The geometry of the city and the use of air conditioning

It's not just a question of climate: height, density and vertical development of buildings affect the demand for urban cooling

How urban planning can mitigate the use of air conditioning — A study analyzed the factors that influence the demand for urban cooling, and found that the shape of the city also has its own specific weight (Photo: Envato)

Global warming and theurban sprawl are making heat management one of the key challenges for the livability of cities around the world. Relying exclusively onconditioned air It risks amplifying the heat island problem, rather than solving it – while also increasing energy consumption, with consequent emissions.

Architecture and design of highly efficient and passively cooled buildings can certainly help reduce urban cooling demand, but also the city structure, and its way of expanding, have a weight.

The demand for urban cooling does not only depend on the climate

Ever larger cities in an ever hotter world. Dense, concreted urban agglomerations that amplify the effects of heatCooling is already a serious problem in many cities around the world. First and foremost, because too many people can't afford air conditioning or ventilation systems at home, it's ultimately up to the city to ensure everyone has access to livable spaces.

Even if everyone had access to cooling devices, we'd still have a problem: air conditioners don't remove heat, but transfer it outdoors; in large, densely populated cities, the exhaust heat expelled by millions of outdoor units can raise the surrounding air temperature by up to 1-2°C during the evening and night hours.

The extensive use of air conditioning Not only does it contribute to the urban heat island phenomenon, but it also significantly impacts energy consumption, straining electricity grids and increasing the reliance on the fossil fuels that brought us this far. Air conditioning is not a sustainable solution. Or rather, it can't be the only one. Therefore, in recent years, the attention of technicians and urban planners has shifted to developing strategies that allow for reduce cooling demand at the root. We are therefore talking about passive cooling and bioclimatic architecture, urban greenery, insulation and reflective surfaces that can lower temperatures in cities and inside buildings. Yet, even the the very structure of the city It has a weight when it comes to cooling demand.

Beyond Green: The Three-Dimensional Geometry of Our Cities

To seriously address the demand for urban cooling, the city must be designed in such a way that its very structure – its three-dimensional evolution, made up of morphology and demographic pressures – helps reduce the need for cooling devices. This is what emerges from an Indian study published this year in Nature Communications., which analyzed data relating to 88 Indian cities and 52 global cities To identify spatial factors that can significantly influence the demand for urban cooling, they concluded that, indeed, some specific elements can increase the need for indoor cooling.

Urban densification, the reduction of greenery and the increase in waterproofed surfaces show a positive correlation with the trend towards increasing
Cooling Degree Days (CDD-hum), that is, the total amount of energy needed to keep a cool and dry environment. But increasing building heights also appear to contribute to the demand for cooling.

“The spatial extent and configuration of built structures — particularly volumetric expansion and growth of cities, height development, consolidation through void filling, and volumetric densification — contribute significantly to variations in energy demand for urban cooling, both in low- and middle-income regions and in high- and upper-middle-income regions.”

we read in the research.

Cities are getting hotter, but air conditioning isn't enough. — Air conditioning cannot be the only solution in the field, also because its extensive use can amplify the problem (Photo: Envato)

Vertical growth and thermal footprint: a question of structure

Regional climate and geographical location are not sufficient to define a city's cooling demand. Cities located in the same region and with the same characteristics—for example, some cities in the hinterland of the Indo-Gangetic Plain and in the hot, humid coastal zone—show quite different cooling profiles. On the other hand, cities with distinct climatic conditions but with similar volumetric profiles they showed comparable UCD (Urban Cooling Demand) levels, highlighting the possible role of urban building configuration in modulating cooling demand.

“Our study shows that the energy demand for cooling in cities does not only depend on the regional context, local climate and urban size, but rather arises from the interaction between horizontal expansion, vertical development, building saturation and population density, in combination with the regional-climatic context,”

it is written in the study.

In particular the volumetric growth, where cities grow taller rather than sprawl, is emerging as a key factor in shaping the growing demand for urban cooling.

“The findings suggest that future urban climate responses will need to take this shift into account, as vertical densification continues to reshape the thermal characteristics of cities,”

explain researchers from the Indian Institute of Technology in Kharagpur.