Alice Lane Building 3, a mixed-use development, is the final of three buildings that together form a new urban precinct within Sandton’s CBD. The building received a 4 Star Green Star SA Office V1 Design certification, with the As Built submission underway.

At the centre of the Sandton CBD, the Alice Lane precinct is within easy walking distance of the Sandton Gautrain station as well as embassies, hotels, and various commercial, retail and leisure amenities.

Duanne Render, director at Paragon Architects, says proposals for the site began in the early 2000s, and the first designs were quite conservative, employing conventional construction methods. However, over time a more integrated approach was adopted that included a piazza and a more sensitive urban interface.

“The focus was to tie the buildings together, draw people in and provide quiet places for office workers through the use of elements like artworks and a carefully designed water feature,” says Render.

A single super basement unifies the site, with three entrances off Fredman Drive, 5th Street and Alice Lane respectively to minimise impact on traffic and optimise internal circulation. Access to the three buildings is through three individual cores, and there are three public access points for the piazza.

Karen Marais, director at The Ochre Office, the landscape architects on the project, says: “The core design principle was opening the precinct to the street edge and welcoming users from all directions.”

Deriving from this intention, the key design elements for the piazza were open edges to allow free flow of pedestrian movement; the idea of a gateway announcing entrance into the precinct; an active core with a number of restaurants; fluidity of design, with paths of movement sweeping below the buildings; affordability and practicality, including considerations around security, adaptability of space, maintenance, navigation, structural, drainage, and level implications; and an aesthetic that incorporated a common design language, construction-type and materiality while allowing for interest in the design.

Three important elements define the visitor’s experience of the piazza – a water feature, artworks and planting.

A surface water feature runs from the entrance off Alice Lane, channelling water and creating a line of sight through into the central piazza. The two major artworks installed to date are the gateway sculpture Synapse by Marco Cianfanelli, and the 5th Street staircase by Lorenzo Nassimbeni.

Distinctive design

Building 3, the final building to be completed in the precinct in January 2017, comprises offices designed for anchor tenant law firm Bowman Gilfillan, together with retail units. “The concept for Building 3 was an iterative process to satisfy the needs of the primary tenant,” explains Render. “The nature of a law firm dictates a high percentage of cellular office space – in this case 60% – and all offices required windows. The design response was to create two wings, north and south, with a central atrium. In this way, all offices are equally exposed to natural light and views.”

The design concept driver was the idea of a crystal. Working with site line analyses and sun studies, the conceptual design used sunlight to generate refined massing and bring light into the central public space.

The central atrium is the heart of the building and, upon entering, the visitor’s gaze is drawn upwards through a 15-storey-high dramatic internal volume. This, plus the idea of a continuous “racetrack” circulation space tying the two wings together and slick finishes, creates an awe-inspiring internal space.

Material of choice

The design language of a crystal offered the opportunity to showcase the latest in glass technology and provide contrasting experiences of the building during the day and at night. Saint-Gobain’s Cool-lite ST 120 solar control glass was specified to reflect the Gauteng sky, allowing the building’s appearance to change with the weather.

Internally, light, textured and carefully-detailed ceilings – comprising flush plaster, wallpaper, Barrisol and cove lighting – are complemented by the sculptural form of the balustrading, which uses both solid and glazed portions.

Active sustainable design

Dash Coville, sustainability consultant at Solid Green Consulting, says: “Because of the relatively narrow floor plates of the north and south wings, it was possible to give over 80% of the usable area a visual connection to the external environment. The building’s form also provides good levels of daylight for building users, with over 30% of the usable area having a daylight illumination of at least 250lux. Higher efficiency LED lighting also made it possible to design a lighting power density of under 2W/m² per 100lux in the usable area.”

To minimise solar heat gain through the floor plates, a high-performance double-glazing was used throughout. Internally, visible glazing was cut to 50% by creating a solid spandrel that spans from window sill level through to the ceiling below.

David Vince, director at C3 Climate Control Consulting Engineers, says in order to gain efficiencies in both heating and cooling of the building, a four-pipe chilled water air-conditioning system was installed. Air-cooled chillers are located on the roof, with some of the chillers being reversible heat pump units to provide heating – a technology that is up to three times more efficient than electric heating.

In the basements, the ventilation systems were fitted with carbon monoxide sensors and variable speed drives, allowing the fans to slow down when the basement’s carbon monoxide levels are low. These upgrades greatly reduce the electrical consumption compared to ventilation systems that run at full speed at all times of the day.

Water and energy meters were installed and connected to a Building Management System (BMS) to support proper management of water and energy consumption. Water-efficient fittings for toilets, taps and showers were installed throughout the building, with drip irrigation to all landscaping on the piazza.

In terms of management, a commissioning agent was appointed so that all systems would be installed, commissioned and used in line with Chartered Institution of Building Services Engineers (CIBSE) commissioning requirements.

Tarryn Long, green building coordinator at WBHO, confirms that an Environmental Management Plan (EMP) was developed for Building 3, and an internal auditor appointed to ensure environmental compliance during construction. She says: “On this project we targeted 70% reduction of waste-to-landfill. As we were able to recycle a lot of the builder’s rubble that was generated during the construction of the building, we are on track to surpass that figure in our final calculations. We also sent all steel off-cuts for recycling.”

A landmark development

The Alice Lane precinct has set a new standard for design in the way that commercial buildings meet the ground and the interaction, at an urban scale, between people and structures. Now that the third of the buildings at its helm is complete, the iconic precinct firmly stakes its claim on the Sandton skyline.

By Karen Eicker

See earthworks magazine issue 39 August-September 2017 for the full feature.