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BSRIA model project - 66 Waterloo Road, SydneyJune 2010

Australian property developers are working hard to reduce the energy consumption and carbon dioxide emissions of commercial property. In the process they can teach the UK a thing or two. G S Rao and P C Thomas explain.


Photograph copyright Geoff Sumner
The development at 66 Waterloo Road, Macquarie Park in Sydney is a 10,000 m2 five-storey office commercial office building. On the surface there is nothing particularly unusual about it. As is usual in Australia, a concept design was put out to tender by a portfolio property owner and building companies competed for the right to build and deliver the project. As in the UK, there is a 12-month defects liability period after practical completion, after which full control of the building's maintenance and facilities management is taken on by the building owner.

What makes 66 Waterloo Road notable was the effort to ensure that the building reached its aspirational performance target within 12 months of normal operation. This was measured on the NABERS Energy rating scheme (the National Australian Built Environment Rating System, previously the Australian Green Building Rating Scheme, AGBR) where the building initially achieved 4.5 stars, then exceeded the requirement by reaching 5-star performance within 18 months (January 2009).

Furthermore, 66 Waterloo Rd is currently listed on the NABERS energy website as having achieved this exemplary level of performance for base building operation without the assistance of green energy sources. This is equivalent to a 58 per cent reduction in greenhouse gas emissions against the average performance of an equivalent Australian building constructed in 1999.

So, how was it done?

Design and construction

In late 2005, a sustainability consultant reviewed the building's design from an energy-efficiency perspective and developed a strategy by which the building's in-use performance could achieve a 4-star NABERS energy rating. This involved the creation of a whole-building energy model to predict the building's energy and environmental performance.

This original design was developed without regard for a performance target. When modelled, the building was predicted to have the potential to perform to a theoretical rating of 4.28 stars on the NABERS scale. As there's always a difference between theory and practice, there was a risk that the original design would not achieve this target.

Based on the outcomes of a whole building energy simulation, a number of changes were proposed. For example, the original design had two air-handling units (AHU) serving four perimeter zones, but it was felt that this configuration would impose a large reheat energy penalty. The design was changed to four AHUs servicing a variable air volume system. The mechanical contractor overcame limitations on plant room space by stacking the units.

Fan-speed control was also proposed on the main air-handling fans, with the individual VAV boxes having very low turn-down ratios. This was to be achieved by the use of induction VAV boxes (IVAV) and standard room diffusers. IVAV boxes allow the primary air supply from the AHU to be reduced significantly while maintaining close to full design flow at the diffuser outlet. A supply air reset strategy was proposed, and electric reheat was also deleted on all zones.

As the energy from the foyer air-conditioning would be included within the AGBR rating, it was proposed to use the base building chilled water plant for the foyer AHU, rather than packaged plant. The central plant was deemed to provide chilled water at significantly higher COP. High-efficiency screw chillers with minimum COPs of 5.5, a condenser water reset strategy, and variable speed drives for the cooling tower fans were proposed.

High performance double-glazing was proposed on all office floors, with a shading co-efficient of 0.3 and a U-value of 1.8 (both centre-glass values). The height of the glazing was reduced to 1800 mm by raising the spandrel sill level to 900 mm (by far the most contentious of the proposed changes).

The lighting loads were reduced to 8.5 W/m2 in the office floors, with lower (actual) loads for car park basements, toilets and the foyer. Equipment loads were reduced in the model from 25 W/m2 to 20 W/m2.

All of these changes were agreed by the design and contracting team in design meetings. The change in glazing height in particular had a major effect on the building's visual aesthetic.

To their credit, while there were several vigorous discussions, every member of the delivery team was keen to achieve the developer's performance targets and willingly participated in developing practical solutions. This collaborative approach, more than anything else, contributed to the later success of measured performance of 66 Waterloo Road.

During the design and construct stage, the sustainability consultant made three interventions:

  • a concept stage energy model analysis, with a series of options to improve performance as described above
  • a 50 per cent detailed design model, which began to incorporate contractor equipment selections for lighting, air conditioning and building envelope; and 
  • a final contract design model that incorporated a significant amount of detail, particularly in terms of air conditioning equipment, such as coil sizes, AHU supply air temperatures and flow rates, individual chiller part-load curves, and specific pump head pressures.

The stated intention, at all times, was to deliver a building that was capable of real performance, rather than simply meet a design benchmark.

The predicted results from the initial models led to a review of equipment sizes for the HVAC equipment based on the new facade, building envelope and internal load configurations. Equipment sizes were reduced to more appropriate levels from the original design.

Commissioning and post-occupancy evaluation

At the project's practical completion in 2007, Team Catalyst was appointed to ensure that 66 Waterloo Road met its modelled performance targets. The sub-contractors had completed system commissioning, and building occupancy was already over 75 per cent.


The winter gardens, a small area on the north east corner of the floor plate. It is developed as a breakout space that can be naturally ventilated by automated louvres, but has been air-conditioned by almost all tenants as more than six months of the year are quite warm in this region of Australia. Photograph copyright Geoff Sumner.
Team Catalyst brought together representatives from the building owner and the supply chain. A decision was made by all parties to collaborate on achieving the performance targets. No-one wanted the process to dissolve into finger-pointing and vitriol.

