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client: Ministery for Regional Development and Public Construction , Sofia,
Bulgaria.
architects: Dominique Perrault Architects, Paris
engineering: Arup, London
location: boul. Tsarigradsko Shosse, Sofia, Bulgaria
site area: 65 ha
program: Government district, office buildings, hotels, housing buildings, sports facilities, knowledge center, exhibition center, park land area.
Government district: 325 000 m2
Office and housing buildings, hotels area: 555 000 m2
Knowledge center: 50 000 m2
Exhibition center: 60 000 m2
Park land area and sports facilities: 190 000 m2
Additional residential areas : 200 000 m2

Description by DPA:

This project is an urban development strategy. It is not an architectural project; more precisely architecture is used as a device to create a territory with its specific landscape. We do not want to build towers, but an architectural ensemble which silhouette evokes the hilly landscape of a small mountain. Inside this topography not only is a river flowing, but also a park-garden which preserves the existing trees. We want this new district to develop harmonious relationships between nature and architecture. This long green space runs through the site and joins the two entrance crossroads, offering to public transports new possibilities of connections and services. The strategy consists in proposing a regulation envelope which will define the silhouette of the district and its density. Inside this “virtual” envelope, the buildings are arranged according to the programs as well as the property and economical opportunities. This piece of city gets built “under” this envelope with freedom, fluidity and flexibility. Each architecture has its own architect, its own design, its own client, but all of these architectures show gradually the specific outline of this territory. The movements of this silhouette are interrelated with the urban and geophysical environment, scoring with high points the gates of the district, or accompanying with low points the surrounding streets. This park has to become the great public space, the spine of the district. It is this silhouette that shall be controlled by the public power, the private power being in charge of the building varied and mixed architectures. Dominique Perrault, April 2009

The project presented by Dominique Perrault architecture + ARUP is based on issues of sustainability. The world environmental problems get more attention and consequently reaction on local level could be seen more clearly. This project certainly has high aesthetical value and good outlook, but the reason why it is the most successful is probably in the fact that it is connected more adequately to the surroundings, it is environmentally friendly and it is a real strategy for development with the possibility of step-by-step construction and later design of the buildings. The plan is composed by separate blocks with pitched tops because of the convenience of the penetration of light. The buildings are divided in different zones according to the demands for secondary center of Sofia. The blocks are getting higher gradually and so they create harmonic flow of forms that remind mountain relief. Between the two sides of new developments is designed a park. The idea that DPA propose for an open district is rather appealing as everybody could easily benefit from the facilities in the area. The blocks are united in different groups by the urban semi-transparent envelop that gives the final outlook of the complex and corresponds to the mountainous relief around Sofia. For the groups of different constructions are developed different sustainable strategies. They could be summarized in: use of photovoltaic panels, natural ventilation, green spaces, re-use of the rain water, heat recovery system and even wind turbines. Hopefully the program in the project will be completed entirely and the city of Sofia could enjoy its secondary mixed-use center.

A LANDMARK ECO CENTER

Mixed functions
Rather than monofunctional plots which would raise on and off site transports needs and infrastructures, the project aims at mixing the majors functions (Offices, Commercial, Hotels, Residential and Sports facilities) on each plots, with variant gradient depending on their location and density, thus improving social interactions, safety and pedestrian movement. transport and infrastructure New zero-emission fast trams and trolleybuses will create strong transport links to the city centre, to neighboring areas of the city, to the airport, and to the nearest subway stations. With a maximum distance of 150m to the nearest transport link and amenities, the dense network of car free paths encourages walking and cycling and social interactions. Car traffic will be kept to a minimum by creating large scale plots and off-street car parking located at site entrances. urban envelope and building outline The urban envelope has been designed to preserve a maximum of daylight in all open areas, especially in the Central Parkland. Buildings orientations and heights are optimized to maximize the benefit of passive solar heating in the winter and sun shading in the summer. Office blocks are orientated to the South to maximize the potential of daylight harvesting.

Energy strategy
The proposal aims to achieve 40% of energy use from renewable sources based on biomass Combined Heat and Power to meet the base thermal load. Wind turbines, solar panels on buildings’ roofs and façades and ground source cooling for high heat density offices will help reducing energy reliance from fossil fuels.
Waste strategy
The waste hierarchy will be used to determine opportunities for waste separation and recycling opportunities and waste management facilities will be fully integrated. Compost stations for organic waste recycling will be available to all users of the future district.

Water strategy
Existing interrated water streams will be used to create a wide network of canals, including the restoration of pre-development water bodies. It will help to restore previous wildlife habitat and wetlands. A large water reservoir will be created in the Central Parkland and will be used for building cooling and sport practicing and to mitigate downstream flooding.

Landscape
More than 50% of the site surface is devoted to landscape areas, gardens, squares, passages, parks. The buildings implementation allows preserving half of the existing trees, and all new plantations will use native flora. The proposed devices result to a LEED Platinum certification of Sofia Secondary Center in the LEED for Neighborhood Development rating system.