Urban planning, conventionally understood, has had little to say about the thermal comfort of cities. One exception could be the landscape and urban design professions who have, for a long time, been cognisant of the importance of tree canopies, soft surfaces, green space, and microclimatic sensitivity to site orientation. Thermal comfort has tended to be left to building owners and managers, with little interest or incentive to attend to the thermal conditions encountered between buildings. Indeed, it could be argued that the advent of inward facing, courtyard oriented buildings have been a deliberate attempt to treat climate as ‘the other’, as an enemy to be tamed and excluded rather than engaged with.
The growing awareness of the impact of climate change on cities has prompted a rethink. However, this remains patchy. There has been a growing amount of research that has used the concept of ‘eco-cities’ to describe how resilience can be engineered, or retrofitted, into the urban environment, with the likes of Abu Dhabi’s Masdar City being promoted as a test-bed of future urban development. Certainly, many eco-innovations are cheaper and easier to integrate with conventional property developments from the outset.
However, there is a huge amount of sunk capital in existing cities, with many urban areas still dominated by a stock of buildings designed and constructed in another era. A major challenge is thus to reorient the synoptic and regulatory goals of urban planning practice towards the retrofitting of existing structures. A good example of this is Smith and Gill’s Toward Zero Carbon: The Chicago Central Area DeCarbonization Plan.This is a major survey by one of Chicago’s leading architecture and design practices which focused on the central business district of the city. Working through a range of criteria, from building age, use, size, parking, energy type and intensity of use, and carbon emissions, the firm developed a parametric map of the central city that colour coded individual buildings based on their performance. This allowed them to identify the owners and tenants of these buildings, who could be encouraged to undertake energy audits and – ideally – major capital retrofits to improve energy performance. What is notable about the study was this proactive attempt to benchmark the performance of individual buildings against the area as a whole. As they put it in the introduction:
“What if we could tap into Chicago’s latent potential by using the existing built environment as a carbon asset? What if we could redefine energy as a commodity to be traded between buildings, blocks, cities? What if we could transform Chicago’s Loop into a net carbon-positive district?”
To do so, they conducted an audit of the buildings in the central area. They make a distinction between four different phases of office building, each with their own specific building systems: the heritage (1880-1945), mid-century modern (1945-1975), post-Energy Crisis (1975-2000), and Energy Conscious (2000 to present). Each of these had their own distinct energy loads, based on a range of factors including heating, lighting, air-conditioning, envelope performance (ie façade and windows) and elevator use.
They identify several possible approaches to encouraging retrofitting, including the creation of a minimum performance level for existing buildings, direct metering of tenants to decentralise energy use (rather than a bulk billing via the building managers), training of building managers, and significant funding innovations, such as grants to undertake energy audits, and equity access for major building retrofits.
It is the funding section of the report that is perhaps the most interesting. They provide an illuminating case study of how this might work:
“Building X has an energy audit performed. It determines that, in addition to several no-cost or low-cost solutions, substantial energy savings could be realized by replacing Building X’s chiller with a new, more efficient one. Using an estimate for improvement arising out of such an audit, Building X is then able to determine that such a chiller replacement would cost approximately [US]$4 million. However, in many situations, the projected cost savings from an upgraded chiller do not adequately repay the debt available from the traditional sources of such improvements.”
To overcome this obstacle, they suggest that certain funding regimes (specific to Chicago) could be provided, such as tax increment finance (where increased revenue from long-term capital improvements can be used to undertake the initial capital works), or through the issue of low interest bonds that could be repaid via a specific taxation levy on the building.
Smith and Gill recognise that only certain buildings in the central area are candidates for retrofitting, and advocate demolition of low performing buildings at various points. To be sure, there is significant profit to be made by several interested partners in driving forward high energy performance skyscrapers, perhaps given additional height allowances as incentive, and this has been the case in cities around the world.
More generally, a major task for urban planners in certain contexts is to provide comfortable spaces for pedestrians and cyclists (assuming that car drivers have access to some kind of in-car cooling system, which is not always the case). In Singapore, this has been achieved through a highly developed underground link system, where pedestrians can cross substantial swathes of the city without being exposed to the external climate. It goes without saying that this creates its own problematic heat externalities, with added surface area heat being a corollary of the move underground.
However, there has been a growing incorporation of urban climate and related concepts into the urban planning lexicon. For example, Jankovic and Hebbert have argued very strongly for a closer attention to what they term ‘urban meteorology’:
“The city is a producer of weather. It generates atmospheric gradients with major effects on comfort, health, traffic, leisure, property value, and infrastructure. The three-dimensional complexity of built environments makes intricate microclimates of real weather and patterns of sharp contrast at every scale of resolution. As cities have changed, so have their climates, challenging traditional climatic responses that were learned by experience and embodied in local design vernaculars.”
Facing up to these ‘city weathers’ is a key – and urgent - task for urban planners.