GB1558504A

GB1558504A - Composite panel more more particularly facade element

Info

Publication number: GB1558504A
Application number: GB30912/76A
Authority: GB
Original assignee: BFG Glassgroup GIE
Current assignee: BFG Glassgroup GIE
Priority date: 1975-08-12
Filing date: 1976-07-23
Publication date: 1980-01-03
Also published as: DK144278B; FR2321025A1; FR2321025B1; ATA473176A; NL7608873A; NL182499C; SE413255B; DK362176A; NL182499B; AT352967B; SE7607588L; NO145518C; CH615478A5; NO762789L; DK144278C; NO145518B; IT1062485B

Description

(54) COMPOSITE PANEL, MORE PARTICULARLY FACADE ELEMENT (71) We, BFG GLASSGROUP, a French body corporate, of 43 Rue Caumartin, F75009 Paris, France, do hereby declare the invention, for which we pray that a patcnt may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a component panel having a substantially transparent first panel, a substantially opaque second panel, situated at a distance behind the first panel to produce a gas-filled inter-panel space and an edge structure which maintains the two panels at a distance from each other.

For architectural reasons there is a constantly growing demand for the external walls of buildings to be clad with facade elements which are matched to the glazing units which cover the window openings of the building so that the impression of a completely uniform facade is given to the observer of the building. To this end, it is necessary that the visual impression given by reflection of light from the facade elements is the same as that produced by the window panes, usually insulated glass panes, by means of which the window openings are glazed. If these are insulated glass panes with a heat-reflecting coating of the type used to an increasing degree to give protection against sunlight and more particularly for reasons of energy conservation, it will also be appropriate to construct and coat the facade panel elements through which the external building wall portions between the window openings are clad, by analogy to the glass panes, more particularly insulated glass panes, so as to ensure that the facade produces a uniform impression for the observer.

The German Offenlegungsschrift 2,141,509 already discloses a component panel, namely a facade element, of the initially described kind for cladding those wall portions of buildings or the like that are situated between window openings, are glazed with insulated glass panes comprising of individual panes situated at a distance from each other and whose reflection properties are modified by contrast to multiple glass panes comprising untreated glass panes, more particularly by a heat-reflecting coating of a surface which is associated with at least one of the individual panes and is nearest to the space between the panes, the first panel being a transparent external panel corresponding to the external panel of the insulated glass panes and being situated on the outside after installation and the second panel is an internal opaque and substantially grey panel situated behind the first panel whose colour and brightness impression when viewed from the outside of the building in conjunction with the external panel simulates the colour and brightness impression of the internal space which is enclosed by the insulated glass panes. In the facade element according to the German Offenlegungsschrift 2,141,509 the internal panel comprises an opaque metal plate which is coated with pigmented or dyed coating materials on the surface nearest to the interpane space which is filled with air.

The metal plate is coloured, substantially grey, so that an observer of the building receives the impression of a continuous facade comprising the insulated glass panes which cover the window openings and the facade panel elements when seen in conjunction with the reflection properties of the said facade element. In the known facade element the air-filled inter-pane space between the outer panel comprising a glass pane and the inner panel situated at a distance behind the outer panel and consisting of metal, has a thickness by which the resistance to thermal conductivity through the facade element is made as large as possible.

A known facade element of this kind can be satisfactorily used as parapet slab on a ventilated cold facade where the facade element is disposed at a distance from the external wall of the building. However, difficulties arise if the known facade element is to be utilized for an unventilated cold facade or with a hot facade since the absence of back ventilation causes a build-up of the heat absorbed in the inner panel due to the sun radiation which passes through the transparent outer panel. The build-up of heat is due to the fact that either, namely in the case of an unventilated cold facade, there is an air cushion between the building wall snd the inner panel to prevent the dissipation of heat energy absorbed in the inner panel, or in the case of a hot facade, the inner panel itself is thermally insulating or is backed by a thermally insulating stratum.

The object of the invention is to propose a component panel, more particularly a facade element of the kind described hereinbefore, which can be used in conjunction with unventilated cold facades and can also be used as a hot facade element, avoiding excessive temperature rise of the inner panel.

