Drainage plate and roof greening construction comprising same

Abstract

The invention relates to a drainage panel (1) for a roof greening system (2), which is designed as a surface element with a bottom surface (10) for orientation towards a roof surface (D) and a top surface (11) opposite the bottom surface (10), and which has a plurality of projections (12) open towards the bottom surface (10), which project towards the top surface (11) and each have an end surface (120), wherein the end surfaces (120) form a bearing surface (110) on the top surface (11). In at least some of the projections (12), at least one through-opening (121) is provided, which is located in the end surface (120) or a side wall (122) of the projection (12), wherein the total area of ​​the opening surfaces of all the through-openings (121) is 2 to 15%, based on the total area of ​​the drainage panel. Furthermore, the invention relates to a roof greening structure (2) comprising at least one such drainage panel (1).

Description

TECHNICAL AREA

[0001] The invention relates to a drainage board which can be used in a green roof system, in particular on a flat roof with a roof pitch of at most 5°. Furthermore, the invention relates to a green roof system which includes at least one drainage board according to the invention. BACKGROUND OF THE INVENTION

[0002] Green roof systems are becoming increasingly important in times of advancing climate change, as they are able to absorb precipitation and delay or even completely prevent its release into the sewer system. This is particularly important in larger cities with extensive soil sealing, given the increasing frequency of heavy rainfall events. Furthermore, green roofs contribute to an improved urban climate. In many cities, the installation of a green roof is mandatory for new buildings of a certain size. When constructing a new building, the green roof can be factored into the structural calculations from the outset. This option is not available for retrofitting a green roof onto an existing building.Here, the weight of the green roof system – especially if it is a green roof system with water storage – must be adapted to the load-bearing capacity of the roof. Such green roof systems often use drainage panels according to the preamble of claim 1 with openings that can drain excess water (e.g., DE 30 45 390 A1 and DE 43 28 787 A1). In all cases, it is preferable to design the green roof system to be as light as possible, since unnecessarily heavy green roof systems increase the cost of the roof construction.

[0003] Roof structures are subject to considerable stress due to wind suction caused by wind flowing over the roof. This wind flow creates a negative pressure on the surface of the roof structure, which can lead to the roof structure lifting away from the roof membrane. This effect is particularly pronounced at the windward edge of the roof and especially at its corners, as vortices form in these areas, intensifying the wind suction. DIN EN 1991-1-4:2010-12 contains regulations for identifying the most vulnerable areas of a roof and calculating the corresponding wind load, thus enabling a safe design of the roof structure based on these calculations.

[0004] Green roof systems are subject to wind suction just like other roof structures. Due to increasing wind speeds and the growing likelihood of strong gusts, also a consequence of climate change, the safe design of green roofs is becoming ever more important. This is especially true for extensive green roofs with their relatively shallow depth and correspondingly low ballast. Currently, it is often impossible to install extensive green roofs with a substrate depth of less than 10 cm on certain roofs due to their susceptibility to wind. This is true even if the height of the green roof system is increased in the most wind-prone areas to raise the ballast there.As a result, roof greening is often not feasible at all, since a comparatively light extensive greening would not withstand the expected wind suction and a heavier intensive greening would exceed the permitted load-bearing capacity of the roof structure.

[0005] The object of the invention is therefore to solve the problems of the prior art described above and to provide a roof greening structure which, despite its low weight, can withstand the expected wind suction in all areas of the green roof. SUMMARY OF THE INVENTION

[0006] This problem is solved by the drainage board according to claim 1, which is a component of the roof greening system according to claim 6. Preferred embodiments are described in the respective dependent claims.

[0007] In its broadest aspect, the invention relates to a drainage panel for a green roof system, which is designed as a surface element with a bottom surface for orientation towards a roof surface and a top surface opposite the bottom surface, and which has a plurality of projections open towards the bottom surface, which project towards the top surface and each have an end surface, wherein the end surfaces form a bearing surface on the top surface. In at least some of the projections, at least one through-opening is provided, which is located in the end surface or a side wall of the projection, wherein the total area of ​​the opening surfaces of all the through-openings is 2 to 15%, based on the total area of ​​the drainage panel.

