Green Square Corporate Office Park comprises two office towers (North and South) and a connecting plaza and comprises over 40,000 sqm of commercial space.

The North Tower is the first completed building in Queensland to receive a 6 star Green Star — Office Design v2 rating. It is also registered for a Green Star — Office As Built rating.

Partway through construction, the Green Star target changed from 5 stars to 6 stars. “Changing to that 6 star design was the highest risk approach we took possible, and then we had to rely on our negotiation skills with Brisbane City Council and our design teams to try and make the whole thing as efficient as possible,” Mark Sanders says.

To improve water efficiency at the building, the team installed a co- generation plant. The plant generates power on-site using a gas engine driven generator, with the waste heat used to provide cooling through an absorption chiller. It reduces the tower’s nitrogen oxide emissions by 85 per cent and carbon monoxide emissions by 90 per cent.

“Co-generators put less pressure on our existing power stations and minimise the actual transmission losses. Co-generation also partially future proofs the power costs of the building due to the pending Emissions Trading Scheme,” Nigel Harris says.

Harris says there are also operational and financial benefits. “Seventy per cent of the cooling to the building is free.”

Adhering to the Green Star requirements took elements of learning from past experiences, particularly from previous work on the South Tower. Sanders says Leighton Contractors used concrete at the South Tower which was 40 per cent fly ash replacement, with the concrete mix on that project causing problems.

“Because we had that knowledge already in place for the South Tower, we were able to adjust the mix specification of the concrete, so we made it more workable and easier to manage for the subcontractors so there was no difference between a conventional concrete mix,” Sanders says.

Early on in the project, Cox Rayner Architects and Leighton Contractors pre-strategised sustainability measures that could be included in the project. This included controlling artificial lighting to minimise power consumption, vortex diffusers to distribute conditioned air and the harvesting of rainwater from the roof for toilet flushing and site irrigation.

Non-VOC paints were also used. Garden rooms were also included on each level, which can be enclosed or opened up to the internal floor areas and the outdoor climate and are clad in vines to filter sunlight and reduce heat loads. Ninety per cent of construction waste was also recycled.

For Sanders, a large part of reaching the project’s sustainability goal was making sure everyone on- site was briefed with a sustainability induction, “as well as about what the project goals are to make sure that they’re on board with you. They’re all part of the same machine driving forward and trying to achieve over and above a better building than the building next door.”

Communication with the architect, builder and subcontractors was helped with the implementation of 3D computer technology. Harris says “it helped speed up the process and created a greater ease of communication and understanding of the complex issues associated with a large project of this size.

“Issues were resolved by a mutual agreement through a process of prioritising the importance of the design modification to the overall success of the project. The client also had an active involvement in the decision process, having a representative on-site full-time.

“The greatest lesson that was learnt and continually re-emphasised was that good communications at all levels of the design and construction team minimised the time and back tracking required due to misunderstanding and misconception.”

Stephanie McDonald

Stephanie McDonald

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