HydroSpacer revolutionises Sponge City Roofs

Green Roof Innovation with Capillary Action

or over ten years now, ZinCo has been a pioneer of high-performance systems for the retention and evaporation of stormwater on roofs. Their latest innovation, the HydroSpacer, adds yet another dimension to the market. This allows ZinCo to come closer to its goal of bringing the water balance of a developed area closer to that of an undeveloped area. Following a rainfall event, the HydroSpacer in the System Build-up “Sponge City Roof” can store up to 160 l of water per m² of roof area and can provide up to 11 l of water per m² daily to the plants – and this is done all by itself, thanks to the physical effect of capillarity. 

In order to avoid rainwater being drained off too quickly in the future into the sewage systems in towns and cities, the set of rules of the German Association for Water, Wastewater and Waste (DWA) (Leaflet M 102-4) provides for measures that will bring the water balance of developed areas closer to that of undeveloped areas.  This means specifically an evaporation proportion of more than 50 per cent of the annual precipitation. Therefore, it goes without saying that roof surfaces should be equipped in such a manner that they contribute to achieving this goal. ZinCo is now even more successful in this respect thanks to the innovative HydroSpacer in the System Build-up “Sponge City Roof”.  The basic idea is to have as much storage space as possible beneath the substrate and plant level. On the one hand this is to efficiently absorb heavy rainfall events and on the other hand to store water so that it is available to the plants. The accumulated water will supply the plants during dry periods, and in so doing will maintain their evaporation capacity over a long period of time. The vegetation will develop more dynamically and overall with greater biodiversity, depending on the natural distribution of precipitation.

Accumulated water available to the plants

Water accumulation in the ZinCo build-up “Sponge City Roof” is contingent on a flat and professionally installed waterproof roof. Each of the 60 x 60 cm and 17 cm high elements of the “HydroSpacer HS 170” made of polypropylene has a cavity proportion of approximately 95%, which means that it can absorb up to 160 l of water per m². At the same time, the structure is so robust that it can take loads of up to 50 t per m², and is therefore suitable for walkway and driving surfaces. The longer-term water accumulation of about 8 cm that is available to the plants is located in the lower part of the spacer. It is created using dam-up plates that are placed beneath the retention run-off limiter. Where additional water accumulates during rainfall – up to a maximum of 8.5 cm is possible – this water will flow gradually through the retention run-off limiter into the roof drain or ideally into downstream tanks.

Operating principle with capillary action

The highlight of the “HydroSpacer HS 170” is its covering of a highly absorbent fleece. When the spacer is installed, the fleece is fitted on all four sides down to the lower edge. Once water begins to accumulate in the spacers, the fleece absorbs it at the contact surfaces and draws it upwards in a capillary action. Depending on the accumulation depth, up to 11 l of water per m² can be absorbed by the fleece and subsequently distributed to the overlying substrate layer. The plant roots in that area will take up just as much water as they need at any given time – it is specifically this function that comes closest to natural conditions.The “HydroSpacer HS 170” including high capillary performance fleece covering, in this form, is a true innovation and is registered for patent.

Therefore, “Sponge City Roof” is the way to fully exploit water management on and with roofs.