[0008] The drainage plate according to the invention corresponds in its basic structure to drainage plates already known from the prior art. Such drainage plates are offered by the applicant, for example, under the designations FKD 15, FKD 25, FKD 25 plus, and FKD 40. In their shape, these drainage plates resemble a studded plate or an egg carton. Typically, the drainage plates are manufactured from a flat plastic sheet by deep drawing or compression molding, with the projections being formed in such a way that they enclose a cavity open towards the underside of the plate. The shape of the projections is not fundamentally restricted. As a rule, the projections taper conically towards the top of the drainage plate and, for example, have the shape of a truncated cone. In this case, the end faces of the projections are circular.However, other cross-sectional shapes, such as rectangular or polygonal forms, are also conceivable, with the corners preferably being rounded to simplify manufacturing. Advantageously, the projections all have the same height, so that the end faces lie in the same plane, where they then jointly form a (non-continuous) bearing surface on the top of the drainage board. Further layers can be applied to this bearing surface in the green roof system. The thickness of the drainage board (greatest distance between the top and bottom surfaces) is, as in the prior art, a few centimeters, for example between 1 and 6 cm, and particularly in the range of 1.5 to 4 cm.

[0009] The drainage plate according to the invention discloses at least one through-opening, which is located in an end face on the upper surface of at least a portion of the projections or which is arranged in a side wall of the projection. Of the two possibilities, the arrangement in an end face is preferred because creating a through-opening in the end face is simpler due to the better accessibility of this area than creating the through-opening in the side wall of the projection. If a through-opening is present in the side wall of the projection, it is preferably located in an upper region of the projection towards the upper surface of the drainage plate. For example, the at least one through-opening is located in an upper third, an upper quarter, an upper sixth, or the uppermost 10% of the side wall, in each case with respect to the total height of the projection.Preferably, the through-opening is located far enough from the underside of the drainage board that water accumulating on the drainage board cannot enter the through-opening, or only at extremely high water levels. If the drainage board is designed to provide a storage area for the permanent retention of water, the through-opening is located above this storage area.

[0010] In principle, a wide variety of combinations of through-openings can be used in the drainage plate according to the invention. For example, it is possible to provide several through-openings per end face of a projection or per side wall of a projection, as long as the available space allows this and the stability of the drainage plate is not impaired. In extreme cases, a through-opening in the end face of a projection can occupy practically the entire end face. The through-opening could, for example, have been created by cutting off the tip of the projection, so that it would only be surrounded by the side wall of the projection. Combinations of through-openings in both the end face and the side wall are also conceivable. The number, shape, and size of the through-openings can also vary from projection to projection.A uniform design and / or distribution of the openings across the projections is preferred, as this simplifies the production of the drainage panel and eliminates the need to consider a specific orientation when later arranging the drainage panel within the green roof structure. The openings are preferably incorporated into the drainage panel during its manufacture. This means they are created during the deep drawing or compression molding process. Alternatively, the openings can be added to the drainage panel in a subsequent step, for example, by punching. The shape of the openings is generally arbitrary. Round openings are preferred, but oval or polygonal openings are also possible.

[0011] The opening area of ​​the through-holes is dimensioned such that rapid pressure equalization can occur through the drainage plate. This equalization balances the increased internal pressure on the underside of the drainage plate with the negative pressure on the top side caused by wind suction, thus preventing the drainage plate and the layers above it from lifting off the roof. Unlike in the prior art, the through-holes in the projections of the drainage plate according to the invention are therefore not water flow openings, but pressure equalization openings.

[0012] To fulfill this pressure equalization function, the drainage plate according to the invention has through-openings for pressure equalization such that the sum of the opening areas of all through-openings is 2 to 15%, based on the total area of ​​the drainage plate. The total area of ​​the drainage plate is understood to be the area covered by the drainage plate on the roof surface (or another flat surface). In other words, the total area of ​​the drainage plate is the area bounded by the outline formed by projecting the outer edge of the drainage plate onto a flat surface on which the drainage plate is placed with its underside facing downwards.The opening area of ​​a through-opening is accordingly the area bounded by the edge of the projection surrounding the through-opening, or, if the through-opening is located in a non-planar region of the projection, conventionally the area bounded by an outline formed by projecting the edge of the opening onto a planar surface. Preferably, the total area of ​​the through-openings in the projections, in relation to the total area of ​​the drainage plate, is 2.5 to 10%, more preferably 4 to 8%, and particularly 5 to 7%.

[0013] The percentage of through-openings present in the projections of the drainage board according to the invention, and preferably only in their upper region, is comparatively high. Accordingly, a relatively large opening area is generally obtained for each individual through-opening, even if a through-opening is present in each of the projections. Typically, each through-opening will have an opening area in the range of 40 mm² to 180 mm². Preferably, the opening area of ​​a through-opening is between 60 mm² and 160 mm², more preferably between 80 mm² and 160 mm², and particularly between 90 mm² and 150 mm². This opening area is large compared to the opening areas of other through-openings, such as those found in conventional drainage boards as ventilation openings or drainage openings in their base.Due to the high surface area of ​​all openings and the relatively large opening area of ​​each individual opening, the drainage panel according to the invention enables rapid and sufficient pressure equalization. This significantly reduces the likelihood of the drainage panel lifting off the roof due to wind suction, compared to conventional drainage panels, or in most cases, simply not possible. As a result, the drainage panel according to the invention allows for the construction of green roof systems that, despite their low height and minimal load, are practically unaffected by wind. This is achieved without additional ballast in the wind-exposed edge areas of the green roof system.

