Detention Layer
REVOLUTION GREEN ROOF: THE PURPLE ROOF SYSTEM AS A PIONEER IN HEAVY RAIN & FLOOD MANAGEMENT
"Fighting Floods the Purple Way": A motto that Browatech takes seriously with its textile drainage system. Our core technology integrates into the roof installation of the globally recognized Purple Roof System and revolutionizes the functionality of conventional green roofs through its detention effect.
THE TRADITIONAL GREEN ROOF
Conventional green roofs absorb rainwater, thus reducing runoff only when the roof is largely dry. Once the green roof is saturated, every additional drop flows off directly.
A traditional green roof can reduce the volume of rain reaching the street by 30–65% through evapotranspiration, depending on the geographical location. This amount of water evaporates through retention. The remaining 35–70% literally falls through, especially during heavy rain, severe weather, and persistent rainfall, and can lead to devastating flooding. Therefore, a traditional green roof is not a sustainable water management solution for protecting against flooding events and preventing costly damage during heavy rain or days of rainfall. Detention in the Purple Roof structure, on the other hand, ensures that flood damage or sewer overflows can be prevented by temporarily retaining rainwater and releasing it at a reliably calculated rate. Retention reduces and delays the storm peak. This means that the intensity of the water flowing onto the ground or entering the sewer system is reduced, allowing for better infiltration into the soil, significantly reducing the load on sewer systems, and having a positive impact on the groundwater level.
Both retention and detention are important processes, but serve different purposes.
Further information on understanding the terms can be found here:
GAME CHANGER:
PURPLE ROOF SYSTEM
DETENTION ROOF OF THE PRESENT AND FUTURE
Purple-Roof was developed by green roof experts as the "next generation of green roofs." It supports the sponge city principle, in which rainwater and surface water are retained and intelligently managed on-site instead of being channeled and diverted. Integration into the sponge concept enables Browatech to pursue various collaborations.
Since August 2023, the Digital Sponge School Schauenstein has been built not far from our location, with Germany's first Purple Roof ( TV report ).
The Schauenstein project is led by the Institute for Sustainable Water Systems at Hof University of Applied Sciences – INWA.
We also work closely with Green Roof Diagnostics , a US research and testing laboratory for green roofs. This manufacturer-independent and therefore neutral facility has tested the effectiveness of our detention layer over 3,000 times – including under extreme weather conditions. The world's largest research center with the most comprehensive green roof data confirms its exceptional effectiveness and unique selling point.
Our textile drainage system, integrated as a key component into the roof structure, ensures rainwater retention and a controlled "drainage" of rainwater, preventing sealed surfaces from being flooded by excessive amounts of water. Its true potential is revealed during heavy rainfall events or periods lasting several days.
The Purple Roof offers the advantages of a traditional green roof – excellent retention, reduction of heat islands, improved air quality, and increased biodiversity – while also acting as a highly efficient tool for precipitation control and extending the lifespan of the roof membrane due to its capillary action.
The Purple Roof works on flat-pitched roofs and offers a simple solution for new or existing roofs. Use the freely accessible retention calculator for your roof project or contact us for access to the personalized retention modeler.