According to the invention there is provided a composite panel for use as a facade element for cladding wall portions of buildings which are disposed between window openings and are glazed by insulating glass panes, the panel comprising a first transparent panel and a second, opaque panel parallel with the first panel and spaced therefrom to define therewith an inter-panel space, the edges of the panels being supported by an edge structure, said inter-panel space being filled with a gas, the nature of the gas and the width of said inter-panel space, corresponding to the gap between said first and second panels, being such that the resistance to heat flow across said interpanel space, between said first and second panels, is no greater than would be the case if said gas were air and the width of said space were 3 mm.

Composite panels embodying the invention are particularly suited to cladding those wall sections of buildings which are situated between window openings which are glazed by insulating composite glass panes, each comprising individual panes situated at a distance from each other, and in which the reflection properties of each said insulating glass pane has been modified, as compared with a composite glass pane comprising untreated individual glass panes, more particularly by providing a heat-reflecting coating disposed on a surface, adjacent the space between the individual panes, provided by one of the individual panes. When panels embodying the invention are used for cladding such a building, they are mounted with the transparent first panels exposed outwardly of the building and the second panels are so coloured that the colour and brightness impression afforded -by- the composite panels when viewed from the outside of the building, i.e. when the second panels are viewed through the transparent first panels, simulates the colour and brightness impression of the internal space enclosed by the individual glass panes of the composite insulating panes with which the window openings are glazed.

If the inter-pane space in the composite cladding panel is filled with air, the width of the said space should not exceed 3 mm.

A minimum width of the inter-pane space is not specified as it is merely necessary to ensure that there is some separation between the first and second panels, providing a gas filled space, in order to ensure between the inner and the - outer panel (the first and second panel will be referred to hereinbelow throughout as the outer and inner panel respectively) a change in refractive index between the transparent first panel and the gas or air in the inter-panel space as required to achieve the desired reflection properties.

A particularly preferred embodiment of the invention which confers upon the facade element the thermal insulating properties which are desirable for use with a hot facade is characterized by an insulating layer with low thermal conductivity bearing upon the side of the opaque second panel, i.e. the inner panel, which side, when the composite panel is installed, is nearest to the building wall and therefore faces away from the interpanel space. In this preferred embodiment, the problem of heat build-up in the inner panel is in all other respects the most serious but is avoided by dissipating the absorbed heat to the outer panel via the inter-panel space which is very narrow.

In embodiments of the invention, a heatreflecting coating may be provided either on the internal surface of the outer panel which is nearest to the inter-panel space or on the external surface of the inner panel which is nearest to the inter-panel space, more particularly if the insulated glass panes which cover the window openings have the same construction, so that a completely smooth facade is obtained which no longer reveals the difference between the window openings and wall parts.

In another embodiment, which can be used for unventilated cold facades as well as for hot facades, an insulating stratum of glass foam, foam plastics or the like, is provided on the rear, i.e. on the inner surface of the panel which is situated at a distance behind the outer panel and is nearest to the building wall, and it is also possible to provide a closing plate consisting of a metal or the like, to complete the facade element. In known component panels of the kind to which the invention relates, the fact that the heat absorbed in the rear, grey panel (which simulates the building interior as viewed through glazed window openings), cannot be dissipated is due in significant measure to the thermally insulating properties of the inner panel construction. In such known panels, if subjected to strong sunlight, the inner panel and the insulating layer associated therewith can be heated to temperatures in excess of 100"C. Such large temperature rises cannot be tolerated not only because of the mechanical stresses on the edge bonding resulting therefrom, but also because it can cause severe distortion of the outer panel and in some cases of the inner panel, thus impairing the facade element reflection properties which are very sensitive to changes of form of the panes. This would vitiate the desired object, namely to provide a unified facade in which the insulated glass panes or the like that cover the window openings as well as the facade elements disposed therebetween and covering the wall portions provide ifi ois .vcr with the same impression of reflection.

The problem of heat, which is a1Jsor'szd h the said rear grey panel, and cannot be sufficiently rapidly dissipated because of the high thermal conductivity resistance of the thermally insulating layer between the inner panel and the wall of the building is solved according to the invention in a surprisingly effective manner in that by complete contrast to the method provided for insulating glass panes and also adopted for the cold facade element according to the German Offenlegungsschrift 2,141,509 the thickness of the inter-panel space is reduced so that the heat absorbed in the inner panel or in its pigmented layer can be readily transferred by thermal conduction to the outer panel from which it is dissipated to atmosphere.

