10 April 2012 – One of the frustrations facing people working in the green building space is the lack of information on how our award winning buildings actually perform. We need to learn from what has worked well, and what hasn’t been so successful.
The 60L Green Building in Carlton was completed in late 2002. The developer was a green philanthropic organisation and the anchor tenant was the Australian Conservation Foundation. So there was a strong commitment to delivering a practical green outcome.
My business partner in Sustainable Solutions, Bro Sheffield-Brotherton and I were the independent environmental consultants engaged by the client to work with the project team, develop complementary documents, and monitor achievement of environmental outcomes.
We worked closely with Alistair Mailer, the client’s project manager, and with the project team. This was quite an unusual organisational model for a building project, but it was fundamental to the delivery of an ambitious green agenda. The building is now owned and managed by the Australian Conservation Foundation.
For a variety of reasons, including limited resources, public performance data on 60L has not been available. In 2011, Masters of Sustainable Energy Engineering student Nathan Chapman took on the task of sifting through the enormous amounts of raw data to find the underlying story.
His work built on some data analysis done by building manager Andrew Gemmell, and a post-occupancy study done by veteran New Zealand buildings researcher George Baird, part of a 30 building international comparative study.
I was asked by AIRAH to present the 60L case study at one of the regular Melbourne Forum events, along with several other case studies. So I have drawn together information from these sources to paint a picture of 60L’s energy, water and occupant satisfaction outcomes.
The overall picture
Over its operating life, energy use (all electricity) has averaged 77 kilowatt-hours per square metre per annum for the whole building (that is, base building plus tenancies). This compares with the NABERS five star equivalent of 127 kWh a sq m normalised consumption for Melbourne. Note that 60L consumption should really be normalised according to NABERS methodology before formal comparison with the NABERS benchmark, but it looks very good.
Energy consumption increased slightly to 83 kWh a sq m in recent years, due mainly to energy use by the sewage treatment plant and increasing occupancy. It is expected to decline again, as the sewage plant has been decommissioned and some energy efficiency measures (for example, high efficiency exit signs) have been implemented.
The small photovoltaic array on the roof has contributed an average of 3.2 kilowatt hours a sq m a year so gross consumption has been around 80 kWh a sq m per year. All grid power purchased is certified Green Power, so the building is carbon neutral from an operating energy perspective.
Melbourne has been in drought for most of the time 60L has operated, with average annual rainfall of around 500 mm pa compared with a long term average for Melbourne of 650 mm. Yet it has averaged 460 kilo litres a year mains water consumption, or 0.4 litres a sq m a day.
In average conditions it has the potential to get fairly close to self-sufficiency, although it may need some more storage to cope with the trend towards less frequent but more intense rainfall. So actual performance would score around 2.5 – 5 points under the Green Star rating but, in typical design rainfall conditions, it would be likely to score close to maximum points.
From an occupant perspective, George Baird’s work is very interesting (Sustainable Buildings in Practice, 2010). He compared a sample of 30 green buildings around the world, using a variety of rating scales and criteria.
On one rating, the seven point scale, 60L was “exceptional”, scoring 96 per cent. On the “all factors” rating scale, it scored 83 per cent – at the upper end of the “good practice” band. A number of the issues he identified have been addressed since his study.
On 45 criteria surveyed, 60L scored ‘’better’’ than average on 30 criteria, ‘‘similar’’ on 12 and ‘‘worse’’ on 3. The weak points were noise and some aspects of environmental conditions (comfort).
Overall, 60L seems to have delivered well on its environmental objectives. But there have been some interesting and challenging issues along the way, which I will now discuss.
Sewage and rainwater treatment
This has been a challenge from Day 1. The initial design was not a great success: 60L’s extreme water efficiency measures meant that the nutrient content of the sewage was unusually high, and the bacteria in the treatment plant were overwhelmed.
Over an extended period, the consultants and building manager tried many modifications, without great success. In recent years when it was running, it used large amounts of electricity and required high levels of maintenance. Indeed, it made the Wonthaggi desalination plant look very efficient!
The main lesson seems to be that the plant was too small to reach efficient and stable operating conditions and capture efficiencies with the variable organic output of an office building.
The rainwater treatment system (using cartridge filters and UV treatment) has used around 10 kWh a day, close to what was expected. However, during the design process we managed to avoid much higher energy use.
First, high pressure drop sand filters were replaced with low pressure drop paper cartridge filters. Second, sensors were used to control the circulation pump and UV treatment, rather than running them continuously. Regular testing of water quality at outlets provided a check that all was working well.
Heating and cooling
The ground floor tenancies have been somewhat cooler than desirable, and have used more heating energy than other tenancies. This reflects their overall lack of insulation and high air leakage. But they’re great in summer!
60L uses reverse cycle split system airconditioners in each tenancy, topped up by a tempered outside air ventilation system. The building also runs in natural ventilation mode at ambient temperatures of 19 to 26C.
This approach has its pros and cons. On the positive side, each tenancy controls its own usage, and pays for it as part of the tenant electricity bill.
Since 60L tenants work widely varying hours, this flexibility avoids a need to condition large parts of the building when just a few people are present. This solution was also much lower in capital cost than a conventional HVAC system, so the savings were able to be invested in other measures.
On the negative side, the units selected are commercial units that are relatively noisy and not inverter controlled. On balance, it would probably have been better to use cheaper, quieter and more efficient residential split systems.
Overall, the building seems to have a winter energy usage peak. Most Melbourne office buildings tend to be summer peaking, so this is an interesting outcome. It may be that 60L’s limited glazed area and high mass helps, or that the lack of insulation drives heating usage higher.
There is potential to utilise heat from near the top of the atrium for heating of the ground floor, but this requires a major study to work out how it might be best done. Some insulation and air leakage management will also help.
60L has wonderful daylighting via the central atrium, so much of the building operates without artificial lighting for much of the time. The office lighting is T5 fluorescent tubes in efficient luminaires, with an installed lighting density of about 5.5 watts per square metre.
At the time of construction, the extra cost of smart dimming and controls could not be justified, so simple light switches and zoned lighting are used. There is room for improvement, but the outcome seems quite good.
Strong fitout guidelines and a ‘’green lease’’ were key elements of the strategy to limit tenant energy use and environmental impacts. This seems to have been fairly effective, in conjunction with some enthusiastic tenants who have worked to set up energy efficient computing facilities.
It may be useful to conduct evaluations of tenancy compliance to see if there has been any drift in terms of energy waste. There seems to be little evidence of this from the overall energy data, but there is substantial variation in power usage from one tenancy to another.
To achieve its green objectives, the 60L project adopted a comprehensive approach. Inclusion of detailed environmental requirements in all specifications was crucial, as were processes that ensured the requirements were met.
Independent review of design features led to significant improvements. Tenants were engaged before fit-out and during occupancy with a fit-out guide, green lease and detailed monitoring.
See the website
Alan Pears is adjunct professor at RMIT and director of Sustainable Solutions Pty Ltd