Retro-commissioning a 55,000m² office in Melbourne, Australia

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Retro-commissioning a 55,000m² 

office in Melbourne, Australia

Dr Paul Bannister, M.AIRAH, managing director, exergy Australia sam Moffitt, consultant, exergy Australia

1. IntRoDuCtIon

In the decade since the introduction of the Australian Building Greenhouse Rating (ABGR) scheme (latterly renamed, and henceforth in this paper referred to as, NABERS Energy), there has been a significant improvement in the ability of the market to deliver high-rating buildings. This has been partly due to the adoption of new technologies such as chilled beams and displacement ventilation, but has also significantly been driven by improvements in the design, control and commissioning of conventional variable air volume (VAV) systems in buildings. One of the factors influential in achieving this change was the introduction of the NABERS Energy Commitment Agreement, by which developers could claim a rating in advance of construction and occupancy. The Commitment Agreement requires three basic activities to be undertaken:

• The building design must be subject to an Independent Energy Efficiency Design Review by a member of the NABERS Energy Efficiency Design Review Panel. • The building must (for commitments above 4 stars) be

simulated following guidelines set out by NABERS to encourage realistic assessment of in-practice performance; • The building must be rated post-occupancy to demonstrate

that the proposed performance level has been achieved. At the time of its introduction (approximately 2000) the then ABGR was still very much a fledgling scheme with relatively low rates of adoption, and market understanding of what was required to achieve a high rating involved was very weak. Indeed, at this early stage there were essentially no precedents of 4.5 star base building ratings, so a commitment to achieve such a rating was largely speculative. It would be fair to say that many early

buildings were committed to high ratings based largely on hope and indeed arguably bravado rather than detailed technical analysis or a clear understanding of how such a rating would be achieved.

This paper describes the experience of the Commitment Agreement process in relation to Freshwater Place, which was still one of the early adopters of the Commitment Agreement when it signed on in 2004 and was furthermore the first Victorian building to make such a commitment. The project shares many common features with projects of the time, both at a technical design level and in terms of the speculative manner under which the Commitment Agreement was undertaken. However, what differentiates this project from some of its contemporaries is that the spirit of the Commitment Agreement was followed through to the achievement of the 4.5 star rating in October 2009 followed by formal accreditation of the rating in March 2010.

2. fResHWAteR PlACe:

teCHnICAl oVeRVIeW

Freshwater Place is a 55,000m² office building located on Southbank Boulevard, Southbank, Melbourne. The building consists of a podium with A Grade services and the office tower, which has generally premium grade services. This paper relates largely to the office tower, as the podium has separate servicing and was not subject to the Commitment Agreement.

The building is as described below:

Floor plate: The building floor plate is approximately rectangular with long faces to the east and west. Freshwater Place is a 55,000m² office building in Melbourne Australia, which was built in 2003-2004 and occupied in 2005. The building was one of the first group of buildings to be signed to a pre-commitment to achieve a post-construction performance rating under the National Australian Building Environment Rating System (NABERS) Energy rating. In common with many of its contemporaries, the building initially fell well short of its performance target.

In late 2007 a project was launched to make the building to achieve its target rating of 4.5 stars, requiring a reduction in total carbon emissions of 35%. Rejecting the initial emphasis of plant replacement or the use of cogeneration as a means of meeting the target, the project focused almost entirely on retro-commissioning of the building’s HVAC and lighting systems. Works included a near-complete reprogramming of the building management and control system, extensive works on the tenant condenser water system, reprogramming of lighting controls, replacement of inefficient light sources and the removal of unnecessary servicing. The overall savings achieved are of the order of 40% relative to the initial post-construction performance, which was NABERS 2.5 stars – roughly equivalent to market average.

This paper describes the measures, successes and failures of this program, which ultimately led to the building achieving its performance target in October 2009 (rating certified in March 2010). Commentary is made on technical and operational measures as well as the organisation factors that led to success in this project where many others have failed.

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Glazing: The building has a high window wall ratio, and is glazed using a grey tint low-e double glazed unit of shading coefficient 0.37.

HVAC: The office floors are serviced by Variable Air Volume (VAV) air handlers in three rises (L9-L18, L20-L29, L30-36), each of which has two perimeter air-handlers (nominally north/west and south/east) and two (low and mid rise) or one (high rise) internal zone AHUs. L19 and L8 have separate AHUs, with a single AHU on both floors. Minimum supply air temperatures are conventional (12-14°C). Internal zone boxes are parallel fan assisted while perimeter boxes are provided with hot water reheat.