While a relatively thick inter-panel space is selected for insulated glass panes in order to increase the thermal conductivity resistance in the same way as in the facade element according to the German Offenlegungsschrift 2,141,059, which was explained initially, the distance between the outer panel from the inner panel according to the invention is so small, i.e. the inter-panel space is so thin, that the heat which cannot be dissipated from the facade element to the rear through the insulating layer is transferred by thermal conduction to the outer panel and can be dissipated from there to atmosphere.

In the facade element according to the invention in which the outer and inner panel are spaced as closely as possible, i.e. less than 3 mm if the inter-panel space is filled with air-the inter-panel space can of course be thicker when using a gas such as helium in accordance with the improved thermal conductivity of the said gas by virtue of a reflection coating which is provided on the outer panel or inner panel surface nearest to the inter-panel space, the said reflection coating corresponding with that of the window panes associated with the same facade and being also disposed on the same surface as in the window pane to ensure that the windows and the wall sections which are clad by the facade elements have the same reflection to the exterior. The inner panel is either backed with a grey colour surface which simulates the space background of the window or has throughout the colour of the part thereof affording that face of the second panel which faces toward the first panel so that the external appearances of windows and facade portions are made as like to one another as possible since the identical reflection properties of window panes and facade elements are not sufficient to this end. The insulating layer preferably provided on the rear of the facade element permits the desired use of the same as a hot facade element, the resultant heat dissipation problem being solved by the extremely short distance between outer and inner panel as provided by the invention by contrast to the conventional procedure adopted for insulated glass panes or the like.

It is possible, in embodiments in which such an insulating layer is provided on the rear of the facade element, and in which said insulating layer at least partly comprises an insulating space, to fill said insulating space with a gas having a lower thermal conductivity than air, more particularly a heavy gas, so that the facade element thickness can be substantially reduced while maintaining satisfactory thermal insulation (hot facade element). The thickness of said inter-panel space must of course be kept correspondingly small. Gases having a poor thermal conductivity include CO2, SFG and gaseous fluorocarbon or fluorohydrocarbon compounds such as sold under the Registered Trade Mark "Freon". Thermal transfer with an unchanged thickness of the facade element can be substantially reduced if the heavy gas fills cavities of the insulating layer and spaces between said layer and the rear closing plate and thus occupies a substantial volume.

Composite panels according to the invention, referred to hereinbefore and subsequently briefly as "facade elements", can of course be used not only in building construction for cladding the outer elevation of buildings but also in other applications.

Thus composite panels embodying the invention may be used in all cases in which wall portions situated between glazed window openings, for example including those of the control stands or crane cabs in hot plants or in other internal structural applications, are to have reflection properties identical with those of the glazed window openings.

The term "outer panel" therefore always refers to the panel of the facade element nearest to the observer and distal with respect to the wall. This side of the building or the like is therefore also described as the "outside of the building" although this is not intended to express a restriction to building walls.

A further improvement of the facility for using the component panel according to the invention as a hot facade element is achieved in a further preferred embodiment of the invention by the insulating layer being formed through a gas-filled space disposed between the second panel and the closing panel, said space being subdivided into a plurality of chambers by at least one intermediate bulkhead extending parallel with the second panel and the closing panel.

The essential feature of this embodiment of the invention is that by utilizing the satisfactory dissipation according to the invention to the outside of the heat absorbed in the insulating layer or in the inner panel, the thermal insulation which is achievable with reference to the thickness of the insulating layer is increased by using a "sandwich construction" of gas-filled chambers and by using bulkheads to divide said chambers from each other instead of using a solid insulating layer. Preferred embodiments also provide that the insulating layer has two, three or four bulkheads each having a maximum thickness of 1 mm, with a corresponding number of gas-filled chambers It has also been found that the step by which the gas-filled inter-panel space between the outer panel and the inner panel is made as small as possible not only has the effect of avoiding excessive temperature rise of the inner panel or of the insulating layer due to the sun energy absorbed therein, but in addition minimizes the transmission of the facade element for sun energy in optimum manner. This results from the consideration that the thermal transfer resistance between the inner panel which absorbs the transmitted residue of the sun radiation and the outer atmosphere must be as small as possible in relation to the thermal transfer resistance between the inner panel and the building wall if the transmission of the facade element for sun energy is to be minimized in the manner described above.

