The Arch: Umhlanga’s new iconic landmark

By Yashika Naidoo, director at Spoormaker & Partners KZN

Mixed-use living and working aims for excellence across the board.

This addition to the booming KwaZulu-Natal city includes a full spectrum of work and living opportunities through luxury apartments, AAA-grade office spaces, the South African flagship Hilton Garden Inn, bespoke retail, and a place to have drinks with friends at Back Yard rooftop bar.

Construction of this iconic development commenced in mid-2018, with completion of the first phase, an SMG Car Dealership, by mid-2019. The total gross leasable area (GLA) consists of approximately 45 000m² with nearly 14 000m² of ducting.

The HVAC solutions ranged from direct expansion (DX) splits and variable refrigerant flow (VRF) systems to a water-cooled chiller plant catering to the specific requirements of each ‘sub-development’. These sub-developments can be separated into five main areas:

• The SMG Car Dealership is just over 3 000m² and is positioned just below the iconic Arch – the centrepiece of the architectural design. The dealership includes a vehicle workshop, mezzanine office level and a double-volume glass box. The dealership is conditioned via multiple DX constant volume air-handling units for comfort control in the various zones. The workshop required industrial extraction for exhaust of fumes; and the system also doubles up as a smoke extract system.
• The European-styled high-street offers approximately 15 upmarket stores, which include a bookstore, café, restaurants, and several clothing stores. One of the main attractions to the Podium is probably the Legacy Yard Food Hall with a rooftop bar. The retail shops are conditioned via unitary DX hideaways with a central DX fresh air plantroom. The Legacy yard is naturally ventilated, with mechanical extraction for specialised cooking apparatus.
• The Arch further boasts the first Hilton Garden Inn Hotel in South Africa; with a conference centre and restaurant in the podium and 207 luxury suites. The central chilled water HVAC system contributes to the niceties added to hotel; ensuring that guests are left experiencing maximum comfort. Each room is fitted with a dedicated ducted chilled water fan coil unit and conditioned fresh air from a central plant to ensure humidity levels are maintained.
• The high-rise building, together with the loft studio apartments in the podium; contains approximately 200 luxury residential spaces. The high-rise is topped out with a pencil club on the upper levels for the ultimate entertainment experience. The HVAC solution for this multi-tenanted building is a VRF System with the condenser-kits hidden out of site. Each apartment has a dedicated ducted unit.
• The AAA- office block is a five-storey ‘Arch-shaped’ glass building. The 6 000m² footprint office is multi-tenanted. The HVAC solution for this building is a VRF System, with internal and perimeter zones on separate condenser circuits for each wing of each level. Conditioned fresh air is ducted to the various levels from the central plant.

Layout modelling of the plant areas. Photo by Samsung

Design specifications

Each component of the mixed-use development (retail, office, residential, car dealership and hotel), had specific HVAC requirements.

The residential block and office required a decentralised HVAC system, and the main addition of individual billing was a priority for this area.

The hotel’s main focus was stringent humidity and climate control. The acoustic treatment was also high on the agenda.

The retail portion required standalone systems for individual tenants and billing.

“The correct selection of air terminals was also essential to ensure the correct air flow patterns with the considerable supply air volumes required.”

The HVAC system and installation

Through numerous iterations of life cycle costing and consideration of the specific requirements for each building component, the HVAC Solutions were agreed upon.

Residential Block

The high-rise residential block is fitted out with a VRF 2-pipe system. The condenser kits are located in a well-ventilated common plantroom on every alternate level on the building.

Ducted hide-away units are centrally located within lowered ceilings in the passage of each apartment. Supply air is introduced into each occupied space via sidewall grilles due to limited ceiling void in these areas.

The VRF system has smart home adaptability should a tenant choose to control the HVAC remotely.