[0014] As mentioned previously, it is preferable to distribute drainage openings as evenly as possible across a drainage board, so that the drainage board does not need to be installed in a specific orientation on the roof surface. However, it is also conceivable to provide more numerous and / or larger openings on the side of the drainage board that faces the direction from which the wind primarily strikes the roof surface. It is also possible to combine different types of drainage boards on the roof surface, using drainage boards with a particularly large total opening area in areas of the roof exposed to wind, while in areas with lower wind loads, drainage boards with a smaller total opening area, or possibly even conventional drainage boards, are used.However, it is preferred that drainage panels according to the invention, and in particular those with a uniform distribution of the passage openings, are used uniformly over the entire roof area intended for roof greening, as this simplifies the construction.

[0015] In a preferred embodiment of the drainage panel according to the invention, a through-opening is provided in the end face of each projection. Additional through-openings in the side wall are preferably not provided. In another preferred embodiment, at least one through-opening, and in particular exactly one through-opening, is provided in each projection. In this case as well, no further through-openings are preferably provided in the side wall. Suitable drainage panels have, for example, 270 to 1200, preferably 400 to 900, particularly preferably 500 to 800, and particularly 600 to 700, through-openings per square meter. If through-openings are provided in the side wall of the projection, they are preferably located in an area above a section of the drainage panel designed for water storage.If there are no openings in the end surface of the projection, the projection can also be tapered to a point and the end surface can be correspondingly very small.

[0016] In a particularly simple version, the drainage panel according to the invention has only projections that extend upwards from a flat base plate, which forms the underside of the drainage panel, towards the top of the drainage panel. Preferably, all projections are identical in design and have the same height. This type of drainage panel does not itself offer the possibility of permanently storing water. However, a water reservoir could be provided by arranging, in a manner known per se, a water-retaining outer wall for one, several, and especially all drainage panels of a green roof system, as well as flow restrictors above the roof drains present in the area of ​​the green roof system. These restrictors are designed such that water can only flow out through the roof drains once a predetermined water level has been reached.

[0017] In a preferred embodiment of the invention, the drainage plate itself is designed to provide a storage space for water. For this purpose, the drainage plate has recesses projecting towards the underside between the projections. These recesses typically form the lowest areas of the drainage plate. Accordingly, the bottom surfaces of the recesses advantageously form a base for the drainage plate, which is placed on the substrate. The recesses form a water reservoir in a manner known per se, providing water for supplying the plants of the green roof system.

[0018] Like the drainage board itself, the roof greening system according to the invention can also correspond in its basic structure to that which is already known from the prior art. The roof greening system according to the invention differs from a conventional roof greening system in that it comprises at least one drainage board according to the invention, which differs from a conventional drainage board by means of the perforations that bring about rapid and sufficient pressure equalization, thus preventing the roof greening system from lifting off the roof surface. Advantageously, the at least one drainage board is arranged in an edge region of the roof, and in particular in an edge region of the roof located in the direction of the prevailing wind. Here, as already described, the wind load is greatest.In some cases, it may therefore be sufficient to arrange drainage panels according to the invention exclusively in this particularly wind-exposed area, while conventional drainage panels can be used in less wind-exposed areas. However, to simplify the construction, it is preferable to lay drainage panels according to the invention over the entire surface of the green roof system. These can be connected to each other at their adjacent edges in a manner known per se.

[0019] The use of the drainage board according to the invention makes it possible to install lightweight green roofs, such as extensive green roofs, on virtually any flat roof surface with a roof pitch of no more than 5° and even with a low parapet height, without the need for additional measures to fix the green roof system to the roof. In particular, it is very rarely necessary to add weight to the wind-exposed edges of the green roof system to ensure that the system is not lifted from the roof surface by wind suction. A green roof system according to the invention can therefore be implemented with a very thin layer, which significantly reduces the cost of the system and the effort required for its installation. For example, the height of the substrate layer above the at least one drainage board can be limited to a maximum of 8 cm.This applies even when using very lightweight single-layer substrates weighing only approximately 650 kg / m³. The thickness of the substrate layer can be kept uniform across the entire surface of the green roof system, since, as mentioned, an increase in ballast in the wind-exposed edge areas is not necessary. With somewhat heavier substrates, wind-resistant green roof systems with a substrate thickness of no more than 6 cm, or even a maximum of 4 cm, and in particular no more than 3 cm, are achievable.