It has been found that in a facade element in which the thickness of the gas-filled interpanel space is 9 mm, 27.6% of the energy absorbed in the opaque inner panel or insulating layer is transmitted into the inner space where the corresponding value for a facade element with an inter-panel space of only 3 mm thickness amount to 11.3%. In a facade in which the ratio between window and parapet surface area is 1:1 this is equivalent to an increase of energy transmission through the window pane of 27.6- 11.3, i.e. approximately 16%.

It is therefore of particular interest if the thickness of the inter-panel space can be made even smaller than 3 mm. This can be advantageously achieved by facade elements having suitable edge configurations. It should be noted that facade elements whose pane nearest to the outer space comprises a reflecting single pane, are of course advantageous in terms of transmission for sun energy and this is also the case in relation to an aluminium facade panel of low reflection.

In an embodiment of the invention, in order to increase the thermal insulation of the insulating layer, that the space between the inner panel, situated at a short distance behind the outer panel, and the closing panel which closes the facade element with respect to the building wall, is filled with a gas of low thermal conductivity, more particularly with a gas heavier than air, and is subdivided into thin chambers by means of a plurality of heat-reflecting thin bulkheads, for example by means of bulkheads of tensioned aluminium foil or other material coated with aluminium foil so that the transfer of heat through the gas which fills the space forming the insulating layer takes place only by conduction without convection. Since the metal foil, to which preference is given, more particularly aluminium foil, almost completely interrupts the exchange of radiation between the individual bulkheads it follows that part-chambers are formed with a high thermal transfer resistance. As an example, SF, may be used as the charging gas, and the distances between bulkheads may be between 1 mm and 5 mm.

It is particularly advisable to construct the bulkheads so that both sides thereof are heat-reflecting, namely by using a core of plastics sheeting or the like, both sides of which are again covered with heat-reflecting metal foil or by constructing the bulkheads completely of tensioned metal foil such as aluminium foil or the like. If the core of the thin bulkheads, covered in heat reflecting manner on both sides by the aluminium foil, is constructed so as to be fire-retardant, for example by the use of asbestos, endothermal material or the like, it will also be possible to utilize the facade element generally as fire-retardant cladding or bulkhead structures.

A particularly preferred embodiment of the invention is also characterized in that part of the spaces are filled with a gas of low thermal conductivity. To this end, the inter-panel space situated between the outer panel and the inter-panel can be sealed in gas-tight manner with respect to the insulating layer.

It should also be noted that the thickness of the chambers in the insulating layer and the total number thereof and therefore the number of bulkheads must be optimized with reference to two criteria: on the one hand, the sum of the partial chamber thicknesses must not be excessive because of the anticipated "pumping effect", on the other hand, it should be noted that the thermal transfer resistance, referred to the thickness of the chamber, increases with a diminishing thickness of such chamber. By itself the last-men tioned effect would encourage the construction of the chambers to be as thin as possible because the convection of the charging gas in the appropriate chamber diminishes with a diminishing thickness of the chamber.

However, the number of bulkheads and therefore the thickness of the entire facade element would increase unless tensioned foils of the minimum possible thickness are used as bulkheads as provided for in the invention. By measuring the thermal transfer resistances in dependence on the thickness of the part-chambers and number thereof and of the pumping effect of a facade element, whose closing panel nearest to the building consists advantageously of a metal plate of 1 mm thickness, for example aluminium plate, it is however, possible for these effects to be readily controlled to achieve the desired optimization.

Embodiments of the invention are described below with reference to the accompanying drawings, in which: Figure 1 is a first embodiment of a facade element according to the invention shown in a section which is perpendicular to the panel surface; Fig. 2 shows another embodiment in a view corresponding to Fig. 1; Figs. 3 to 6 show different kinds of joining the inner and outer panels of a facade panel element according to the invention, also shown in sectional form: Figs. 7 and 8 show different embodiments of the edge configuration of a facade element according to the invention, also as a diagrammatic section: Fig. 9 shows a section through the edge region of another embodiment of a facade element according to the invention, perpendicularly to the panel surface; and Figs. 10 to 14 show sections similar to those of Fig. 9 but of different embodiments in which the construction of the insulating layer is not shown.

