RETENTION ARRANGEMENT

Description

[0001] The invention relates to a retention arrangement for the retention of rainwater, particularly during heavy rainfall events in urban, densely populated building areas.

[0002] The technical field of application of the invention lies in building technology, specifically in the area of ​​the facade surfaces of buildings, whereby the term "building" is to be interpreted broadly in the sense of the invention and includes, in particular, residential or commercial buildings, industrial halls, noise barriers, bridges or the like.

[0003] Measures to retain rainwater and protect against flooding are increasingly coming into focus for architecture, urban planning and construction, as extreme events - such as heavy rain and flooding - are occurring more frequently as a result of climate change.

[0004] Cities are of particular importance in this context. Due to increasing urbanization, they are characterized by high building density and a high degree of soil sealing. This high degree of sealing, the low infiltration potential, and the increasing soil compaction exacerbate the consequences of heavy rainfall events.

[0005] Various state-of-the-art measures exist for rainwater retention. These include the unsealing of surfaces, above-ground or underground infiltration measures, above-ground retention (in open water bodies, ditches, retention basins, on roofs, etc.), underground retention (in cisterns, infiltration trenches, etc.), and temporary retention on traffic areas, green spaces, and through green roofs and tree planting. Direct building protection measures, such as sewer backflow prevention or waterproofing, are also employed. These measures achieve different effects. Firstly, water ingress is prevented. Secondly, water infiltration is facilitated, water is released in a delayed manner, or water is redirected.

[0006] Green roofs and retention roofs are increasingly used in urban areas, with the latter primarily designed for rainwater retention. The substrate depth and the design of the drainage layer are key factors in achieving water retention. This allows the water to be diverted over long distances, thus delaying runoff. Many existing buildings are unsuitable for retention roofs due to structural requirements, as the overall weight increases with the water storage capacity. As a rough approximation, the total weight of extensive green roofs is approximately 50 to 70 kg / m², while intensively vegetated roof gardens can exceed 1,000 kg / m².During heavy rainfall events, green roofs are a component of an optimized urban rainwater management system in terms of their retention capacity, but they can reach their limits because the percentage of rainwater retention decreases with increasing rainfall intensity and the additional rainfall is subsequently passed on directly and without delay.

[0007] Innovative drainage concepts are being developed worldwide in the field of urban planning and development. These concepts focus on the infiltration and drainage of rainwater. Playgrounds, sports fields, and other public spaces are designed as staggered surfaces. By lowering the ground level and adjusting the gradient, these areas function as temporary water basins.

[0008] Such measures usually require complex and costly construction work. Large areas need to be redesigned, and roads must be included. The scope of action is generally limited to public spaces; private land can hardly be integrated into the plans.

[0009] Measures for rainwater retention on facade surfaces can also be found in vertical greening concepts, as plants and substrates absorb rainwater and / or use it for irrigation. However, in these vertically installed gardens, rainwater retention is only a secondary and minor component. Furthermore, large-scale facade gardens are rare due to the high installation and maintenance costs and, because of their considerable weight, are unsuitable for rainwater retention. Such vertical gardens are usually only installed as individual projects, either as art or advertising objects.

[0010] Document EP 2 904 895 B1 discloses a system for vertical greening, constructed from building elements designed as clinker bricks or masonry blocks, each element having a front surface with a receptacle for planting substrate and the building elements being made of a water-absorbing and water-permeable material. This material can be calcium silicate brick, clay brick, aerated concrete, expanded clay, pumice, or lava.

[0011] The object of the present invention is to provide a retention arrangement that, in a structurally simple manner and at low cost, can contribute to mitigating the consequences of heavy rainfall events by absorbing and storing water. Preferably, the retention arrangement should offer the potential for economical mass production and be applicable in various construction applications. The retention structure should be particularly suitable for the industrial implementation of utilizing the facades of buildings and other structures for rainwater retention. Water absorption and storage should preferably be achievable without additional equipment, surrounding seals, or enclosures. Furthermore, in addition to water absorption and storage, the retention arrangement should optionally also be designed and usable for water extraction and / or drainage.The use of the retention arrangement according to the invention should preferably have a positive influence on the microclimate of buildings, in particular making it possible to humidify and cool the buildings in a simple manner.

[0012] The aforementioned problems are solved according to the invention by a retention arrangement having the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0013] The retention arrangement according to the invention comprises a porous and absorbent and / or swellable water storage material, wherein the retention arrangement forms a retention facade and / or a retention wall of a structure, such as a residential or commercial building, an industrial hall or noise barrier or bridge or the like, or is designed as a freestanding, essentially vertical retention structure, for example in the form of a (sculptural) water tower, in particular with a surface area to volume ratio of less than 5.0, preferably less than 2.5.

[0014] According to the invention, the retention arrangement is connected to a building structure for draining rainwater from at least one roof and / or facade surface of the building structure to the retention arrangement and for at least temporary storage of the drained rainwater in the retention arrangement. The retention arrangement can form a retention facade of the building, from whose roof and / or facade surface rainwater is directed to the retention arrangement. However, it is also possible for the retention arrangement to receive rainwater from other adjacent structures, such as residential or commercial buildings, industrial halls, noise barriers, bridges, or the like, via a suitable pipe system. For this purpose, the retention arrangement is fluidically connected to the building structure, in particular via appropriate water-carrying inlets and / or outlets.

[0015] According to the invention, the retention arrangement is designed and configured for the inflow of rainwater. The term "designed and configured" refers in particular to a directed and / or forced inflow, preferably a controlled and / or regulated inflow, of rainwater. A control and / or regulation device may be provided for the controlled and / or regulated automatic adjustment of the amount of water supplied to the retention arrangement during heavy rainfall events. The retention arrangement according to the invention is thus to be distinguished from vertical arrangements with water-storing material, such as green walls, in which rainwater may be accidentally stored in the arrangement, but these arrangements primarily serve other purposes, such as green roofs and walls.For the supply of rainwater, the retention arrangement according to the invention has at least one technical device which is designed for the directed and / or forced and / or controlled and / or regulated supply of rainwater to and / or into the retention arrangement.

