fter a long occupancy at 101 Miller Street, a tenant's departure provided Mirvac with the opportunity to complete a full refurbishment - minus any occupants.

The original building was constructed in 1992. The refurbishment included transforming and reconfiguring the groundfloor lobby, an upgrade to ser vices and amenities, including lifts, air- conditioning, bathrooms and showers, and the introduction of a trigeneration plant as the primary energy source.

Although the lack of tenants provided a greater opportunity in getting con struction delivered on time, it also posed some problems. Restricted access to the building from the existing tenant prior to construction allowed only minimal inves tigation of the existing building.

"The actual condition was not entirely known until the demolition phase was underway. At this stage, the design and construction teams worked closely together in managing design issues so as to not delay the program and main tain budget," says Thomas Catalovski.

To bring the building up to 5 star Green Star standards, the lifts underwent a major refurbishment. Office lighting was replaced with T5 high efficiency lamps with electronic ballast and a light ing control system with daylight sensing and potential movement detection was installed. Also, over 80 per cent of con struction waste was recycled off-site.

Alternative light fixtures to the base ment were also used for greater energy efficiency. "These lights were more expensive than the standard specified lighting, but the electrical contractor was able procure them in time to meet the program requirements," Catalovski says.

"Overall there weren't many changes required due to the research undertaken by the design team prior to the specifi cation of products. This was achieved by both the design and construction teams talking with subcontractors and suppliers in collaboration during pre-planning."

Mirvac partnered with Cogent Energy to design, install and operate the trigen eration plant. Trigeneration uses natural gas engines to generate electricity. The waste by-product that results from the power generation can provide heating and cooling processes. The generators work in conjunction with North Sydney's power grid, so in the event of a failure from the trigeneration system, grid power will take over. It saves 6,500 tonnes of CO₂ emissions per annum and can provide up to 2.4 MW of electrical power and 1.5 MW of cooling capacity.

The majority of the Green Star points achieved were in the management and energy categories, with results also in the water category. "Energy improvement was targeted due to the ongoing savings possible. Among the energy reduction measures undertaken were the replace ment of the existing BMCS system with current technology to provide a more robust control environment, the replace ment of two chillers with a high efficiency Carrier VSD screw chiller and numerous minor items," says Robert Graham.

The most difficult part in obtaining the Green Star rating was in providing the documentation required for the submis sion, particularly with an existing build ing. Another challenge associated with the age of the building was sourcing materials that matched existing and/or original finishes. The solution? Graham says they "matched materials which had to be imported either from the original supplier or where practical, salvaged pieces were modified and re-used."

For example, the paving for the entire podium level apron fronting Miller Street and elsewhere was originally paved using a granite paver which was no longer available. Existing stock could not be salvaged for reuse, so choosing a visually compatible paver that matched the existing building façade, the traver tine clad foyer and the sandstone paving of the footpath proved problematic.

"The final selection was subject to considerations, including cost, wearabili ty, durability, fitness for purpose, as well as being visually appealing and compati ble with those finishes," Graham says. "Following an exhaustive investigation, a 30 thick 400 x 400 flame-finished granite paver was selected." This was supplied by Ace Ceramics.

With the completion of the project now months behind him, Catalovski says: "of the lessons learnt, the major change would be greater pre-planning for tenan cy co-ordination issues and flexibility in the construction program to accommo date leasing obligations, with fewer challenges to the continuity of the works. Overall though this was managed successfully by all parties involved."

Stephanie McDonald

Stephanie McDonald

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