[0020] In accordance with standard green roof constructions, the substrate can either be applied directly to the drainage board, filling the spaces between the board's projections. Alternatively, the top of the drainage board can be covered, for example, with a layer of filter fleece, onto which planting substrate or a vegetation mat is then applied. The area of ​​the drainage board around the projections can then either be left open, forming a cavity that can absorb water, or it can be filled with loose material, for example, to increase the load-bearing capacity of the drainage board within the green roof structure, such as when the drainage board is located beneath a pedestrian or vehicular traffic area. This loose material can include planting substrate, expanded clay, gravel, pumice, foamed glass gravel, or similar materials.If the loose material is not a planting substrate, a vegetation mat is laid on top of the loose material layer. Alternatively, the loose material can be covered with a filter fleece layer, onto which planting substrate is then applied. The planting substrate is preferably a predominantly mineral substrate, such as those already used in established technology for extensive green roofs. It consists, for example, mainly of expanded shale, expanded clay, lava, pumice, crushed brick, Porlith, and green waste compost. BRIEF DESCRIPTION OF THE FIGURES

[0021] The invention will be explained in more detail below with reference to the accompanying drawings. The drawings are purely schematic and not to scale. They serve only to describe preferred embodiments of the invention, without limiting it to the embodiments described. In the figures, the same reference numerals denote the same objects or parts, without all objects or parts being provided with reference numerals in each case.

[0022] The figures show: Fig. 1 a top view of a flat roof showing the roof areas and their dimensions, which are essential for the division of the roof areas; Fig. 2 a bar chart showing the classification of green roof installations according to the frequency of the wind loads occurring; Fig. 3 a partial perspective view of a first example of a drainage board according to the invention; Fig. 4 a partial perspective view of a second example of a drainage board according to the invention; Fig. 5 a partial perspective view of a third example of a drainage board according to the invention; Fig. 6 a partial cross-sectional view of a green roof assembly according to the invention; Fig. 7 a partial cross-sectional view of another green roof assembly according to the invention; Figs. 8(a) to 10(b) graphical representations of the results of investigations into the wind uplift resistance of three different green roof assemblies according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] Figure 1 This figure shows a top view of a flat roof with a roof pitch of no more than 5° to illustrate the different roof areas that play a role in calculating wind suction according to the standard DIN EN 1991-1-4. As mentioned earlier, the greatest wind load occurs in the roof area facing the wind. The wind flow directed against the building facade is indicated by the arrows on the left side of the figure. The total width of the roof surface in the wind direction is denoted by d, and the length of the roof perpendicular to the wind direction by b. The individual roof areas F, G, H, and I denote areas of varying wind load, which is highest in the corner areas F and decreases through G to H and I. The dimensions of these areas are calculated from the value e, which represents the minimum of the effective facade width and twice the building height. As in Figure 1For example, the length of the areas F is one quarter of e and their width is one tenth of e.

[0024] To make a green roof system wind-resistant, the corner areas F are of particular importance. Here, the risk of the green roof system lifting off the roof membrane is especially high due to the formation of funnel-shaped vortices. Vortices can also form at the roof edge in area G, so the risk of wind uplift is also high in this area. The wind uplift effect is less pronounced in area H and least noticeable in the inner area I.

[0025] The applicant for the present application has been intensively studying the risk of wind suction for roof greening structures for some time and has conducted investigations on this topic using her own roof greening projects. Figure 2The evaluation of one of these studies, based on 81 different green roof projects, shows this. These projects were classified according to their respective wind load, specified as gust pressure in kN / m². As can be seen from the bar chart of the Figure 2The results show that a large proportion of the investigated structures have a gust pressure of 0.5 to 0.75 kN / m². Calculations of wind uplift resistance for the structures using conventional drainage panels (Optigrün® FKD 25) in an extensive green roof system (Optigrün® lightweight roof with 3 cm substrate depth) – even assuming optimal parapet design – revealed that in area H, only 7 of the 81 projects could have been constructed to be wind uplift resistant. In area G, this figure would have been only 2 of the 81 projects. However, the calculations for corner areas F showed that not a single one of the 81 projects would have met the wind uplift resistance requirements. Therefore, even with the most favorable parapet design, not a single one of the 81 projects could be implemented to be wind uplift resistant with a conventional extensive green roof system.