In the embodiment according to the invention of a hot facade panel element illustrated in Fig. 1, an outer panel 10 situated nearest to the outside of the building after the installation of the facade element and therefore nearest to the observer of the building and comprising a silicate glass pane in the illustrated embodiment, is coated on the inner surface nearest to the wall of the building, not shown, with a heat-reflecting coating 12 of known kind, for example a vacuum coating, a pyrolytically applied metal oxide coating or the like. An inner panel is situated at a distance behind the outer panel 10 to form an air-filled interpanel space 14. In the embodiment illustrated in Figure 1, the inner panel is of composite form and consists of a transparent silicate glass pane 16, of which the inner surface which is distal with respect to the inter-panel space 14 and is nearest to the building wall, not shown, is provided with a pigment coating 18. The pigment coating 18 which backs this transparent pane 16 of the inner panel has a colour and brightness, substantially a grey colour tone, so as to simulate the colour and brightness impression of an internal room which is closed by an insulated glass pane which covers the window opening adjacent to the facade element after the attachment thereof to an external wall of the building. On the inner side of the pigment coating 18, i.e. the side of coating 18 remote from the transparent pane to which coating 18 is applied, is an insulating layer 20 which can comprise plastics film, glass film or the like, if preferried the pigment coating 18 can instead be applied to the side of the transparent pane 16 which is nearer the inter-panel space 14 and further from the building wall. An inner panel which has throughout the colour of the part thereof affording that face af the inner panel which faces towards the outer panel can of course also be used in place of the inner panel comprising a transparent pane 16 backed with the pigment coating 18.

It is also not necessary for said pane of the inner panel to be constructed of silicate glass since another material can also be provided.

It is also possible to replace the composite inner panel comprising pane 16, the pigment coating 18 and the insulating layer 20 of the embodiment illustrated in Figure 1 by a unitary panel of foamed grey glass.

As can readily be explained by reference to the embodiment illustrated in Figure 1, the structure comprising the outer panel 10, the heat-reflecting coating 12, the interpanel space 14 and the pane 16 as well as the pigment coating 18 when viewed from the outside should have a reflection and provide a colour impression which is nearly identical to that of the insulated glass panes with which the window openings of the building wall are glazed. A completely uniform, architecturally desirable external appearance of the building will be achieved only under these conditions.

To this end, it is not only of decisive significance that the heat-reflecting coating 12 is applied in the same manner as for the insulated glass panes, i.e. on the internal surface of the outer panel nearest to the inter-panel space 14 in the illustrated embodiment, but also that the colour and brightness impression provided by the inner panel, whether of the composite form illustrated in Figure 1 or of a uniform form, has the appropriate grey colouring needed to simulate the interior of the room which would be visible through the window openings or through the insulated glass panes which cover such openings. The said gray colouring, however, results in the sun radia tion which passes through the heat-reflecting coating 12 disposed on the transparent outside 10, giving up its residual heat energy sub.antially to the inner panel 16, 18, 20 which is thus intensively heated due to the absorption which takes place. The absorbed heat cannot be readily dissipated to the building wall, through the inner panel, for example through the insulating layer 14 where the inner panel has the composite form iLlustrated. For this reason, the interpanel space 14 when filled with air, is confined to a maximum thickness of 3 mm, in the illustrated embodiment of 1 mm, by contrast to the conventional procedure in insulated glass panes in which efforts are normally made to provide a relatively thick inter-panel space 14 in order to increase the thermal resistance of the insulated glass pane.

This step surprisingly achieves the dissipation to the outer panel 10 of heat absorbed in the inner panel, for example by the pigment coating 18 and by the insulating layer 20, which heat could otherwise lead to a rise of temperature above 100"C, as shown by investigations, and the said heat can thus be readily dissipated to the external atmosphere. This prevents substantial volume changes of the inter-panel space 14 such as have been observed in comparable spaces in known facade elements and avoids substantial differences in the expansion of the differently heated inner and outer panels.

Neither high mechanical stresses of the edge connections which join the inner and outer panels nor severe deformations of the inner and outer panels can thus occur, which deformations would otherwise lead to substantial local changes and distortions of the reflected image which would in turn vitiate the purpose of the invention, namely to achieve a uniform appearance of the facade.

