Next level

A new mixed-use development in Melbourne’s Collins Street has brought a sophisticated combination of work, retail and accommodation to one of the city’s most desired addresses. Sean McGowan reports.

Completed in 2020, 80 Collins Street is one of the largest mixed-use precincts in Melbourne’s CBD.

Built by Multiplex for QIC (Queensland Investment Corporation) and Dexus, the premium commercial development consists of a new 38-storey, 43,000m² commercial office tower (South Tower), and a new 27-storey, 255-room hotel. The project also includes major refurbishments to the site’s existing 50-storey A-grade commercial office tower (North Tower) – including a reactivated entry – with this work carried out while the building remained occupied. Designed by architects Woods Bagot with Dutch firm UN Studio, the project’s new South Tower, with its faceted glass exterior and diagonal bracing, is a striking addition to the city’s existing skyline. But it is at street level that the tower’s design really makes it mark, cantilevering 12m over existing Victorian-era buildings at the “Paris End” of Collins Street. Multiplex says the cantilever is an Australian first.

Achieved through a tailored engineered solution requiring the use of five customfabricated “mega trusses” to support the 32 levels above, it has been built to withstand 30,000kN of tensile force. The concrete core removed the need for additional structural support columns. All three buildings on the site have been interlinked and interconnected, with retail and dining spaces on the ground and podium levels featuring a unique urban design that taps into Melbourne’s laneway culture.

The 27-storey hotel tower at 80 Collins Street is now home to Next Hotel.

Image: Greg Elms

All three buildings on the site have been interlinked and interconnected

FAÇADE FANTASTIC

The high-performance façade and passive chilled beam integration were a crucial element in successfully achieving cooling capacity and comfort conditions in the South Tower.

AECOM’s Drew Toscan says alternative design approaches would otherwise have impacted the project’s budget and sustainability targets. “The building structure, with its offset structural core and one-third cantilever design, resulted in significant structural elements within the ceiling spaces that made coordination critical to the design,” he says. “The use of 3D Revit modelling in the design process allowed this to be assessed in real-time, and integrated into the final design.” ❚

Photo by Greg Elms

A PREMIUM DESIGN

AECOM joined the project’s original design team in 2012. The multidisciplinary consultancy delivered engineering design services for both of the new towers, the North Tower’s new entrance, and the initial enabling works for the continued operation of that tower for the duration of the project. Multiple disciplines were involved including mechanical, electrical, hydraulic, fire protection, vertical transport, structural and civil engineering. “All building services are separated between the three towers, to allow future flexibility for the development to be divided into individual titles if required – with the exception of the common basement,” says AECOM associate director Drew Toscan. Toscan says the client sought to provide a premium product to the Melbourne CBD commercial leasing market through the completion of the South Tower. He says the design objectives and criteria were therefore set to meet this objective. Other aims were satisfying the criteria for the Property Council of Australia’s Premium grade, as well as high-end sustainability targets. The new South Tower was designed to achieve a 6 star Green Star Office v2 rating, 5 star NABERS Energy Operational rating, and is targeting a 4 star NABERS Water Operational rating. To this end, the selection of passive chilled beams and a 100 per cent outdoor air ventilation system was deemed to meet these requirements. The bonus is increased comfort conditions, low levels of drafts and noise. “Chilled beams were ultimately selected for the project, as they achieved the sustainability objectives in terms of operational energy savings,” says Toscan. “They also provided the client with the highest available net lettable area (NLA) and increased floor-to-floor heights as a result of the reduced supply air quantities required by the system.” The air handling plant selected is a 100 per cent outside air system. It is sized to provide 150 per cent increase on the minimum outdoor air rates required by Australian Standards. This equates to 18.75L/s per person.

The delivery of outdoor air is split between air handling plant located at podium level, and on the rooftop. To rationalise riser sizes and save floor space in the building, the chilled water thermal plant was located with the mezzanine plantroom, with heat rejection achieved via cooling towers at roof level. “The passive chilled beams are supplied from a dedicated set of high-temperature chillers, independent from the primary chilled water chillers, to gain maximum efficiencies of the systems at all times,” says Toscan.

DRIVING FORCES

As building services engineer at 80 Collins Street, AECOM spent eight years on the project – from concept stage to completion. AECOM associate director Drew Toscan, shares some of the lessons learned over that time.

