Big gestures

The southern end of Sydney is undergoing a major architectural renaissance, with buildings by several of the world's leading architects.  The developments include the brownfield site of the former Carlton and United brewery, but also the University of Technology precinct on the other side of Broadway, one of Sydney's major road arteries. Partly to satisfy the agenda of the Sydney City Council, partly driven by the involvement of the University, sustainability is meant to be high on the list of priorities.

It is a moot point what, besides some default bolt-ons, is really being incorporated in these high-density developments.  But there are certainly some signature items that make the architectural community and the casual lay observer think that something radical is going on.

On Jean Nouvel's twin residential towers, some of the vertical greenery by Patrick Blanc are being installed, but they have just been upstaged by the lifting into place of the 110 tonne frame of a very large heliostat cantilevered from the 29th floor.

I was involved with an earlier tedious, painstaking, and ultimate pointless attempt to optimise solar access to generate the massing of a larger number of residential buildings on the same site. So I am under no illusions that Nouvel's bold gestures, and Foster's overwhelmingly methodical presentation of their contribution, broke through a previous barrier to the sensible development of this complex piece of Sydney. But that said, I have to work hard to maintain my enthusiasm that either the vegetative facades or the heliostat are anything but distractions.

The planting on the otherwise unrelieved glass curtain walls still produces a somewhat cynical response, to what might be more sensibly scaled and varied ways of living at high density in the city.  Effective passive environmental control, even in Sydney's benign climate – or perhaps especially in this climate – they certainly are not.

The heliostat makes me edgy for another reason.  The renderings have been spectacular, the promise of the night-time display of LED lighting undoubtedly likely to impress.  But for the life of me, I have not been able to find a sensible diagram that actually shows how winter sun angles might interact with the surfaces available for the installation of the mirrors.  The latest image, part of an online announcement on ArchitectureAU after the lifting of the frame, illustrates my point.

It shows the heliostat slung off the bottom of the cantilevered sky garden (complete with swimming pool).  The two-storey depth of the truss is clearly necessary structurally, but as far as I can tell develops exactly the sort of overshadowing of the mirrors, that will make the heliostat least effective in the middle of the day in winter when reflected sun is most needed.  By the same token they will receive the least shade in midsummer, when in Sydney shade in public places is a precious commodity.

But I have learned never to guess the complex 3-D geometries of sun and shade without the benefit of a 3-D model.  I could be wrong.  I just wish the architects would stop publishing renderings of what they hope will happen, and let us have instead some of the evidence which I sincerely hope they have bothered to investigate.