For years, cities responded to heat with emergency measures: cooling centres, adjusted outdoor working hours, health advisories. This year, some have written cooling into long-term building rules.

The two most common measures concern roofs and ground. New-build standards in several places now require high-reflectance coatings on flat roofs, and pale, permeable paving for pavements and squares, to cut surface temperature and stored heat.

Canopy cover becomes a hard number

The second measure repeatedly emphasised is street tree canopy cover. Research shows continuous canopy shade can cut felt temperature on a pavement by several degrees — more effective than standalone shade structures.

A dense urban district, where the heat island effect is pronounced in the afternoon.
A dense urban district, where the heat island effect is pronounced in the afternoon.
  • Roofs: high-reflectance coatings now mandatory in new-build standards
  • Ground: pale, permeable paving preferred
  • Planting: canopy cover a hard planning target
  • Contested: how retrofit costs are split between owners and the city

The dispute is mainly about cost. Who pays to retrofit existing buildings varies by jurisdiction: some offer public subsidy, others require the work at the next major refurbishment.