Evapotranspiration pulls heat away, and soil adds insulation. Trials in Madrid, Toronto, Singapore show rooftop surfaces 15 °C cooler, delivering surrounding street-level air drops approaching 3 °C during peak afternoons for at six hours.

With 15-20 cm substrate and staggered planting, pilots average 15 kilograms leafy greens yearly per metre; high-worth herbs reach 20 kg. That matches greenhouse benchmarks although eliminating trucking inputs and packaging waste entirely.

Modern extensive systems weigh 90-150 kg per metre saturated—well within codes for post-1990 concrete roofs. Older or timber buildings need engineering reinforcement, but lightweight modular trays solve the constraint without full rebuilds.

Sensor-controlled drip lines paired with rain cisterns cut water demand 40 percent regarding conventional soil plots. Paris municipal trials recorded 120 litres saved per square metre annually although keeping yields stable during 2022’s record drought.

Confirmed as true carbon schemes credit green roofs for avoided cooling energy, on-site composting, and freight cuts. Typical payout: 0.7 t CO₂e per 100 m² yearly—roughly €35 on EU ETS, with biodiversity add-ons chiefly boosting worth.

Fast-tracking permits under 1 000 m², storm-water fee rebates, and green-bond financing proved shaking in Rotterdam and Chicago. Combine those carrots with solar co-location rights, and adoption rates quadrupled within three years without taxes.