Mauritius Commercial Bank: Ebene Building
By: Jean Francois Koenig, Architect
The Mauritius Commercial Bank, the oldest bank in Mauritius and the Indian Ocean islands founded in 1878 and based in the capital city Port Louis, February 2006 saw me design offices and training facilities in Ebene, in the centre of the island, which decentralised them from Port Louis for the first time in history.
Their brief came with instructions to keep it simple and inexpensive. They got something different that went far beyond the brief. The building reinvented the client’s way of working and thinking about the workplace and the environment.
To put it in context, it started at a time before many Green Building Councils around the world had been formed and it became the first building in the southern hemisphere to obtain a British Research Establishment Environmental Assessment Method (BREEAM) certificate. The building also became the first Mauritian work of architecture to represent with four others the best of African architecture at the International Union of Architects (UIA) World Congress inTokyo 2011, a triennial event and with it, I was elected as one of the ‘100 Architects of the World 2012’ in a competition organised by the Union of International Architects (UIA) and the Korean Institute of Architects (KIA).
It has become so popular with the client that they all want to work there and sometimes board meetings traditionally held in Port Louis have been switched from head office to the new building. Energy savings begin with a well insulated building and optimum orientation. The concrete shell is insulated with 50mm rigid polystyrene, an air gap of 350mm and an 8mm thick honeycombed aluminium external skin. The portholes in the glass rings all around the ellipse are double glazed and with the air gap of the outer reflective glass skin creates a triple glazing solution. The two glass facades of the ellipse are true north-south with sunscreens whose projection depths were determined by sun path analyses. They are 1.8m on the north face and shallower at 1.2m on the south to prevent direct sunlight hitting the full height double glazing during working hours from 8.30am to 4.30pm. During this period, the blinds remain up to allow maximum glare free daylight to enter the 22m deep floor plate eliminating the need for artificial lighting entirely. Low angled early morning and late afternoon sun is controlled by perforated blinds which drop down automatically from sun sensors relayed to the computerised building management system.
The building is the expression of an abstract geometric shape in the form of a pure ellipse. It is held aloft on four pillars. Born from the need to accommodate both auditoria and offices, it is the architectural synthesis of these two different requirements fused into one single shape. It is an example that Islands care about, and can make a leading contribution to global sustainability even though they have a low carbon footprint and insignificant impact on climate change.
The orientation of the elliptical glass facades is true North-South. The blank curved East and West ends are well insulated and the portholes are triple glazed. The photovoltaic cell farm contributes to over one third of the total energy needs at peak with clean solar power.
The Board Room on the top floor shows the expressed steel structure, natural light entering from the roof and the sides, and the ample space provided for the long table as well as two rows of plants under the glass rings.
Plant rooms, traditionally situated on the roofs of buildings, are situated on lower levels for ease of access and maintenance. This liberates the roof allowing large spans and column free spaces on the upper floors facilitating internal planning.
Full height double glazing allows in a maximum amount of natural daylight. The depth of sunscreens, deeper on the north facade and shallower on the south facade are determined from the study of sun paths. Sensor controlled perforated venetian blinds are activated automatically to control glare. To eliminate interference from external noise from the nearby motorway the glass walls of the auditoriums are triple glazed.
There are no suspended ceilings in the building, not even in the acoustically engineered auditoriums. The underside of the concrete slabs are kept bare and painted white.
Underfloor cooling passes through a stabilised air plenum without ducts optimising flexibility. No ceilings allow cold energy stored within the thermal mass of the structure to radiate directly into the floor below keeping ambient temperature down and diminishing cooling loads.
The ‘all air’ air conditioning uses ‘free cooling’ in winter months. Three large thermal storage tanks insulated and clad in polished stainless steel store energy to further reduce cooling loads.
Night time illumination accentuates the shape of the building whereby its beauty, like the soul, comes from within. Five glass rings encircle the building accentuating the purity of its geometry. Portholes enhance the air and space ship quality of the architecture gives the sense that the building is ‘landed’ on its base.
Access to the plant rooms are through “gull wing” doors. The materials chosen are long lasting and mostly maintenance free. The pillars are clad in travertine marble. The louvers are in semi-matt stainless steel. The shell is clad in aluminium and, in an honest expression of function, no attempt is made to hide the blue insulation of the shell which is seen through the glass rings. The drop off entrance porte-cochere lights are recessed in the thickness of the concrete slab. Kerbs, bollards and the sloping and curved retaining walls are in white off -shutter precast concrete.
Source: The Green Building Handbook Volume 6
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