FIELD OF THE INVENTION

The invention relates to a covering element for covering a water receiving part of a building. The invention more specifically relates to a covering element promoting the growth of wanted plant species and preventing growth of unwanted plant species. The invention further relates to a method of constructing such a covering element.

BACKGROUND OF THE INVENTION

Developments for building construction is moving toward the use of more sustainable materials. Furthermore, the buildings should add to the sustainability of the environment of the building.

A development is disclosed in US 2012/0260572. Disclosed is a construction element covered with vegetation for horizontal, pitched and/or vertical surfaces of structures, comprising: a lower base plate that is embodied as an insulating board; an upper vegetation layer with shorter and/or taller plants, a plant-tolerated adhesive layer arranged between the insulating board and the upper vegetation layer, and a layer of a material that renders possible plant growth for shorter and/or taller plants adhered on the plant-tolerated adhesive layer; wherein the plant-tolerated adhesive layer is embodied in a non-vapor retardant manner, so that it is permeable for water vapor. A disadvantage of this construction element is that the layers may separate over time. Another disadvantage of this construction element is that non intended plants such as weeds or grasses may grow on the construction element.

EP1243703A1 discloses a panel consists of a backing layer e.g. of metal, plastic, concrete or rot-proof wood, covered with layer of material that supports plant growth. The covering layer is made from lightweight stone fragments e.g. expanded schist or clay held together by binding agent. The backing layer can be fixed to structure mechanically, by bolts/rivets, or chemically, by mortar/resin. A disadvantage of this panel is the use of an organo-earth substrate in the panel. The organo-earth substrate easily spills into the environment of the panel contributing to clogging of e.g. drainpipes and growing of plants, such as grasses and weeds, at undesirable places.

JP2003023851A discloses a greening plate consisting mainly of natural zeolite and is formed through the following steps: adding plaster, cement and water to the natural zeolite, and solidifying the mixture so as to be in a plate-like shape having leg parts slightly projecting toward the bottom side. The natural -turf court is made by planting natural turf (a) to be spread all over the surface of the sufficiently water-bearing greening plate. A disadvantage of this plate is that it needs continuous sprinkling. Another disadvantage is that the greening plate grows natural grass, which may spread to the surroundings of the greening plate, which spread out natural grass may be considered as a weed in those surroundings.

SUMMARY OF THE INVENTION

An object of the invention is to overcome one or more of the disadvantages mentioned above.

According to a first aspect of the invention, a covering element for covering a rain-water exposed part of a building and growing, comprising:

- a tile having a thickness of at least 1 cm and a porosity of at least 0.05, wherein the tile comprises:

- pebbles;

- an inorganic binder material for binding the pebbles;

- a plurality of pores; and

- at least one tile support for spacing the tile at least 0.5 cm from the building; and

- plants having water retaining properties and having roots arranged in the plurality of pores; and wherein the thickness, the porosity and the spacing are configured to promote the growth of plants having water retaining properties and reducing the growth of plants having non-water retaining properties.

Sustainable buildings may be provided with so-called green-walls or green-roofs. These green-walls or roofs contain tiles with plants that are maintenance free or hardly need any maintenance. Maintenance may be that the green-walls or green-roofs do not need a lot of caretaking, watering, potting compost, remains limited to the area of the tile and/or removal of weed. The tile is configured such that conditions are set for promoting or at least facilitating the growth of a specific type of plants, more specific promoting or at least facilitating the growth of the plant roots, while the conditions are set for reducing or even eliminating the growth of other plants, more specific reducing or even eliminating the growth of the plant roots. The effect of the configuration of the tile is that maintenance is reduced, thus sustainability of a building equipped with the invention is increased. Further, the carbon footprint of the covering element is reduced or low. A further effect may be that the covering element reduces and/or damps environmental noise. A further effect may be that the covering element may be a fire retardant, such as an A1 class fire retardant. A further effect may be that the covering element may be used as an isolating material, providing dampening or suppressing of high and low temperatures reaching the insides of the building via the walls or roof covered with the covering element. A further effect may be that the plants filters particulate matter, such as fine particulate matter, from the air in the environment, thereby cleaning the air. A further effect may be that the covering element filters water flowing through the tile providing cleaner water draining from the covering element. A further effect may be that water is retained at least temporarily in the covering element or in the space under the covering element, for advantageously regulating the amount of water in the environment, such as after local heavy rain.