[0026] If the calculation of wind uplift resistance is performed for the same 81 buildings and the same extensive green roof structure – with the sole difference that drainage panels according to the invention, with higher air permeability, are used instead of conventional drainage panels – it turns out that a wind uplift-resistant design is possible in all 81 of the 81 buildings. Wind uplift resistance can be achieved in all roof areas, including the corner areas F, even under the most unfavorable conditions for the parapet construction. Additional ballasting is not required in the majority of cases, even in the corner areas.Since, apart from increasing the air permeability in the drainage panels, no changes to the roof greening system are necessary, all the advantageous properties of conventional roof greening systems are retained in the roof greening systems according to the invention, in particular the water drainage and water retention capacity. There are also no changes or disadvantages in the construction of the roof greening system. On the contrary, the invention now makes it possible to realize wind uplift-resistant roof greening systems, which were previously impossible. Compared to roof greening systems that could only be realized with the help of additional ballast, material, weight, additional effort, and thus costs can be saved.

[0027] Figures 3 to 5 Illustrate various examples of drainage panels 1 according to the invention, with which wind-suction-resistant roof greening structures according to the invention can be realized. Figure 3Figure 1 shows a top view of a section of a drainage panel 1 according to a first embodiment of the invention. The drainage panel 1 is designed as a planar element whose length and width are considerably greater than its height. The height of the drainage panel 1 is the distance between the plane 100, with which the drainage panel is positioned towards a roof surface, and a plane 110 on the upper surface 11 of the drainage panel facing away from the roof surface.

[0028] Drainage plate 1 is essentially equivalent to drainage plate FKD 25, as supplied by the applicant, but differs from it in its significantly increased air permeability. Like FKD 25, drainage plate 1 has a multitude of projections 12 that extend from the underside 10 of the drainage plate to the top side 11. Some of the projections 12 are cut open at the edge of drainage plate 1 facing the viewer. This reveals that the projections 12 are hollow inside and each has an opening on the underside 10 of the drainage plate. Each projection 12 has an octagonal cross-section with rounded corners to facilitate the manufacture of the drainage plate. It is manufactured, for example, from a flat plastic sheet (e.g., HDPE) by deep drawing.

[0029] All projections 12 extend from the underside 10 at the same height. They taper conically towards the upper side 11 and terminate in a flat end surface 120. All end surfaces 120 lie within the plane 110, which can serve as a support surface for at least one further layer, for example, a filter fleece, if the drainage panel is installed in a green roof system. The individual projections 12 are connected to each other by half-height partition walls 123. "Half-height" here is not to be understood literally, but refers to any type of partition wall whose height is less than the height of the projections 12. The partition walls 123 are also open towards the underside 10 and hollow inside. These cavities, together with the cavities of the projections, form a channel network through which water can flow.

[0030] Between the projections 12 are recesses 13, which are surrounded by the partition walls 123 and sections of the side walls 122 of the projections 12. The recesses 13 are closed off towards the underside 10 of the drainage panel 1 by floor surfaces 130. All floor surfaces 130 lie in the same plane, namely the plane 100 indicated by dashed lines, which defines the base on which the drainage panel 1 is placed on a roof. The recesses 13 form a water reservoir for the drainage panel 1, which can hold water up to the height of the partition walls 123. This water is used to irrigate the vegetation of the roof garden.

[0031] The FKD 25 drainage board differs from a conventional one in that it is Figure 3The drainage plate 1 shown has through openings 121 in each of the end faces 120 of the projections 12. In the example shown, the through openings 121 have an approximately circular cross-section and are arranged approximately centrally in the end faces 120. The cross-sectional area of ​​the through openings 121 is significantly larger than that of the ventilation openings previously found in drainage plates. The opening area of ​​each of the through openings 121 in the example shown is between 40 mm² and 180 mm², preferably between 60 mm² and 160 mm², particularly preferably between 80 mm² and 160 mm², and especially between 90 mm² and 150 mm². With reference to the total area of ​​the drainage plate 1, this results in a total opening area (the sum of the opening areas of all passage openings 121 of the drainage plate 1) of 2 to 15%, preferably 2.5 to 10%, particularly preferably 4 to 8% and especially 5 to 7%.The total area of ​​drainage plate 1 corresponds to the base area of ​​the drainage plate, i.e., the area surrounded by outlines that correspond to a projection of the outer edges of drainage plate 1 onto the plane 100.

