First Dutch Detention Roof for Soft drinks supplier Vrumona
Posted on Monday 07 February, 2022In October 2021 the first Detention Roof in the Netherlands was installed on the Vrumona business premises in Bunnik. The blue-green roof was the result of a collaboration within Green Business Club Bunnik. On 8 November, the 588 m² green roof was officially opened by local councillor Jocko Rensen. This innovative green roof concept drastically reduces the risk of flooding from extreme rainfall on the site.
Innovative blue-green roof concept against flooding
The Detention Roof is a green roof system on which rainwater is temporarily collected before it slowly drains away. With a normal roof, without greening, the precipitation immediately enters the sewer system via the downpipe. During heavy rainfall this can cause flooding of the sewage system, resulting in flooded streets. A Detention Roof can store rainwater even in a fully saturated state and drain it away in a controlled manner. As a result, the green roof system fulfils the rainwater ordinance and/or other, growing requirements of the local municipalities and water boards.
Vrumona's new Detention Roof was officially opened on 8 November with (from left to right) Jocko Rensen (Councillor Bunnik), Evelien Sanders - de Boer (General Director Vrumona) and Stephan Beerends (Director Sempergreen).
Healthy breeding ground
In the Dutch province of Utrecht, several green initiatives have emerged in recent years, in which companies can also participate. Sempergreen, a supplier of Detention Roofs, recently signed the Province of Utrecht's Climate Friendly Building Memorandum of Understanding, with the aim of making the Utrecht region more climate resilient. Both Vrumona and Sempergreen are participants in the Green Business Club (GBC) Bunnik. Thanks to this green initiative, the companies have come into contact with each other and managed to realise this ambitious project.
Evelien Sanders-De Boer, General Manager Vrumona: “This green roof is a wonderful example of local cooperation. It fits perfectly with the circular and sustainable mission we pursue within Vrumona. Water is an essential part of our product and we consider a good water supply at our site very important.”
Sjors Wessels from Sempergreen, GBC Bunnik participant: “We are very pleased with the extensive cooperation that has been established to realise this innovative project. It shows that local initiatives in sustainability can be a healthy breeding ground for projects that make the region more climate resilient. With the help of this initiative, Vrumona is taking a good first step in addressing the water issues around the business park.”
Preliminary exploration with the help of the water board
At the beginning of the process, the parties within GBC Bunnik's Climate Adaptation Project Group, together with De Stichtse Rijnlanden Water Board, identified issues that could lead to flooding in the area. The preliminary exploration showed that the site was mostly paved and would benefit from a Detention Roof. This green roof system provides delayed water runoff, relieving pressure on the sewage system during extreme rainfall events, solving much of the water problem in the area.
Installation within two days
Sempergreen worked with several parties on the installation. The application of a new bitumen layer was carried out by Van Doorn Roofing Specialist. The Dakdokters (roof doctors) then installed the Detention Roof. The green roof of 588m2, spread over two roof areas, was completed within two days.
The green roof was installed by 'De Dakdokters' October 2021.
Further advantages of a Detention Roof
The Detention Roof can be used on roofs with a pitch of up to 2⁰ and it is a lightweight system. These two advantages ensure that a Detention Roof can be placed on existing buildings as well as new-build projects, as the former are almost always slightly sloped and often cannot support much weight. The top layer of the Detention Roof consists of sedum. These strong plants withstand extreme temperatures and absorb CO2 and particulates. In addition, the green roof has a cooling effect on the environment, both inside and outside the building. The plants also help to improve local biodiversity. Finally, the roof is the most efficient place for water storage, leaving the rest of the plot available for other uses.
The new roof, directly after installation
The system structure of a Detention Roof
The unique feature of a Detention Roof is its structure. The system structure consists of four layers:
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Sempergreen® Sedum-mix blanket: the top layer consists of vegetation blankets, pre-vegetated with 6-8 different sedum species.
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Knauf Urbanscape® Green Roll: this water-absorbing intermediate layer absorbs water evenly across the entire roof and also serves as a growth medium for the vegetation blanket above.
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Sempergreen storage layer HC40/60: this intermediate layer with a honeycomb structure serves as a temporary water column during extreme precipitation. In cooperation with the underlying T5 detention layer, rainwater can be temporarily stored here.
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Sempergreen detention layer T5: this bottom layer is the slowing factor in the whole construction. The layer consists of thousands of threads that are machine stitched next to each other. These seams, in combination with the hydrophobic underside, ensure that the water is pushed upwards by means of negative pressure in the storage layer. This layer can delay the excess rainwater for up to 24 hours or even longer. The length of the delay depends on the exact project specifications.
For more information on the Detention Roof, visit detentionroof.com.
Peach stones
In addition, a durable edge finishing from Nocciolo was used for this Detention Roof, consisting of peach stones (also called peach pits or seed), which are extracted from residual streams. Peach stones do not rot, are resistant to algae growth and do not absorb moisture, which means that they do not mould. They also have a lifespan of more than 30 years, making them an extremely sustainable solution for the project.
More information about the Detention Roof
Are you interested in a Detention Roof for your company headquarters or office building? Our experts will be happy to advise you. Of course you can also request a free quote.