In an embodiment of the covering element, the thickness of the tile is in a range of 1 cm to 10 cm, preferably 1.5 cm to 8 cm, more preferably 2 cm to 7 cm, even more preferably 3 cm to 6 cm, such as 4 cm to 5 cm, such as around 4.5 cm. The thickness of the tile determines part of the amount of water getting through the tile in a certain period of time. The thickness of the tile together with the other properties, such as how well the roots of the plants seal or close the plurality of pores, the amount of water retainment may be in a range to promote the growth of plants, more specific plant roots, having water retaining properties.

In an embodiment of the covering element, the tile support provides a spacing to the tile of at least 1 cm, preferably at least 1.5 cm, more preferably at least 2 cm, even more preferably 2.5 cm. In an embodiment of the covering element, the tile support provides a spacing to the tile of at least 1 cm, preferably at least 1.5 cm, more preferably at least 2 cm, preferably if the covering element is arrangeable to an inclined and/or vertical part of the building, such as an inclined roof or wall of the building. In an embodiment of the covering element, the tile support provides a spacing to the tile of at most 15 cm, preferably at most 12 cm, more preferably at most 10 cm, most preferably at most 8 cm. In an embodiment of the covering element, the tile support provides a spacing to the tile of around 2.5 cm. In a further embodiment of the covering element, a combination of the preceding extremes for forming a range.

The spacing should be large enough to allow air, specifically wind to dry the tile or transport moist away from behind and/or within the tile. The spacing should be small enough to prevent wind gusts or storms to get behind the tile and apply excessive forces on the tile or at least one covering element. If the covering element is arranged in a horizontal position, or substantially horizontal position, or to a substantially horizontal part of the building, the spacing may be selected large enough to store water in the spacing between the building part and the tile, still leaving enough space behind the tile for drying the back part or inner part of the tile, such as between inner facing surface area of the tile and the maximum retained water level. The stored water may prevent, or reduce flooding of streets, and overflowing sewer systems in case of excessive rain.

In an embodiment of the covering element, the porosity, more specific an effective porosity, of the tile is in a range of 0.07 to 0.5; preferably 0.1 to 0.4; more preferably 0.125 to 0.35; even more preferably 0.15 to 0.30; most preferably 0.20 to 0.25; such as around 0.225.

Porosity may be defined as wherein f = measure for the porosity as a fraction between 0 and 1 V _v = volume of void space V _T = volume of bulk material

F is typically the effective porosity. Vv is typically the volume of voice space that is reachable from outside the porous tile. Vv does not comprise the void space between the pebbles and binder material that is not reachable from the outside, such as by plants such as Crassulaceae, more specific Crassulaceae roots, and/or water cannot reach this void space. VT is typically the volume of the porous tile when the outside measures are taken of the tile. The VT of a tile having a concave shape, or continuous concave shape, may be measured by wrapping this tile in a sheet and calculating the volume enclosed by the sheet. As an example, the VT of a cuboid, such as a cube, may be calculated by multiplying the length, width and height of the cuboid.

As the tile is porous, the water will flow through the tile, with a limited amount or none of the water over time remaining in the tile. For a plant to survive on the tile for longer dry periods, the plant needs to be able to store water. And although all plants are capable of storing some water, only plants able to store considerable amount of water inside the plant are able to bridge these drought periods. Alternatively, the water retaining properties may be typed as drought resistant properties. A drought period may be a period of several days, such as several weeks, or may even stretch for months. Specific plant types are known to grow only or also with dew, specifically morning dew, to fulfil their water needs. The water may be stored or retained in the roots, stem or leaves of the plant, preferably in the leaves of the plant. The combination of the thickness, the porosity and the spacing is arranged such that it provides a growth bandwidth for plants having water retaining properties. This combination is typically selected such that the covering element dries up such fast that during droughts periods that non water retaining plants cannot survive these droughts periods. The configuration may further be dependent on a local climate the covering element is used. The local climate may comprise the amount of shadow e.g. of another building the covering element receives, the amount of wind is blown over the covering element, the orientation of the covering element e.g. horizontal, sloped or even vertical, and/or the positioning of the covering element e.g. facing North or South.

In an embodiment of the covering element, the covering element is configured for being arranged sloped. Configuring the covering element may be comprise selecting a tile thickness which prevents too quick drying of the covering element. The selected tile thickness for sloped covering elements is typically thicker compared to horizontal orientation to compensate for the less or even absent capillary effect holding water in the pores. In an alternative embodiment, the covering element comprises rockwool or the like arranged in the spacing for the sloped covering element. The rockwool retains water such that the tile does not dry out as fast as in the absence of rockwool providing a growth bandwidth for plants having water retaining properties.

In an embodiment of the covering element, the plants are selected from plant families of Agavaceae, Aizoaceae, Apocynaceae, Asphodelaceae, Cactaceae, Crassulaceae, and Saxifraga, or a combination thereof. Crassulaceae may also be referred to as the stonecrop family. These are plant families that have water retaining properties or features. In an embodiment of the covering element, within the Aizoaceae plant family the plants are preferably Delosperma. In an embodiment of the covering element, within the Crassulaceae plant family the plants are preferably selected from Sedum, Sempervivum, Jovibarba, Coral Carpet, and Tripmadam. In an embodiment of the covering element, within the Sedum plant group the plants are preferably selected from the group of Sedum Album, Sedum Album Minor, Sedum Sieboldi, Sedum Acre, Sedum Mircranthum, and Sedum Lydium. In an embodiment of the covering element, within the Sempervivum plant group the plants are preferably selected from the group of Arachnoideum, Tectorum, Montanum. In an embodiment of the covering element, within the Jovibarba plant group the plants are preferably Globifera. In an embodiment of the covering element, the plants are preferably selected from Sedum, Sempervivum, and Jovibarba. The selected plant families, specifically the selected plants within the families provide the advantageous of plants growing in specific conditions needing none or reduced maintenance when arranged in specific conditions, such as on the tile according to the invention. Reduced maintenance may be maintenance once per 1 to 5 years, more specific 3 to 5 years. The plants that have water retaining properties typically comprise a wax layer or wax type layer over the pores or stomatal apertures of their leaves. This wax may be typed as the epicuticular wax. As soon as the drought period sets in, the leaves will shrink just slightly by the loss of water in the leaves. The wax layer or wax type layer will not shrink or shrink less. This layer will then close over the pores of their leaves preventing further loss of water. This effect prevents further loss of water due to vaporization and diffusion of the vapor through the pores or stomatal apertures.

In an embodiment of the covering element, the inorganic binder material comprises an acid for providing a pH value below 8.4, preferably below 8.3, more preferably below 8.2, most preferably below 8.0. Rainwater falling on the tile and dripping through the tile remains relatively pH neutral, such that contamination to the environment is advantageously minimized or even absent. Furthermore, a tile with a pH value as claimed promotes the growth of plants with water retaining properties, such as Crassulaceae, more specific Sedum. The pH value of the tile is preferably kept above 5.5, more preferably above 5.8, even more preferably above 6.0, most preferably above 6.5. The acid may bind with the other alkaline substances in the inorganic binder material to form chalk or chalk like products for strengthening the mechanical properties of the tile. This advantageously causes a pH value inside the specified range, e.g. a slightly acid environment, typically promoting the growth of the selected plant.

The pH value of the tile may advantageously be added to the thickness, porosity, spacing, and plant selection to provide a favourable growth bandwidth for the selected plant.

In a further embodiment of the covering element, the acid is acetic acid. The use of acetic acid advantageously prevents the forming of smelly, reeking or even stinking gasses during the manufacturing of the tile or covering element. The use of acetic acid may advantageously even prevent the forming of asphyxiating gasses, and flammable gasses during the manufacturing of the tile or covering element. The use of acetic acid may advantageously even prevent the forming of gasses at all during the manufacturing of the tile or covering element. The acid may be 80% acetic acid CAS-Nr.64-19-7. Test have shown that a tile constructed with 80% acetic acid CAS-Nr.64-19-7 and cement ENCI CEM 1 52,5 R provides a more scratch-resistant tile. Also, a tile constructed accordingly resists more pressure, such as centre pressure.

Test have shown that the tile according to an embodiment of the invention, the tile may weigh 5 Kg per 12,5 L volume. The tile according to the invention is typically such lightweight that the tile or more specific multiple tiles may be arranged on a roof or top of a building without the need for additional support for the roof.

In an embodiment of the covering element, the tile comprises 30-74 v/v% pebbles, preferably 35-65 v/v%, more preferably 40-60 v/v%, most preferably 50-65 v/v%. These ranges are advantageously selected from experiments.

In an embodiment of the covering element, the pebbles are recyclable pebbles advantageously making the tile, or at least part of the tile, recyclable and thus more sustainable.

In a further embodiment of the covering element, the pebbles are ceramic pebbles advantageously providing pebbles that won’t interact with the plants or the surroundings of the tile, making the tile, specifically the pebbles, more sustainable.

In an embodiment of the covering element, the ceramic pebbles are selected from recyclable silica, glass and/or clay pebbles advantageously making the tile, or at least part of the tile, recyclable and thus more sustainable.

In an embodiment of the covering element, the tile comprises pebbles in two average cross-sectional ranges; the first average cross-sectional range is 2.5 to 12.5 mm, preferably 3 to 10 mm, more preferably 3.5 to 9 mm, most preferably 4 to 8 mm; and the second average cross-sectional range is 0.3 to 2.5 mm, preferably 0.5 to 2 mm, more preferably 0.75 to 2 mm, most preferably 1 to 2 mm. The size of the pebbles may attribute to the size of the pores. If the pebbles become too large, the pores become too large for plants to have their roots well wedged into the porous. If the pebbles become too small, the pores become too small for roots of the plants growing into the pores at all. Furthermore, the selections of two ranges of pebbles provides the advantage that together with the inorganic binder material a tile with a higher structural integrity, such as an increased load on the tile and/or integrity of the tile over a longer period of time, may be produced.

In a further embodiment of the covering element, the plants are arranged at a side of the tile; and the pebbles in the second average cross-sectional range are arranged substantially in a layer at an opposite side of the tile. The combination of smaller pebbles together with inorganic binder material provides a layer of increased structural integrity. The combination typically also comprises a substantial amount of larger pebbles increasing the structural integrity. The layer is typically arranged away or opposite from the layer holding the plants, or more specifically the roots of the plants. This provides the advantage that the pores at the side of the plants are larger for receiving roots. Further, the two different cross- sectional ranges allow the permeability of the tile for water to be substantially even over the complete thickness of the tile.

In an embodiment of the covering element, the tile comprises wherein the tile comprises 5-35 v/v% inorganic binder material, preferably 10-35 v/v%, more preferably 15- 30 v/v%, most preferably 20-25 v/v%. The inorganic binder material is typically present in an amount less than the volume of the pebbles and the porous combined. In a more preferred embodiment, the inorganic binder material is typically present in an amount less than the volume of the pebbles alone. In a preferred embodiment, the inorganic binder material is present in an amount less than the volume of the porous alone. The binder material may bind the pebbles together and leaves enough pores between the pebbles such that the plants can settle with their roots in the pores. The binder material also may bind the pebbles together in such a way that typically the porous remain open from the outside, or preventing enclosed spaces.

In an embodiment of the covering element, the inorganic binder material is selected from or is a combination of the group of metal oxides, such as CaO, A1203, CuO, MgO, Si02, Fe203; metal carbonates, such as CaC03; metal hydroxides, such as Ca(OH)2; phosphates, and metal sulphates, such as CaS04, such as cement, such as Portland cement, such as clay minerals, such as cement ENCI CEM 1 52,5 R. The inorganic binder material typically comprises amounts of substances, such as oxides, which can be used by the plants, typically in low or extreme low quantities, for growing the plants. These substances may be typed as minerals. The quantities used by the plants may last over more than a decade, typically multiple decades, making the tiles provide essential elements for plant growing almost inexhaustible. The substances may be seen as vitamins supporting the growth of the plants for allowing the plants to survive, blossom, grow, have resilience and/or have colour over a longer period of time, such as over years.

In an embodiment of the covering element, the inorganic binder material is stable over time/durable. The tile is typically used on or on top of buildings for longer periods of time. As the binder material remains stable over time and/or durable, the maintenance is reduced and/or minimalized and the sustainability advantageously increased.

In an embodiment of the covering element, the inorganic binder material advantageously comprises nutrients and/or minerals for promoting or at least facilitating the growth of plants. In an embodiment of the covering element, the inorganic binder material is advantageously substantially pH-neutral. This may prevent or reduce the burning of the roots. It has a further advantage over hydro-cultures in that hydro-cultures require water containing essential supplements for the plants to grow as well as that the pH value of this water needs to have a specific value for allowing the plants to grow. In contrast the current covering element allows plants to grow when only receiving rainwater.

In an embodiment of the covering element, the at least one tile support comprises at least one base, footer and/or at least one spacer. The at least one spacer is advantageously arranged for maintaining the space between the tile and the part of the building whereupon the tile rests or wherefrom the tile is suspended. In another embodiment of the covering element, the at least one tile support comprises at least one surface of the tile arranged for supporting the tile. This at least one surface is advantageously suitable to carry the rest of the tile. In a typically embodiment, the tile seen from above is a rectangle, such as a square, the at least one tile support comprises four tile supports, and the four tile supports are arranged to, at or in the corners of the rectangular tile.

In an embodiment of the covering element, the porous tile is a roof tile. In an embodiment of the covering element, the water exposed part of the building is a roof part and/or a part of the outside side of a vertical wall. In an embodiment of the covering element, the porous tile may advantageously be used to construct a roof.

In an embodiment of the covering element, the tile comprises a plurality of plug holes. The plug holes are adapted to receive a plant, more specifically the root of a plant. The plug holes may be provided with an insert, such as a thimble shaped insert, for receiving the plant, more specifically the root of the plant, in the insert. The insert may support retaining water at a crucial moment in time, such as when the tile is provided with plants or even seeds for growing and settling into the pores of the tile. The inserts may be of material that remains intact over time, or may be of a material dissolving over time. The dissolved material may support the growth of the plants, specifically the plant inserted in the insert.

In an embodiment of the covering element, the pebbles are expanded pebbles comprising internal cavities typically inaccessible to plants, such as roots, and/or water. The expanded pebbles provide the advantage that the total weight of the pebbles, specifically the whole tile or the covering element, is reduced making the covering element more suitable for placement on a roof or suspending the covering element on the side of a wall of a building.

In a preferred embodiment of the covering element, the tile provides a growth bandwidth to the at least one plant, wherein the growth bandwidth of the tile depends on the combination of the plant species, the thickness of the tile being between 1-10 cm, the porosity of the tile being between 0.05-0.5, and the spacing being larger than 1 cm. In a preferred embodiment of the covering element, the growth bandwidth of the tile is configured to promote the growth of plants having water retaining properties, such as water retaining roots, stem and/or leaves, and/or reducing the growth of plants having non water retaining properties, such as roots, stem and/or leaves.

In an embodiment of the covering element, the tile comprises 10-30 v/v% pores, preferably 15-25 v/v%, more preferably 17.5-22.5 v/v%, most preferably around 20 v/v%. Selecting a v/v% for the pores may depend on the type of plant selected to grow on the tile. Grow test may therefore be done to determine the optimum v/v% for the pores.

In an embodiment of the covering element, the covering element is arranged for promoting or at least facilitating growth of plants having water retaining roots, stem and/or leaves, and/or for reducing or even eliminating growth of plants having non-water retaining roots, stem and/or leaves. More specifically in a further embodiment of the covering element, the covering element is arranged for promoting or at least facilitating growth of plants having water retaining leaves, and/or for reducing or even eliminating growth of plants having non-water retaining leaves.

According to another aspect of the invention, a method for producing a covering element for covering a rain-water exposed part of a building and growing plants having water retaining properties, comprising:

- providing a tile having a thickness of at least 1 cm and a porosity of at least 0.05, wherein the tile comprises:

- pebbles;

- an inorganic binder material for binding the pebbles; and

- a plurality of pores;

- providing at least one tile support for spacing the tile from the building at least 0.5 cm; and wherein the thickness, the porosity and the spacing are configured to promote or at least facilitating the growth of plants having water retaining properties and/or reducing or even eliminating the growth of plants having non-water retaining properties;

- providing plant cuts of plants having water retaining properties;

- distributing the plant cuts over the tile; and

- allowing the plant cuts having water retaining properties to grow into the pores of the tile, such that the plant cuts develop roots arranged in the plurality of pores. The advantages of this method are specified throughout the description and figures. According to another aspect of the invention, a method for producing a covering element for covering a rain-water exposed part of a building and growing plants having water retaining properties, comprising:

- providing a tile having a thickness of at least 1 cm and a porosity of at least 0.05, wherein the tile comprises:

- pebbles;

- an inorganic binder material for binding the pebbles; and

- a plurality of pores;

- providing at least one tile support for spacing the tile from the building at least 0.5 cm; and wherein the thickness, the porosity and the spacing are configured to promote the growth of plants having water retaining properties and/or reducing the growth of plants having non-water retaining properties plants;

- providing plant cuts of plants having water retaining properties;

- arranging each of the plant cuts in respective plugs, wherein the plug forms a water retaining cup;

- arranging each of the plugs in respective pores and/or the prefabricated holes

- optionally

- allowing the plant cuts having water retaining properties to grow typically directly into the pores of the tile, such that the plant cuts develop roots arranged in the plurality of pores. The advantages of this method are specified throughout the description and figures. Arranging each of the plant cuts in respective plugs may comprise prepare and selecting plant cuts. Arranging each of the plugs in respective preferably prefabricated holes of the tile typically comprises arranging each of the plugs in respective prefabricated holes on the top side of the tile.

According to another aspect of the invention, a method for producing a covering element for covering a rain-water exposed part of a building and growing plants having water retaining properties, comprising:

- providing pebbles;

- coating the pebbles with inorganic binder material, wherein the inorganic binder material is able to flow;

- filling a mould with the coated pebbles, wherein the mould has a height;

- waiting until the inorganic binder material solidifies for forming the tile having pores and a thickness; - providing at least one tile support for spacing the tile from the building at least 0.5 cm; wherein the thickness, the porosity and the spacing of the tile are configured to promote or at least facilitate the growth of plants having water retaining properties and/or reducing or even eliminating the growth of plants having non-water retaining properties; and

- arranging the plants having water retaining properties in the pores.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which:

Figure 1 schematically shows a cross-section of a covering element;

Figure 2 schematically shows a first detail of a cross-section of a covering element;

Figure 3 schematically shows a second detail of a cross-section of a covering element;

Figure 4 schematically shows a third detail of a cross-section of a covering element;

Figure 5 schematically shows a fourth detail of a cross-section of a covering element; and

Figure 6 shows a covering element.

The figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

LIST OF REFERENCE NUMERALS

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS The following figures may detail different embodiments. Embodiments can be combined to reach an enhanced or improved technical effect. These combined embodiments may be mentioned explicitly throughout the text, may be hint upon in the text or may be implicit.

Figure 1 schematically shows a cross-section of a covering element 23. The covering element comprises a tile 24 and plants 4. The tile comprises pebbles 1 and an inorganic binder material 2. The inorganic binder material is arranged between the pebbles for binding the pebbles together. As the inorganic binder material does not fill up all the voids between the pebbles, the tile comprises a plurality of pores 6 coming forth from the combination of pebbles and inorganic binder material.

The covering element comprises a tile support 25, in Figure 1 two tile supports are shown in 2D. The tile support may comprise a spacer 10. Typically, a square tile has four supports or spacers typically arranged at the four comers of the square tile. The tile support spaces, suspends or places the tile at a distance 8 from e.g. a roof 15. The roof may be covered by a roof finishing layer 14 e.g. making the roof waterproof. The spacing of the tile relative to the roof allows a ventilation 11. The ventilation may cause water coming through the tile to evaporate, such that water or even moist cannot build up behind the tile.

The plants have roots 5 filling part of the pores 6. The tile has a thickness 7. The combination of the thickness, the pores and the plants filling part of the pores cause a permeability 9.

During production, the pebble is typically covered or coated 3 with inorganic binder material in a state that the inorganic binder material is fluid or in a state that the material may flow. When thereafter the inorganic binder material is hardening, the inorganic binder material is solidifying and binding the pebbles in a predefined shape, such as a mould for a tile.

Figure 1 further shows another tile arranged at a mutual distance 12 horizontally from the tile 24. The mutual distance advantageously stimulates the ventilation 11.

Figure 2 schematically shows a first detail of a cross-section of a covering element 23. A detail of the tile 24 is shown. The tile may comprise a support layer 16 arranged at an opposite side of the side holding the plants. The support layer typically comprises pebbles having on average a cross-sectional size smaller than the pebbles arranged in the layer holding the roots of the plants. The combination of the pebbles of smaller cross- sectional size with the inorganic binder material provide a layer with increased structural integrity allowing more weight to be carried by the tile and/or maintaining the integrity of the tile for a longer period of time.

The tile may further comprise a comer having pebbles having on average a cross-sectional size smaller than the pebbles 18 arranged in the layer holding the roots of the plants. The corners of the tile may therefore be provided with increased structural integrity for providing a surface whereupon the tile can rest on the tile support 25, such a spacer 10. The spacer may comprise an attacher 19 for attaching the spacer to a part of the building, such as a roof. The attacher may comprise glue or any other binder. The attacher may comprise a screw.

Figure 3 schematically shows a second detail of a cross-section of a covering element 23. A detail of the tile 24 is shown. The covering element comprises a tile support 20 integrated with the tile. The integrated tile support provides increased integrity to the tile. The integrated tile support may comprise a protrusion e.g. a pultruded profile, such as a spacer or distance holder for spacing the tile at a distance from a part of the building.

Figure 4 schematically shows a third detail of a cross-section of a covering element 23. A detail of the tile 24 is shown. The tile comprises a support layer 16 comprising an internal raster structure increasing the structural integrity of the tile as a whole. This support layer may prevent the tile from disintegrating over time into lose parts that even could cause damage.

Figure 5 schematically shows a fourth detail of a cross-section of a covering element 23. A detail of the tile 24 is shown. The detail further shows a tile support 25 comprising a spacer 10, and a fastener 22. The tile, preferably also the spacer, has a through hole configured for receiving the fastener. The fastener is arranged for fastening the tile to the spacer and preferably also to the part of the building, such as the roof. The tile support may optionally comprise a damper 21. The damper provides resilience and bias for controlled play for absorbing contraction and expansion of fastener relative to the tile and preferably also the spacer. The damper thus reduces the amount of uncontrolled play that may occur over time.

Figure 6 shows a covering element 23 comprising a tile 24 and plants 4. The covering element further comprises at least one tile support, not shown in Figure 6. Figure 6 further shows a tile having a support layer 16.

Tests or measurements have shown that per square metre of tile about 50 litre of pebbles may be used. Further, the inorganic binder material may be composed of 12-13 Kg cement, such as of enci CEM I 52.5 R, 200 gr of minerals and water to mix the inorganic binder material to a slurry capable for coating the pebbles and flowing between the pebbles when setting inside a mould for thereafter drying out and binding the pebbles in the shape of a tile. The amount of inorganic binder material may vary depending on the average cross- sectional size of the pebbles.

The inorganic binder material, such as cement, is typically also porous, adding to the pores between the pebbles. Notable is that the pores in the inorganic binder material are such small that the capillary effect will hold the water or moist over a longer period of time. The capillary effect and/or the absorption effect may account for about 10-12 litres of water per square metre to remain in the tile, when the covering element is arranged to a horizontal part of the building. These effects may account for about 5-6 litres of water per square metre to remain in the tile, when the covering element is arranged to a vertical or inclined part of the building. The amount of water directly absorbed by the inorganic binder material and/or pebbles is estimated to be around 2 litres of water. This amount of water may at least partly become available to the plants growing on the tile for sustaining specific types of plants on the tile. Furthermore, at least temporarily storing these amounts of water may contribute to regulating or at least clipping the peak of high volumes of water from downpour, such as heavy downpour, for limiting the overload of drainage systems of houses or even cities. The combination storing at least temporarily water under as well as inside an elevated covering element may retain a 100 mm downpour or rain. Retaining water is typically interpreted as creating a restricted and/or controlled run off to eliminate the peak load and/or quantity of water.

Examples, embodiments or optional features, whether indicated as non-limiting or not, are not to be understood as limiting the invention as claimed.

It should be noted that the figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

The term “substantially” herein, such as in “substantially all emission” or in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

The term "functionally" will be understood by, and be clear to, a person skilled in the art. The term “substantially” as well as “functionally” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective functionally may also be removed. When used, for instance in “functionally parallel”, a skilled person will understand that the adjective “functionally” includes the term substantially as explained above. Functionally in particular is to be understood to include a configuration of features that allows these features to function as if the adjective “functionally” was not present. The term “functionally” is intended to cover variations in the feature to which it refers, and which variations are such that in the functional use of the feature, possibly in combination with other features it relates to in the invention, that combination of features is able to operate or function. For instance, if an antenna is functionally coupled or functionally connected to a communication device, received electromagnetic signals that are receives by the antenna can be used by the communication device. The word “functionally” as for instance used in “functionally parallel” is used to cover exactly parallel, but also the embodiments that are covered by the word “substantially” explained above. For instance, “functionally parallel” relates to embodiments that in operation function as if the parts are for instance parallel. This covers embodiments for which it is clear to a skilled person that it operates within its intended field of use as if it were parallel.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices or apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device or apparatus claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to an apparatus or device comprising one or more of the characterising features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.