25 August 2010 – It’s not often that a building exceeds its targetd NABERS Energy rating, but the five-star building at 66 Waterloo Road, at Macquarie Park in Sydney has done just that after a workout by PC Thomas’ Team Catalyst consultancy.
Develped by Stockland and designed Team Catalyst, the 10,000 square metre, five floor commercial office building originally set out to achieve a NABERS Energy rating of 4.5 stars within 12 months of normal operation by developer Stockland.
But after 18 months of operation, the result was an impressive five stars, with a 58 per cent reduction of greenhouse gas emissions compared to the performance of a 1999 building.
According to PC Thomas, the fast-tracked achievement came as a result of a number of late changes to the building’s design commissioned by Team Catalyst.
“In late 2005, Stockland invited Team Catalyst to work with the project delivery team and contribute to ESD initiatives on the development,” Mr Thomas said.
“After reviewing the original concept design documentation that had been drafted two years prior, we proposed a number of changes to the building’s design to enhance both energy and greenhouse performance.”
Highlights of those changes follow:
- The original design had two air-handlers serving four perimeter zones. It was felt that this configuration would impose a large reheat energy penalty. It was agreed to change to a four perimeter air-handling unit, “face zoned” variable air volume design. There was an implication on plant room space, which was tight, but the mechanical contractor proposed to overcome this by stacking the AHUs.
- Fan speed control was also proposed on the main AHU fans, with the individual VAV boxes to have very low turndown ratios. This was proposed to be achieved by the use of “induction VAV boxes” and standard room diffusers. A supply air reset strategy was proposed. Electric reheats were originally deleted in the internal zones, and later deleted on all zones.
- It was proposed to use the base building chilled water plant for the foyer AHU, rather than the package plant originally documented. The central plant was deemed to provide chilled high efficiency screw chillers with minimum coefficient of performance of 5.5; a condenser water reset strategy, and variable speed drives were proposed for the cooling tower fans.
- High performance double glazing was proposed on all office floors, with SC of 0.3 and U-value of 1.8 (both centre-of-glass values); the height of the glazing was reduced to 1800mm by raising the spandrel cill level to 900 mm. According to Team Catalyst, this was by far the most contentious of all the changes proposed and the change in glazing height in particular had a major impact on the visual and aesthetic impact on the building.
- The lighting loads were reduced to a design lighting power density of 8.5 watts a sq m in the office floors, and lower (actual) loads for car park basements, toilets and the foyer.
- Equipment loads were reduced in the model from a originally proposed 25 watts per square metre to 20 watts per square metre; while it was felt that the actual loads might be lower, the team was unwilling to go below this value for this project.
With the building nearing completion and operating at a 75 per cent occupancy rate in late 2007, Team Catalyst met with Stockland to ensure that 66 Waterloo Road met the performance targets that were modelled earlier.
During this review there was also a clear decision to separate “defects” from “aspirations”, with a clearly defined process of handling the two. “Defects” were equipment and processes already outlined in the design and construct documentation that were not installed or not working as documented, and to be paid for from Stockland’s pocket; while “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 “variations”, to be paid for by the building owner.
One of Team Catalyst’s first actions was to advise the building owner in finalising a sub-metering system configuration that was being designed and installed for the building. The second action taken was to review the operation of building systems, which had already been commissioned by the various sub-contractors, against the “final contract design” energy modelling report produced at design and construct stage.
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 condenser water reset strategy was not implemented correctly.
- The enthalpy control economiser cycle was not working correctly; damper operation was not synchronised, static pressure and speed control tracking of AHU fans were not consistent.
- Some of the induction VAV boxes were not setup correctly in terms of max/min flow and calibration of temperature and flow sensors.
As the mechanical and control sub-contractors carried out appropriate re-calibration and re-commissioning activities based on the above, it rapidly became clear to Team Catalyst that the building would easily achieve the required “aspirational” 4.5 star NABERS Energy performance rating. In fact the building operation improved to about 4.8 stars by the time the re-calibration and re-commissioning was completed.
At this point Team Catalyst approached Stockland with a proposal to improve performance of 66 Waterloo Road to beyond five-star NABERS Energy with a small capital investment. The proposal was immediately accepted and the sustainability and facility management teams from the building owner’s side worked with us to rapidly achieve this goal.
A series of interventions were carried out, including:
- Ancillary energy systems were found to contribute to almost half the base building energy use. Car park and base building lighting were found to not be adequately controlled and remained energised for long periods of time. The facility management team was responsible for the rapid installation of motion detector control for the basement and foyer lighting circuits to rectify this issue
- Ground floor areas were originally designed for retail operation and fitted with full height single glazing for this purpose. These areas were later converted to office tenancies. Heat loss through the glazing led to discomfort complaints from tenants which were addressed by addition of electric re-heats in the air-conditioning system. These systems were operating in an inconsistent manner, and were re-commissioned to operate correctly, resulting in lower energy use and reduction of tenant complaints
- Sub-metering data suggested use of the central cooling plant between 10 pm and 2 am. This was traced back to inappropriate use by tenant cleaners, and was virtually eliminated by the building owner’s representative suggesting that an appropriate after hours fee would be imposed, which lead to a re-training of cleaner operation protocols.
According to Team Catalyst, the initial design resulted in a building with good “bones”, which achieved a performance of beyond 4 stars NABERS Energy, even when some of the major energy sub-systems were not properly calibrated and operating correctly.
Re-commissioning, by calibrating sensors and ensuring clearly documented control strategies were correctly applied resulted in the building performance improving to well beyond the 4.5 star level, closer to 4.8 stars NABERS Energy. Controlling the ancillary energy sub-systems in an effective manner easily improved the performance beyond 5 stars NABERS Energy level.
It is noteworthy that the building design does not pander to any one attribute for achieving this high level of performance for reduced greenhouse emissions, for example there are no chilled beam systems, ventilated facades or tri-generation systems installed. In contrast, the building achieves this level of measured and verified performance, through an integrated approach that.
- Used a concept design strategy that relied on building energy simulation analysis to re-configure systems, reduced over-sizing and integrated the building design across the envelope, facade, electric lighting, air and water sides for HVAC, controls and used sound design and practical, Keep It Simple Stupid (KISS) engineering principles to combine a well understood HVAC system with modern components and control strategies to achieve extraordinary performance
- Carried out a post occupancy evaluation of building energy performance after the building had been occupied to 75 per cent and operating for about six months, and then followed through with remedial actions, clearly divided into “defects” and “variations”
This article was first published by Ecolibrium, a publication of the Australian Institute of Refrigeration, Air-conditioning and Heating. Minor amendments have been made