Stone wool secures ‘Langelands Plads’ against extreme rains

Frederiksberg, Denmark

Credit: Andy Hoang, Dines Joergensen
More frequent cloudbursts and floods are a growing threat. Copenhagen experienced this in September 2017, when sewage systems gave out, while basements and roads were under water. At Langelands Plads in Frederiksberg, near Copenhagen, a new solution called Rockflow from Lapinus, a part of Rockwool Group, is being used which can both collect and divert the excess water at a more controlled pace - thereby countering flooded cities.

The violent cloud bursts that has hit Danish cities in recent years are not a passing phenomenon. They are part of the new reality that cities, citizens and all aspects of the building and construction value chain must take into account. Unfortunately, the infrastructure in many Danish cities is not built to handle the rising waters, which results in flooded roads and cellars and insurance claims in the millions.

To counter this development, the project around Langelands Plads in Frederiksberg has chosen to use the material Rockflow from Lapinus, part of Rockwool Group, says Ole Larsen director of CALL Copenhagen, an organization which works for climate adaptation and green growth. The organization is a collaboration between the supply company HOFOR in cooperation with the City of Copenhagen, Region Hovedstaden and the waste water company BIOFOS.

Climate change is here now and will still be here tomorrow. The likelihood of bad cloudbursts within the next 50 years is great - and especially in big cities, the massive amounts of water can mean floods in houses and cellars. One can choose to do two things when it comes to climate change. You can sit with your hands in your lap and pay what it costs when the city is hit by extreme amounts of rain. Or you can choose to reduce the damage by using sustainable rainwater management. The latter is far cheaper for society, says Ole Larsen, who emphasizes:


Project location

Rockflow gives us better opportunities to build the sustainable city that is climate-ready.

Ole Larsen

A flexible product with high performance

Rockflow is similar in appearance to the well-known insulation material that Rockwool Group is known for, but the product's properties are significantly different. Rockflow has a void volume of 95 percent, which means that a block with a volume of 1 liter of Rockflow can absorb and retain 950 milliliters of water.

At the same time, the material is extremely flexible and suitable for renovation projects in the cities, where existing underground infrastructure, such as cables and piping, increases the need for a solution that can be adapted to all situations, says cloudburst and LAR expert (local drainage of rainwater) Andy Hoang from the consulting engineering firm Dines Jørgensen, who is involved in the project at Langelands Plads.

As a product, Rockflow is quite innovative and flexible compared to ordinary, closed cassettes to direct water away. Where cassettes are made in metal and fixed dimensions, Rockflow can be cut in all three dimensions without changing the strength. Although we plan construction from official records of cables and other installations, we often encounter another reality when the excavation work begins - there is a huge advantage to being able to adapt the material to existing installations, says Andy Hoang.

Void Volume

Rockflow is quite innovative and flexible and has a void volume of 95 percent.


One liter of Rockflow is capable of absorbing almost the same amount of water.

Absorptive Capacity

One liter of Rockflow can absorb and retain up to 950 milliliters of water.

Langelands Plads shows the way

According to Andy Hoang, there is a need for urban renewal projects as well as for new construction to think about water retention rather than just diversion. The reason being that the current network of sewers, especially in existing urban areas, is not able to handle the amounts of water generated by the most severe cloudbursts, which only become more frequent.

Before, we talked about 100-year incidents that statistically only occurred once per 100 years, but today it is not unrealistic to experience three of that kind of cloudburst in a year. The project at Langelands Plads has therefore been built to handle a 100-year incident, as we have made evaporative basins on the parking garage and two large delay pools under the roads. That way, we can slowly lead the water away and avoid flooding, says cloud-burst and LAR expert Andy Hoang.

Rockflow Copenhagen Video Thumbnail