8 Chifley: the journey to high performance

6 February 2014 — As reported on The Fifth Estate on 16 July last year, 8 Chifley Square is one of a new breed of buildings currently being introduced to the Sydney commercial market.

This new breed is providing the City of Sydney with ingenious and unorthodox designs that are leading the international field in sustainable building design in their technology and systems, along with the less tangible element of societal change.

I’ve been an engineer with Arup for seven years now and have had the good fortune to be involved with 8 Chifley Square all the way from concept design to construction. Perhaps one of the best demonstrations of this link and the fateful nature of my involvement dates back to 2008, when I took an 18 month sabbatical with Arup’s building physics team in the UK. Almost simultaneously, 8 Chifley paused to draw breath for the Global Financial Crisis. Fortunately for me, Mirvac took the bold decision to reactivate the project in 2010, restarting almost simultaneously with my return… perfectly timed!

The decision to reactivate the project was a bold one from Mirvac at a time when the market in Australia was uncertain. However, as the current occupancy rates will attest, the decision was very well timed as it presents a very high quality space that delivers on its promise of world leadership.

So, what are the sustainability credentials that 8 Chifley has achieved? There are many, including the world leading 6 Star Green Star design, and the target of achieving 5.5 star NABERS Energy performance. Rather than simply listing a load of facts about the design, I thought it might be more interesting to step you through a small selection of the building’s sustainability features, some of the challenges we faced, and the solutions we found. In doing so, I hope to perhaps explain our motivations, our approach and ultimately our achievements.

Building envelope

The façade (or skin) of a building really is, from a sustainability perspective, the most critical part to get right. All other design features, from mechanical design and thermal comfort all the way through to the building’s appearance to the wider city and the social interaction this fosters depend upon it.

The architectural desire was for a high clarity façade. The intent of this was to provide profuse levels of natural light, but also transparency and connection outward; but even more importantly, inward. Combined with this was the commercial desire to maintain the views of Sydney Harbour using floor to ceiling glazing.

These desires present a number of challenges including energy, glare and occupant comfort where the objective is the balance and optimisation of the often conflicting desires.

The combination of these challenges has resulted, I think, in a pretty interesting response in the façade treatment where shades have been included on each of the northern, eastern and western facades.

The interesting part of this is the reversal of common logic where the northern façade has included the biggest shade, with an additional vertical element compared with the east and west.

For those of you who were paying attention at school, you’ll know that the sun rises in the east and sets in the west, which means that the east and the west of a building typically get the harshest (low angle) solar exposure and so need the greatest protection from the sun. So, why have we reversed our design thinking on this building, providing the most shading to the north?

The answer lies in the blind use. While a more transparent, clearer glass means more daylight and connection, it also usually means blinds are drawn more to minimise the glare. Because of this, an early and key area of focus for the façade was blind operation.

Blinds can have numerous functions including improving thermal comfort through blocking sunlight and heat from the windows, but are primarily used to reduce glare. This then begs the question: why have high clarity glass if the blinds are drawn all the time?

For 8 Chifley Square, the answer to both of the above questions was to provide improved shading to the north where the comparatively high sun makes it easier to block with external shades.

These almost eliminate the need for internal blinds and so maximise access to those wonderful harbour views. On the east and west the very low sun meant that blinds were needed in the morning and evening no matter what. Therefore high performance reflective blinds have been integrated into the mechanical design on the east and west, working in concert with the high clarity façade to control occupant visual and thermal comfort while reducing plant size and annual energy.

Testing and proof of the envelope performance came through a number of means, including assessing the probability of glare (and hence likelihood of blind use) for each hour throughout the year. At the time (2007) this was one of the first times this had been done – and on the forefront of architectural science.

What are the outcomes of all the work undertaken? 8 Chifley is able to use very high clarity glass, which brings profuse levels of daylight, allows a greater sense of occupant connection with the outdoor environment and, most notably, improves the connection between the building and streetscape, allowing people to see into the building.

