THE CATHOLIC UNIVERSITY OF EASTERN AFRICA
- Architect & Environmental Design Experts: Musau Kimeu, Architect
- Quantity Surveyor: Musyimi & Associates
- Structural and Civil Engineer: Novaya Engineers
- Mechanical and Electrical Engineer: Geomax Consulting Engineers
- Main Contractor: Lalji Meghji Patel & Co. Ltd
The LRC (Learning Resource Centre) at the Catholic University of Eastern Africa in Karen is an inspiring development. It is an example of ecologically sustainable design in the region. This project is in line with the position that the architecture of the 21st Century is about environmental design in terms of architectural thought, innovation and also environmentally friendly-solutions that are easy to realise.
The LRC offers a new paradigm for future projects. It is as a touchstone of environmental design quality and relevance. It demonstrates convincingly that it is possible to design and put up green buildings in the region. Here below are the sustainable design strategies used in the development that make it the first convincingly green building in the region.
The LRC consists of three buildings namely a 3000 seater ultra modern Library, a 1200 seater state-of-the-art Conference facility and a 500 seater Cafeteria, all arranged around a 50m by 40m central Square and tied together by a covered walkway with outdoor seating.
Measuring approximately 50mx40m, the Square acts as the datum, dictating placement of different elements within the site. Its 6m wide paved walkway is finished with a combination of patterned Njiru blue stone, a hard grey stone and cut mazeras paving. The walkway’s roof drains towards the buildings. To the inside of the walkway is a storm water drainage filled with smooth river bed round stones. The central area of the Square is planted with grass and on one corner of the Square is the fountain of the Professor and the student and diagonally juxtaposed is a three metre high statue of Pope Paul VI by Ugandan artist Leonard Kateete. Pope Paul reigned from 1963 to 1978.
Sustainable design strategies shared by the three buildings
For prevention of heat gain and provision of cooling, the strategies used include
The Buildings orientation: Sun-movement dictated the orientation of the buildings with their long axes along East – West with most of the windows on the North and South facing facades and minimal openings on the East and west facing facades.
Sun-shading of glazed areas: All glazed areas are fully sun-shaded throughout the project with diverse devices such as precast concrete fins, concrete egg-crate, and horizontal metallic sun shading devices to avoid monotony.
Use of natural ventilation to provide cooling: The “Stack Effect” principle is used in removing exhaust air in all the buildings. The natural pressure difference between the buildings interiors and the rooftops is enhanced by the exhaust “chimneys” protruding from the top of the library and conference hall capped with ventilation cowls. Their surfaces are heated by the sun, lowering air pressure at the outlet to draw air upwards through the chimneys. Air is exhausted naturally by buoyant convective effects with no mechanical assistance in all the three buildings.
The project uses high thermal mass (thick walls) to reduce solar heat gain through the external walling.
Other sustainable design strategies include:
Choice of materials
The buildings use locally available materials, with low embodied energy, with none or minimal maintenance. These include
- Njiru blue stone for the external walls and some of the internal walls
- Cut Mazeras stone, Njiru blue stone and Rongai grey stone for external paving around the Square
- Cut Mazeras stone on the walls behind the reception areas of both the Library and Conference hall
- Mvule timber ceilings in selected areas in the three buildings
Renewable energy: Wind energy is utilised in operating the ventilation cowls above the thermal chimneys.
Rainwater harvesting is incorporated into the development, with an underground water storage tank whose top doubles up as the podium for an outdoor amphitheatre. The harvested water is used for irrigation and cleaning purposes.
Sanitation: Use of environmentally friendly sewerage system. The sewerage system for the entire Campus consists of oxidation ponds, which is environmentally friendly. Waste from the washrooms in the LRC is directed to these ponds, ensuring high standards of environmental sanitation.
Outdoor landscaping has been done using evergreen local plants, especially fruit trees defining ‘outdoor rooms’ and creating unique visual interest. In addition, ramps for the physically challenged have been provided in all the buildings.
Each of the three buildings has its environmental design strengths, which are highlighted here below
With a seating capacity of 3000 users on five floors and being the only building in the original brief, the Library building is the focal structure of the development, placed in-between the Conference hall and the Cafeteria. It is inviting, with a totally glazed framed entrance shaded by a 8.4m high canopy projecting above the entrance floor level. Raised 2 metres above the natural ground level, the flight of steps to the main entrance gives it a clear commanding sense of entry, while side ramps direct you to the entrance and to the Lower ground level.