[0016] A key aspect of the invention is that the retention arrangement is designed and configured to absorb and store a specific minimum amount of water. Since the invention relates to the retention of rainwater during heavy rainfall events, the retention arrangement must be able to absorb a sufficiently large amount of water, specifically in relation to a certain duration of the heavy rainfall event and a certain surface area of ​​the building structure, from whose roof and / or facade surfaces water is to be channeled to and absorbed by the retention arrangement during a rain event. In order to capture heavy rainfall events, or rather...To mitigate the effects of rainfall, the invention proposes a retention arrangement for absorbing and storing a minimum amount of water, based on the floor area of ​​the building arrangement and a rainfall duration, of 10 l / (m²<h) to 50 l / (m²<h), preferably 15 l / (m²<h) to 40 l / (m²<h), with a floor area of ​​the building arrangement of at least 50 m², in particular at least 100 m², and particularly preferably at least 200 m², and with a rainfall duration of at least 0.25 h, more preferably at least 0.5 h, and particularly preferably 0.75 h. If the minimum amount of water to be absorbed is, for example, 10 l / (m²<h), this results in an absolute amount of water of 125 l, based on a floor area of ​​the building arrangement of 50 m² and a rainfall duration of 0.25 h.In the last described example, the retention arrangement must therefore be designed and configured to store at least 125 liters of rainwater for a building with a footprint of 50 m² when rainfall amounts to 10 l / (m² < h). For a larger footprint of the building, a correspondingly larger storage volume of the retention arrangement is required. The minimum water quantity specified according to the invention is thus always based on a minimum footprint of the building and a minimum duration of rainfall to ensure that the objective of mitigating the effects of heavy rainfall events through water absorption and storage in the retention arrangement according to the invention can be achieved.

[0017] The "floor area" of the building arrangement is understood to be the built-up area of ​​the ground on which the building arrangement stands, as seen from above, including roof overhangs, canopies, or the like. According to the invention, the floor area is bounded by the contour line of the building in a top view.

[0018] For a building with a floor area of, for example, 120 m², the minimum storage volume of the retention arrangement according to the invention can be, for example, between 300 l and 3000 l, preferably between 450 l and 2400 l. However, the minimum storage volume can also be larger.

[0019] The retention arrangement according to the invention is particularly preferred for water absorption and storage of several times the minimum storage quantity.

[0020] The invention further provides that the retention arrangement is designed and configured for water absorption of 0.1 to at least 2.0 kg water / (kg WSM,tr. min), preferably from 0.25 to at least 1.5 kg water / (kg WSM,tr. min), particularly preferably from 0.5 to at least 1.0 kg water / (kg WSM,tr. min), with: kg water = mass of water absorbed by the water storage material in [kg] and with kg WSM,tr. = mass of the dry water storage material (drying at 105 °C for 24h) .

[0021] In this context, the mass of the dry water storage material refers to the mass after drying the water storage material at 105 °C for 24 hours.

[0022] The determination of water absorption kinetics (FSC value, "Free Swelling Capacity") can be carried out using the method of determining water absorption by free swelling in excess liquid. This method may involve pretreating the water-retaining material by drying it at 105 °C for 24 hours. A defined dry quantity of the water-retaining material, for example, 10 g, is placed in a heat-sealable tea bag. The sample is immersed in water at 20 °C and removed after defined times (1, 2, 5, 10, 30, and 60 minutes), and the sample weight is determined each time. The water absorption is expressed as the relative mass increase corrected for the weight of the moist tea bag, where the relative mass increase in [%] corresponds to the ratio of the mass of the water-retaining material after water absorption to the mass of the dry water-retaining material, expressed as a percentage.A relative mass increase of 100% corresponds to a doubling of the dry mass of the water storage material. To determine the absorption kinetics, absorption is assumed to be linear in the range of 0 to 5 minutes.

[0023] The kinetics of water absorption determine the retention arrangement's ability to absorb and store a sufficiently large quantity of water within a specific timeframe. The retention arrangement according to the invention is designed and configured to rapidly absorb large quantities of water, thereby at least mitigating the effects of heavy rainfall events. This distinguishes the retention arrangement according to the invention from building walls and facades known from the prior art, which, for example, consist of calcium silicate bricks and thus do possess a certain water storage capacity. However, these known building walls and facades are not designed and configured to absorb large quantities of water in a short period of time. Consequently, during heavy rainfall events, the water runs off such building walls and facades without mitigating the impact of the heavy rainfall.

[0024] Particularly preferably, the retention arrangement according to the invention can be set up and designed to receive and store a quantity of water of at least 2 l / m 2< , preferably at least 3 l / m 2< , further preferably at least 4 l / m 2< , based on a roof and / or building surface of the building.

[0025] With reference to the outer surface or outer skin of the retention arrangement, the water storage capacity of the retention arrangement can be at least 8 l / m 2< , preferably at least 10 l / m 2< , particularly preferably at least 12 l / m 2< .

[0026] According to the invention, at least one inlet and / or outlet opening, cavern, or water-conducting structure for the introduction, conveyance, distribution, and / or discharge of rainwater can be provided on and / or in the retention arrangement, particularly in a roof-level and / or ground-level area of ​​the retention structure. This allows the retention arrangement according to the invention to be used not only for water storage and retention but also for the production of process water, and is then preferably connected or connectable to a mains water network and / or a collection tank.

[0027] The invention proposes, for the first time, retention facades and / or retention walls, or even freestanding, for example sculpturally designed, spatial structures, as vertical water storage units for rainwater during heavy rainfall events, particularly in urban areas. The retention arrangement according to the invention makes it possible to achieve water retention on or adjacent to building facades for the absorption and storage of rainwater, with lower installation and maintenance costs compared to vertical water retention concepts such as green roofs.

[0028] The improvements and advantages over the prior art offered by the invention relate in particular to the development of previously unused areas for rainwater retention in order to reduce the consequences of heavy rainfall events, such as flooding, overloading of the sewer system, or the like. Furthermore, the solution according to the invention can contribute to resolving inner-city competition for space between housing construction and climate adaptation measures. Economical industrial production of the retention system is fundamentally possible. The retention system can be used in new construction projects and for modifications to existing buildings. With suitable design, good structural properties can be achieved, allowing for modular construction of the retention system, for example, in the form of curtain walls, or as independent wall structures or freestanding elements or retention sculptures.The use of suitable materials allows for a beneficial influence on the urban microclimate and simultaneously opens up the possibility of extensive greening. At the same time, the retention structure can meet structural engineering and building code requirements.

[0029] In particular, the retention structure enables water absorption and storage independently of water storage in tank-like containers within the retention wall, whereby the water absorption and storage capacity of the retention structure depends at least substantially or even entirely on the water storage material used and its proportion of the total volume of the retention structure. However, water storage in tank-like containers in addition to water absorption and storage in the water storage material of the retention structure is not excluded.

