Built with a green heart

Garden City at Exit 7, Thika Highway, Nairobi is a 32 acre mixed use development combining retail, residential and business facilities that integrate handsome international design with local expertise, while at the same time incorporating Kenya’s regional priorities of saving energy and water.

Phase 1 – the mall, selected residential units and park – will be completed in May 2015, while the remaining residential and business sections are due for completion within the next three years.

Garden City’s retail section is targeting a Leadership in Energy and Environmental Design (LEED) Silver certification, and the residential units will be seeking a 4 Star Green Star SA MultiUnit Residential V1 rating.

Most significantly, the development has heralded the founding of the Kenya Green Building Council, chaired by Elizabeth Wangeci Chege, the CEO and lead consultant of WEB Limited, sustainability consultants on the Garden City project.

“I think the main challenge was programming, because at an early stage you have to decide how you are phasing out the different developments, so you are not expanding into the construction areas,” Chege says of the unique challenges thrown up by Garden City.

“We had to implement integrated design from an early stage, and we had to get the facilities management company on board a year prior to completion – this was a local first. We were also faced with the issue of design silos, getting a skilled design team for mixed use,” she says.

The solution was to find concept guardians, international teams of architects and engineers, who were then anchored by local teams that delivered in terms of construction.

For Arup engineers, input at the construction phase meant another first – a piled foundation solution which is not commonly used in Nairobi. “Through various design iterations, we were able to introduce piling as the preferred foundation solution and save the client significant costs and time,” says senior engineer Matthew Lilley.

Regional priorities for phase 1 included reducing energy by 25% relative to a similar building in a similar location. For Arup, this meant drawing on their collective experience in sustainable building.

Passive Ventilation

“We looked at the orientation of the building, and took into account the local climate and prevailing wind direction,” says Chege. “The design team worked on an open envelope, allowing for a lot of cross ventilation.”

The central mall area is fully ventilated naturally, says Lilley: “This also allows the retail units to draw fresh air direct from the mall, simplifying their needs and potentially making it possible to naturally ventilate the smaller units and kiosks.”

Energy and Bulk Solar Feed-in

After a feasibility study on covering the car parking bays with solar PVs, and reviewing the return on investment, the developers, Actis, gave the nod to Africa’s largest solar carport – where the panels provide shade while also feeding clean energy into the distribution system. Solar power will be used alongside standby diesel generators.

The decision to include solar right from the outset was unique, says Daniel Davies, director of Solarcentury in East Africa. “Often solar is an after-thought, which makes it harder to integrate into the build.”

For NVI Energy, which facilitated the investment, the integrated design posed some challenges. “All our designs had to be meticulously checked and signed off,” says executive director James Irons. “Our system is really integrated into the building.” The shaded parking is also appealing to shoppers.

A solar fuel saver enables the solar system to operate in parallel with the mall’s standby generators, says Irons. The total capacity of the solar carport is 858 KWp, and it has been estimated to reduce CO2 emissions by about 748 tonnes per year.

Landscape and Water

Garden City is designed to its name, and a central feature is what landscape architect David Price, director of Hyland Edgar Driver, calls its green heart: a 3ha central park, around which the three sectors interface.

“It’s an inclusive multi-functional space consisting of water features and dining terraces, wet play areas with fountains and jets for children, a large green park and gardens, and an amphitheatre with a stage for outdoor performances,” he says.

“The sustainability response runs right through the project from macro-scale in the masterplan, where the emphasis was on improving microclimate, down to micro-scale in the use of sustainable local products,” he says.

The water for irrigation is sourced entirely from rain. A 390 m2 buried tank stores the rainwater collected from the building roof. “It’s then pumped to a series of points for manual watering,” says Price. “The amount collected is finite and so a watering regime will be in place to water those areas that matter the most.”

Building Knowledge

“The vision for Garden City was always to create something that was market-leading in terms of design, scale, concept and quality,” says Michael Turner, managing director of international developers Actis in Nairobi.

“Green building principles are still new to East African property development, so we’ve had a lot of interest in the fact that sustainability is at the core of this project, and hope that Garden City will be the showcase for projects that come after us.”

The full feature appears in the April-May 2015 issue of earthworks magazine.