🌆 World Cities Day: Cool, Resilient, Sustainable

Melanie Galpin
Oct 27
2 min read

Every year on October 31, the United Nations celebrates World Cities Day, a moment to reflect on the challenges and opportunities of urbanization. With more than 55% of the world’s population now living in cities — a number expected to reach 68% by 2050 — the future of humanity will be decided in urban environments.

But today’s cities face unprecedented pressures:

Rising heatwaves — urban heat islands make cities hotter and more dangerous.
Water stress and flooding — rainwater is either wasted or overwhelms drainage systems.
Plastic pollution — construction and consumption add to a global waste crisis.

This year’s World Cities Day calls for sustainable, resilient, and inclusive urban solutions. At WaterRoofs, we believe the answer may be right above us: the rooftop.

🌡️ Rooftops as the Frontline of Urban Cooling

Rooftops cover up to 40% of urban surfaces. Conventional roofs absorb solar heat, often reaching 70–80°C in summer, which radiates back into the city, intensifying heatwaves.

WaterRoofs turns these heat traps into cooling engines:

Evaporates stored rainwater, reducing rooftop surface temperatures by up to 15°C.
Lowers surrounding air temperatures by 1–5°C, improving urban comfort.
Reduces reliance on air conditioning, cutting emissions and energy bills.

Instead of heating cities, rooftops can help cool them down.

💧 Restoring the Water Cycle in Cities

Urban design has long treated rainwater as a problem to be removed quickly. But by draining water into sewers, cities disrupt the natural hydrological cycle — leaving air drier, rainfall less stable, and floods more frequent.

WaterRoofs restores this missing link:

Micro-channel PET tiles retain rainfall and release it gradually through evaporation.
Each square meter can return up to 750 liters of water annually to the atmosphere.
This rebalances humidity, supports local rainfall, and reduces urban drought risk.

Every rooftop becomes part of the natural water cycle again.

♻️ Cutting Plastic Waste with Circular Materials

The construction sector generates over one-third of global waste, much of it plastic. WaterRoofs tackles this head-on:

Tiles are made from 100% recycled PET, one of the most common plastic wastes worldwide.
PET can be regenerated up to 40 times without losing quality.
Every roof installation reduces the need for virgin materials and prevents plastic from entering oceans and landfills.

Instead of adding to the waste problem, WaterRoofs turns plastic into climate-positive infrastructure.

🌍 Building Cities Aligned with Global Goals

WaterRoofs contributes directly to the UN Sustainable Development Goals (SDGs) that shape World Cities Day:

SDG 6 – Clean Water & Sanitation: Restores evaporation and balances the water cycle.
SDG 11 – Sustainable Cities: Improves urban resilience to heat and floods.
SDG 12 – Responsible Consumption: Uses circular, recycled PET materials.
SDG 13 – Climate Action: Reduces emissions and strengthens adaptation strategies.