[0030] Furthermore, the retention structure can be free of planting substrates and otherwise unplanted. As explained above, the retention structure can also be used as an additional, secondary function, particularly as a vertical greening concept, in which case corresponding areas of the retention structure can be provided for the intake of plants and the supply of nutrients to the plants.

[0031] The invention particularly preferably provides for a direct or indirect connection of the retention arrangement according to the invention to a roof and / or building drainage system with corresponding collection and piping devices for rainwater, so that rainwater accumulating in the area of ​​the building roof and / or the building facade can be captured and directed to the retention arrangement.

[0032] Furthermore and / or alternatively, an indirect connection of the retention arrangement according to the invention to a storage tank can be provided, in which rainwater accumulating from roof and / or building surfaces is collected. The storage tank is then connected to the roof and / or building drainage system and can be located at any point, even at a distance from the building. Rainwater can then be supplied from the storage tank to the retention arrangement according to the invention, in particular via a pump or via wick structures with capillary action.

[0033] The retention arrangement according to the invention can also be connected to a collection container below normal ground level, for example, to underground tanks or a seepage pit, or to other rainwater retention and / or collection basins. Use of the retention arrangement for flood protection is also possible, whereby the retention arrangement can be designed and configured to draw water from the subsurface and / or store floodwater. Floodwater can be supplied to the retention arrangement, for example, via pumps and / or capillary-based wick structures.

[0034] Furthermore, the retention facility can be used for water storage in arid regions.

[0035] Furthermore, the retention arrangement according to the invention can be set up and designed for the supply of tap water from a tap water network.

[0036] A structure, such as a residential or commercial building, an industrial hall, a noise barrier, a bridge or the like, has at least one retention arrangement of the type according to the invention, either connected to the structure or freestanding, wherein, preferably, the retention arrangement is connected and / or connectable to a rainwater collection area of ​​the structure, in particular to a roof and / or building drainage system of the structure, and / or to a mains water network.

[0037] Furthermore, it is possible that the retention arrangement or structure is connected and / or connectable to an external water reservoir, i.e., a water reservoir separate from the structure.

[0038] Preferably, the retention arrangement is firmly connected to the structure and / or forms a particularly load-bearing part of the structure.

[0039] The retention arrangement according to the invention can be provided on at least one side of a building, preferably on at least two opposite sides of a building, particularly in the case of buildings arranged in a building complex, such as terraced houses, and further preferably on all sides of a building, particularly in the case of detached buildings, such as single-family houses.

[0040] In a preferred embodiment of the invention, at least a portion of a building facade is formed by the retention arrangement. The retention arrangement can be suspended in front of and / or positioned in front of a building facade. The retention arrangement can be connected to a building wall as a suspended facade, particularly in modular construction. Thus, the retention arrangement according to the invention, as a so-called "retention facade," can form at least a portion of the building's outer shell, in particular the predominant portion, and more specifically, the entire outer shell. A "facade" within the meaning of the invention is the visible shell (building envelope or outer skin) of the building, excluding roof surfaces and open areas, as well as window surfaces, door surfaces, supply lines, drainage lines, balconies, and the like.

[0041] For a retention facade according to the invention, a retention area factor can be introduced with ϕ = m Wasser F Total S ρ W SK with m Water: amount of water to be stored [kg] F Total: total (entire) facade area of ​​the building [m²< ] S : Strength / Thickness [m] of the retention facade ρ : Density [kg / m 3< ] of the dry water storage material of the retention facade W SK: Water storage capacity [wt. %,]

[0042] The retention area factor indicates how much of the total facade area can be designed as a retention facade to enable sufficient rainwater retention.

[0043] For different scenarios regarding rainfall, water storage capacity and the thickness of the retention facade, it can then be calculated what proportion of the available facade area must be designed as a retention facade in order to completely store the collected water.

[0044] Kinetics are not taken into account here. It is assumed that, given the known water absorption coefficient of the water storage material used and directed and / or forced supply, the resulting quantity can be stored in the facade.

[0045] Water absorption coefficients of known water storage materials are described, for example, in EP 2 904 895 B1. However, the solution according to the invention is not limited to the building materials and water absorption coefficients described in EP 2 904 895 B1.

[0046] In calculating various scenarios, it was found that, according to the invention, even facades only a few centimeters thick are suitable for absorbing sufficient quantities of water. This distinguishes it from vertical greening concepts, which require a significantly greater minimum thickness to accommodate planting substrates.

[0047] The thickness of the retention arrangement, particularly in the case of a retention arrangement designed as a retention facade or retention wall, is preferably less than 15 cm, preferably less than 10 cm, and most preferably between 2 cm and 5 cm. This ensures a sufficiently high water storage capacity.

[0048] For sufficient rainwater retention, it may already be sufficient if the area share of the retention facade in the total facade area of ​​a building is less than 15%, preferably between 2% and 10%, particularly preferably between 5% and 8%.

[0049] The retention arrangement according to the invention can be self-supporting and / or designed as a load-bearing, stiffening or non-load-bearing wall or as a retaining wall of a building.

[0050] The retention arrangement can be formed by or include one or more components that consist of and / or may contain the water storage material.

[0051] The retention arrangement can also include at least one monolithic, in particular cast, component and / or be formed by it.

[0052] The retention arrangement can be further formed by several modularly and preferably flush-mounted components connected to one another, whereby the components can be monolithic.

[0053] The retention arrangement according to the invention can particularly preferably be constructed as masonry, especially as a solid wall, made of pressure-resistant building elements such as shaped blocks, wherein, preferably, the building elements consist of and / or are made of and / or incorporate the water storage medium. The thickness of the shaped blocks and / or the masonry can be less than 15 cm, preferably less than 10 cm, and particularly preferably between 2 cm and 5 cm. This ensures a sufficiently high mechanical load-bearing capacity on the one hand and a sufficiently high water storage capacity on the other.

[0054] Preferably, building components made of absorbent and liquid-storing materials are used, preferably based on mineral materials such as calcium silicate bricks. However, materials such as bricks or aerated concrete are also possible, provided they are appropriately absorbent and liquid-storing and self-supporting. When mineral materials such as calcium silicate bricks are used, the series production of building components as basic modules can be achieved by selecting a suitable tool geometry, without modifying the established manufacturing process. The individual calcium silicate bricks can then be easily and systematically assembled into walls and large-area elements.

