Clustering buildings by use may cool cities, study of 101 cities finds

The brief in 5 cards

1. Note1 / 5

   WHY IN NEWS?

   • A study covering 101 cities examined how the arrangement of buildings affects city heat.
   • It found that larger clusters of buildings with similar functions had lower surface temperatures.
   • Each 100-metre increase in cluster size was linked to about 4.5% lower urban heat island intensity.
   • The researchers say urban layout, not just greenery or materials, shapes how hot a city gets.
2. Note2 / 5

   WHY SIMILAR BUILDINGS MAY HELP

   These are the study's suggested reasons, as reported.

   • Similar shapes: Buildings of the same type tend to have similar heights and forms, letting wind pass more smoothly.
   • Similar schedules: Offices, homes or factories release heat at similar times, so heat builds up less in pockets.
   • Fewer hot spots: Mixed, irregular layouts can trap heat in narrow gaps.
   • Caution: The finding is an association across cities, not proof that rearranging buildings will cool any city.
3. Note3 / 5

   KEY CONCEPTS

   1. What is an urban heat island?

   It is when a city is warmer than the countryside around it. Concrete and asphalt absorb heat, there is less vegetation, and vehicles and air-conditioners add heat.

   2. What is albedo?

   It is the share of sunlight a surface reflects. Light surfaces reflect more and stay cooler; dark roads and roofs absorb more and heat up.

   3. What is urban morphology?

   It is the physical form of a city — the size, height, spacing and arrangement of buildings and streets.

   4. What are ventilation corridors?

   They are open strips, such as parks, rivers or wide roads, aligned with prevailing winds to carry heat out of a city.

4. Note4 / 5

   RELEVANCE FOR INDIA

   • Heatwaves: Indian cities face rising heatwave days, raising health risks for outdoor workers and the poor.
   • Heat action plans: Ahmedabad's 2013 plan was India's first; NDMA has since issued national guidelines.
   • Planning gap: Most master plans focus on land use, not heat or airflow.
   • Mixed-use trade-off: Mixing homes, shops and offices cuts commuting. Planners must balance this with any cooling gains from clustering.
5. Note5 / 5

   WAY FORWARD

   These are suggested measures, not approved policy.

   • Add heat to planning: Use heat mapping in city master plans.
   • Cool surfaces: Promote cool roofs and reflective pavements.
   • Keep wind paths open: Protect ventilation corridors from encroachment.
   • Green and blue spaces: Expand trees, parks and water bodies.
   • Test locally: Check whether clustering findings hold for Indian climates before applying them.

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