Forum: Evaluate effect of heat-reflective paint, so it doesn’t cause issues

It is true that cool paint coatings reduce the heat absorbed by buildings, thereby lowering electricity consumption by reducing the use of air-conditioners (

Heat-reflective paint initiative to be rolled out to all HDB estates by 2030

, Feb 3).

However, the sun’s energy does not disappear. Cool paints increase several folds the amount of reflected solar radiation, which ends up trapped in the urban atmosphere, with environmental effects that need to be properly assessed before extending the use of such paints to the entire city.

Depending on the architecture and layout of the buildings, the amount of reflected energy can create greater discomfort for those walking in the streets, especially during sunny days.

More reflected radiation will also boost chemical reactions in the air and lead to more harmful pollutants such as ozone and airborne particles being produced.

Trees will also be affected by this increase in reflected solar radiation. To prevent excessive water loss, leaves will close their stomata, stop photosynthesis and release reactive chemicals that contribute to the formation of the pollutants mentioned.

The massive application of cool paint will alter the vertical structure of the atmosphere at night.

Buildings, streets and sidewalks take in and store a significant amount of solar energy during the day.

This energy is released as heat at night, producing thermal turbulence that helps ventilate air.

If this heat release is reduced, moisture and pollutants will concentrate near the surface and worsen the atmospheric environment, especially during dawn, when the city wakes up.

Furthermore, as cool paints wear off over time, the discharge of microplastics and other chemicals into soil and water increases.

Therefore, it is necessary to evaluate the application of heat-reflective paint comprehensively to mitigate urban warming. Otherwise, we may end up creating other environmental problems instead.

Erik Velasco