Extension Tønder City Hall
“Context: playing it different”
A circular building has no facade, or better: it only has one facade. Our extension however offers two very different readings depending on whether we are approaching it from the north, the city or from the open fields. From the city, it is only its particular geometry that reveals the building: both in extension and volume, the new building hardly shows behind the old city hall. In the distance, coming from the west (the festival) or from the river, we were aiming at readability and clarity. The new building, even though discreet, deserves to join Tønder´s skyline.
The horizontal composition of the existing Halldor Gunnløgsson city hall (1970) is dynamized and strengthened by the cylindrical shape of the extension. Its height and proportions are carefully chosen to harmonize also with the old water tower, twice its height, the museum and the old mill house. We discovered through the old city a dialogue of simple geometries.
As it did to Gunnløgsson, the presence of the river has guided us: the naves of his building seem to be displaced by the Vidå´s meander. Our building, in its continuous rotation. also acknowledges the southbound movement of the Vidå waters.
The new building could not be a barrier toward the south from the old city hall: its relation to the open fields, the river and the southern light, should be preserved as much as possible.
We soon understood the necessity of a compact solution. That would minimize its footprint, not competing in extension with the old building but engaging the existing with institutional pride, through a clearly different geometry.
Description. Social synergies. Conquering the scenery
In doubling the capacity of the city hall, one of the challenges of the extension was to provide good view from all the offices. The other, to design spaces that would invite the spontaneous encounter of people: instead of the generic corridor of most offices, the promenade across our building is a sequence of spatial episodes, unexpected points of view, and contact with the landscape.
The body of offices, individual and collective is set at the perimeter, where tranquility and concentration might be desirable. We use the synergies that the central space produces, to create places of informal encounter, meeting rooms open to the double height spaces and to the light.
The new canteen animates and opens the old building to the landscape, allowing new institutional and also informal uses, like receptions and celebrations. Because of its configuration, orientation and situation in front of the river, it will be an attractive place that could function also outside the town hall normal working hours and in the weekends.
When the weather allows the canteen will colonize, with tables, chairs and shades, the new public space that the union of the old and new building create. This new square, overlooking the river is a privilege that the citizens and visitors of Tønder recover. To free this space from car and buildings is to conquer the river banks for the town. Here we address a wider concept of sustainability in which the social, the collective, is enhanced by a new use of natural resources, in this case the water landscapes, the open fields: that which always was there, for those who wanted to discover it, and that constitutes a great part of Tønder´s magic.
The new building completes and makes stronger the north-south axis that the assembly hall in the old city hall had initiated. We descend three steps following this axis through a strongly directional space between two walls that ends in a room open to the landscape. This room is a counterpoint to the existing assembly hall: perhaps less institutional, suitable for art and culture.
This space of transition between the old and new building is a key feature that establishes the quality of the relation between extension and existing city hall. This transition has a vertical direction, after the horizontal communion with the landscape.
The two walls that depart from the existing building support the structure of the extension. From the first floor of this structure, a staircase descends to carry us to the new building.
The new building is basically a cylinder made of perimeter rings of offices and an ascendant spiral of common spaces, meeting rooms.
Each floor is slightly different. The stairs are always found following a clockwise movement. They are always placed by strategic openings that reveal the landscape sequentially: at times the city, or the river, or the tower.
As we ascend, the building opens up, allowing the light to flood the interior spiral. When we reach the top, from the penthouse-terrace-gazebo, the landscape becomes the protagonist.
Enclosure: looking through the reeds
We were after a facade with depth, porous, that would register the slow movement of light through the hours. We propose a screen made of clear thin ceramic tubes, with varying radius, that will cover the building. Its density would change depending on the orientation and privacy demands. These tubes, reinforced with steel, will be finished at times in mat clay and other times shiny tile.
This enclosure, which is also structure, brings up the delicate variation of a vegetal filter. It reproduces the textile quality, lattice like, of the riverbank vegetation. We gaze at the river through threads or reeds.
In choosing a clay facade we were considering the context (the old town hall, the mill house, the tower...in fact almost the whole city is made of brick) but also made this filter a capital part of our sustainable strategy. A devise for solar control, getting denser towards the south, where direct radiation and reflections can become a problem.
The play of light, the absence of pillars, help to dematerialize the basic cylinder that becomes almost like a wicker basket.
Sustainability: in good shape
The building shows a large interior volume covered by a very limited skin, presenting an excellent “form factor”, thermically extremely efficient due to the lesser surface presented to the exterior, and minor wind pressure.
Its cylindrical shape and the enclosure minimize the exposed surface to direct sunlight, except in the roof were solar energy is harvested by photovoltaic panels.
These panels provide the necessary energy to pump up subterranean water that will be used in the cooling systems. This system seems very adequate giving the very high water table of the area. That way Tønder city hall will only use a fourth of the energy used by a typical climatization system in office buildings.
An important technique to save energy is the use of the chimney effect, offered by the central space that incorporates natural ventilation controlled by mechanized openings at the roof.
The slender micro pillars system, more dense towards the south, avoids unwanted reflections on working areas, and opens up towards the north. These variations motivated by energy saving and comfort provide vibration and diversity to the facade, creating a real effect of riverside reeds.