Chillers: The building has four chillers, being three 1855kW centrifugal chillers and one 1280kW screw chiller. These are configured on a primary/secondary loop servicing the AHUs plus a number of fan coils serving tenant meeting

rooms. All chillers are water cooled via open-cycle cooling towers on a common header. Separate closed-cycle cooling towers service the tenant condenser water loop.

Boilers: The building has three 1744kW modulating gas boilers on a primary-only pumping arrangement. • Lighting: Base building lighting is controlled

on a CBUS control system.

The design is a good example of best-practice design from the first half of the 2000-2009 decade, following conventional and generally conservative design practice but with limited specific energy efficiency features.

The building was completed in 2005, with the anchor tenant (PriceWaterhouseCoopers) taking up occupancy mid-year. In addition to the Commitment Agreement, the building owners (Colonial First State and Australand) had placed a contractual requirement upon the builder (Baulderstone Hornibrook) to achieve the 4.5 star rating.

Commitment Agreement process

As part of the preparation for the Commitment Agreement, the building was subject to a design review by Exergy in 2003, which identified a range of issues for consideration, including: • The building had been simulated at 4.7 stars but there

was no precedent for similar buildings achieving 4.5 stars. Also it was noted that the simulated chillers appeared to be more efficient than most chillers that could be accepted under the specification.

• The lack of true facade zoning of AHUs was noted as a potential problem. Furthermore concerns were raised about the potential presence of chilled water fan coils on the chilled water circuit causing low efficiency operation of the chiller system in winter; however, the documentation used for the final review indicated that no such units were to be installed under then base building design.

• A wide range of control and commissioning issues were noted as requiring further attention as the design progressed. It is worthwhile to note that the design review was one of the first that had been performed for a Commitment Agreement, so the process was at that stage not itself fully developed.

The subsequent treatment of the design review recommendations is not known although, anecdotally, the communication of the review between the various players within the construction process was incomplete. We had no further role in the building until 18 months after occupancy.

Initial performance

In the first 18 months, the building commissioned and operated to normal industry practice for a building of this stature, with a higher than average level of facilities management input and continued input from the builder targeted at improving the performance of the building. However, the initial NABERS Energy assessment for the building was disappointing – 2.5 stars, which is equivalent to industry average performance. This result needs to be understood in context – all data reviewed by us in the early phases of the ABGR/NABERS Energy indicated that new buildings typically performed at around this rating, so the building was in many ways typical of the time – a conventional VAV design performing at industry average.

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The operation and ownership teams were understandably frustrated at this point, especially as there was considerable corporate

commitment – as well as public and contractual commitments – to the achievement of 4.5 star rating. Indeed, options were being canvassed for large-scale capital projects such as cogeneration and chiller replacement to improve the building’s performance. It was in this environment that we were invited to review opportunities for improvement of the building, based on our proposition that a significant improvement could be made through controls and commissioning without major capital expenditure.

stage one works

The initial review of the building identified a number of significant areas of opportunity for performance improvement, including:

• The tenant condenser water loop, which was operating at a continuous pump load of 80kW, plus the fact that this loop also served podium offices and the ground floor retail areas of the building;

• AHU fan control, which appeared not to be achieving good turndowns;

• VAV terminal control, which showed signs of inefficiency and excess terminal reheat operation as well as a significant level of error in box operation;

• Secondary chilled water pump design, as the secondary chilled water pumps did not appear to be capable of operating at the flow required to balance correctly against the primary flow of the smallest chiller;

• Limited chiller efficiency, in that the units selected were all of average rather than best practice in terms of efficiency, all being constant speed units;

• Extensive use of throttling for flow balancing on chilled water and condenser water pumps; • Excessive gas use caused by overcooling

from night purge operation;

• Significant complexities and uncertainties in the metering; • Significant low-load winter chiller operation caused

by the operation of a number of chilled water fan coils installed in fit-out.

At the time, no attempt was made to quantify savings against measures – rather, an action plan was drawn up consisting of the following major initiatives:

• A complete review and revision of the HVAC control system operation, to provide an integrated set of solutions to the identified deficiencies in fan control, VAV terminal operation, pump control and night purge operation; • Installation of a new low-load secondary chilled water

pump and VSDs for the primary chilled water and condenser water pumps to manage flow balancing more efficiently; • No changes were made to tenant chilled water fan coils,

as these were deemed uneconomical;

• Installation of automatic shut-off valves on tenant package units throughout the building and the installation of metering to enable the exclusion of retail and podium office areas from this loop;

• Review of the electrical metering arrangements. Proposals for chiller upgrades and other high-capital cost measures were considered but deferred awaiting the outcome of the initiatives above.