In the embodiment illustrated in Fig. 2, the heat-reflecting coating 12 is disposed on the external surface of the pane 16, in this case comprising a silicate glass pane, nearest to the inter-panel space 14 in accordance with the requirements of the insulated glass panes which are used for glazing the window openings. A grey colour coating 18 of the kind already described is once again provided on the internal surface of the pane 16 nearest to the wall of the building. This is adioined by the insulating layer 20 and finally, towards the wall of the building, by a closing panel 22 which can also consist of a metal plate or the like.

Surprisingly, it has been shown that despite the short distance between panel 10 and pane 16, i.e. despite the small thickness of the inter-panel space 14 of no more than 3 and preferably 1 mm, physical contact between panel 10 and pane 16 due to manipulation faults or the like cannot occur either in the installed state or during transportation, thus precluding any damage to the heat-reflecting coating 12. Substantial changes of the pressure and temperature conditions or severe mechanical loading of the facade element surfaces after manufac- the construction of the glass panes which cover the window openings, both the outer panel and the inner panel can be provided with further coatings which are not provided on the window panes but which must not influence the reflection so that the uniform impression of the facade is obtained. Panes of prestrcssed glass or glass-plastics laminate can also be used both for the outer panel and where appropriate for the inner panel.

The coating 18 on pane 16 which simulates the room background can also consist of a suitablc foil instead of p.gmcAited paint or the like.

Furthermore, the inter-panel space 14 caal be filled with a gas whose conductivity for heat is greater than that of air, for the additional reduction of the thermal resistance between the inner and outer panels. An example of a gas of this kind is helium whose thermal conductivity at 25"C exceeds that of air by a factor of 5.76. In a case of this kind the inter-panel space can of course be thicker than in the case of air, namely in accordance with the ratio of thermal conductivities.

Methods other than those illustrated in Figs. 3 and 6 are of course possible for the edge connection. For example, Fig. 7 shows a construction in which the closing panel 22 comprises a metal plate which is bent to the outside, i.e. towards the outer panel 10, and has a flange 38 which extends parallel with the edge zone of panel 10. A desiccant 27 is disposed in a spacer 40 which is situated between the flange 38 and the edge zone of the outer panel 10 which is larger than the inner panel. The flange 38, the spacer 40 and the outer panel 10 are joined to each other by adhesive compound 38 in the illustrated manner which is known for insulated glass panes.

The embodiment illustrated in Fig, 8 differs from that illustrated in Fig. 7 by virtue of the flange 38 of the metal plate 22 being directly bonded to the edge of the outside 10, for example by an adhesive compound. The external surface of the insulating layer 20 which is distal with respect to the pane 16 has a chamfered surface 42 so that a space is produced between the metal plate 22 and the chamfered surface 42, the desiccant 27, embedded in the spacer 40, being disposed in the said space.

Mounting of the pane 16 is not shown in the embodiment illustrated in Figs. 7 and 8. There are a number of methods, for example by means of adhesive which is provided on the edge of the pane or by means of an edge strip which bears on the spacer 40-shown in Fig. 7-or on the metal plate 22-in Fig. 8. A layer of adhesive can also be provided between the inner panel, which is backed by the absorption layer 18, and the insulating layer 20. By contrast to the construction illustrated in Figs. 7 and 8, a small air space could of course be provided between the coating 18 and the insulating layer 20.

Instead of the metal plate 22 being dished as shown in Figure 7 so that the plane of its rim is offset from that of the major part of plate 22, the plate 22 may be entirely planar and may be connected to the outer panel 10 by means of a spacer 40 corresponding in width to the distance between the outer panel and the major part of the plate, said spacer being bonded, for example adhesively joined to the outer panel 10 and to the metal plate 22. A spacer of this kind could also be provided with the necessary devices such as grooves or the like for accommodating and fixing the inner panel 16 and where appropriate the insulating layer 20.

It is particularly advantageous for the insulating layer 20 to be situated in the air-tight, sealed compartment defined between plate 22 and the outer panel 10 because this permits the use of moisturesensitive insulating materials. It is also feasible to embed any desired quantity of the desiccant 27 in the insulating layer 20 itself. This enables a substantially larger quantity of desiccant to be introduced into said compartment than would otherwise be the case so that the service life of the facade element can be substantially prolonged.