Sustainable design strategies used in the Library
With the Library’s long axis along East – West, its window openings are located on the North and South facing facades, with minimal windows on the East and West-facing facades except for lobbies to the wet areas. The Library building is exceptionally lit naturally throughout daytime using the atrium roof glazing and side windows. So well is the natural lighting in the interiors that the users do not need to turn on artificial lights throughout daytime and thus cutting on running costs significantly.
The Library interiors are light-coloured to render both natural and artificial light sources more effective. The combination of clear glass, light finishes, and Nairobi’s natural bright sky provides good natural lighting in the interior spaces. The library central atrium has a barrel-vaulted roof whose 2 metres wide central section is raised up along the entire length of the library. The raised section is fully glazed with laminated glass to admit natural lighting into the building through the atrium. However, to reduce direct solar radiation through the glazed atrium roof, large aluminium aerofoil louvres have been installed below the glazed roof to sun-shade and cut off glare from entering into the library.
With a decision to use natural ventilation over mechanical ventilation in all the Library spaces, significant running costs have been saved. The chosen design approach was to have air intake through the side windows on the walls and exhaust the used hot air through the roof. This is achieved by use of airshafts on the attic floor and above the roof combined with the atrium. These act as thermal chimneys to discharge hot air, which enters the building through double louvred panels on the side window glazing on the lower floors. The double louvred aluminium panels are fitted with mosquito or insect proof wire gauze in between which run the full height of the windows. This principle of natural ventilation is very similar to that found in termite hills.
Moderating external heat sources
A combination of high thermal mass ‘250mm thick hand dressed Njiru blue stone walls’ and extensive concrete sun-shading in the Library and Conference hall moderates temperature extremes. The sun shading is made of pre-cast concrete vertical elements combined with in-situ concrete horizontal sun shading elements and a concrete deep roof eave overhang around the Library building. The sun shading devices were calculated and properly sized for effective sun shading throughout daytime. To reduce heat gain and noise through the roof, 50mm thick Styrofoam was installed throughout the entire roof beneath the roofing tiles and GCI waterproofing. We should note that Styrofoam is composed of 98% air and thus has excellent insulating properties.
Other green building design strategies used in the Library include
Building services such as toilets, kitchenettes, stores, ducts and fire-escape staircases are located on the East and West facing facades. Being non-habitable spaces, they shield the habitable spaces against the morning and harsh afternoon sun. In addition, the building uses locally available materials, with low embodied energy, minimal maintenance, non-toxic, those with minimal internal pollution and damage to health and easy to re-cycle or to re-use.
The Conference Hall
The conference hall seats 1200 people, 400 of whom sit in the 7 breakout rooms, all inter-linked using the latest conferencing technology to ensure that one can follow an event in the main hall while seated in any of the rooms. This facility achieves several firsts. It is arguably the largest conference hall in the region with excellent acoustic design. The voice of a person speaking on stage is crystal clear to the audience seated at the rear row of seats in the gallery, 40m away and the person at the back of the gallery can clearly communicate with someone on stage without use of any public address system! Talk of going back to the basics in verbal communication. If you are in doubt, find time and visit the facility! The level of clarity is just amazing. In addition, the Conference hall is the second and the largest ROCK BED cooled naturally ventilated building in Africa. Universal access especially for the physically challenged is provided for in the auditorium seating area and stage using ramps. From the gallery, one can walk out to the side balconies for a break.
In designing the Conference hall, a reverberation time of about 0.5 seconds considered and used. For Conference halls, clarity of speech is key. Clarity is in this facility is achieved through strong “early” reflections following the direct sound to the listener. In the design, this is ensured by placing sound reflectors above the stage area and the overall shape of the ceiling above the central seating area. The architect chose the ‘horse shoe’ balcony seating arrangement and a ‘vineyard terracing’ form for the relationship between the main seating area and the balconies, hence the balconies have the concept of breaking up the seating into blocks (like vineyard terraces). The overall form of the hall was developed primarily from the desire to have quality acoustics and best practice. From an acoustics point of view, the end result is obviously pleasing and has set new acoustic design standards in conference halls in the region.
The various acoustic considerations forced early decisions to be made on the type of lights and luminaries’ to be used and thus due to the high ceiling of 12.5m above the finished floor level in front of the stage, LED general and concealed lighting at the ceiling was an obvious choice because of their long life. The special effects lighting including the stage lighting were also meticulously chosen with the overall effect and ambience in mind.