Of the initial initiatives, the chilled water loop modifications were relatively straightforward and require no further discussion. However, the other initiatives were more complex and are discussed below.

Controls modifications

The controls modifications undertaken were very extensive, and indeed amounted to an almost complete reprogramming of the system. Key initiatives included the following:

• VAV terminals. These were reprogrammed as pure

proportional (flow to temperature) with a 1°C deadband and 1°C proportional bands. Minimum flows were dropped to 20-30% of maximum flow. Poorly performing boxes were targeted and repaired.

• AHU fans. These were reprogrammed with variable static pressure set-point that was adjusted dynamically to maintain a minimum of one group of four adjacent VAV terminals with average damper positions approaching 100%.

• AHU temperature control. This was originally reprogrammed with an algorithm that adjusted the supply air set-point by an increment in response to

control zone temperature. Control zones were established on the basis of groups of four adjacent VAVs. However,

it was found that this control interacted in an unpredictable way with the fan control, with some AHUs operating consistently in a high-flow, high-temperature condition and others in a low-flow, low-temperature condition. As the latter condition was deemed to be preferable, the incremental algorithm was replaced with a direct reset control from control zone temperature to supply air temperature; this was selected to drive a low-flow, low-temperature outcome. The perimeter control was based on a high select mechanism while the reheat system was enabled and average zone temperature when no reheat was available. The internal AHUs were controlled on average zone temperature at all times. A further adjustment was put in place to ensure that the low – flow, low-temperature configuration did not discourage economy cycle use. This was achieved by the application of an outdoor air temperature reset to the minimum supply air temperature.

• Chiller control. The chiller staging was changed to routines that more aggressively attempted to hold chillers at full load, this being the maximum efficiency point for this chiller type at fixed condensing conditions. This was achieved through staging up based on failure to meet chilled water temperature set-point and stage down based on the load being less than 80% of the stage below. The low-load operation to service the chilled water fan coils in winter was met through more aggressive cooling call mechanisms plus cycling of chiller operation to maximise the use of the thermal inertia of the chilled water loop. Latterly, these were enhanced by measures that actually used the AHU cooling coils as a means of cooling the chilled water for the fan coils when conditions permitted (by running an outside air cycle during cool temperature conditions with chilled water running through the chilled water coils). Secondary chilled

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water pumping was also minimised through the use of an algorithm that forced the pump to maintain close to the design temperature drop across the chilled water loop rather than working to a fixed static pressure set-point.

• Hot water system. A hot water system lockout was

implemented at 18°C ambient temperature and controls were modified to limit pumping energy use.

• Commissioning. All chilled water systems, hot water systems and AHUs were recommissioned to check for duct/riser leakage and the correct location and commissioning of static pressure controls.

• BMS interface. The BMS interface was significantly

enhanced via the provision of a number of on-screen reports that were designed to facilitate the diagnosis of operational issues particularly in relation to the VAVs and AHUs. This included an AHU summary table, which provided a text listing of all key AHU variables to enable comparison of each AHU with the others and the provision, for each AHU, of a VAV summary table that listed the operational parameters for all VAVs associated with that AHU.

The implementation of the controls upgrades itself was a learning experience. In the initial phase of the project, a detailed functional description was drawn up and agreed among all parties. However, it took several attempts before the controls company was prepared to implement this agreed description literally into the BMS. For instance, in spite of the functional description clearly specifying proportional control for the VAV boxes, it took three attempts before PI control was eliminated from the programmed flow-zone temperature relationship for the boxes. This perhaps highlights a larger problem with the controls industry, which is unused to taking detailed direction. Nonetheless, once this discipline was established, the controls were upgraded successfully over a period of approximately four months, with few issues.

tenant Condenser Water loop

The tenant condenser water loop was recognised as a

major load – the better part of half a star – early in the project. At this early stage, it was believed that the majority of the actual load on the loop was excludable – being the podium and associated retail tenancies. Thus it was considered that exclusion was a potential route to resolving the performance issues associated with the loop. Thus magflow and electricity meters were specified to enable the separation of the office tower condenser water loop from the retail and podium areas. At the same time, measures were put in place to minimise pump energy use, being the provision of automatic shut-off valves to tenant package units (configured to open only when the unit compressor was running) and the recommissioning of flows throughout the system. Once these measures were complete, the tenant condenser water loop pumping load dropped from 80kW to merely 8kW (which is remarkable given that the pump motor was rated at 110kW). Furthermore, the metering identified that the original assertion that the podium and retail constituted most of the load on the loop was incorrect – indeed, more than 80% of the load was actually within the office tower. Furthermore, it was found that the commissioning and monitoring of the meters to the standards required under NABERS was very difficult. As a result, the measures to exclude the retail and podium tenant condenser

water loop energy were dropped, illustrating perhaps that efficiency is a better solution than compliance.

