129 Rivonia (The Marc): all-round integrated sustainability

129 Rivonia (The Marc): all-round integrated sustainability

By Harmen von Zwietring of Spoormaker and Partners
The iconic jewel of Sandton, The Marc building at 129 Rivonia, boasts sophistication not only in its unique architectural design, but in the design of its multiple HVAC systems, too.

During July 2014, a group of architects, engineers, and various other consultants gathered in the boardrooms of ERIS Property Group in Sandton to start the journey of what would become one of Sandton’s latest landmarks.

When driving through Sandton, you instantaneously notice this new development situated on the corner of Maude and Rivonia streets; affectionately christened as ‘The Marc’. The jewel-shaped structure with the gold and black triangular façade catches your eye when driving down Rivonia Road. The Marc is an abbreviation for Maude And Rivonia Corner, which is a mixed-use development that consists of the following:

1. Tower 1: 16 levels 25 000m2 useable area
2. Tower 2: 12 levels 36 000m² useable area
3. Retail: 2 levels 17 000m2 useable area
4. Basement parking: 7 levels 108 000m2 useable area

 Under normal circumstances, 12-level and 16-level office buildings are not that unheard of — neither is a two-level retail development. What makes The Marc unique is that all these buildings have been incorporated into the same development. The retail section is situated on ground floor with both office towers situated on top of the retail section. A seven-level super basement provides parking for all tenants as well as the retail tenants and customers.


Photos by Ilana Koegelenberg

Design criteria

The design criteria for The Marc called for an energy-efficient air-conditioning system that would contribute towards attaining Green Star ratings. Tower 1 and Tower 2 have been designed to attain 4-Star and 5-Star Green Star ratings, respectively. Ventilation within the buildings is provided based on the requirements stipulated in the National Building Regulations.

The challenge that had to be overcome was the integration of these buildings onto a single site. Ventilation of the basements increased in difficulty since the entire basement was covered with retail shops. Just imagine the look on the architects’ faces when you request nine shafts spaced throughout the basements and each shaft requiring access to ambient for fresh air intakes and exhaust discharges. Five of these shafts were used for extraction purposes, with each shaft housing four 1 400mm-diameter axial extraction fans extracting a total of 940m3/s. Four shafts provided fresh air to the basements, with each shaft also housing four 1 400mm-diameter axial fresh air fans providing a total of 752m3/s of fresh outside air. The remaining 20% of fresh air is provided by means of the ramp leading into the basement. All fans are equipped with speed controllers to allow for a more efficient design.

All extraction shafts are equipped with carbon monoxide (CO) sensors situated on the lowest levels of the shafts. The CO sensors enable the fresh air and exhaust fans to increase rotational speed when the CO levels within the basements reach predefined levels specified in ASHRAE. Mentis grid platforms are provided to allow for access to the fans for maintenance. Since 1 400mm-diameter axial fans consume a lot of energy, sophisticated logic was implemented to activate extraction fans in sequences to reduce the energy demand of the basement ventilation system.

Pressurisation systems are provided to each staircase by means of a dedicated pressurisation fan in accordance with the rational fire design. Galvanised ducting is used to transport air for pressurisation and is introduced into the staircase at every second landing. In the case where the ducts are situated within concrete shafts, galvanised ducts have been excluded due to cost saving and value engineering. Effective pressure control within the pressurised staircases is achieved by manipulating the PID loops to effectively react to pressure changes within the staircases. This allows for effortless opening and closing of fire escape doors while maintaining the pressure difference within the staircases as prescribed by BS12101.

Retail HVAC system

Cooling is provided to the retail section by means of a dedicated condenser water system. Condenser water is provided to the system by means of three hybrid cooling towers with a total heat rejection capacity of 2.55MW. In addition to the hybrid cooling towers, two additional heat pump chillers were installed with a total cooling capacity of 1MW.

In the colder months, the heat pumps generate warm water to enable more efficient operation of the direct expansion package units within the retail shops and to provide backup cooling during times of water-shedding in Sandton. Condenser water, supplied at a temperature of 30°C, is supplied to direct expansion package units by means of a reverse return condenser water ring main. An efficient primary-secondary pumping arrangement, using variable speed pumps, circulates condenser water to the retail shops, based on the thermal demand of the system.

Three anchor tenants are situated within the retail development. The design of the air-conditioning system of each anchor tenant was done by the anchor tenant’s individual design team and not Spoormaker and Partners. Again, not all that uncommon.

What makes the retail area more interesting is the fact that 133m3/s fire smoke extraction is required within the general retail space. Since the towers are situated on top of the retail development, positions where extract fans can be placed are very limited. The only visually appealing method for the architect was to lift the skylight section by 600mm to allow for space to install the extraction fans within an upstand at the skylight perimeter.

