PolderRoof - smart green roof for water management and climate resilience

Wavin PolderRoof is a smart blue-green roof system that transforms flat roofs into controlled water reservoirs. It addresses the growing challenge of urban water stress - a condition now affecting 25% of large cities - by embedding a circular water economy directly into the built environment.

• Water Retention & Attenuation Proactive water level adjustment and increased storage capacity deliver retention rates of 70–97%, reducing runoff volumes and easing pressure on drainage infrastructure.

• Self-Watering Irrigation Passive capillary action draws stored water from the reservoir to the substrate, providing continuous self-watering irrigation.

• Evapotranspiration The system achieves up to 70% evapotranspiration, with evaporation rates reaching 4 mm/day.

• Thermal Performance PolderRoof maintains significantly more stable roof surface temperatures compared to a conventional black roof. Differences include up to -15°C during hot periods and +5°C during cold periods.

• Solar Panel Efficiency The cooler roof surface created by the system improves the performance of co-located solar PV installations.

• Flood Risk Reduction By attenuating stormwater and releasing it slowly, PolderRoof reduces peak flows to drainage network and lowers flood risk.

• Drinking Water Conservation Captured rainwater supplies roof vegetation directly, reducing reliance on mains water for irrigation.

• Biodiversity Enhancement Rooftop green space creates habitats for wildlife and supports urban ecological networks.

• Living & Recreational Space Roof areas can be reimagined as accessible green spaces. =

• Drought Resilience During prolonged dry periods, the storage layer can be actively replenished from an alternative sustainable water source to maintain vegetation, biodiversity and cooling benefits.

Applications

Suited to urban buildings with flat roofs, new build or retrofit:

• Sustainable stormwater management and drainage attenuation

• Green roof installation with enhanced water performance

• Building cooling and energy efficiency improvement

• Biodiversity net gain compliance

• Circular water economy integration

• Rooftop amenity or habitat creation

System Composition

The PolderRoof is a fully integrated, multi-layer assembly:

When rainfall occurs, water infiltrates the substrate, collects within the AquaCell 85/160 system, and is drawn back up to the vegetation layer via capillary action - keeping the roof irrigated through dry periods without active watering.

Performance Data