The design team worked closely from the chilled beam system in a mock initial concept stage to really understand arrangement with high-performance the driving forces for the project’s façade. This confirmed design success. This allowed the design to assumptions and provided be developed to ensure key elements greater assurance to the client of of a premium-quality and sustainable the outcome of the installation. development were achieved while working with the restraints of a brownfield site with an operating office tower in a high-profile CBD location. Leveraging 3D Revit modelling, the AECOM services and structural teams were able to deliver a coordinated design that incorporated the complexity of We sought early engagement with the high-performance façade, offset the mechanical contractor to test structural core location and a third of the actual installation of the passive the cantilevered floor plates. ❚

BALANCING BEAM

The selection of chilled beams to serve all office levels (levels 4–38) in the South Tower carried the greatest capital expenditure of all the options considered by the design team. However, the multiple benefits offered by the system – including energy efficiency, increased NLA and reduced floor-to-floor heights – were considered to be of greater importance by the client. ❚

The delivery of outdoor air is split between air handling plant located at podium level, and on the rooftop

ACCOMMODATING DESIGN

The 27-storey hotel tower – now home to Next Hotel Melbourne – was designed to achieve targeted 5 star Green Star Design and As-Built ratings. Front-of-house areas are served by a floor-by-floor, air-cooled VRF (variable refrigerant flow) system with the 255 individual hotel rooms provided with concealed bulkhead fan coil units (FCUs).

Outdoor air and toilet exhaust are provided by common ducted risers, with the hydraulics riser passing through each floor to the mezzanine and rooftop plantrooms. ❚

The chilled water thermal plant was located on the mezzanine plantroom, with heat rejection achieved via cooling towers at roof level.

Image: Ellis Air.

ON THE JOB

Mohammed Iftekar, M.AIRAH, engineering manager (Victoria) at Ellis Air, details some of the key learnings from the mechanical services design and construction at 80 Collins Street project.

Assessment of pipe riser anchor design during the early stages of the project was important in highlighting any structural issues. We sought earlier engagement and discussions with the ICA to address any project scope gaps and any additional design expectations. Frequent liaison with the project site and commissioning team was critical in rectifying ongoing and future issues in a timely manner so the project program was not impacted. Chilled beams are very fiddly when completing fit-outs. Our recommendation would be that if it can be done as part of integrated fitout works, then they are lot simpler to deal with. ❚

The cantilevered facade has become a feature of the “Paris End” of Collins Street.

Image: AECOM. Designed to provide the bulk of the cooling to the space, the passive chilled beams also allowed the supply air volume (and relevant ductwork) to be reduced in size.

A decision to not incorporate heat recovery from the relief air system was made based on a detailed whole-oflife analysis. This demonstrated that the additional fan and pump energy required did not offset the energy savings.

FROM DESIGN TO CONSTRUCTION

Ellis Air was appointed by Multiplex as the D&C (design and construct) mechanical services contractor following two years of involvement in the design and value-management phases. Working closely with AECOM throughout the course of the project, Ellis Air proposed a list of alternative designs as part of the value-management process. This sought to reduce the project’s installation and equipment cost, labour costs and overall energy consumption. “There was a strong emphasis on energy efficiency, and this was the key driver

Ellis Air was appointed as the D&C mechanical services contractor.

for the adoption of the passive chilled beam system,” says engineering manager (Victoria) Ellis Air Mohammed Iftekar, M.AIRAH.

This led Ellis Air to select chilled beams that have a higher radiant and natural convection heat transfer. “These help to provide better thermal comfort within the occupied spaces,” says Iftekar. In order to reduce overall energy use, Ellis Air worked to maximise the cooling provided by the chilled beams while simultaneously reducing the cooling

Image: Ellis Air.

Sees everything, thinks for you.

The new thermal imager testo 883 with the best image quality and professional reports – the efficient reinforcement for energy consultants.

• Resolution of 320 x 240 pixels and NETD of 40 mK: Identify every weakness • Intuitive analysis software testo IRSoft:

Comprehensive analysis of thermal images • Impressive reports, the fast and easy way:

Make a lasting impression on customers

HIGH AND LOW

The South Tower features both low-rise and high-rise AHU plantrooms located on Level 3 and Level 39, respectively. Chilled water is provided to these AHUs via the low-temperature chiller set located within the Level 3 plantroom. The high temperature chillers are also located within this plantroom, and serve the passive chilled beam circuits serving levels 4 to 38.

Due to the building head height, the high temperature chilled water circuits are provided with pressure breaks on Level 3, and with satellite risers running up the building. Cooling towers, heating hot water boiler plant and cogeneration plant are all located on Level 40. ❚

Professional reports

CONDAIR MC

New evaporative humidifier and cooler for air handling units

Whilst operating on <0.15kW of electricity, the new Condair MC can provide up to 360kg/h of humidity and approximately 245kW/h of adiabatic cooling to an air handling unit.

Evaporative cooler Supply air

Return air

CIBSE approved CPD seminars available

Discover more about the new Condair MC

Tel: 02 9987 2006 Email: au.sales@condair.com Web: www.condair.com.au

The Barrel Room – where the Next Hotel has its own wood-ageing program for spirits, cocktails and herbal liquors on show.