Although not shown in the drawing, the closing panel 22 can be provided with projections and corresponding complementary recesses to permit mounting of the individual facade elements with suitable mounting devices, such as screw fasteners or the like, on the wall of the building so that after attachment of a specific facade element the other facade element can be attached in sealing-tight configuration. The external perimeter of the closing panel 22 would project over the perimeter of the external panel 10, at least in the region of the prosections, so as to facilitate the use of fastening tools.

In the embodiment of a panel-shaped hot facade element according to the invention as illustrated in Fig. 9 an internal surface of an outer panel 10 which is a silicate glass pane in the illustrated embodiment and faces an observer of the building after the facade element is installed on the outside of the building, is provided with a heat-reflecting coating of known kind but not shown, for example a vacuum applied coating, a pyrolytically applied metal oxide coating or the like. An inner panel 16 is arranged at a distance behind the outer panel 10 to form an air-filled inter-panel space 14. The inner panel 16 in the embodiment illustrated in Fig. 9 also consists of a silicate glass pane and its side which is distal- with respect to the inter-panel space 14 adjoins an insulating layer the construction of which will be described in detail below.

A closing panel 22 in the form of an aluminium plate of 1 mm thickness is disposed on the side of the insulating layer 20 which is distal with respect to the inner panel 16 and is nearest to the wall of the building.

The inner panel 15, the external dirnensions of which in all embodiments shown in Fig.

9 et seq are smaller than those of the external panel 10, is connected in Fig. 9 by means of adhesive compound 34 on the one hand to the outer panel 10 and on the other hand to a spacer 40 which in turn is joined by means of adhesive compound 34 to the closing panel 22.

As can be seen by reference to Fig. 9, the insulating layer 20 comprises a plurality of chambers 43 which are filled with a gas, for example SF6, the thermal conductivity of which is less than that of air, the chambers being separated from each other by means of bulkheads 41. The bulkheads 41 can also permit gas exchange between the individual chambers 43 but they can also adjoin in sealing-tight manner on the spacer 40, as illustrated in Fig. 9. If at least the chamber which adjoins the inner panel 22 is sealed in gas-tight manner with respect to the remaining chambers, as can be provided according to one preferred embodiment of the invention and if the said chamber in turn communicates with the external atmosphere, it is possible to compensate for the known "pumping effect" without deformation of the closing panel 22 and also without deformation of the panes 10, 16 since the chamber adjacent to the closing panel 22 permits inward curvature of the bulkhead 41 which seals it with respect to the other chambers, the said bulkhead consisting of resilient sheeting, thus permitting volumetric expansion of the chambers which are adjacent to the inner panel 16 which absorbs heat.

In the embodiment illustrated in Fig. 9, each of the thin bulkheads 1, which prevent all convection in the insulating layer and have a heat-reflecting action, have a thickness of 1 mm and each of the chambers 43 have a thickness of 3.3 mm. The inter-panel space 14 between the outer panel 10 and the inner panel 16 communicate through the compensating port 44 as illustrated in Figure 9, with the space between the inner panel 16 and the closing panel 22 which form the insulating layer 20 so that the thickness of the inter-panel space 14 must be selected in accordance with the requirements dictated by the heavy gas.

The embodiment shown in Fig. 10 in which, as in the embodiments shown in Figs.

11 to 14 the internal construction of the insulating layer 20 is not shown in detail, differs from the embodiment shown in Fig.

9 in that the trapezoidal spacer 40 extends from the outer panel 10 to the plate 22 and is directly joined by adhesive compound 34 to the outer panel 10 as well as to the plate 22 which is of a metal plate of 1 mm thickness. The inner panel 16 in this case is connected in gas-tight manner to the outer panel 10 by means of a film 36 of bonding agent and does not therefore communicate with the insulating layer 20 so that in this case it is possible to provide a gas of high thermal conductivity between the outer panel 10 and the inner panel 16, i.e. in the interpanel space 14, to encourage heat dissipation to the outside, while a gas of low thermal conductivity, for example freon, CO2, SF6 or the like is used in the insulating layer 20.

The closing panel 22 of Fig. 11 is bent, adjacent its periphery towards the outer panel 10 and has a flange 38 which in turn is connected through the spacer 40 to the outer panel 10. The embodiment illustrated in Fig. 12 differs to the extent that the spacer 40 is not directly connected to the outer panel 10 but merely surrounds the insulating layer 20 and is connected to the inner panel 16.

