The climate change agenda has clearly reached a world-wide tipping point. Yet while there is growing consensus that the phenomenon poses a major threat to future human well-being, legitimate debate remains about what is to be done to reduce atmospheric carbon levels, as well as to adapt to changes that already appear likely. 

In particular there is ongoing debate about how the cost of various options correlates to potential benefits.  Debate also continues about how the issue of climate change relates to the larger agenda of sustainable development.

The built environment is well known to be one of the largest current contributors to greenhouse gases.   Therefore those who work in the planning, design and building professions have a key role in working to reduce atmospheric carbon dioxide. While much work has been done to decrease contributions from individual buildings, the role of urban design in addressing climate change remains more obscure, and more contentious.   

To be sure, buildings are not passive emitters of greenhouse gases.  They shape the patterns of activity and consumption of their occupants, which in turn profoundly affect emissions.  Must occupants drive between scattered locations, perhaps for long distances?  Do they spend large percentages of time in buildings isolated from a functional public realm, with high patterns of consumption and emissions?  Are those buildings sited in remote new developments where significant areas of existing vegetation have been replaced with paved or reflective surfaces?  How does the urban street and block pattern contribute?  What about the mix of uses, and the distribution of daily activities and needs?

There has been much discussion of the dramatic carbon reductions possible per person in a higher-density urban morphology, particularly in comparison to automobile-dominated “sprawl” development.  But what are the factors to be teased out?  If we are to pursue such a goal, what are the issues to be addressed in economics, market dynamics, project permitting, legal regulation?  How are these issues being addressed successfully, and what further challenges and opportunities remain?

What about the preference of some consumers for lower density neighborhoods, or the argument that it is more sustainable to accommodate a settlement distribution or “transect” from  the highest human use to the most pristine natural environment, including lower-density agricultural settlements?  Does the new agenda imply, as some argue, that only very high densities will be viable?  Or can a mixture that includes some lower-density morphologies be sustained in combination with other forms of mitigation?  Is such a range of densities more economically sustainable, as some argue?   

Even at high densities, a wide range of morphologies is possible. What are the benefits and tradeoffs of the alternatives?  For example, are dense high rise cities the inevitable best option? What about the negative energy impacts of tall buildings that may feature extensive curtain wall glazing, or require other high-energy conditioning, maintenance or repair?  How do tall buildings perform across socio-economic classes, or in promoting social diversity and economic sustainability? How do they perform in repairability, adaptive re-use, or typical life-cycle?

What about the advantages of “green” retrofits of existing buildings, in comparison to new green buildings?  Since roughly half of the energy use of a building is in its construction, is there credible evidence to suggest that adaptive re-use of heritage buildings should be a greater priority?  Are there examples of traditional urban fabric that offer better models of sustainable morphology, such as medium rise “liner” buildings, or high-density terraces?  And do traditional buildings offer any significant morphological benefits for the sustainability challenge?

These questions remind us that emissions are a cumulative phenomenon, and must be considered over whole systems and whole life cycles.  Clearly a reduction in one targeted parameter is of little use if it results in the increase of another parameter by an equal or greater amount.  Moreover, greenhouse gas emissions are only one parameter of sustainability that must be considered in balance with others.

From the Vigeland sculpture park



 Regenerated industrial area along Akerselva river