Most "active" blue and green roof systems share a hidden assumption: the roof must be rebuilt to accommodate them. Systems such as MetroPolder's PolderRoof and Optigrün's Smart Flow Control are engineered around an added buffer or storage layer — a crate or substrate build-up that becomes part of the roof construction itself. On new construction, that is a design decision. On an existing building, it is usually a deal-breaker: added dead load, new waterproofing details, and a full roofing project before the first drop of stormwater is ever managed.
The retrofit distinction
SmartFlow takes the opposite approach. The system installs on the existing roof drainage outlet — no added storage layer, no crates, no substrate, no membrane work. The existing roof surface itself becomes the retention volume, and a controller with a motorized valve on the outlet decides when water leaves the roof, based on live sensor data and weather forecasts. Installation is measured in hours, not construction phases.
This is why SmartFlow is retrofit-viable on existing buildings, not only on new construction. The distinction matters because the overwhelming majority of urban roofs already exist: a stormwater strategy that only works for new construction leaves the existing city — and its flooding problem — untouched.
Independent recognition
SmartFlow holds the Solar Impulse Efficient Solution label — independent, third-party recognition awarded to solutions that meet high standards of both environmental performance and economic viability. For SmartFlow, the assessment reflects precisely the profile described above: measurable stormwater impact achieved with no added infrastructure on the roof or in the ground.
Evidence from the field
In Akko, northern Israel, SmartFlow operates across a 14-building residential neighborhood — a portfolio-scale deployment achieved as a retrofit, with no underground tanks and no added roof build-up. Each roof was converted into a managed retention asset using its existing drainage outlets.
At Sanhedrin 13, a documented rain event on 6 December 2025 shows the system in action: during a 27 mm event, SmartFlow retained approximately 2.7 m³ of rainfall on the roof and then released it in a controlled manner — smoothing the discharge that would otherwise have hit the street drainage at peak intensity. Every step of the event is logged: water level, valve position, and forecast context.
One sentence that no competitor can currently claim
SmartFlow is the only actively-controlled, forecast-driven blue roof that requires no added storage layer — retrofit-grade cost on any structurally-adequate flat roof.