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.