Feldstadt
am Heidjöchl
Authors: J. Raffetseder, E. Ableidinger & K. Jörg
The city of Vienna is one of the fastest growing metropolises in Europe, a fact that is especially apparent in the surroundings of the Heidjöchl project site with multiple ongoing large-scale developments. This urban growth sparked societal protest concerning the loss of farmland and the construction of a new highway (‘Stadtstrasse’) in direct adjacency to the site. Although Vienna is well known for its unparalleled social housing model, construction is typically carried out in concrete, covering large areas of open soil. The city’s housing strategy needs yet to address the demands posed by the climate crisis. Feldstadt Heidjöchl therefore proposes an urban model that takes climate protection through soil management, bio-based building construction, and climate adaptation equally into account. By preserving and recultivating large areas of the agricultural land, the project offers its inhabitants to play a part in their own food supply. Living next to the field, the new district empowers its inhabitants to take an active role in confronting the climate challenges of today.
Phase 0 - Building the ground
Connecting people and agriculture is the underlying principle of the urban design proposal. Agriculture, as a central element of the development, will therefore be able to act as a point of attraction beyond the immediate surroundings and bring life to the district already before construction starts.
Phases of Development
Continuing to build the city
The building process is phased in seven
self-sufficient districts, growing from the well-
connected sides to the central fields. In this
way, the urban development remains flexible to
the actual housing demand of the city and
leaves a chance for less soil to be built upon.
The contrast between the wide field and the
dense district produces a differentiated urban
experience with a diversity of places and
microclimates.
Climatic Urban Design
Climate adaptation considerations inform the height and orientation of buildings. Buildings are predominantly south-facing to allow for a simple shading of the summer sun and a deep insolation during winter. As the city will move to the humid subtropical climate zone by 2050, outdoor areas are increasingly in need of shade. The street widths are therefore consciously held narrow and lined with trees. Medium rise buildings as well as the Early Green tree lines in front of those alleys serve as wind barrier for cold winter winds. Tall buildings are conceived as sun- and wind catchers and placed in western adjacency to the major squares. Thereby the public space profits from the building‘s summer evening shade, the wind catchment of south-eastern summer winds and the blockage of westerly winter winds. The towers’ stepped façade and ground floor podium alleviate the wind downwash effect.
Surface sealing and Energy Production
Three different building types correspond to a different treatment of the ground. While the Shadow Catchers have underground floors, the Community Houses are limited to a simple ground slab and the Living Lines are lifted off the ground on spotpile point foundations. Those pile foundations serve at the same time the geothermal probes (2200 probes) supplying the whole district with sustainable heating and cooling and thus creating a energy self-sufficient living quarter. The geothermal ring lines correspond the proposed phasing zones and thus allow autonomous development of the individual areas. The reduction of sealed ground to an absolute minimum improves the water infiltration of the ground and cools the district through re-evaporation. PV roof area: 60.700 m2 = energy harvest potential of 8700 kWp
Shadow Catcher
21. Juni 16:30
Buildings Types
To enable an urban development that takes climate
protection through bio-based building construction into
account, the max. height for buildings is defined by the
limits given by the Viennese fire protection regulations for
bio-based materials. "Linear Living Lines" open up towards
the central field, while slightly taller "Community Houses"
provide collective spaces in direct adjacency to self-
harvesting areas. "Shadow Catchers" point to the site‘s
main public spaces and lead to public transportation links.
Educational facilities and social life
Restraining urban development to the perimeter leaves a widely open field of 10 hectares with bio-intensive agriculture, self-harvesting areas, and a large orchard in the center. Raised garden beds and fruit trees also reappear throughout the network of streets and squares in the Feldstadt. The social infrastructure and learning facilities are spread throughout the district in proximity to public transport connections. The educational campus of the city and the federal high school are located at the very heart of the district and encompass the central orchard. The fields and orchard are accessible to all inhabitants and provide both an educational and recreational environment. Members of the Heidjöchl Farm provide professional guidance to farming and are responsible for social, cultural and educational activities for inhabitants and pupils. It is associated to the city’s educational campus.
Circulation and Soil management
The internal network prioritizes pedestrians and cyclists while only allowing punctual access for motorized vehicles. A clear hierarchy of accessibility is established between: all traffic, emergency & delivery, cyclists & pedestrians, and pedestrians only. A key goal of the project is to keep the sealed area to the minimum. Whereas only the two crossing roads are conventionally paved, other connection lines are either infiltration capable or water permeable. The alternating access pattern for the Living Line buildings allows a clear differentiation of private courtyards and access roads for delivery and emergency. These access roads are limited to an elevated drive lane with adjacent green strips open to filtration. Due to the elevation of the living lines infiltration water is gathered inside the communal courtyard, channeled and let along overflow basins for irrigation to infiltration basins in the fields. In this way, rainwater usage as well as protection from future heavy rain events is ensured.
Community House
21. Juni 13:30
Community House
The point-block form of the community house interrelates its neighboring rows and mediates changes in orientation between them. It is conceived in adjacency to small squares and acts as a local center with an active ground floor use. Often directly neighboring the central field, its ground floor hosts communal and commercial uses related to urban agriculture. The small square is formulated as transition zone between living area and the field. A communal rooftop terrace with garden beds completes the building and acts as an additional attractor point for the local community. The slightly higher elevation (building class 5a) and north south elongation protects the facing row-courtyards and streets from the prevailing winds.
The hybrid timber-wood construction is organized around a central circulation and offers east or west oriented flats with a generous room height to ensure daylight provision. Balconies with trellis mediate between the inhabitants and the field. The larger building depth allows for storage facilities around the concrete core and thereby renders the construction of a basement obsolete.
The living line
Slightly bent housing rows are the base element of the project’s urban layout. Inspired by the linear arrangement of fields, the orientation of the buildings lead to - and form - the central field of the site. The vertical circulation elements bundle the balcony access act as green shelves that pair up two lines creating an intimate courtyard. This is also reflected in the topography and width of the street, resulting in an alternating pattern of wide public access ways and lowered communal courtyards, equiping each flat with a more public and a more private façade. Studio flats at the southern façade benefit from a more public appearance, making a semi commercial use possible. Minimizing the use of concrete, the building is elevated on pile foundations enabling a ventilated wooden base floor slab. The dimensions and the maximum height is set to building class 4 (GK4), making a wooden construction also in terms of fire precaution economically and ecologically feasible.
Living Line
21. Juni 13:00
Shadow Catcher
The four highest buildings of Feldstadt Heidjöchl are located next to the main access points to the district. The adjacent squares host small agricultural functions such as farmers markets, wine bars (“Heuriger”), and snack gardens that communicate the nature of the district at first sight. The greenhouse roofing of the Shadow Catcher acts as visual guide within and outside of the development. The buildings shape and placement in the westernmost parts of the squares follows a microclimatic strategy that protects from wet and cold westerly winds and captures the beneficial summer winds from the southeast. Furthermore, the far west setting summer sun is shaded on the square, while not impairing the low standing southern sun in winter. The timber-concrete hybrid construction combines commercial, living and parking uses in 13 to 19 upper and two basement floors. The bundling of the technical facilities for the geothermal energy system in their basement frees all other buildings in the Feldstadt from the need for underground construction.
