Polygrow is a hydrophilic polyurethane foam, basically developed as a substrate (growing medium) for the professional horticultural sector and now adapted to urban greening. The material is available in six varieties. Unique is the PG D2 system which acts as a substrate, drainage and water buffer in one single layer, substituting current multi-layer green roof systems. It is easy and fast to install and saves with 50kg/m2 (saturated, including sedum) 50% of the weight compared to traditional build-ups. Buffering minimum 30 l/m2 water, also over a long period of time, the Polygrow D2 system is decreasing the need of irrigating as well as counteracting the peak loads. The PG SD 80 is the bonded foam version with a better stiffness and capillarity. This makes the foam suitable for using on pitched roofs with a maximum angle of 40 degrees.