Image: Greg Elms

provided by the airside cooling from the air handling units. This resulted in a 70/30 split being adopted. “Considering the design is based around a constant-air-volume system, the first stage of cooling was to utilise lower Melbourne ambient conditions where possible,” Iftekar says. “If the ambient conditions aren’t

favourable, and the space conditions are not met with 100 per cent supply air, then a second stage of cooling is met via the chilled beams.”

In the event that the chilled beams are not able to meet the thermal loads, then the supply air temperatures are reset to provide top-up cooling via the primary air. The aesthetics of the building’s architectural design dictated that louvres for outside air intakes be incorporated only into South Tower’s north façade. Iftekar says this presented some challenges in terms of reticulation of services from the northern-most point of the floor plate to all other areas of the floor.

“By providing tenant outside air and exhaust air via façade louvres, we eliminated the need for separate risers for these systems,” he says, “and therefore maximised the floor NLA.”

The first stage of cooling was to utilise lower Melbourne ambient conditions where possible

WORKING WITH BEAMS

According to Iftekar, one of the major challenges of the project was the handling of the chilled beams onsite.

“Due to their lightweight construction, it made it difficult and challenging to store the chilled beams onsite, as well as installing them while other services were working around us,” he says.

MANAGEMENT AND CONTROL

All building services across 80 Collins Street’s South and hotel towers are controlled and monitored via an IP BACnet open protocol control system, incorporating a specialised energy-management system. The system includes the mechanical services system controls and monitoring, as well as monitoring of electrical, hydraulic, vertical transport and fire systems across the site. ❚

Additionally, with piping to the chilled beams configured in a reverse return set-up, it was important to get the right lengths and bends over a series of chilled beams connected to the one circuit.

Extensive flushing and chemical treatment of this chilled beam pipework was also required to maintain a low pH, due to the soft soldered joints. To facilitate improved planning and achieve a faster, safer onsite installation, prefabrication was utilised in the assembly of some of the larger fans and attenuators installed within the South Tower, as well as the chilled beam valve trains.

But perhaps the biggest challenge confronting Ellis Air was to be found in the design and installation of secondary structure (anchors) used to support chilled water, heating hot water and condenser water pipework risers. Due to the massive, combined weight of these pipes – estimated to be around 120,000kg – and the structural requirement to support this only in the Level 3 plantroom – the secondary structure had to be carefully designed by Ellis Air. “This was a unique challenge,” says Iftekar. “It was overcome by sub-contracting the structural steel design to an independent structural engineering consultant who also provided their own certification upon completion.”

OPEN FOR BUSINESS

80 Collins Street’s 38-storey South Tower reached completion in March 2020, with the 27-storey hotel completed in September 2020. The first occupants of the South Tower arrived in mid-2020, but due in part to the COVID-19 pandemic and subsequent restrictions, the building’s systems are yet to operate fully due to low occupancy levels. “But since restrictions have eased, the systems have performed well, with ratings targets achieved and minimal issues encountered to date,” says Toscan, “even with ongoing fitouts occurring across the building.” As Melbournians return to their city after almost a year away, 80 Collins Street is sure to become a favoured destination both at day and night. ❚

DOUBLEDECKER

In a Victorian first, double-decker lifts were incorporated into the design of the South Tower.

These minimise the core configuration and enable maximum NLA while providing premium-grade vertical transport capacities that offer a fast, reliable and efficient service. ❚

PROJECT AT A GLANCE

The personnel

▲ Architect: Woods Bagot + UN Studios ▲ Builder: Multiplex ▲ Building services engineer: AECOM ▲ Client: QIC and Dexus ▲ ESD engineer: WSP ▲ Façade engineer: Arup ▲ Independent commissioning agent:

Commissioning & Advisory

▲ Mechanical services contractor: Ellis Air ▲ Structural engineer: AECOM

The equipment

▲ AHUs: GJ Walker ▲ BMS: Alerton ▲ Boilers: AIRA ▲ Chilled Beams: ACS (Lindab) ▲ Chillers: Daikin ▲ Convectors (in-floor): Holyoake ▲ Cooling Towers: Evapco ▲ CRAC Units: Vertiv ▲ Dampers: Celmec ▲ Diffusers: Shapeair + Trox ▲ Fans: Fantech ▲ FCUs: GJ Walker and Temperzone ▲ Grilles: Shapeair and Trox ▲ Heat exchangers: FluidPro ▲ Outside air intake vents: Fantech ▲ Pumps: Wilo ▲ Sensors: Alerton ▲ VSDs: ABB The LINEO range are specifically designed for horizontal or vertical installation for ventilation of residential, commercial or industrial premises.

The fans in the renewed LINEO range boast HIGH PERFORMANCE, LOW ENERGY CONSUMPTION, LOW NOISE EMISSIONS AND EASE OF INSTALLATION AND MAINTENANCE placing them at the top of the category.