Being a development in Sandton, there was even more pressure from the architect to ensure that the mechanical plant was not visible from the natural ground level.

Extraction of 133m3/s is achieved by providing two 800mm-diameter axial fans as well as twenty 560mm-diameter axial fans equipped with non-return closers situated within the raised skylight area.

To make the ventilation and the heat control of the retail development more efficient, individual smoke extraction axial fans are equipped with motorised dampers that open during predefined temperature conditions to allow for natural ventilation of buoyant heat. The two 800mm-diameter axial fans are equipped with variable speed drives as well as sound attenuators to allow for the removal of built-up heat at the skylight as well as carbon dioxide within the general retail area.

Restaurants are situated throughout the retail development. The infrastructure for the kitchen extraction systems is provided as part of the baseline design, with the canopy connection and fans forming part of the tenant’s scope. Due to the complexity of the site and limited discharge positions, kitchen extraction ducting routes are in excess of 80m from the kitchen origin to the discharge position.

Kitchen extraction discharge positions are placed in such a way as to ensure that fresh air intakes to the towers are not compromised. Access panels are provided for the kitchen extraction ducting in accordance with local regulations. Mentis grid walkways and access platforms are provided along the kitchen extraction ducting routes to allow access to the access panels for cleaning of the ducting.

During the late stage in the project, the client requested to change a retail shop into a restaurant facility. Since this area was not demarcated as a restaurant, no kitchen extraction infrastructure had been provided as part of the baseline design. The only option to provide extraction for this restaurant was to add an electrostatic precipitator within the basement vent shaft. The duty of the precipitator is 4m3/s and the precipitator is equipped with double-pass precipitator cells.


Photos by Ilana Koegelenberg

Tower 1 HVAC system

Cooling is provided to Tower 1 by means of two high-efficiency air-cooled chillers and two heat pump chillers. Chilled water is provided to the building at a temperature of 8°C and hot water is provided at 40°C. During warmer months, the heat pump chillers supplement the chillers and produce chilled water. Switch-over butterfly valves are provided in the chilled water pipe headers to enable the system to operate either as a fully cooling/heating system or as a combined cooling and heating system depending on outdoor conditions and indoor requirements.

Four-pipe fresh air units, supplying fresh air to the office areas, are situated within plant rooms on various levels. The coils within the fresh air units are used to temper fresh air to neutral office space temperatures before the fresh air is introduced into the office space. To reduce installation costs, fresh air units were combined to supply fresh air to a typical cluster of three floor levels per office floor wing.

Since Tower 1 would predominantly be occupied by a law firm with privacy and confidentiality requirements, it was decided to recommend a fan coil unit (FCU) installation to reduce the transfer of sound between offices. In-ceiling FCUs are equipped with EC type fans to allow for greater acoustic and comfort control within offices. Tempered fresh air is introduced into each office cubicle by means of a supply grille.

Various rational fire ventilation and extraction systems are provided within this building. Pressurisation systems consist of three staircase pressurisation systems, one firemen’s lobby pressurisation system, as well as a firemen’s lift pressurisation system. A common header at roof level, with individual smoke sensing control, provides fresh air for the pressurisation system during a fire condition. Effective pressure control within the pressurised staircases allows for effortless opening and closing of fire escape doors during a fire condition while maintaining the pressure difference within the staircases as prescribed by BS12101.

Smoke extraction is provided for each office tower wing at a rate of 10m3/s. An additional 10m3/s of smoke extraction is added to Level 16 where a restaurant is situated, requiring increased smoke extraction rates as prescribed in the rational fire design. Make-up air is provided by means of automatically opening doors on the fire floors.


Images by Spoormaker and Partners

Tower 2 HVAC system

Cooling is provided to Tower 2 also by means of two high-efficiency air-cooled chillers and three heat pump chillers. Again, on Tower 2, the heat pump chillers supplement the chillers to generate chilled water during the warmer months. Motorised switch-over valves are also provided in the chilled water headers to allow the chilled water plant to operate as a fully cooling/heating system or as a cooling and heating system depending on outside conditions and indoor requirements.

Chilled water is provided to the building at a temperature of 8°C and hot water is provided at 40°C. FCUs are provided in areas that have been earmarked for boardrooms to allow for individual temperature control. EC FCUs again allow for greater noise regulation as required in noise sensitive areas. Tempered fresh air is provided to the office spaces by means of two four-pipe fresh air units situated on the roof. Fresh air is pumped through a shaft to small plant rooms where secondary fresh air units distribute the air onto the office floors. These fresh air shafts double up as smoke extraction and make-up air shafts during fire conditions.