[0032] The large proportion of the total opening area in relation to the footprint of the drainage panel illustrates the high air permeability of the drainage panel 1 according to the invention, which is significantly higher than the air permeability of drainage panel FKD 25 and other conventional comparable drainage panels. This high air permeability enables rapid and comprehensive air exchange between the top and bottom surfaces of the drainage panel. This, in turn, means that any negative pressure on the top surface 11 resulting from wind suction, or any increased internal pressure on the bottom surface 10, is dissipated almost immediately. Therefore, the rapid pressure equalization prevents the drainage panel 1 and the other layers of a green roof system arranged on it from lifting off the substrate. This generally applies even if the layered structure is not subjected to additional ballast in the wind-prone edge and corner areas of the roof surface.

[0033] Figure 4 Figure 1 shows a further embodiment of a drainage plate 1 according to the invention in a partial top view of its upper surface. The basic structure of this drainage plate essentially corresponds to that of the drainage plate according to [reference to figure]. Figure 3Unlike the latter, the drainage plate now has frustoconical projections 12 that terminate in circular end faces 120. A key difference lies in the design of the through-openings 121. These are now located not in the end faces 120, but in the side wall 122 of the projections 12. Specifically, there are two through-openings 121 per projection, each with a rectangular cross-section. The through-openings are located in an upper end region of the side wall 122 on opposite sides of the projection. They are situated just below the end faces 120 and above the half-height intermediate walls 123 that surround the depressions 13. Even when the depressions 13 are completely filled with water, the through-openings 121 are thus located above the water level in the depressions 13.The ability to equalize pressure is therefore not impaired by the water stored on the drainage plate 1. Excess water can drain away through the cavities 14 and, if necessary, be directed to a roof drain.

[0034] Figure 5 shows another example of a drainage plate according to the invention, which differs from that of the Figure 4The arrangement of the through-openings 121 distinguishes them. In the example shown, the through-openings are again located in the end faces 120 of the projections 12. This example is intended to illustrate that different types of through-openings can be used in combination within a drainage panel. Here, through-openings 121 with a hexagonal cross-section are located in the end faces 120 of those projections 12 that are arranged at the edge of the drainage panel. In contrast, those projections located in the interior of the drainage panel only partially have through-openings. To clarify this, the through-opening 121' is shown with a dashed line.The projections 12 in the interior can therefore, in the example shown, either have a circular opening 121' with a cross-sectional area smaller than that of the hexagonal openings 121, or they may not have an opening in the end face 120. It is important to note, however, that there must be enough openings on the drainage plate to achieve a percentage of the total opening area of ​​at least 2.5, relative to the surface area of ​​the drainage plate.

[0035] Figure 6Figure 1 shows a partial cross-section of a roof greening system 2 according to the invention. This differs from a conventional roof greening system in that the drainage layer 24 is composed of drainage panels 1 according to the invention. These are laid next to each other in the usual manner and preferably, as is also known from the prior art, connected to each other at the edges. The drainage panels according to the invention are particularly suitable for lightweight roof greening systems, especially those for extensive green roofs, since the load is low and the risk of the roof greening system being lifted off due to wind suction is particularly high. An exemplary layer structure of an extensive green roof for a lightweight roof is shown in Figure 1. Figure 6The green roof system is arranged on a roof surface D, which is covered in the usual manner with a fleece layer 25 to protect the roof waterproofing DA. The drainage layer 24, already described, consisting of drainage panels 1 according to the invention, is arranged on the fleece layer 25. In the example shown, the spaces between the projections 12 of the drainage panels 1 are filled with loose fill material 21. This loose fill material 21 can be, for example, pumice or another lightweight mineral loose fill material. A vegetation mat 22 is then laid on top of the loose fill layer. This mat serves as a growth substrate for the plants 23, which are generally already present on the vegetation mat 22 before it is laid. The layers of loose fill material 21 and vegetation mat 22 on the drainage layer 24 together form the substrate layer 20 of the green roof system 2.The height of this substrate layer does not need to be increased, even in the particularly wind-exposed corner and edge areas of the roof, to weigh these areas down, because the high air permeability of the layer structure reliably prevents the roof greening structure from lifting off due to wind suction.

[0036] Another embodiment of a roof greening system according to the invention is described in Figure 7 shown as shown in the structure according to Figure 6 The roof greening system 2 is shown in a partial cross-section. The lower layers D, DA and 25 correspond to those of the structure of the Figure 6 The drainage plates 1 according to the invention (for example, those of the Figures 3 or 5The drainage layer 24 has depressions 13 in which a water reservoir W is stored to supply the plants 23 with water. In the upper part of the drainage layer 24, the projections 12 with their end faces 120 form a support surface for the filter fleece layer 26 arranged above the drainage layer. This prevents plant substrate 21 from penetrating the drainage layer 24, while water passes through it.

