For sake of simplicity, let's get the definitions right.
The building industry has come under scrutiny through the application of numerous rating systems. Frameworks such as the United States' LEED, the U.K.'s BREAM, Japan's CASBEE all set up ways of evaluating a variety of impacts created by the procurement and use of proposed buildings.
But it is really important to understand that almost none of the claims for sustainable buildings being made in the current rating systems actually translate to a sustainable built environment. Common to them all are metrics (ways of measuring) that compare the impacts of the proposed building – such as its protected energy use – to the average impacts of comparable buildings which we have built before. In other words, they really just tell us that the proposed building is less bad, not necessarily that it is sustainable in the longer term.
Of course, even those restrictive definitions can actually be stretched, so that we see some glimmer of hope. So, for instance, with regard to energy used in running a building, we can conceive of a situation where the demand for energy has been reduced by good design to a very small amount, and that small amount of energy can actually be generated on site by renewable means, such as photovoltaics. Hey, I can even imagine generating a surplus. Remembering that there is a limit to the amount of solar energy falling on the site, and that we have to recover the energy spent on producing the photovoltaic panels. We might call a building which succeeds in doing this, a 'healing building'.
One is tempted to think that it is easier to produce such a building by high tech new build, rather than accepting the limitations of some older building, built to lower standards. But in fact, there is no such logical link. To the contrary, emerging evidence is that appropriate retrofit of older buildings, tends to produce better energy efficient outcomes than new build, and that the generating capacity is mainly 'bolt ons' which can be equally supported by a brand-new, or an adapted older structure. The clincher, however, is when we look at the embodied energy, and the waste stream. Both of these considerations become much more important, as we refine the recurring energy balance. And here, retrofit is intrinsically likely to be way ahead.
And finally, the intangibles. Opening up an apparently unresolvable argument, we have the opposing sentiments of what buildings and cities represent. Typically in a thrusting, developing economy, building express our aspirations for progress and modernity.Contrast that with the familiarity of typically more human scaled, older cities, gently engendering responses like 'fondness'.
I have wrestled with this one, and I have decided that the precautionary principle does apply – incremental change is better able to be monitored for success, and design in constrained environments tends to be smarter and more ingenious. In my considered opinion, a conservation ethos combined with acceptance of radical adaptive reuse, produces much better outcomes than bullish demolition and new build.Fortunately for my peace of mind, more and more retrofit is turning up in the architectural mainstream. The two examples that happen to trigger this post are both drawn from the regular features in the Guardian newspaper:
PwC creates the most sustainable building in the world, describes the refurbishment of the UK's first "air rights" building – constructed on top of an existing structure – 1 Embankment Place, built over Charing Cross Station in London in the early 1990s.
John Robertson Architects – the most sustainable building is an existing one may not provide much technical detail, but does make a claim that I find very credible – the principle of marginal gains: that a lot of small improvements can lead to a substantial gain overall.