As is the case in good auditorium design, parallel surfaces must be avoided so as to minimise multiple reflections. In our case, a rectangular shape was chosen for the ground floor and a horseshoe shaped layout for the galleries. To eliminate parallel sidewalls, sinusoidal (sine wave shaped) walls were used. It is on the surfaces of these curved walls, facing away from the stage that the glazed windows are located. Throughout the auditorium interior space, the principle of having ‘perforated’ cavity walls is used. For the external wall, Njiru hard blue stone is used, whereas a hand dressed grey hard stone is used on the interiors with the cavity in-between. Mineral wool is then sandwiched in between the cavity walls with no cement mortar on the vertical joints. Further, to avoid internal sound reflections, all internal columns, the main gallery beams and doors are padded with 50mm thick foam and covered with fire resistant vinyl padding.
Along the circulation aisles, the ceiling consists of mvule timber joists with perforated plywood, hessian cloth and 50mm thick mineral wool above the hessian cloth. A similar ceiling is used in the entrance lobby. In the central area of the auditorium, acoustic ceiling and purpose made sound reflecting profiled MDF ceiling is used. This also includes sound reflectors above the stage area. Due to the fact that a high volume is strongly recommended for good acoustic qualities in auditorium design, in our case the ceiling is 12.5m above the flat area in front of the stage. For the flooring, “regupol” by the BSW (Berleburger Schaumstoff-Werk) is used. This is a rubber-polyurethane composite, viscoplastic, which is friction enhancing. It is long lasting, resilient and can be recycled.
At the stage and the rear wall of the gallery, aesthetically designed acoustic timber panelling with adjustable panels are used. This gives the hall its signature identity. These panels are mounted on perforated MDF panels, creating a cavity with the rear masonry wall, within which mineral wool and hessian cloth are installed. The proscenium is padded with high sound absorbent vinyl covered panels for quality acoustics too.
Sustainable design strategies
Natural ventilation: From the onset, the architect who is also an environmental design expert and an acoustics specialist made the decision to use natural ventilation in this large gathering space. This had a major bearing on the building design. Natural ventilation implies opening windows while mechanical ventilation implies significant running costs. The chosen design approach was to have a naturally ventilated hall without compromising on external noise. The building is oriented on an East-West long axis with windows facing North and South and uses high thermal mass consisting of 250mm solid walls and 600mm thick cavity walls to reduce solar heat gain into the interiors.
The facility’s glazed openings are effectively sun-shaded against direct solar radiation throughout the day using a deep roof overhang, balconies and for some of the windows concrete sun-shading fins. One of the most innovative passive cooling strategies in this development is found in the hall. This is in the cooling and ventilation of the hall using a rock bed cooling system. Granite rocks have been arranged beneath the raked (stepped) seating. The space has louvred openings on the sinusoidal walls through which air is drawn into the rock bed. It then passes through the rocks before being introduced into the hall beneath the seats.
The passive ventilation and cooling principle employed relies on capturing nighttime ‘COOLTH’ or coldness stored in the rock surfaces in exchange of heat from the warm air entering the chamber from outside. The air is pre-cooled before entering the hall. At night, cool night air is blown through the building via the rock bed, cooling down both the rocks and the exposed building structure and fabric. During the cold season, the rocks which are warmer than the hall, warm up the air supply. Isn’t this amazing! Talk of rocket science made simple.
From the hall, the used air is exhausted through four timber louvred ducts, two behind the seating area, and the other two on either side of the stage. Above the roof, these ducts become thermal chimneys capped with wind driven ventilation cowls or cyclones for effective exhaustion of the used air.
In this development, the Cafeteria is the only building, which is not sunken into the ground. The Cafeteria boasts of a high-ceiling double volume immediately after the entrance door with two spiralling chandeliers on its white ceiling.
Sustainable design strategies
The cafeteria building uses high thermal mass and horizontal aluminium louvred sun-shading system to cut down on direct solar radiation. Air intake into the building is through double-sided louvred openings with inbuilt mosquito or insect proof wire gauze. Warm air is then exhausted to the outside at high level through the roof using the ‘stack effect’ principle. The Cafeteria does not have any vertical sun-shading fins in front of the glazed windows so as to avoid blocking of views.