[0055] At least one component or element of the retention arrangement according to the invention can have recesses and / or perforations, wherein, preferably, perforations are designed as through-openings and extend over the entire height, width, or length of the component. The perforations can serve as water conduits within the retention arrangement and, in conjunction with the components / elements of the retention arrangement, form a conduit network, in particular a vascular system, for water transport.

[0056] The proportion of recesses, cavities, and perforations can range from 2.5% to 75% by volume, preferably from 12.5% ​​to 55% by volume. Recesses, cavities, and perforations can be perpendicular to the bearing surface and / or horizontal to the bearing surface. Recesses, cavities, and perforations can be round, square, pointed, and / or have other cross-sectional geometries. Furthermore, recesses, cavities, and perforations can be distributed symmetrically and / or differently on the surface of the component.

[0057] In an alternative embodiment, the retention structure according to the invention can also be designed as a freestanding retention structure. A preferably independent, freestanding retention body can optionally be arranged in front of a building wall and connected to it, or, in particular, arranged as a sculptural spatial structure further away from a building and form a freestanding structure that serves for water storage.

[0058] With regard to a building from which rainwater is collected and directed to the retention arrangement according to the invention, the retention arrangement can extend over at least one story height of the building, preferably from the ground upwards over several stories, and more preferably over all stories.

[0059] The water storage capacity of the retention system per floor of a building with an average floor height of 3 m can correspond to several times the amount of precipitation during heavy rainfall events, thus ensuring sufficient storage capacity even during heavy rain to prevent flooding and precipitation-related damage. For example, the water storage capacity of the retention system per floor of a building with an average floor height of 3 m can correspond to several times the amount of precipitation of 15 l / m² < h for a rainfall duration of 0.25 h to 0.5 h, in particular at least 1 to 4 times, and furthermore, in particular, 1 to at least 8 times.With a rainfall amount of 40 l / m² < h, the water storage capacity of the retention arrangement per floor of the building with a mean floor height of 3 m can correspond to 0.2 times to at least 4 times, preferably 0.4 times to at least 2 times, the rainfall amount with a rainfall duration of 0.25 h to 0.5 h.

[0060] Depending on the design and the water storage material used, the maximum water volume that can be stored in the retention arrangement according to the invention can be at least 25%, preferably at least 40%, and more preferably at least 50% of the total volume of the retention arrangement, and / or the maximum water volume that can be stored in the retention arrangement can be less than 90%, preferably less than 80%, and more preferably less than 75% of the total volume of the retention arrangement. Particularly preferably, the maximum water volume that can be stored in the retention arrangement according to the invention is between 55% and 65% of the total volume of the retention arrangement. This ensures high load-bearing capacity and mechanical stability of the retention arrangement.

[0061] The water storage material can have a pore structure for storing water and a maximum water storage capacity WSK between 1 wt.% and 200 wt.%, preferably up to 150 wt.%, further preferably in the range between 30 wt.% and 150 wt.%, and / or be swellable and then have a maximum water storage capacity between 1 wt.% and 20000 wt.%, preferably 30 wt.% to 5000 wt.%, wherein the water storage capacity is based on the ratio of the maximum mass of water that can be stored in the pore structure to the mass of the dry water storage material, in particular with a residual moisture content of the water storage material of less than 5 wt.%, preferably of 2 wt.% to 3 wt.%.

[0062] The water storage capacity can also refer to the mass of the dry water storage material, dried at 105 °C for 24 h, as a reference basis.

[0063] The dry mass-related water storage capacity W SK is calculated using the following equation: W SK = m Wasser m TR in % with m water: maximum amount of water that can be stored in equilibrium; m TR: dry mass of the water storage material (residual moisture 2 wt.% to 5 wt.% and / or dried at 105 °C for 24h).

[0064] Typical values ​​for water storage capacity can range from 2 wt.% to 30 wt.%, for example, when calcium silicate brick is used as the water storage material.

[0065] Preferably, the water storage material can be selected from the group of granules, in particular pumice granules and / or lava granules. The grain size of the granules can be between 0.5 and 5 mm, preferably up to 2 mm. The bulk density of the granules can be between 700 and 1400 kg / m³, depending on the grain size, and in particular between 850 and 1250 kg / m³.

[0066] Typical values ​​for water storage capacity can range from 30 wt.% to 150 wt.%, for example, when pumice or lava granules are used as water storage material.

[0067] When water is stored in a porous water storage material, the time until the maximum mass of water is stored in the pore structure can be less than 1 h, preferably less than 30 min, further preferably 15 min and / or more than 10 min.

[0068] Water can escape from the retention arrangement by gravity in the case of a porous water storage material, wherein at least 80 wt.%, preferably at least 90 wt.%, further preferably at least 95 wt.%, of the water stored in the retention arrangement is stored in the retention arrangement for a water retention period of at least 10 min, preferably at least 15 min, further preferably at least 20 min, particularly preferably at least one hour.

[0069] Water leakage from the retention arrangement can occur largely through evaporation in the case of a porous water storage material and / or when the switching temperature of a gel-like water storage material is exceeded, the switching temperature preferably being in the range between 20°C and 40°C.

[0070] The residual moisture content of the retention arrangement after a water leak can be less than 20 wt.%, preferably less than 15 wt.%.

[0071] The retention arrangement can consist of at least 50% by volume, preferably more than 75% by volume, and further preferably more than 90% by volume, of the water storage material. This means that the majority of the retention arrangement is available for water storage.

[0072] The static load-bearing capacity of the retention arrangement can be essentially determined by the mechanical properties of the water storage material. Water absorption and storage are possible, in particular, without components or devices that increase the static load-bearing capacity of the retention arrangement; specifically, no reinforcements made of steel or other materials are provided.

[0073] Water storage preferably takes place in a substantially uniform distribution within the retention arrangement according to the invention, in particular in uniformly distributed macroscopic cavities (openings) of the retention arrangement.

[0074] The retention arrangement can include at least one preferably self-supporting structural element, in particular designed as a bulk material cassette or lattice girder, for receiving a layer of water storage material. The structural element is particularly preferably equipped with openings for ventilation, in particular for allowing ambient air to flow through the material, and / or for water to pass into and / or out of the material. Liquid water can also drain or drip out through the openings when the water storage material is saturated.

