ROCKWOOL Group launches Rockflow rainwater management system for urban areas

October 9, 2019

Designed to help urban areas protect people and valuable infrastructure from urban flooding caused by extreme rain events.

Rockflow installation at Langeland Plads in Frederiksberg, Denmark.

Damaging floods caused by extreme rain events are happening with greater frequency around the world.1

For urban areas with lots of asphalt, inadequate sewer systems and limited unbuilt spaces to absorb the water, this means a rising risk of urban flooding. To help communities protect residents, valuable infrastructure and businesses from the impacts of extreme rains, ROCKWOOL Group is proud to launch Rockflow from Lapinus.

“Rockflow gives urban areas a new and cost efficient tool to manage the increasing risk of floods due to sudden heavy rainfall. It helps channel the excess water to the underground Rockflow buffer and thus away from sewer systems so communities can keep their businesses, public squares, parks, playgrounds and homes dry,” says Thomas Kähler, Senior VP, Head of Systems Division at ROCKWOOL Group.

Rockflow video thumbnail

Creating urban rain resilience

Here’s how it works: A buffer of specially engineered stone wool is installed underground with connections to a system of pipes, drains and gullies. As it rains, the water is quickly absorbed and then gradually discharged over the following 24-hours into the surrounding soil or sewer system. The stone wool in the Rockflow system can absorb 95 percent of its volume in water.

Note: Stone wool made for insulation purposes does the opposite, it repels water.

Some other key characteristics of Rockflow are:
  • Strength. Designed to be installed under roads and surfaces that may have heavy human or machine traffic; Rockflow is strong like stone even when it is full of water.
  • Flexibility. Easily cut-to-fit, Rockflow is ideal for city renovation projects where existing underground infrastructure like cables and piping require adaptability.

Is your city prepared?

“Before, we talked about once-in-a-hundred-years rain events, but those can happen three times a year now,” says Ole Larsen, Director of CALL Copenhagen, an organization advising the city of Copenhagen and others in Denmark on climate adaptation and green growth.

Larsen advised ROCKWOOL and the city of Frederiksberg, which borders Copenhagen, on a recent installation of Rockflow underneath Langeland Plads, a newly renovated public square. It is an example of many measures city leaders are taking to make Copenhagen and its environs more resilient to extreme rain events like the one that happened on July 2, 2011 when 100mm of rain fell on the city in two hours, flooding 80,000 homes and causing damages of more than EUR 1 billion.  

“The cities of Frederiksberg and Copenhagen already know the risks and what’s at stake. For all cities, it’s far better—and far cheaper— if we take the needed steps now to make them resilient to these more frequent and heavy rains.”

Rockflow is currently available in Denmark and the Netherlands. Over 10,000 m3 are installed in 40+ locations under roads, schools, playgrounds, parks, public squares and more. In the coming years, ROCKWOOL plans to introduce Rockflow to other key markets affected by extreme rainfall. 


  • Stone wool is made from volcanic basalt rock and is fully recyclable
  • A Rockflow stone wool buffer can absorb up to 95 percent of its volume in water—950 litres per m3—within 10 minutes, making it ideal for managing extreme rain events.
    • Stone wool made for insulation purposes does the opposite, it repels water. 
  • Rockflow is strong like stone even when full of water
  • Because it of its strength, Rockflow requires only 35 cm of coverage under the road surface.



1.EPA, “Climate Change Indicators: Heavy Precipitation” Global Institute for Water Security at the University of Saskatchewan