 mm is needed for the mansard windows in Stuttgart. The Georgian bars from SWISSPACER consist of the same highly insulating composite as the SWISSPACER spacer bars, which were also used here in the form of the SWISSPACER Advance. They minimise the thermal bridges around the edge of the glass. With the continuous glass, Ugvalues of between 0.9 and 1.0 W/m²k can be achieved in the windows for Stuttgart’s New Palace.
The restoration works being carried out by Holzmanufaktur Rottweil at Stuttgart’s New Palace are on schedule and proceeding on schedule. The use of Georgian bars enables the reconciliation of heritage protection and energy efficiency, leaving the client, planner and trades delighted with the results.