[0075] Several structural elements can be combined to form a unit, particularly where the combined structural elements are designed and configured for water supply and / or transport beyond the boundaries of the structural elements within the unit. For example, pipes can be provided within the structural elements to enable water distribution within and / or between the individual structural elements.

[0076] The structural element can particularly preferably be designed as a bulk material cassette and provided for receiving a bulk of water storage material. The bulk material cassette can preferably be a flat component with preferably flat opposing boundary and / or retaining surfaces and a receiving area for the water storage material formed between them. At least one boundary and / or retaining surface, preferably several opposing boundary and / or retaining surfaces, can each have openings for flow and / or water passage.

[0077] A bulk material cassette can be formed by a preferably circumferential frame that laterally defines the receiving area. Openings may also be provided in the frame for ventilation and / or water passage. This particularly aids the dehumidification of the water-storage material through evaporation.

[0078] Boundary and / or holding surfaces can be formed by perforated plates or sheets or grid arrangements, which are held or attached in particular to a frame of the bulk material cassette.

[0079] Several cassettes can be connected to each other via frame constructions, for example by being screwed together.

[0080] Inside the cassettes, a conduit system can be provided that extends beyond the frame boundaries to allow water to be transported into and out of the cassettes or the water storage material contained within them.

[0081] The cassettes can be made of sheet metal or steel materials, or possibly also of plastic.

[0082] Alternatively, a grid element can be provided to receive a layer of water storage material, wherein the grid element can have at least two opposing grid areas, between which a receiving area for the water storage material is formed. The water storage material is then also in the form of a layer within a grid girder. The grid areas can allow the grid girder to deform in order to adapt to the geometry of a section of the structure, in particular through a low bending stiffness of the grid structure.

[0083] The retention arrangement according to the invention can have at least one recess, cavity, or perforation for receiving the water storage material, wherein, preferably, at least one swellable water storage material is introduced into the recess, cavity, and / or perforation, and wherein, further preferably, the water storage material only partially fills the recess, cavity, and / or perforation in its dry state (i.e., not completely). This takes into account the swelling behavior of swellable storage materials and prevents excessive mechanical stresses due to swelling pressure.

[0084] The water supply can also be provided at least periodically independently of the rainwater connection, for example by connecting to a mains water network or by irrigation via an external water source using a hose, which enables active cooling of the surroundings at elevated temperatures in summer.

[0085] Water can be supplied via guide plates, which, in addition to water from the roof drainage, can also directly direct rainwater to the retention arrangement.

[0086] The water supply can be taken directly from the roof surface of the building without a rain gutter.

[0087] Water can be supplied by deflecting and / or collecting precipitation via rainwater collection surfaces of awnings, films, fabrics, photovoltaic elements, shading elements such as shutters, cloths or similar, dew and fog nets, via funnel elements and movable structural elements (kinetic architecture) and / or via guide plates connected to the retention arrangement and / or the structure according to the invention. The term "rainwater collection surface of the structure" is thus to be interpreted broadly and includes all surfaces of the structure that are exposed to precipitation and from which rainwater is directed directly or indirectly to and / or into the retention structure.

[0088] Water can also be fed into the retention structure via a central feed device, for example, a pipe or a pipe system. Pipes can be designed to extend the rainwater's path, for example, by having a meandering shape and / or bends.

[0089] Water can also be fed into the retention structure from inside the house.

[0090] Water can be fed into the retention structure via several feed devices arranged evenly and / or unevenly across the outer surface of the retention structure.

[0091] Water can also be supplied by connecting to a retention roof system or a green roof to drain and absorb excess water from flooded retention roofs.

[0092] Water can also be supplied from below, for example from a water basin, through capillary forces of the water storage material.

[0093] Furthermore, water can be supplied from below the normal level or underground, for example from seepage pits or other underground collection tanks.

[0094] Water supply devices can apply water from the outside and / or inside, distributing it evenly and / or at specific points, for example via guide plates or nozzles such as spray or slot nozzles. Water supply devices can also be connected to a circulation / pump system.

[0095] Water distribution through internal and / or external structures and / or channels applied to the surface of the retention arrangement, which may also be interconnected, is advantageous. Structures on the outer surfaces of the retention arrangement and / or channels can have different vertical and / or horizontal angles of inclination, thereby generating varying water distribution velocities. Structures and / or channels can be symmetrically and / or asymmetrically wave-shaped. They may also feature undercuts, which further influence water flow velocity and absorption.

[0096] The design of water-conducting and / or water-distributing structures and / or channels can be based on bionic methods, for example, for modeling vascular systems. The term "vascular systems" refers in particular to a system of water-conducting channels whose cross-sections decrease monotonically in the same flow direction, for example, from top to bottom in the retention arrangement or in a vertical direction, and / or in which a certain quantity of water is initially distributed in a flow direction of the retention arrangement, for example, from top to bottom or in a vertical direction, to a smaller number of flow channels with larger cross-sections and, with increasing extension of the retention arrangement in the flow direction, to a larger number of flow channels with smaller or the same flow cross-sections.In other words, this means, for example, that a certain amount of water supplied to the retention arrangement is initially distributed across fewer flow channels and, as the retention arrangement extends further in the direction of flow, across more flow channels.

[0097] Furthermore, the retention arrangement can include additional elements to promote water absorption and / or water conduction, particularly through capillary action, whereby the additional element acts like a wick and supplies the water to be absorbed to the water-storing material. Fabric elements, for example, can be used as wicks.

[0098] The water storage material is preferably selected from the group of mineral materials, in particular calcium silicate bricks, clay bricks, or aerated concrete, and / or selected from the group of swelling materials. The retention structure can consist of the water storage material and / or incorporate at least one such water storage material. A combination of different water storage materials is also possible.

[0099] Suitable swelling substances include natural and / or synthetic polymers and / or mineral substances.

