The layers of a Detention Roof.

The Detention Roof is built up of four layers. Each layer has its own unique effect in the total structure. Read more about the added value per layer below the image

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Sempergreen® Sedum-mix blanket (EVAPOTRANSPIRATION)

The Sempergreen® Sedum-mix blanket has the ability to store water in the leaves of its Sedum plants. The instant green Sedum blanket also detains water laterally within the dense foliage, which mimics nature. During rainstorms the water is ‘trapped’ in the leaves and has time to percolate into the soil. By means of evapotranspiration the surplus water is released into the air. Sedum has a great adaptability to survive under various (extreme) weather conditions, both hot and cold, wet and dry. The ten to twelve different types of Sedum plants grow on a coconut fiber carrier in a substrate specially developed by Sempergreen.

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Urbanscape® Green Roll (SPONGE)

Urbanscape® Green Roll is a water-absorbing intermediate layer that also serves as a growth medium for overlying Sempergreen® vegetation blanket. Due to its large water-absorbing properties, the Urbanscape® Green Roll functions just like an ultra-sponge. Thanks to the unique capillary effect, the collected rainwater first spreads sideways over the layer, before releasing a drop of water to the underlying layer. This is unlike soil-based systems, that have preferential outflow through funnel-shaped escape routes in the soil, causing the water to escape too easily from the roof. Thanks to the Urbanscape® Green Roll the degree of water retention and evapotranspiration is increased. The Urbanscape® Mineral Wool is specially designed to easily reabsorb water, even after dehydration, up to 8 times its own weight. Another purpose of Urbanscape® Green Roll is the ability to filter out any fine soil particles.

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Storage layer HC40 (STORE)

The Storage Layer HC40 serves as a temporary water column in case of heavy rainfall. This layer consists of small diameter, solid-wall tubes, vertically oriented which are fused as a panel. This honeycomb structure consists almost entirely of macropore space (> 90% void space). The horizontal water flow is negligible. This is especially crucial for pitched roofs with an incline of up to 5 degrees. In cooperation with the underlying Detention layer T5, the stormwater can be temporarily stored in this layer.

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Detention layer T5 (SLOW)

The patented Detention layer T5 is the bottom layer in the structure and is the retarding element in the whole. It is a three-dimensional layer, made entirely of sustainable recycled polyester, in which a machine-woven pattern of thousands of vertical threads are stitched together side by side. These stitching creates friction, so that the water column is pushed up to the overlying storage layer HC40. This layer can delay rainwater runoff by up to 24 hours.


Installation of a Detention roof

For the ultimate functioning of the Detention Roof it is important that the installation instructions for the Detention Roof are followed properly. The installation instruction for a Detention Roof is provided at a project specific level.

Water calculation for your project

Would you like to know how a Detention Roof can contribute to your project? Request a water calculation.

Request here
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