Set to be Africa’s third tallest building after South Africa’s Carlton Centre and Ponte Tower in Johannesburg, the elegant prism-shaped Britam Tower will stand proud over the city skyline of Nairobi, Kenya by February 2017. It features an innovative performance facade and – despite being 31 floors tall – is nearly 100% naturally ventilated.
Britam Tower is a 31-storey office development nearing completion in Upper Hill, Nairobi. The building stands at over 200m tall, offering unimpeded views of Mount Kilimanjaro and Mount Kenya, from which design inspiration was drawn. The building will attract both local and international tenants such as private companies, blue chip financial services firms, and government and diplomatic bodies that operate out of Nairobi. Financial services company Britam will also occupy a small portion of the building, placing it in the unusual position of being developer, landlord and tenant. This will be one of the most populated buildings in the capital city, occupied by 3000 people on a daily basis, with a gross lettable floor area – combined across all storeys – of 33000m2.
MAXIMISING PERFORMANCE THROUGH INNOVATIVE DESIGN
Britam Tower is a quintessential example of a building that maximises performance through innovative design. By adopting passive design strategies (shading devices and natural ventilation) with active technologies (LED light fittings, motion sensors and a centrally located air-conditioning system), Britam Tower follows world-renowned architect Norman Foster’s guidelines for the optimal design of green buildings. Foster’s guidelines suggest that by incorporating passive design principles first, the biggest environmental gains can be achieved at the lowest cost. After passive design has been optimised, efficient green “active” technologies – those that require less resources to operate or manage – can be incorporated to work together with the passive design elements. If this is achieved, then the building will be environmentally friendly, have lower operating costs, and allow for a comfortable and healthy internal environment for its users – even at a large scale and using materials such as glass.
The passive design extends to the specially engineered facade. Chris Kroese, director at GAPP Architects, explains that “special high-performance glass, which had to conform to certain design requirements with regards to heat and light transmission, and impact resistance, was used for the external facade of the office building”. Much of the sun’s heat is reflected or blocked before it even reaches the glass because of the precisely designed shading devices. “A large majority of the building facades are covered by a ‘veil’, which is made up of horizontal ceramic ‘baguettes’. Each of these is a square ceramic tube, 50mm by 50mm, and spaced about 150mm apart. They provide excellent shading – virtually all of the glass is shaded most of the day.” Jacqueline Nyaguthii, a representative from Britam, notes that cleaning the expansive glass also incorporates sustainability principles. “Most of the glass used on the facade has a self-cleaning coating, meaning that minimal water is required to clean it,” she adds. To further maximise shading, the designers allowed for a gap of 600mm between the shading veil and the glass. There is a catwalk in this space on the outer edge of each floor, which can be used for maintenance purposes.
Britam Tower is nearly 100% naturally ventilated – only the areas surrounding the lift lobbies make use of mechanical cooling. Designing for natural ventilation throughout the building was a priority, according to Nyaguthii. “As research continues to indicate that people are increasingly spending more time in the workplace, it has become equally important that offices are designed to enhance productivity and performance,” she says. “We wanted to focus on creating an environment conducive to this, and the key attributes we identified were natural cross-ventilation and optimised use of daylight.” High-level and low-level windows that can be opened on each floor draw fresh air into the building while also providing occupants the flexibility to regulate the internal thermal comfort in each individual space. The facade shading devices stop short of each of the faceted joins of the building, which creates vertical corner “channels” from which fresh air is pulled into each floor through the open windows.
GAPP Architects incorporated the flexibility to install an air conditioning system in future should the need arise. “The building has 31 floors. Near the middle, on the 20th floor, is sufficient space for air conditioning condensing units,” explains Kroese. Thus, because the building does not provide the infrastructure for air conditioning for each of the tenants, they are forced to make the most of natural ventilation and alternative options. While reducing energy consumption, this approach also makes occupants aware that it is possible to create comfortable internal environments without mechanical HVAC systems.
Energy saving light fittings were installed throughout the building. “More than 95% of the lighting in the office areas is LED. We have also used motion sensors in each space, and so unused lights are turned off automatically when a room is vacant,” says Kroese. The building also receives plenty of natural daylight despite the “veil”. This is because the shading devices are installed at a specific angle, which allows the sun’s rays to bounce off them and hit the ceiling inside the building, illuminating the spaces with natural light.
The initial conceptual design included a wind turbine on the roof of the building to actively generate energy. After numerous feasibility studies, however, the turbine was omitted. “When we had tests done, it turned out that the local wind was too weak to produce enough energy to make installing the turbine financially feasible. This was unfortunate as we were fully committed to having it,” explains Kroese. The final design still incorporates the “idea” of the wind turbine. “There is a tall mast on the roof that will receive a sculptural feature resembling a helical wind turbine,” Kroese says.
Nature is brought into the building by way of a Zen garden located on the ground floor, which is partially indoors and partially outdoors. The water used to irrigate the garden is drawn from rainwater harvest tanks on the ground floor. “All of the plants in the Zen garden, and in other parts of the building – both inside and outside – are indigenous to the area,” explains Kroese. “This means that they require less water to maintain.”
Britam Tower is a practical demonstration of a new mindset focused on the design of environmentally appropriate skyscrapers. According to Kroese, Britam Tower will target a green building certification in the near future but the specific rating tools have not yet been decided. The building’s environmental performance will be monitored and tracked after practical completion in order to fine-tune and improve the systems where possible. The monitoring process is essential in order to maximise the building’s operational efficiency.
Nyaguthii adds: “We [Britam] are a socially responsible corporate citizen striving to uphold environmental sustainability in all of our endeavours.” At the same time, it is expected that Britam Tower will bring a good return on investment. “Due to the design, we expect the running costs of the building to be significantly reduced,” she says. Savings will also be passed on to the building’s tenants. Meeting a building’s financial and environmental goals is something every developer should strive for, and Britam Tower is a clear demonstration that the two can go hand in hand.
WORDS DEVAN VALENTI PHOTOGRAPHY AXEL FASSIO