[0100] Natural substances that can be used include, for example, polysaccharides selected from alginates, alginic acid, amylose, amylopectin, callose, carrageenan, cellulose, chitin, dextran, guluronic acid, inulin, laminarin, lichenin, pullulan, pustulan, starch, starch derivatives, xanthan gum, or mixtures thereof. Synthetic polymers that can be used include, for example, materials made from highly absorbent synthetic polymers selected from polymers based on (meth)acrylates, poly(meth)acrylic acid and its salts, polyacrylamide, polyalcohols, and copolymers of the aforementioned synthetic polymers, as well as other crosslinking and processing aids and property enhancers. Mineral substances that can be used include, for example, clays such as bentonite or calonite. The substances are used as powders and / or granules with a particle size range of preferably 60 to 5000 µm. Preferably, powders and / or granules with a particle size range of 100 to 400 µm are used. Example of implementation

[0101] Within the scope of the present invention, pumice granules and lava granules were investigated as water-storing materials for a retention arrangement according to the invention. The starting point was the minimum and maximum rainfall amounts per m² of floor area of ​​a building arrangement or a building. The kinetics of water absorption of the granules were determined using the method described above for determining water absorption during free swelling in excess liquid. Based on the determined kinetics of water absorption, the respective volume of the retention arrangement required to absorb and store a specific amount of rain falling per minute of a rainfall event and per m² of floor area of ​​the building arrangement was determined using the bulk density. Finally, a design calculation was performed, on the basis of which building planning is possible.

[0102] Two rainfall scenarios were considered: Scenario 1 with 15 l / (m²1 / h) and Scenario 2 with 40 l / (m²1 / h). Pumice granules with a grain size of 0.5 to 2 mm and a relative mass increase at equilibrium after 24 hours of 145 wt% were investigated, as were pumice granules with a grain size of 1 to 5 mm and a relative mass increase at equilibrium after 24 hours of 65 wt%. Lava granules with a grain size of 2 to 5 mm and a relative mass increase at equilibrium after 24 hours of 40 wt% were also included in the analysis. The water absorption kinetics (absorption measurement during free swelling, 20 °C, tap water, assuming linear absorption kinetics in the range of 0 to 5 minutes) yielded values ​​of 0.95 kg of water per kg of dry pumice granules (0.5 to 2 mm) per minute. 0.57 kg water per kg dry pumice granules (1 to 5 mm) per minute and 0.5 kg water per kg dry lava granules (2 to 5 mm) per minute.

[0103] Bulk densities of pumice granules (0.5 to 2 mm) of 950 kg / m³ and of pumice granules (1 to 5 mm) of 880 kg / m³ were used as a basis for calculation. The bulk density of lava granules (2 to 5 mm) was taken into account at 1200 kg / m³.

[0104] From this, an exemplary design scenario for a building planner for a building with a floor area of ​​200 m² and an estimated duration of a heavy rain event of 45 minutes, as well as a rainfall amount for scenario 2 of 0.67 l / (m² h), could be determined, which led to a volume of pumice granules (0.5 to 2 mm) of 6648 l, pumice granules (1 to 5 mm) of 11962 l and lava granules (2 to 5 mm) of 10000 l required to store rain per minute and square meter.

[0105] It was assumed that the retention system was not yet 100% filled during the design calculations. The maximum water absorption capacity is then determined by the maximum storage capacity of the granules. Water absorption calculations blue: is entered red: will be calculated Rainfall amounts

[0106] Rainfall Scenario 1 (min.) 15 Liters / m² per hour Rainfall amount Scenario 2 (max.) 40 Liters / m² per hour Rainfall Scenario 1 (min.) 0,25 Liter / qm pro Minute Rainfall amount Scenario 2 (max.) 0,67 Liter / qm pro Minute Water storage capacity (maximum at equilibrium) Relative mass increase at equilibrium after 24 hours

[0107] Pumice granules (0.5 to 2 mm) 145 % Pumice granules (1 to 5 mm) 65 % Lava granules (2 to 5 mm) 40 % Kinetics of water absorption (absorption measurement during free swelling, 20 °C, tap water) Kinetics of water absorption from 0 to 5 min are approximately linear.

[0108] Pumice granules (0.5 to 2 mm) 0,95 kg Wasser pro kg tr. Material pro Minute Pumice granules (1 to 5 mm) 0,57 kg Wasser pro kg tr. Material pro Minute Lava granules (2 to 5 mm) 0,50 kg Wasser pro kg tr. Material pro Minute Amount for water absorption from rain (density of water = 1,000 kg per m³)

[0109] min max Pumice granules (0.5 to 2 mm) 0,263 kg 0,702 kg per minute of rain and square meter of building Pumice granules (1 to 5 mm) 0,439 kg 1,170 kg per minute of rain and square meter of building Lava granules (2 to 5 mm) 0,500 kg 1,333 kg per minute of rain and square meter of building bulk density

[0110] Pumice granules (0.5 to 2 mm) 950 kg per cubic meter 0,95 kg pro Liter Pumice granules (1 to 5 mm) 880 kg per cubic meter 0,88 kg pro Liter Lava granules (2 to 5 mm) 1200 kg per cubic meter 1,2 kg pro Liter Granule volume for absorbing the amount of water generated per minute and square meter of building floor area

[0111] min Pumice granules (0.5 to 2 mm) 0,000277 teaching and learning activities 0,277 Liter per minute of rain and square meter of building Pumice granules (1 to 5 mm) 0,000498 teaching and learning activities 0,498 Liter per minute of rain and square meter of building Lava granules (2 to 5 mm) 0,000417 teaching and learning activities 0,417 Liter per minute of rain and square meter of building max Pumice granules (0.5 to 2 mm) 0,000739 teaching and learning activities 0,739 Liter per minute of rain and square meter of building Pumice granules (1 to 5 mm) 0,001329 teaching and learning activities 1,329 Liter per minute of rain and square meter of building Lava granules (2 to 5 mm) 0,001111 teaching and learning activities 1,111 Liter per minute of rain and square meter of building Exemplary design scenario for the building planner

[0112] note

[0113] The retention arrangement is not yet filled to 100% in the above design calculation.

[0114] The maximum water absorption capacity is then determined by the maximum storage capacity of the granules.

[0115] The invention is described below by way of example with reference to the drawing. The drawing shows Figs. 1A-C a concept illustration showing the effect of retention facades on reducing the flood risk of densely populated urban areas during heavy rainfall events, Fig. 2 a schematic representation of the use of retention facades on buildings, Figs. 3-5 different embodiments of perforated building elements for constructing a retention arrangement according to the invention, Fig. 6 a schematic representation of a building element for a retention arrangement according to the invention with a cavity for receiving a swellable water-storing material in a horizontal configuration in the dry state of the swellable material, Fig. 7 the building element made of Fig. 6in the swollen state of the water-storing material, Fig. 8 a schematic representation of a component for a retention arrangement according to the invention with several transverse cavities with swelling material in a horizontal configuration, Fig. 9 a component with vertically extending cavities into which a swelling water-storing material is introduced, in the non-swollen state of the water-storing material, Fig. 10 the in Fig. 9 Fig. 11 shows the component in the swollen state of the water-storing material; Fig. 12 shows an example of the precipitation storage quantities achievable with retention facades; Fig. 13 shows a schematic representation of a cassette element for receiving a water storage material for a retention arrangement according to the invention; Fig. 14 shows a schematic representation of several cassette elements of the in Fig. 12The type shown in the composite and Fig. 14 a schematic representation of a grid structure for receiving a water storage material for use in a retention arrangement according to the invention.