electrical metering

The configuration of the metering for the building was made particularly complex by the need to separate the podium from the office tower, a requirement that clearly had not been fully considered by the electrical designers. In the end a relatively detailed audit of the metering was required, which uncovered some issues with meter configuration and some inaccuracies in the as-built single line diagram for the building. Given industry-standard error rates in excess of 20% in this field, the issues identified were limited but nonetheless central to the interpretation of the NABERS rating.

3. stAge tWo WoRks

The stage one measures were put into place over a period of approximately 14 months, and were subjected to a number of refinements and subsequent tuning. However, it started to become apparent at that stage that the building performance was moving towards 4 stars, rather than the required 4.5 stars. As a result a second stage of improvements was initiated. This commenced with the first quantitative study of the energy use in the building – possible now, given the review and recommissioning of the metering. Based on the identified end-use breakdown of energy use, a new set of initiatives were put into place, consisting of the following:

• Lift enhancements. Lift energy for the building was larger than expected at around 15kWh/m² – a high figure given the use of VVVF AC drive lifts with regenerative braking, which represent the generally acknowledged most efficient lift system available.

• Service reviews. These reviews consisted of careful floor-by floor reviews of the timing and levels of service provided to see whether they matched occupant needs.

• Monitoring and tuning. It was recognised that there were further gains to be had through further interrogation of the significant amounts of data available from the building’s energy metering system.

• Base building lighting improvements. The base building lighting was identified as a significant end-use worthy of further investigation.

These measures are discussed below.

lift enhancements

The key enhancements to the lifts were as follows:

• The lift acceleration rate was lowered while maintaining PCA Premium Grade lift wait times correct for the actual occupancy levels of the building. This measure achieved approximately 25% savings on the high-rise lifts – as well as a more comfortable ride – but did not achieve significant savings in the mid or low-rise lifts.

• The lift manufacturer was approached about opportunities to reduce the significant base-load of energy consumption – around 50% of total lift consumption – that appeared to exist irrespective of lift activity. However, no real progress was made in this area.

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• Lift room air conditioning was modified where possible to include an economy cycle. Owing to access issues, this was achieved via heat rejection into a large plant space but without the introduction of outside air.

service reviews

The major areas of service adjustment were as follows: • The deadband for VAVs in the office areas was increased

from 1°C to 1.5°C to 2°C. Interestingly, there was no increase in comfort complaints resulting from this measure.

• A number of excessive service run-ons – where air

conditioning was provided well after the end of occupancy – were eliminated.

• The foyer air conditioning was modified to eliminate

simultaneous heating and cooling, widen deadbands and turn off fan operation in the deadband.

Monitoring and targeting

Sub-metering benchmarks were developed for over 20 different sub-meters based on historical performance. For each of these sub-sub-meters a climate corrected benchmark was defined and a target based on the required percentage reduction. These were then monitored on a detailed basis – sometimes as often as once a week – to check for changes in performance both expected (due to measures undertaken) and unexpected (operational errors and similar).

A benefit of this process was that it was possible to very quickly see how the building was tracking towards its 4.5 star benchmark. Indeed, within a few weeks of the second stage it became obvious that the stage two measures were having a significant impact.

lighting

Two major areas were targeted in lighting works: • The foyer was heavily over-illuminated. A significant

level of delamping was used – with no adverse impact on the aesthetics of the space – to reduce lighting consumption in this area

• Lighting control. It was considered possible that given the level of opportunity identified in the HVAC controls that similar opportunities may exist in the lighting controls. This was confirmed as works progressed and it was found that the considerable capability of the lighting control system was significantly underutilised and largely uncommissioned, resulting in a great deal of spurious operation of lighting.