Servicing and carbon performance

The starting block for servicing and carbon performance should always be passive design, working from the envelope of the building and then overlaying active systems. For 8 Chifley Square, that is exactly what we did. A critical factor in the façade analysis work was our focus on limitation of solar loads.

The development of a high performance envelope allowed a step change in the type of conditioning system used, which in turn reduced the energy use of the building.

These step changes are really important milestones for any design where one step allows the next to happen, with the savings they allow being a multiplication factor, driving energy use (and often overall system costs) down. However, even with these performance systems in place, we were still limited somewhat by the high carbon content of electricity in New South Wales.

8 Chifley Square has pushed the bounds of what is currently considered feasible. A trigeneration plant using gas to provide low carbon electricity, hot water and chilled water to the building services has made it capable of achieving 5.5 Star NABERS Energy performance. This means it is only emitting one third of what a similar building would, a substantial step on our way to carbon neutral design.

However, this isn’t all. The building has been designed to allow the export of electricity. This is the first time this will have happened on the Sydney triplex network. This enables the plant to operate at a higher capacity over longer periods, improving its efficiency, minimising material use and redundancy, and providing low carbon electricity to other buildings.

Again, the use of one system requires a balance and an offset against other drivers, and so it is with the trigeneration system, which results in an increase in water use for the building. Here again, passive design was maximised through efficient fittings and through rainwater harvesting.

8 Chifley Square’s solution was to look at black water harvesting, mining the effluent from others and treating it to drinking water standards for use in cooling systems, irrigation and toilet flushing. However, there is an energy penalty for the processing of the effluent water, meaning more carbon emissions.

And so you can see, it’s a balancing act; trading carbon performance against water use; trying to knit all of the demands together into a holistic solution. So what is the outcome? For 8 Chifley Square 5.5 Star NABERS is achievable, and we see a 90 per cent reduction in potable water demand all while providing a premium level of service and comfort to the building users.

It’s a village in there

The village concept is at the heart of 8 Chifley Square’s design. The villages are a series of split floor plates, linked together in north facing, vertically integrated atria that bring daylight and an expansive volume to the floor plates.

The villages truly are one of the most impressive human-centric features of the building, and I would challenge anyone to go into the space and not be impressed by the sense of volume, openness and connection they provide. However, they also create a number of design challenges for environmental performance.

With a space that is at times four storeys high, how do you service them? Similarly, with a façade of that height, how do you provide comfort in summer with the hot air plume from it moving out onto the upper floor plates, or in winter the cold air sinking down it causing uncomfortable drafts?

While the expanse of height brings profuse levels of daylight, how do we deal with glare and an excess of daylight?

All of these issues had to be worked through. Computer models of air movement were used to show which systems would be needed resulting in an extract system at the top of the atria and low level heating for the winter. Blinds with an advanced control strategy and user override were used to the façade, giving control for the occupants at the differing levels.

Future proof design

Observant readers may have noticed the large shading structure at the top of 8 Chifley. The canopy provides a degree of protection to the roof terrace and has been designed as photovoltaic panel ready. This presents the tenants with the option of truly buying into the sustainability story of the building. As has been borne out in the last few years, the cost of PV panels has dropped massively, and the building is future proofed for both Mirvac and the tenants as the cost of energy continues to rise and the technology rapidly develops.

What do I hope you take away from this article? Well, other than getting a sense of the challenges that we went through, I hope you gain a feeling for the building’s features as well as the design tools and process used to deliver a design that is at the forefront of building technology and environmental performance.

8 Chifley presents a product that addresses the triple bottom line of economic sustainability; environmental sustainability; and, through its transparency, public realm, and village design, it has addressed the third critical area of social sustainability. It is perhaps this social sustainability aspect of 8 Chifley that I’m most proud to have been a part of.

I’ve enjoyed the process and seeing the building come to life and truly see it as the next evolution in the premium office market here in Sydney, raising the bar for all to follow.