[0116] Based on the Figs. 1A to 1C The diagram schematically shows measures for rainwater retention and flood prevention during heavy rain events. Fig. 1A Figure 1 schematically depicts an urban, densely populated neighborhood with various buildings. Due to a high degree of sealing, lower infiltration potential, and high soil compaction, significant problems with rainwater drainage can occur, particularly during heavy rainfall events, leading to the risk of flooding. This is illustrated in Fig. 1A characterized by a schematically represented flood height X.

[0117] Fig. 1BThis shows that retention roofs can be used in urban areas to retain rainwater and reduce the risk of flooding. This is demonstrated in Fig. 1B This is shown schematically by a lower flood level XY in the case of heavy rainfall events. However, retention roofs 2 alone are not suitable to completely eliminate the risk of flooding due to high precipitation amounts during heavy rainfall events.

[0118] Fig. 1C Figure 3 shows the impact of retention facades on the flood risk of urban districts during heavy rainfall events. Retention facades are vertical retention arrangements integrated into the side walls or outer skin of buildings for water retention through water absorption and storage. As can be seen from Fig. 1CThis shows that, with suitable design and the use of appropriate water storage materials, such retention facades 3 can have sufficiently high storage capacities per building 1 to even completely absorb the volume of water generated during heavy rainfall and thus reduce the risk of flooding to zero. The storage capacity per building for rainwater can increase essentially linearly with increasing facade height or the number of stories of the building 1, provided the retention facades 3 are appropriately designed. Retention facades 3 can be formed by building elements positioned in front of and / or suspended from the building facade, particularly in modular construction, or by independent building walls of a building 1.

[0119] Preferably, retention facades 3 are formed by self-supporting wall or building element systems, which can consist, for example, of mineral substrates from which complete walls can be constructed that are simultaneously statically dimensioned and inherently water-storing.

[0120] The water stored in the retention facade 3 can be made available to buildings 1 again for use, either as process water by extraction from the water storage medium or indirectly through water evaporation and the associated cooling with associated microclimate improvement.

[0121] As in Fig. 2 As shown, depending on the construction type, building 1 can have retention facades 3 on two opposite sides of the building (in the case of buildings 1 arranged in a building complex, such as terraced houses, Fig. 2 , below) or on all sides of the building (in the case of detached buildings 1, such as single-family homes or halls, Fig. 2, below).

[0122] As in the Figures 3 to 5As shown, retention facades 3 can be formed by freestanding, load-bearing or non-load-bearing retention walls, which can be constructed of masonry. Such retention walls consist of or feature building elements 4, which can be designed as individual blocks or as plan blocks. For the production of these building elements 4, established manufacturing processes for the production of calcium silicate bricks or for brick production can be used. The water storage capacity of the building materials used can be adjusted by modifying the formula and can therefore be optimized for the specific application. Typical water storage capacities, defined as those determined by the water storage material, are shown below.The mass of water absorbed by the component, relative to the dry mass of the water storage material (with a residual moisture content between 2% and 5%), can be in the range preferably between 5% and 30%, for example 20%, whereby the time required to reach the maximum water storage capacity can be less than 1 h, preferably less than 30 min, in particular 15 min or less.

[0123] The use of caverns, undercuts, water-conducting structures, and / or different inlet points can facilitate optimal, rapid, and efficient water distribution within the retention wall. Connecting it to the roof and / or building drainage system of building 1 ensures that, in addition to directly collecting rainwater, preferably all of the water accumulating on building 1 during a heavy rainfall event is fed into the retention wall.

[0124] When using porous building materials, the existing pore system of the building material also enables gravity-driven water drainage from the building elements 4. If more water is introduced than can be stored via the pore system, the water emerges in the lower area of ​​the building elements 4 and can thus be used, for example, as process water in building 1 or for irrigating surrounding vegetation.

[0125] Figures 3 to 5 Furthermore, the figures show that the building elements 4 can be perforated, with perforations 5 in particular running perpendicular to the bearing surface in order to facilitate water flow and distribution within the building elements 4.

[0126] Instead of perforations 5, other openings can also be provided in the building elements 4 to create cavities in which, for example, a swelling water storage material 6 is introduced. The swelling water storage material 6 can serve to store water in addition to the building material from which the building elements 4 are made. It is also possible, in principle, for water storage to be achieved solely via a swelling water storage material 6. As can be seen from the Figs. 6 and 7The swelling water storage material 6, when dry and unswelled, only partially fills the perforation 5 in the component 4, leaving sufficient empty volume to allow the water storage material 6 to swell. Once fully swollen, the water storage material 6 completely fills the perforation 5. The degree to which the perforation 5 is filled with the water storage material 6 must be dimensioned such that, when swollen, the swelling pressure does not cause any mechanical stress on the component that could compromise its integrity.

[0127] Fig. 8 shows that even horizontally running cavities can be filled with swelling material to provide a sufficiently high water storage capacity.

[0128] The Fig. 8 and 9, 10 show building elements 7 with swelling water storage material 6 in horizontal ( Fig. 8) and vertical ( Fig. 9, 10 ) Openings or perforations 5, wherein in the case of vertical perforations 5 the swelling water storage material 6 is arranged in a dry state in the vertically downward-lying area of ​​the perforations 5 ( Fig. 9 ) and expands upwards as it swells, so that in the fully swollen state the cavities are essentially completely filled by the water storage material 6 ( Fig. 10 ).

[0129] The vertical surfaces available on the buildings have a high potential for water storage. Fig. 11Figure 3 shows an example of the water storage capacity of vertical retention facades. A building with a footprint (roof area) of 120 m², a width of 8 m, and a length of 15 m is considered as an example. During different heavy rainfall events (15 and 40 l / m² h) with varying durations (e.g., 0.25 h and 0.5 h), total water volumes of 450 to 2,400 l fall over the roof area.