4. fInAl Result ACHIeVeMent

The building was awarded 4.5 stars NABERS (0 % Greenpower) in March 2010, having been tracking at this rating since October 2009. It has subsequently achieved 4.5 stars in the period to March

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e Co l I B R I u M • n oV e M B e R 2 0 11 38

2011 (0 % Greenpower) with no further external interventions during this rating period, indicating that the achievement of the rating is stable. Furthermore, for this second rating, the podium building was included, re-integrating the project into its logical whole. The progress towards the 4.5 star target is illustrated graphically in Figure 2. This figure shows the raw emissions and equivalent monthly emissions for the NABERS rating bands. When the building’s yearly consumption reached the level required to achieve the 4.5 star target, the building’s monthly consumption was almost on par with 5 star levels.

lessons learnt

As discussed in the introduction, this project can be considered typical of many buildings of its time – designed before ABGR/NABERS was widely adopted and committed to a superlative performance well before the knowledge of how this performance would be achieved. It is worthwhile to consider the lessons learnt, therefore, as a pointer to other projects. 1. Design review process. The design review process could

have been more effective if it had been more effectively communicated throughout the overall development team. This may have led to the avoidance of some issues that proved very expensive to resolve post-construction. 2. Commitment. This project would not have achieved

the 4.5 star rating had it been left to ordinary industry process to deliver. The commitment of the owners to achieving the NABERS outcome was absolutely pivotal to the project’s success.

3. NABERS compliance. NABERS compliance had a significant role in this project in a number of areas, including:

a. The chilled water fan coils. These were originally and incorrectly thought by the design to be an excludable item

from the NABERS rating. As a consequence what was in essence a lower-efficiency design was developed on the assumption that it could be excluded from the rating. Resolution of the servicing need through better design rather than through a perceived compliance path would have been a better result irrespective of the excludability or the associated chilled water production energy. b. The tenant condenser water loop. The compliance-based

resolution of the tenant condenser water loop proved to be unnecessary in the light of a design-based solution to improve operating efficiency. This resulted in the unnecessary expenditure of a considerable amount of capital on the thermal meters.

c. Electrical metering. The division of the building into podium and tower led to considerable difficulties in the performance of the rating. Compliance with the increased NABERS requirements with regards sub-metering demonstrated flaws in the metering system, validating the importance of the NABERS sub-metering rules. d. Thermal metering. Quite aside from the eventual

irrelevance of thermal metering in the final rating, it was found that the configuration and monitoring of the thermal meters and associated electrical meters to the standards laid out within the NABERS thermal metering rulings were extremely difficult. This is an area where the NABERS rules require simplification to be more practical. 4. Control and commissioning. More than anything, the

experience at Freshwater Place highlights the absolutely central importance of control and commissioning in the achievement of high NABERS ratings. The greatest failing of the original construction process was in these areas; while both were adequate to deliver an operating 1,200,000 1,000,000 800,000 600,000 400,000 200,000 0 Se p – 0 6 D ec – 0 6 M ar – 0 7 Ju n – 0 7 Se p – 0 7 D ec – 0 7 M ar – 0 9 Ju n – 0 9 Se p – 0 9 M ar – 0 8 Ju n – 0 8 Se p – 0 8 D ec – 0 8

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Acknowledgements

The upgrade project was very much a team effort and the author would like to acknowledge and thank the following, whose involvement was critical to the success of the project:

• Colonial first State and Australand, as owners, for setting up the parameters and providing ongoing support for the success of the project.

• Sean McMahon, general manager commercial and industrial, Australand: for providing motivation, encouragement and authority to the achievement of the results.

• Geoff Pountney, tenant facilitator, Australand: for providing the project management and facilitation without which the works would have not been completed.

• Kok Lim Ng, engineering services manager, Jones Lang LaSalle: for constant attention to the detail of operation and continued innovation in the operation of the building.

• Erica Kenna, senior consultant, Exergy: for undertaking much of the original design review process in 2003.

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building, neither were adequate to deliver an efficient building. Rectification of this failing delivered the vast majority of the savings.

the future

The future for the site holds many opportunities, but the focus is rapidly moving towards the achievement of 5 stars for the site as a whole. This target is of interest partly because it represents the next threshold (and increasingly the rating-to-have in the industry generally) and partly because the performance towards the end of the detailed monitoring period was very close to 5 stars. Achievement of this higher rating, however, would require addressing some of the more problematic aspects of the building, such as the tenant chilled water fan coil units.

5. ConClusIons

The paper has presented a case study of Freshwater Place, a conventional VAV building that was upgraded from an initial 2.5 star performance to 4.5 star performance through a series of capital, control and commissioning measures. The project has illustrated the importance of control and commissioning in achieving high NABERS outcomes, but has also confirmed that a committed project team, as was present for this project, is a prerequisite for success. ❚

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