There was also a clear decision, agreed by the owner and the builder, to separate defects from design aspirations. This required two well-defined processes.

Defects covered equipment and processes already outlined in the design and construct documentation that were not installed or not working as documented. The cost of resolving these defects was paid for by the builder. Aspirations were strategies that might require re-programming or installation of additional equipment, and designed to improve the performance of the building beyond what was already documented. These were classified as variations to be funded by the building owner.

Additional effort was needed to ensure the building's energy sub-meters were able to report energy use in the same categories as defined in the energy modelling exercise.

The post-occupancy evaluation set out to review the operation of building systems against the final contract design energy modelling report. The review indicated that there were gaps in calibration of sensors and inconsistencies in the application of documented control strategies, for example:

  • the 'chillers in series' sequencing strategy was not working effectively, and there was excessive use of bypass that was causing increased pumping energy use
  • the chilled water set-point was lower than prescribed, (leading to chillers working harder and using more energy than predicted), and the condenser water reset strategy was not implemented correctly
  • the enthalpy control economiser cycle was not working correctly. Damper operation was not synchronised, and the static pressure and speed control of AHU fans were inconsistent.


Photograph copyright Geoff Sumner
The maximum and minimum flow settings on some induction VAV boxes were not set up correctly, and temperature and flow sensors were poorly calibrated.

Once the systems were re-calibrated and re-commissioned and about six months of energy use data (including the summer season) had been logged, it rapidly became clear that the building would easily achieve the aspirational 4.5 star NABERS energy performance rating.

By the end of the post-occupancy evaluation period the building's performance had reached 4.8 stars. This led to a series of interventions. First, the sub-metering data revealed that ancillary energy systems were responsible for almost half the building's base energy. The car park and base-building lighting were inadequately controlled and remained energised for long periods. The problem was resolved by adding motion detectors to the basement and foyer lighting circuits.

Ground floor areas were originally designed for retail use and fitted with full height single glazing. These areas were later converted to office tenancies. Heat loss through the glazing had led to complaints of discomfort, which were addressed by addition of electric re-heat batteries in the air-conditioning system. These systems were operating inconsistently and were therefore re-commissioned. This reduced energy consumption and reduced tenant complaints.

Sub-metering data suggested that the central cooling plant was operating between 22.00 h and 02.00 h. This was traced back to inappropriate use by the tenants' cleaners. The problem was virtually eliminated by the imposition of an after-hours fee linked to the cooling. The cleaners were also re-trained in how to use the system's controls.

Outcomes

66 Waterloo Road was essentially a sound building, achieving over 4 stars under the NABERS Energy scheme, even when some of the major energy sub-systems were not properly calibrated and operating correctly. Re-commissioning, recalibration of sensors, and ensuring that clearly documented control strategies were correctly applied resulted in the building performance improving to 4.8 stars NABERS Energy.


Photograph copyright Geoff Sumner
Controlling the ancillary energy sub-systems in an effective manner easily improved the performance beyond 5 stars. Furthermore, the building is not straining to meet any of the occupant comfort requirements.

It is noteworthy that the building design does not rely on overtly green systems to achieve its performance. For example, there are no chilled beam systems, no ventilated facades, and no tri-generation system. Instead, the building had achieved its exemplary performance through sound design and practical, 'keep it simple' engineering principles.

The concept design strategy relied on building energy simulation analysis to re-configure systems. This reduced over-sizing of plant, and integrated the building design across the envelope, facade, electric lighting, air and water sides for heating and air-conditioning, controls and sub-metering. The control strategy was well developed and clearly documented.

The post-occupancy evaluation of building energy performance was after the building had been occupied to 75 per cent and had been operating for about six months. The results of the evaluation were followed through with remedial actions, clearly divided into defects and variations.

66 Waterloo Road demonstrates that it is possible to achieve very high levels of verified performance using a conventional VAV system. It is also possible that further improvements in performance would be possible by applying dedicated outside air systems (known in Australia as DOAS), plus control strategies configured to the warm and humid Australian and Asian climates.

Credit must go to the teamwork and collaboration between all parties, and the use of an integrated process of design, delivery, commissioning and post-occupancy follow-through. The importance of teamwork cannot be emphasised enough: it requires only one rotten apple to bring collaboration to a standstill. The team needs to be repeatedly reminded that all are working to a measurable and verifiable performance target.

Building energy simulation analysis, when employed by experienced engineers and designers, has the ability to lead to integrated building solutions that achieve measurable reductions in energy use and carbon dioxide emissions. Building management systems and energy sub-meters are invaluable tools for diagnosing and correcting disparities between predicted and measured building performance.

P C Thomas and G S Rao are with Team Catalyst Pty Ltd. Team Catalyst is participating in reviewing the NABERS Energy benchmarks, providing input towards the development of the Green Star Greenhouse Gas Emissions Calculator Guide methodology.

This paper first appeared in the AIRAH journal Ecolibrium and is re-published with permission.

 

BSRIA has a team of licensed BREEAM assessors and also provides energy compliance services. For more information contact BSRIA:

T: 01344 465600
E: lowcarbon@bsria.co.uk

 

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