The general office space is air conditioned by means of a variable air volume (VAV) system where churning will be more prevalent. A VAV system is a more cost-effective design for churning. Four-pipe VAV air handling units (AHUs) are situated in plant rooms along the façade. Return air is mixed with fresh outside air, drawn from the façade, and conditioned by means of chilled and hot water coils within the AHUs.

Insulated sheet metal ducting and VAV swirl diffusers distribute the conditioned air into the space. Sound attenuators are provided to ensure that NC40 is maintained in all the office spaces while NC35 is maintained in the boardrooms. To make use of the thermally comfortable ambient conditions on the Highveld, an economy cycle system was implemented to allow for the use of full fresh air during times when ambient conditions are favourable.

Extraction is provided to a nine-storey fully glazed north-west facing atrium. The extraction fan allows for stratified heated air to be exhausted to prevent the warm air from drifting into the office space. The office space is kept under positive pressure to ensure that heat from the atrium does not drift into the office area. Tempered fresh air is also blown onto the atrium, glazing through jet nozzles situated along the atrium in an attempt to reduce the head load of the atrium into the office space.

Since Tower 2 is considered as two separate buildings connected to each other by the atrium, the rational fire design calls for two separate smoke extraction and make-up systems, each capable of extracting 16m3/s of smoke during a fire condition. Make-up air is provided by means of fresh air fans situated on the roof. Fire dampers are controlled to provide make-up air to the fire floor where extraction is required.


Photos by Ilana Koegelenberg

Roof plants

Even though excellent glazing was specified for both office towers, the high glazing ratio meant that a substantial cooling plant was still required. The complexity of the tower shapes as well as the various fire ventilation and extraction requirements called for a condensed cooling plant on the roof.

On the roof of Tower 2, space was so limited that all the pressurisation fans had to be positioned on top of each other to allow for sufficient installation space. A mentis grid platform was provided to allow for access to the double-level fans. Being a development in Sandton, there was even more pressure from the architect to ensure that the mechanical plant was not visible from the natural ground level.

Given the relatively small footprint of the tower buildings, this proved to be a design challenge that had to be overcome. Intensive discussions with the architects and vast Revit experience from the draughtsman contributed to appealing and functional plant rooms, for both the architect and the HVAC designers.

The complexity of the tower shapes as well as the various fire ventilation and extraction requirements called for a condensed cooling plant  on the roof.

Both towers are equipped with dedicated smoke extraction and make-up air systems. Each make-up system provides for two fresh air intakes on opposing sides of the building, which are equipped with smoke selection dampers to ensure that smoke-infected outside air is not used to pressurise the staircases during a fire condition. The dimensions of the common pressurisation air ducts are 2 250mm × 2 250mm and 15m long; almost the size of a luxurious apartment in Sandton.

Building management system (BMS)

The Marc precinct consists of three individual Siemens Desigo BMS systems. Each tower has been supplied with an individual BMS for facility management considerations and to allow a tenant to take full control of the building. The basement and retail development share a BMS.

The BMS controls and monitors not only the HVAC system but also the domestic water usage, elevators, fire panels, generators, UPS systems, and energy meters. There was an additional requirement from a tenant in Tower 1 to have a standalone front-end that they can use to monitor their systems. All the backup power equipment as well as server rooms for both Tower 1 and Tower 2 are situated within the basement and are being monitored by the retail and basement BMS. All three systems are interfaced with each other to facilitate data sharing.


Photos by Ilana Koegelenberg

Teamwork

A project such as this can only be a success if a dedicated team of individuals work together and bring their expertise to the table while maintaining an open-minded approach. The architects, Boogertman and Partners Johannesburg, were on the ball in all facets, and working with Bob van Bebber’s team was a delight.

Coordination was done to the tee, and experienced on-site architects were available at all times to resolve any issues. Eris Property Group was involved every step of the way to assist and manage the project together with SIP Project Managers.

Credit must be given to the Spoormaker and Partners draughtsman’s Revit expertise, for making the HVAC project the success that it is. This was fundamental to enable the positioning of all equipment onto the limited roof and plant space, and to resolve the detailed three-dimensional coordination required for such a complex project.

Both HVAC contractors, Luft Technik and Airgro, must also be complimented for their quality and management of the installations during the project.
The Marc is definitely a development to visit when you are in the vicinity. There is a variety of restaurants that cater for all your culinary needs as well as boutiques that would enable you to wear the latest fashion trends. Ample parking is provided in a super basement, which is essential for a relaxing shopping experience.

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