[0037] The following examples describe the investigations into the stability of various green roof structures according to the invention. Examples

[0038] The stability of three different roof greening systems according to the invention, with the structure shown in the following table, was investigated. The layer sequence is listed – as in the actual roof greening system – with the layer adjacent to the roof waterproofing at the bottom. The uppermost layer therefore appears at the beginning of the list. Table 1 Example Roof greening structure 1 Vegetation mat (Optigrün SM / G 20), partially biodegradable fabric with substrate layer, approx. 1.5 - 2.5 cm (weight when saturated with water approx. 15 - 25 kg / m²), pre-cultivated (Sedum) Lightweight substrate (Optigrün L), pumice, approx. 3 cm (weight as delivered moist approx. 650 - 670 kg / m 3< ) Filter fleece (Optigrün FIL 105), PP (area weight 105 g / m², nominal thickness approx. 1.1 mm) Drainage layer made of drainage panels according to the invention, nominal thickness approx. 25 mm Non-woven protective layer (Optigrün RMS 300), PP / PS / acrylic recycled fibers (area weight approx. 300 g / m², nominal thickness 3.6 mm) 2 Vegetation mat (Optigrün SM / G 20), partially biodegradable fabric with substrate layer, approx. 1.5 - 2.5 cm (weight when saturated with water approx. 15 - 25 kg / m²), pre-cultivated (Sedum) Substrate replacement material (Optigrün Urbanscape ®< Green Roll 40), rock wool, approx. 4 cm (dry surface weight approx. 4.4 kg / m 2< ) Filter fleece (Optigrün FIL 105), PP (area weight 105 g / m², nominal thickness approx. 1.1 mm) Drainage layer made of drainage panels according to the invention, nominal thickness approx. 25 mm Non-woven protective layer (Optigrün RMS 300), PP / PS / acrylic recycled fibers (area weight approx. 300 g / m², nominal thickness 3.6 mm) 3 Planting substrate (Optigrün E), predominantly mineral, main components: expanded shale, expanded clay, lava, pumice, crushed brick, Porlith and green waste compost, approx. 4 cm (weight when saturated with water approx. 1140 - 1440 kg / m³) Substrate replacement material (Optigrün Urbanscape ®< Green Roll 20), rock wool, approx. 2 cm (dry surface weight approx. 2.2 kg / m 2< ) Filter fleece (Optigrün FIL 105), PP (area weight 105 g / m², nominal thickness approx. 1.1 mm) Drainage layer made of drainage panels according to the invention, nominal thickness approx. 25 mm Non-woven protective layer (Optigrün RMS 300), PP / PS / acrylic recycled fibers (area weight approx. 300 g / m², nominal thickness 3.6 mm) The drainage panels according to the invention used in the drainage stories of Examples 1 to 3 are based on the Optigrün FKD 25 drainage element. As in the Figure 1 The drainage plate 1 shown has pressure equalization openings in the form of through-holes in the end faces of the projections. The through-holes are circular and have a Each drainage panel has a diameter of 10 mm. There are 1152 openings per panel. This results in a free area of ​​5% of the drainage panel's footprint, corresponding to the total area of ​​all openings in the drainage panel.

[0039] The pressure equalization capacity and a wind load reduction factor, the so-called R-value, were determined for the green roof systems shown in examples 1 to 3. These values ​​are representative of the stability of a green roof system, as rapid pressure equalization between the roof membrane and the top of the green roof prevents the system from lifting due to wind loads. The wind load reduction factor R indicates the factor by which the design wind load according to DIN EN 1991-1-4:2010-12 must be multiplied to obtain the actual load on the green roof system.

[0040] To determine the aforementioned factors, a rectangular test piece of each of the green roof systems according to Examples 1 to 3 is placed on the bottom of a windproof box whose side walls abut the outer edges of the green roof system. A space of approximately 20 cm in height is maintained above the green roof system. Within this space, one end of a hose exits through one of the box's side walls, the other end of which is connected to a vacuum pump. Applying a vacuum creates a negative pressure within the box, simulating the negative pressure that occurs above the green roof system on a building roof due to wind suction and acts upon the green roof.The pressure profile for the dynamic load tests is set to comply with the requirements of DIN EN 16002:2021-12, which describes the determination of the resistance to uplift wind load of mechanically fastened sheet-like roof waterproofing systems. The wind load reduction factor R is then determined from the dynamic and static tests.

