The Annex – 12 Creek Street

Set among Brisbane’s heritage-listed fig trees, The Annex at 12 Creek Street promotes a connection between the indoors and out with a mechanical services solution delivered to compliment the building’s breathable facade.

Constructed by Broad Construction for Dexus, and designed by architect BVN, The Annex at 12 Creek Street is a new 12-level, 7,200m² A-Grade commercial office tower located within the city’s highly sought-after Golden Triangle.

Featuring a services design by consultant NDY that meets the Brisbane City Council’s “Buildings that Breathe” design guide, The Annex has achieved 5 star Green Star Design and As-Built ratings, as well as a 5 star NABERS Energy rating aligning with Dexus’ sustainability approach.

Role of A.G. Coombs

Following a competitive open tender process, A.G. Coombs was engaged by Broad Construction in mid-2018 – during the project’s design phase – under a design and construct (D&C) contract as specialist mechanical services contractor.

Approach and Methodology

Upon its appointment, A.G. Coombs liaised directly with NDY on the performance requirements of the D&C design. These discussions focused on the protection of the base building’s ratings, and flexibility of the interior space to ensure tenants were afforded suitable options for their fitout given the relatively small floor plates.

While an energy efficient, low temperature VAV mixed mode system was the cornerstone of the energy efficient HVAC design, the A.G. Coombs project team recognised opportunities to engineer value into the project.

Instead of requiring a double height plantroom space, another level of commercial office space was able to be accommodated – thereby increasing the building’s NLA by over 600m².

The final mechanical services plant serving The Annex comprises four central, low temperature VAV chilled water air handling units (AHUs) located in the rooftop plantroom – one matched to each external façade and a dedicated internal unit.

These are served chilled water by two 512kWr high-efficiency air-cooled chillers, each with its own dedicated chilled water pump.

Ground floor retail tenancies are served by stand-alone, air-cooled DX packaged systems that allow these spaces to operate independently of the base building mechanical services plant.

Following practical completion, A.G. Coombs Advisory led the Green Star commissioning and tuning of the systems in its role as Independent Commissioning Agent (ICA).

Displaying the breadth of the Group’s capability, ongoing mechanical services maintenance is now being undertaken at 12 Creek Street’s The Annex by
A.G. Coombs Service.

One of the alternatives we presented during the design phase was an air-cooled chiller solution, which resolved a number of spatial issues with the small plantroom footprint.

Sean Mewing, Project Manager A.G. Coombs QLD

Project Overview

Project Name: The Annex - 12 Creek Street

Location: Brisbane, Queensland

Client: Dexus

Project Type

Mechanical Services Design & Construct


4.5 Star NABERS Energy, 3.5 Star NABERS Water and 4 Star Green Star rating

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