[0130] Depending on the building situation (freestanding or in a group), the floor height (for example: 3 and 6 floors, with a floor height of, for example, 3 m) and taking into account unusable window areas, different sized areas of the building facade can be designed or used as retention facades 3 in a building 1.

[0131] If these parameters are taken into account and the retention facades 3 are formed by, for example, 10 cm thick retention walls, for example on a calcium silicate brick basis with a water storage capacity of 12% based on the dry mass with a water absorption time of over 0.5 h, storage quantities of 3,291 l to 10,091 l of water result on the building, which is already about 37% above the maximum amount of water of 2,400 l if three floors are planned and two retention facades 3 (building in a bonded arrangement).

[0132] As can be seen from Fig. 11 Furthermore, in the case of detached buildings, retention facades can be formed on all four vertical exterior surfaces of the building by means of appropriate retention walls. Only the roof surfaces are not designed for water absorption and storage. The storage capacity for rainwater could be further increased by appropriate roof greening or roof retention areas.

[0133] Furthermore, it is not excluded that water can also be supplied to the retention facades 3 via water supply networks, possibly also by feeding water in from inside the buildings 1 or from below from water basins or seepage pits, for example to positively influence the microclimate through evaporation of the stored water and evaporative cooling.

[0134] In Fig. 12A cassette element 8 for receiving a water storage material for use in a retention arrangement is shown. The cassette element 8 is formed by a frame 9 and two perforated plates 10, with a receiving area for the water storage material being formed between the perforated plates 10. The perforated plates 10 have openings 11 through which the water storage material can be dehumidified after water absorption. Dehumidification preferably takes place via both flat sides of the cassette element 8. Accumulating rainwater can also drain from the cassette element 8 via the openings 11. Not shown is the possibility of supplying rainwater via pipes leading into the heat storage material.

[0135] Fig. 13 schematically shows the arrangement of several cassette elements 8 from Fig. 12in a network. The modular design allows for the easy production of retention volumes and areas of varying sizes.

[0136] Fig. 14 Figure 12 shows a grid structure 12 designed and configured to receive a water storage material for use in a retention arrangement for rainwater retention. The grid structure 12 can be, as shown in Figure 12, Fig. 14 shown to have a non-planar surface gradient that is adapted to the contour or surface profile of a building structure, for example, the contour of the outer facade of a building. Reference symbol list:

[0137] 1 Building 2 Retention roof 3 Retention facade 4 Building element 5 Perforation 6 Water storage material 7 Building element 8 Cassette element 9 Frame 10 Perforated sheet metal 11 Opening 12 Grid structure

Claims

1. Retention arrangement for retaining rainwater during heavy rainfall events in urban, densely built-up areas, the retention arrangement comprising a porous and absorbent and / or swellable water storage material, wherein the retention arrangement forms, in particular, a vertical retention facade (3) and / or a vertical retention wall of a structure, such as a residential or commercial building (1), an industrial hall, a noise barrier or a bridge, or is designed as a freestanding, essentially vertical retention structure, wherein the retention arrangement comprises a building arrangement and the retention arrangement is connected to the building arrangement for draining precipitation water from at least one roof and / or facade surface of the building arrangement to the retention arrangement and for at least temporary storage of precipitation water in the retention arrangement, wherein the retention arrangement is designed and equipped to absorb and store, in relation to the floor area of the building arrangement and a precipitation duration, a minimum amount of water of 10 l / (m2h) to 50 l / (m2h) with a floor area of the building arrangement of at least 50 m2 and a precipitation duration of at least 0.25 h, whereby a fluidic and / or pipe-bound connection to a roof and / or building drainage system of the building arrangement is provided for the directed, in particular pipe-guided, and / or controlled and / or regulated feed of precipitation water accumulating on and / or at the structure into the retention arrangement, or wherein the retention arrangement receives precipitation water from other neighbouring structures of the building arrangement, such as residential or commercial buildings, industrial halls, noise barriers or bridges, via a pipe system and is connected to the building complex for this purpose, and wherein the retention arrangement is designed and configured to absorb water from 0.1 to at least 2.0 kgwater / (kgWSM,tr.min), with: kgwater = absorbed water mass in [kg] and with kgWSM,tr. = mass of the dry water storage material.

2. Retention arrangement according to claim 1, characterised in that the retention arrangement is designed and configured to absorb water from 0.5 to at least 1.0 kgwater / (kgWSM,tr. min), with: kgwater = absorbed water mass in [kg] and with kgWSM,tr. = mass of the dry water storage material.

3. Retention arrangement according to one of the preceding claims, characterised in that the retention arrangement is designed as masonry, in particular as a solid wall, made of pressure-resistant building elements (4), such as moulded bricks, wherein, preferably, the building elements (4) consist of the water storage material and / or are made of it and / or contain it.

4. Retention arrangement according to one of the preceding claims, characterised in that the water storage material has a pore structure for storing water and a maximum water storage capacity between 1 wt.% and 200 wt.%, preferably up to 150 wt.%, more preferably in the range between 30 wt.% and 150 wt.% and / or that the water storage material is swellable and has a maximum water storage capacity between 1 wt.% and 20,000 wt.%, preferably 30 wt.% to 5,000 wt.%, in each case based on the ratio of the maximum water mass storable in the pore structure to the mass of the dry water storage material.

5. Retention arrangement according to one of the preceding claims, characterised in that the water storage material is selected from the group of granulates, in particular pumice granulates and / or lava granulates.

6. Retention arrangement according to one of the preceding claims, characterised in that the retention arrangement has at least one preferably self-supporting structural element, in particular designed as a bulk material cassette or lattice girder, for receiving a bulk filling of the water storage material, wherein, preferably, the structural element has openings for ventilation, in particular for ambient air to flow through the bulk filling, and / or for water to pass into and / or out of the bulk material.

7. Retention arrangement according to claim 6, characterised in that several structural elements are joined together to form a network.

8. Retention arrangement according to claim 6 or 7, characterised in that a bulk material cassette is provided for receiving a bulk material of the water storage material, wherein the bulk material cassette preferably comprises a flat component with preferably flat opposing boundary and / or retaining surfaces and a receiving area formed therebetween for the water storage material, wherein, preferably, openings for flow-through and / or for water passage are provided in at least one boundary and / or retaining surface, preferably in both boundary and / or retaining surfaces.

9. Retention arrangement according to claim 6, characterised in that a lattice girder is provided for receiving a fill of the water storage material, wherein the lattice girder has at least two opposing lattice areas between which a receiving area for the water storage material is formed.