[0041] The dynamic and static pressure profiles determined in the tests on the roof structures according to Examples 1 to 3 are in Figures 8 to 10 The diagrams show the results of the measurements on a green roof system according to Example 1. Test 1 (V1) shows the results for the green roof system according to Example 2, and Test 3 (V3) shows the results for the green roof system according to Example 3. Figures 8(a) , 9(a) and 10(a) represent the dynamic pressure profile, the Figures 8(b) , 9(b) and 10(b)Each figure shows the static pressure profile for the corresponding example. The chamber pressure is shown in the lower part of the figures, the differential pressure in the upper part.

[0042] In all three examples, R-values ​​below 0.1 were determined. Specifically, R-values ​​of 0.08 were determined for the green roof systems according to Examples 1 and 3, and an R-value of 0.09 for the green roof system according to Example 2. The R-values ​​are therefore practically identical and indicate that the investigated green roof systems possess high air permeability, allowing pressure equalization through the system almost instantaneously. Accordingly, the investigated green roof systems exhibit excellent stability, and the risk of such green roofs being lifted from the roof membrane by wind load is practically nonexistent. The green roof systems are so air-permeable that less than 10% of the ambient pressure acts as a lifting load on the systems.The investigations further revealed that even with even further reduced substrate depths, wind-load resistant and stable roof greening structures can still be achieved. REFERENCE MARK LIST

[0043] 1 Drainage plate 10 Underside 100 Base surface 11 Top surface 110 Support surface 12 Projection 120 End surface 121 Passage opening 122 Side wall 123 Half-height partition wall 13 Recess 130 Floor surface 14 Cavity 2 Green roof structure 20 Substrate layer 21 Bulk material layer 22 Vegetation mat 23 Planting 24 Drainage layer 25 Fleece layer 26 Filter fleece layer D Roof surface D Roof waterproofing W Water

Claims

1. Drainage board (1) for a green roof structure (2), which is configured as a panel element having an underside (10) for being oriented towards a roof surface (D) and an upper side (11) opposite the underside (10), and which comprises a plurality of projections (12) open towards the underside (10), which project towards the upper side (11) and each have an end face (120), wherein the end faces (120) form a bearing surface (110) on the upper side (11), wherein at least one through-opening (121) is present in at least some of the projections (12), which is located in the end face (120) or a side wall (122) of the projection (12), characterised in that the total area of the opening surfaces of all the through-holes (121) amounts to 2 to 15%, relative to the total area of the drainage board.

2. Drainage board according to claim 1, wherein the total area of the opening surfaces of all the through-holes (121) amounts to 2.5 to 10%, preferably 4 to 8% and in particular 5 to 7%, relative to the total area of the drainage board.

3. Drainage board according to claim 1 or 2, wherein the at least one through-opening (121) has at least one of the following characteristics: - there is one through-opening (121) in a respective end face (120) of a projection (12), - it is arranged in a region of the side wall (122) of the projection (12) adjacent to the end face (120), - there is at least one through-opening (121) and, in particular, exactly one through-opening (121) in each projection (12), - an opening area in the range of 40 mm2 to 180 mm2, - there are 270 to 1200, preferably 400 to 900, more preferably 500 to 800 and in particular 600 to 700, through-holes (121) per square metre of drainage board (1), - through-holes (121) in the side wall (122) of the projection (12) are provided in a region situated above a region of the drainage board (1) designed for the storage of water.

4. Drainage board according to one of the preceding claims, which comprises recesses (13) between the projections (12) projecting towards the underside (10), the bottom surfaces (130) of which form a standing surface (100) of the drainage board (1), wherein the recesses (13) are in particular designed as water reservoirs.

5. Drainage board according to any of the preceding claims, which consists of a deep-drawn or compression-moulded plastic, wherein the through-holes (121) are formed in particular during deep-drawing or compression moulding or are subsequently punched in.

6. Green roof structure (2) comprising at least one drainage board (1) according to one of the preceding claims.

7. Green roof structure according to claim 6, wherein the at least one drainage board (1) is arranged in an edge region of the roof and, in particular, in an edge region of the roof facing the prevailing wind direction.

8. Green roof structure according to claim 6 or 7, wherein a plurality of drainage boards (1) are arranged side by side and, in particular, over the entire area of the green roof structure.

9. Green roof structure also according to any one of claims 6 to 8, wherein a substrate layer (20) is applied above the at least one drainage board (1), the height of which is no more than 8 cm, preferably no more than 6 cm, more preferably at most 4 cm and, in particular, no more than 3 cm.

10. Green roof structure according to claim 9, wherein the substrate layer (20) comprises planting substrate, in particular predominantly mineral planting substrate, a vegetation mat, mineral loose material, rock wool or any combinations thereof, in particular in layers one above the other.

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