URBAN ANALYSIS: URBAN PRESENCE + JONGNO DISTRICT IDENTITY
The new governmental office complex aims to be an open government building. It is planned with an open use and structure so that citizens can naturally enter and exit from external spaces to the ground and basement of the building, with ground and underground spaces of the naturally connected to public pedestrian passages to the north and underground public pedestrian passages. The building, as seat of local government of the city, becomes a place of encounter of the social and the personal, an important union manifest in the relationship between urban and architectural gestures, with a facade composed of both small windows addressing the needs of the building, and super-large windows addressing the building’s unique location at a crossroads in the city, becoming the point of destination for important streets that die off against the building, and the focus of an array of deep urban views to be enjoyed from the building itself.
VIEWS TOWARDS THE SITE: INVITING & WELCOMING BEACON
The building is situated on a privileged site, terminus of visual convergence along several major urban arteries: east to Sambong-gil, west to Sambong-gil, Jongnogucheong-gil looking north, and southwest along Changjindong-gil. All roads lead to Jongnomun, revealing the centrifugal and centripetal relationship between building and surrounding urban context. The facade is articulated to take advantage of the unique privilege of being located at the terminus of three streets with three deep perspectives into which people can gaze as they are occupying and using the building.
JONGNOMUN; Jongno Gateway
A fundamental initial consideration is the sustainable creation of the building’s environment. The greatest attention has been paid to energy conservation in the preparation of the design. Features integrated into the project from initial conception are:
—significantly reduced energy consumption
—building integrated photovoltaic systems
—glazing that achieves better thermal performance than a 30% glazed wall via a ventilated facade system solution, which double-functions as a source of pre-heating during cold weather
—roof garden areas which act as a passively-controlled buffer zone, contributing to energy performance while providing an excellent culture and leisure destination for the public.
Like most other buildings in the area, the building starts as a practical box, providing for the programmatic requirements of the Jongno District Office complex. The box is then hollowed
out to create a well-defined open public space. The form is then sliced, opening the building to the sunlight and creating space that people can occupy above. The sky auditorium puts visitors and users in touch with a wider scale of the city with views of horizon, mountains, and surrounding Jongno District views and skyline. The roof becomes a sequence of indoor gardens that perform both environmentally and also programmatically, transforming the upper level of the building into a public attraction. This can be achieved economically without prohibitive cost or size increase. Working within the allowable gross area, the rooftop gardens are proposed as additional and original form of public space, resulting in a new way to inhabit the city, day through night and year round. This forward-looking approach must be literally grounded on a knowledge of the past. Not only is the building concept borrowing from a traditional typology—that of the madang or courtyard—it features at its lowest level an archaeological vault showcasing the remains of historical buildings to be uncovered by the new construction.
The roof garden areas, while providing an excellent amenity for the public, also make an important contribution to energy performance. They act as a passively controlled buffer zone between the air conditioned interior of the building and the external environment. They also provide a source of pre-heated, oxygenated air for use within the building. The gardens in the building have several benefits:
1. Improve the energy consumption of the building. this is related to the thermal mass concept described in the operation of the gardens. Surface temperatures are greatly reduced, on a 32°c day, the roof surface of a green roof is estimated to be 26.6°c, while a conventional roof is estimated to be 80°c.
2. The reduced surface temperatures also significantly reduce the urban heat island effect of cities like Seoul.
3. Noise absorption/sound reduction (estimated up to 50 db noise reduction) and air filtration.
4. Provide urban amenities and bring nature closer to the occupants of the building improving productivity and health.
The gardens in the building also:
5. Improve the storm water management with rainwater retention and buffering. Our strategy aims to retain 70 to 80% of the water falling onto the roof and using the water for the irrigation systems of the gardens and pools. this concept can be integrated with the grey water system of the building with minimal filtration for all toilet use which accounts for approximately 40% of the typical water footprint of office buildings.
The greatest attention has been paid to energy conservation in the preparation of the design.
A preliminary energy analysis suggests that the building will consume approximately 76 kwh/m2 annually before taking into account on-site energy generation. A typical building with this program would be expected to consume in excess of 200 kwh/m2. The main measures employed to reduce consumption are as follows:
- Building envelope improvements in terms of thermal performance, shading and air tightness.
- Lighting, daylighting and automatic control system optimization.
- HVAC enhancements include the use of high efficiency motors, fans and pumps; local heatpump systems throughout for heating and cooling; sensible and latent heat recovery; outside air ‘free cooling’; seasonal geothermal heat storage; and advanced intelligent bms
- Reduction of floor-to-floor height by carefully integrating building structure and systems. Building integrated photovoltaic systems will contribute about 22 kwh/m2 per year. The net annual energy consumption of the building is therefore estimated to be 54 kwh/m2. The inclusion of significant areas of glazing is important in terms of aesthetics, occupant wellbeing and daylight harvesting. However, there is also the potential problem of increased heat loss and solar gain. To mitigate against this, a ventilated facade system has been devised with integrated shading, low emissivity coatings and spectrally selective glass. the system achieves better thermal performance than an opaque insulated wall with 30% glazing and also provides a source of pre-heat for the building ventilation systems during cold weather. The roof garden areas, while providing an excellent amenity for the public, also make an important contribution to energy performance. They act as a passively controlled buffer zone between the air-conditioned interior of the building and the external environment. They also provide a source of pre-heated, oxygenated air for use within the building.
The structure of the building is very simple and is intended to maximize efficient use of all available space.Thin post-tensioned flat slabs with no drops or beams are used for the majority of the floor plate. These give the thinnest possible structural depth and maximum floor to ceiling heights, allowing more floors to be fit into the available height. They are supported on concrete columns planned about an optimum office and car parking grid. Very high-strength concrete is proposed to be used to keep columns as small as possible. Concrete walls enclosing the stairs, elevators and shafts stabilize the building laterally.
The bridge structure is a light-weight addition supported off the side of the concrete structure. It is proposed to be steel and composite floor slabs, and is planned with a large open space for the auditorium, which makes the volume very lightweight for its size. The volume is then braced on all sides, top and bottom, to create a stiff torsion box that can manage being held eccentrically by the concrete building while controlling deflection. Expansion of the building can be achieved in the future by adding additional floors under the bridge and wrapping these in additional trusses.
The basement box will be in-situ concrete, surrounded with a diaphragm wall. Depending on exact geotechnical conditions, the columns and walls will likely be supported on piled foundations. The plan of the building maximizes use of the site volume without having to alter the foundations of the existing building on the site. By cantilevering over the existing building, the new foundations can be kept outside its footprint. The diaphragm wall could be placed alongside the existing building, or to gain extra space underpinning could be used.