The central fresh air plant is located on the roof of the building. The DX air handling plant delivers pre-treated fresh air to the building. The fresh air system includes variable speed drives linked to pressure differential sensors, to maintain the correct volume of fresh air to the building. An alternative to ducting the fresh air within the shafts was to thermally line the riser shafts internally with insulated boards call P3 ducting.

{os-gal-174}

The air-conditioning system to all apartments is linked to a central management system housed in the operations room in the basement. This system is basically a building management system for monitoring purposes.

A billing module was also integrated into the design to ensure that each tenant’s electrical consumption can be billed separately.

Offices

The office block is also fitted out with a VRF system, with the condensers all on the ground floor. Each office level and wing is zoned separately on individual condenser circuits. The common refrigerant pipework runs in a riser, through a common passage on each level.

This was done to ensure that the pipes are easily accessible by all tenants should the wings be divided.

One indoor unit is allocated per 60m². Perimeter and internal zones are separated on dedicated units. The condensers and piping size and selection are based on this zoning which maybe be refined as a tenant’s specific requirements becomes available.

The central fresh air plant is located on the ground floor. The DX air handling plant delivers pre-treated fresh air to the building.

Car dealership

The large open plan double volume showrooms are conditioned by mean of constant volume DX air handling units. Internal and perimeter areas are zoned separately. The building façade is predominantly glazed with a ‘clear’ glass to allow for maximum visibility into the showrooms. The heat loads from the façade are treated within the first 2 metres of the façade.

Offices within the car dealership are fitted out with DX split units. The indoor units are a mix of ducted units as well as cassette units. The selection was largely dependent on the ceiling void available and the actual type of ceiling that was specified for the building area.

{os-gal-176}

Hotel

The HVAC solution for the hotel and conference centre is a water-cooled chilled water system. Hydronic module chillers are used with an integrated primary variable pumping system. This was mainly done to reduce the mechanical plant footprint on the roof, whilst still achieving high efficiencies. The entire cooling plant including the fresh air plantroom is located on the roof of the Hotel.

Each guestroom contains a ducted fan coil unit with an EC motor to ensure that the necessary acoustic requirements are achieved. Several decentralised chilled water and extract air risers were designed to reduce the number of services that cross within the ceiling void of the passages.

The hotel moved away from the use of access control cards that are also used to keep the lights and air-conditioning on. The fan coil units are linked to thermal occupancy sensors as opposed to the motion detectors to ensure that the system remains active whilst guests are asleep.

{os-gal-175}

Project challenges and solutions

Each component of this mixed-use development brought about its own set of challenges.

The residential apartments and hotel are both high-rise buildings with shallow ceiling void. Intricate co-ordination was required within the ceilings void. Several decentralised riser shafts were required to limit horizontal reticulation where possible.

The double volume car dealership had a significant amount of ‘clear’ glazing. Careful consideration was given to zoning the showroom, by keeping internal and perimeter zones on separate systems to achieve optimal comfort levels.

The correct selection of air terminals was also essential to ensure the correct air flow patterns with the considerable supply air volumes required.

The designs for the office and retail components were initially based on an open plan ‘white box’ design. As tenants came on board, their specific requirement had to be incorporated into the final fit out.

One of the challenges, as is with many residential apartments, is the availability of space for the outdoor condensing units. These units require ventilation in order for them to work at their peak efficiency and within the manufacturer’s restrictions on the equipment. On the 7th floor and every subsequent second floor, there are plant rooms for the outdoor units.

However, these plant rooms have size limitations. Therefore, a request for a Computational Fluid Dynamics (CFD) analysis was sent to the Samsung Head Office in Korea in order to determine if the outdoor units would be able to operate, within these restrictions, inside these plant rooms.

The area of the plant room, as well as its layout and the positions of the condensing units were required in order to perform the CFD analysis. As shown in the layout modelling image on page 29, case 1 was rejected due to the recirculation of hot air caused by the position of the condensers. It was then advised to reposition the condensing units, as per Case 2, as this simulation was successful. 

List of professionals: