The invention relates to an outside wall cladding element for fastening on a wall, comprising a fastening system, outside wall cladding material and an outside wall element having one or several openings which form a passage from the open air to a cavity which is formed between the outside wall cladding material and the wall, a venturi element for use in an outside wall cladding element, an outside wall provided with an outside wall cladding element and a method for fastening an outside wall cladding element to a wall.

Such an outside wall cladding element can be used to ventilate outside walls. Outside walls are mainly ventilated to remove undesired moisture from the outside wall structure which has entered the outside wall structure as a result of leakage or condensation. In addition, the ventilation in ventilated outside walls has a cooling effect. An outside wall which is heated by solar radiation can replace a part of the hot cavity air with cooler ambient air by ventilation. Ventilation thus ensures that a part of the thermal load is emitted to the environment so that the outside wall structure remains relatively cool.

The ventilation of an outside wall can be improved by increasing the number of ventilation openings, increasing the depth of the cavity or by enlarging the ventilation openings.

In a ventilated outside wall, the ventilation openings are generally situated in the following locations:

• as a vertical or horizontal open joint between the outside wall cladding material parts

underneath the roof trim

• underneath the window openings

above the window openings

• on the underside of the outside wall, but above ground level

A drawback of the known solutions for ventilating a ventilated outside wall is that the moisture regulation is indeed controlled efficiently, but that the heat from incident sunlight cannot be dissipated sufficiently. An outside wall which is irradiated by sunlight becomes considerably hotter than the surroundings. This temperature increase results in the heat being conducted through the outside wall structure to the inside of the building. This leads to an increased thermal load of the building. The result thereof is that, on sunny days, the interior of the building reaches an unpleasant temperature or that more energy is being used for cooling the building. It is customary to limit the transfer of this heat to the interior of the building by increasing the thermal insulation value of the outside wall.

When using solar panels in an outside wall, it is also important to reduce the temperature increase in order to cool the solar panels. With the most popular types of solar panels, the electrical yield decreases when the temperature increases. A significant portion of the heat can be dissipated via the cavity of the outside wall, provided there is sufficient ventilation action. In the context of these inventions, solar panels form a special kind of outside wall cladding materials. In the context of the present invention, solar panels are outside wall cladding materials which can convert sunlight into electrical energy.

A drawback of increasing the depth of the cavity is that the total outside wall structure becomes thicker, resulting in an increased use of surface area. In addition, the supporting structure becomes heavier and more expensive due to the increased use of materials.

A drawback of enlarging the ventilation openings is that this leads to a reduction in the aesthetic quality of the outside wall and increases the risk of leakage and also the risk of vermin, such as mice and insects, occupying the outside wall structure.

A drawback of increasing the number of ventilation openings is that this leads to a reduction in the aesthetic quality of the outside wall and that this increases the risk of vermin and also the risk of unacceptable leakage.

A drawback of increasing the insulation value of the outside wall is that this results in increased costs and will also, in most cases, result in a thicker outside wall structure.

This means a less efficient use of the surface area.

Solar panels can be cooled by a known system with a heat exchanger and by installing a liquid or gaseous medium behind the solar panels. There are examples of solar panels which can be combined with thermal solar collectors by installing, for example, a water system behind the solar panel. A drawback is that this may result in an increase in the costs of the outside wall structure and increases the risk of failures. The solar collector operates in an unsatisfactory way because it operates at an undesired low temperature out of necessity.

This known system with heat exchanger and a gaseous or liquid medium can also be used for outside walls without solar panels. The increased costs and the risk of failure of the system are a drawback.

It is an object of the present invention to develop an outside wall cladding element which discharges the energy which an outside wall receives in the form of solar radiation partly via the cavity of the outside wall. It is another object of the present invention to limit as much as possible the temperature increase which solar panels which are incorporated in the outside wall experience through solar radiation by dissipating a part of this heat via the cavity. It is another object of the present invention to improve the ventilation in the cavity of a ventilated outside wall without moving parts.

According to the invention, this object is achieved by an outside wall cladding element for fastening on a wall, comprising a fastening system, outside wall cladding material and an outside wall element having one or several openings which form a passage from the open air to a cavity which is formed between the outside wall cladding material and the wall, with the openings being slit-shaped and the outside wall element comprising a venturi element.

The slit-shaped ventilation openings comprise respectively a venturi element which makes effective use of an air flow along the outside wall and the local air pressure on the outside wall.

In the present invention, for example, a plate-shaped material, such as HPL compact, fibre cement, glass fibre-reinforced composites, aluminium, aluminium laminate, steel or glass may be chosen as outside wall cladding material.

In the present invention, a fastening system may consist of a wooden, metal or fibre- reinforced structure, the main aim of which is' to attach the ou tside wall cladding materials to the building structure. It is customary to attach the fastening system on the inner wall. At locations on the outside wall where the air pressure is relatively high, openings are provided in the outside wall through which air can easily reach the cavity of the outside wall. The air pressure on an outside wall is highest at approximately 2/3 of the height of the building, as air speed is lowest at this height. In a preferred embodiment, the surface around the openings has a shape which uses the air flowing past and the

Bernoulli principles to create a higher pressure at the location of the openings. These elements may have a shape which resembles a dent, an inverted wing shape, an aerofoil or an inverted venturi. In the present invention, all these elements are referred to as positive venturi elements.

At locations on the outside wall where the air speed is high or where the air pressure is relatively low, deformations and elongate openings are provided in the outside wall, as a result of which the air can leave the cavity relatively easily. The openings which are intended to allow the air to leave the outside wall are of a design which uses the air flowing past and the Bernoulli principles to create a reduced pressure at the location of the opening. These elements are elongate and may have a shape resembling a thickening, a wing shape, an aerofoil or venturi. In the present invention, all these elements are referred to as negative venturi elements.

The elongate elements which are used to suck air out of the cavity can be combined with or incorporated in a roof trim, in a ledge, above a window opening, in the joint between outside wall materials or on the underside of an outside wall part. In a preferred embodiment, the elements which are intended to suck air out of the cavity are fitted horizontally.

For the present invention to function satisfactorily, it is not necessary to apply all options to increase the ventilation in the same outside wall. It is, for example, possible to achieve improved ventilation by building a ventilated outside wall according to the prior art in which the roof trim is replaced by a roof trim into which a venturi element has been incorporated.

In another embodiment, the outside wall cladding element may be provided with a weather cornice, in which the venturi element is incorporated in the weather cornice. It is also possible, for example, to achieve improved ventilation in the cavity at the location of a solar panel by incorporating a venturi element in the joint between the solar panel and construction elements of the outside wall cladding material, for example, by installing a profile with a design which has a sucking action. If a grille with or without a special design is placed under the solar panel, the ventilation behind the solar panel can be improved further.

In a further embodiment of the present invention, a valve is installed in the venturi element by means of which the ventilation action of this element can be controlled. On cold days, for example, it may be advantageous to limit the ventilation action. On stormy days, it may be advantageous to limit the ventilation action. In case of fire, it may be advantageous to limit the ventilation action.

In a further embodiment of the present invention, the venturi elements are provided with intumescent materials which expand at high temperatures, for example, in excess of 200° Celsius. In this way, the ventilating action can be substantially interrupted in case of fire.

In a further embodiment of the present invention, the venturi elements are incorporated in outside wall cladding materials by treating these materials, for example, by a bending treatment or by pressing, moulding, milling, sawing, drilling, cutting.

Although the invention will be described with reference to a number of embodiments, the invention is not limited thereto. The embodiments discussed below are only examples of possible interpretations of the invention and it will be clear to the person skilled in the art that the advantages of the invention can also be achieved in another way.

The invention will be described in more detail with reference to the attached drawings, in which:

Fig. 1 shows a known outside wall cladding element near an edge of a roof;

Fig. 2 shows an outside wall cladding element according to the invention near an edge of a roof;

Fig. 3 shows a known outside wall cladding element in which the outside wall cladding material comprises panels;

Fig. 4 shows an outside wall cladding element according to the invention in which the outside wall cladding material comprises panels;

Fig. 5 shows a joint between two outside wall cladding panels in a known outside wall cladding element;

Fig. 6 shows a joint between two outside wall cladding panels provided with a plurality of slit-shaped openings and venturi elements according to the invention; Fig. 7 shows a known outside wall cladding element near the underside of the outside wall;

Fig. 8 shows an outside wall cladding element according to the invention near the underside of the outside wall;

Fig. 9 shows a known outside wall cladding element near a window opening;

Fig. 10 shows an outside wall cladding element according to the invention near the window opening;

Fig. 1 1 shows a top detail of a known outside wall cladding element near a window opening;

Fig. 12 shows a top detail of an outside wall cladding element according to the invention near a window opening; and

Fig. 13 shows an outside wall cladding element according to the invention provided with a roof trim and an adjustable valve. In the figures, identical elements are denoted by the same reference numerals.

Fig. 1 shows a ventilated outside wall provided with a known outside wall cladding element and an edge of a roof. The outside wall comprises a wall 1. The outside wall cladding element comprises fastening elements of the fastening system 3 and outside wall cladding materials 4. Thermal insulating materials 2 may be installed in front of the wall. Locally, fastening elements of the fastening system 3 run through the thermal insulating materials 2 to which the outside wall cladding materials are fitted. Between the outside wall cladding materials 4 and the thermal insulating materials 2, a cavity 5 is provided through which air can move freely. The fastening system 3 hardly forms an obstruction to the movement of air through the cavity. Furthermore, the outside wall cladding element may comprise a roof trim 5 which is fitted at the top of the outside wall. Furthermore, the outside wall cladding element is provided with slit-shaped openings. Ventilation air can be exchanged with the cavity via the slit-shaped opening between the roof trim and the outside wall cladding materials.

Fig. 2 shows an outside wall cladding element according to the invention which is attached to an outside wall, such as the outside wall from Fig. 1. The outside wall cladding element is largely identical to the outside wall cladding element as described in Fig. 1, but differs in that the traditional roof trim 6 has been replaced by a roof trim 7 according to the invention provided with a venturi element. An air flow which flows on the outside, along the outside wall and the convex, spherical shape of this roof trim 7, produces a pressure drop at the location of the slit-shaped ventilation opening to the cavity, thus improving the ventilation of the outside wall. Fig. 2 furthermore shows that a cross section of the venturi element at right angles to the slit-shaped opening has a convex shape.

Fig. 3 shows a known outside wall cladding element, in which the outside wall cladding materials comprise construction elements, for example, panels 4 which may be separated from each other by means of joints. Fig. 3 furthermore shows the structure of a known joint 8 between the panels 4 as often encountered in an outside wall system as described for Fig. 1. This known joint 8 is provided with a slit-shaped opening. Fig. 4 shows a joint in an outside wall cladding element according to the invention. The joint is largely identical to the joint as illustrated in Fig. 3. The difference is that the joint 9 in Fig. 4 is provided with a venturi element according to the invention. An air flow which flows on the outside, along the outside wall and along the convex, spherical shape of the joint 9, produces a pressure drop at the location of the slit-shaped ventilation opening to the cavity, thus improving the ventilation of the outside wall. Fig. 4 furthermore shows that a cross section of the venturi element at right angles to the slit-shaped opening has a convex shape.

Fig. 5 shows a known joint 8 between outside wall cladding materials 4 in a known outside wall cladding element as is often encountered in an outside wall system as described for Fig. 1. This known joint 8 is provided with a slit-shaped opening.

Fig. 6 shows a joint which is largely identical to the joint illustrated in Fig. 5. The difference is that the joint 7 in Fig. 6 has been replaced by an outside wall part 10 provided with a number of, for example, four, slit-shaped openings in which a venturi element has been fitted. An air flow which flows on the outside, along the outside wall and along the concave, hollow shape of these venturi elements and the slit-shaped openings 10, produces a pressure increase at the location of the ventilation openings to the cavity, thus improving the ventilation of the outside wall.

Fig. 7 shows a known outside wall cladding element near the underside of the outside wall shown as is often encountered in an outside wall system as described with reference to Fig. 1. On the underside, a grille 1 1 is provided which makes ventilation possible, but which, due to the small openings in the grille, makes it more difficult for vermin to enter the outside wall.

Fig. 8 shows an outside wall cladding element according to the invention near an underside of an outside wall which is largely identical to the underside of the outside wall as illustrated in Fig. 7. The difference is that the underside of the outside wall is provided with a venturi element. As a result of the convex, spherical shape of this venturi element 12, an air flow which flows on the outside, along the outside wall, produces a pressure drop at the location of the slit-shaped ventilation opening to the cavity, thus improving the ventilation of the outside wall.

Fig. 9 shows a known outside wall cladding element near a window opening.

Underneath the window opening, a ledge 13 is fitted which projects above the top end of the outside wall material 4. Between the ledge 13 and the outside wall material, a slit-shaped opening is provided which makes a ventilation stream possible.

Fig. 10 shows an outside wall cladding element according to the invention near a window opening which is virtually identical to the outside wall provided with a window opening as illustrated in Fig. 9. The difference is that the underside of the ledge is provided with a venturi element 14, in which a cross section of the venturi element at right angles to the slit-shaped opening has a convex shape. As a result of the convex, spherical shape of this embodiment of this profile 14, an air flow which flows on the outside, along the outside wall, produces a pressure drop at the location of the ventilation opening to the cavity, thus improving the ventilation of the outside wall.

Fig. 1 1 shows a detail of an outside wall and a top detail of an outside wall cladding element above the window opening, illustrated as constructed in an outside wall system as described for Fig. 1. A horizontal strip of outside wall cladding material 15 is fitted underneath the thermal insulating material 2 in order to achieve a functional and aesthetic finish for this outside wall detail. Between the strip of outside wall cladding material and the vertical outside wall cladding, a slit-shaped opening 16 is left for ventilation.

Fig. 12 shows a detail of an outside wall and a top detail of the outside wall cladding element above the window opening, which are virtually identical to those of the underside of the outside wall as illustrated in Fig. 11. The difference is that a venturi element 17 is fitted above the horizontal strip of outside wall cladding material 1 , the cross section of the venturi element at right angles to the slit-shaped opening having a convex shape. Due to the spherical shape of this embodiment of this element 17, an air flow which flows on the outside, along the outside wall, produces a pressure drop at the location of the ventilation opening to the cavity, thus improving the ventilation of the outside wall.

Fig. 13 shows an outside wall cladding element of virtually the same

construction of the outside wall cladding element as illustrated in Fig. 1. The difference is that the known roof trim 16 has been replaced by a roof trim 18 according to the invention with a venturi element and a slidable valve 19, the cross section of the venturi element at right angles to the slit-shaped opening having a convex shape. Due to the spherical shape of this roof trim 18, an air flow which flows on the outside, along the outside wall, produces a pressure drop at the location of the ventilation opening to the cavity, thus improving the ventilation of the outside wall. The valve 19 makes it possible to control the effect of the roof trim 18. Example 1 :

On a south-facing outside wall element having a width of 2.4 metres and a height of 1.2 metres in the Netherlands, the average heat flow through the outside wall staicture to the inside of a building is measured on a sunny day at an outside temperature of 25 degrees and an indoor temperature of 20 degrees. The air speed in the cavity is also measured, at a height of 20 metres.

The outside wall is constructed as shown in Fig. 3. The outside wall consists of a concrete inner wall 1 having a thickness of 10 cm, in front thereof a thermal insulating material (2) is arranged having a thickness of 5 cm and an insulation value of 0.045 W/mK. In front thereof, a cavity 5 having a cavity depth of 4 cm is situated. In front of the cavity, a dark grey outside wall cladding material 4 having a thickness of 1 cm is fitted. The outside wall cladding materials are attached to the inner wall (1) via round hardwood elements 3 having a thickness of 9 cm and a diameter of 9 cm which are attached to the inner wall 1 in a grid of 60*60 cm. This construction of the outside wall makes it possible for air to flow freely through the cavity, both in the horizontal and vertical direction. The decorative outside wall materials are 60*60 centimetres in size and they are separated from one another by an open joint having a width of 1 cm. In this outside wall, a conventional roof trim 6 has been used. On the sides, the outside wall part is closed so no exchange of cavity air with the ambient air takes place. On the underside, the outside wall part is provided with a grille having openings with a cross section of 8 mm and an open fraction of 80%.

Measurements show that the air flow in the cavity is directed vertically upwards and has a speed of 0.2 m/s. There is a heat flow of 16 W/m ² through the outside wall structure to the inside of the building.

Example 2:

The same outside wall part as in Example 1 , except that the roof trim 6 has been replaced by a roof trim to which an element 7 as described in the present invention and as described in Fig. 2 is fitted which has a spherical shape with a diameter of 7 cm and a slit-shaped opening with an inner diameter of 8 mm.

Measurements show that the air flow in the cavity is directed vertically upwards and has a speed of 0.6 m/s. There is a heat flow of 9 W/m ² through the outside wall structure to the inside of the building.

Examples 1 and 2 show that replacement of a conventional roof trim with an element according to the invention results in a significant reduction of the heat flow through the outside wall structure to the inside of the building, as it drops from 16 W/m ² to 9 W/m ² . Simultaneously, an increase in the air speed in the cavity from 0.2 m s to 0.6 m s is measured. By means of the element (6) according to the invention, the cavity can dissipate more solar heat by means of the ventilation air.