Figs. 13 and 14 show embodiments in which no spacer 40 is used, as in the embodiments illustrated in Figs. 1 to 4, but in which the flange 38 of the metal plate forming the closing panel 22 is connected directly either to the outer panel 10-Fig. 13 -or to the inner panel 16-Fig. lWby means of a bonding agent 34, the panel 16 being connected to the panel 10 by means of a bonding agent 36. Bonding agents of various kinds can be used for connecting the spacer, closing panel, inner panel and outer panel in the above-described manner at the option of the expert.

In all the illustrated embodiments, the insulating layer 20 can of course have less or more than three bulkheads 41 and can therefore have a correspondingly lesser or greater number of chambers 43. It should also be noted that the kind of edge configuration of the facade element as illustrated in Figs. 11 to 14 can also be used if the insulating layer 20 is not of the construction illustrated in Fig. 1, but is constructed of form-stable material.

The method of operation of the construction of the insulating layer 20 as illustrated in Fig. 9 is disclosed by the following statement: As already mentioned, the space between the inner panel 16 which is situated directly behind the outer panel 10 with the interposition of a very thin inter-panel space 14 on the one hand and the closing panel 22 on the other hand is filled with a gas of low thermal conductivity (SF6). The bulkheads 41, all of which are thin, each having a thickness of 1 mm, are coated with aluminium foil so that the transfer of heat through the charging gas in the chambers 43 is caused only by thermal conduction, convection being eliminated by the close spacing of the bulkheads. Since the aluminium foils nearly completely inhibit the exchange of radiation between the bulkheads, it follows that each of the chambers has a high thermal transfer resistance. SF6 may be used as charging gas as in the illustrated embodiment, and the distances between bulkheads 41 may be between 1 mm and 5 mm.

In the embodiment illustrated in Fig. 9, the distance between the outer panel 10 and the inner panel 16, i.e. the thickness of the inter-panel space 14, is 1 mm. The spacer 40 has a thickness, perpendicularly to the plane of the panels 10, 16 of 16 mm. It will be clear to those skilled in the art how the thermal transfer resistance of the panel may be calculated. It should be noted that the inter-panel space 14, which is filled with the same gas as that used for the chambers 43 in the embodiment of Fig. 9, must be included in the calculation. In the other embodiments in which the inter-panel space 14 is sealed in gas-tight manner with respect to the insulating layer 20, as illustrated in Figs.

10, 11 and 13, a different kind of calculation will naturally apply. It is particularly advantageous in these embodiments that a gas of low thermal conductivity can be used for the insulating layer 20 as already mentioned, while a charging gas of high thermal conductivity, as is desired for good heat dissipation to the external atmosphere, can be used for the inter-panel space 14.

As may be seen by reference to Figs. 10 to 14 an edge closure 46 of plastics compound or the like can be provided in all embodiments.

WHAT WE CLAIM IS:- 1. A composite panel for use as a facade element for cladding wall portions of buildings which are disposed between window openings and are glazed by insulating glass panes. the panel comprising a first trans parent panel and a second, opaque panel parallel with the first panel and spaced therefrom to define therewith an inter-panel space, the edges of the panels being supported by an edge structure, said inter-panel space being filled with a gas, the nature of the gas and the width of said inter-panel space, corresponding to the gap between said first and second panels, being such that the resistance to heat flow across said inter-panel space, between said first and second panels, is no greater than would be the case if said gas were air and the width of said space were 3 mm.

2. A composite panel according to claim 1 wherein said inter-panel space is filled with a gas which has a thermal conductivity higher than that of air and wherein the width of said inter-panel space is no greater than 5 mm.

3. A composite panel according to claim 1 wherein said inter-panel space is filled with air and has a width no greater than 3 mm.

4. A composite panel according to claim 3, in which the thickness of the inter-panel space is 1 mm.

5. A composite panel according to any of the claims 1 to 4, in which the opaque second panel is a thermally insulating panel.

6. a composite panel according to any of the preceding claims, in which a heatreflecting coating is disposed on the side of the first panel nearest to the inter-panel spnce.

7. A composite panel according to any of claims 1 to 5, in which a heat-reflecting coating is provided on the side of the second panel which is nearest to the inter-panel space.

8. A composite panel according to any of the preceding claims, in which the first panel and/or the second panel consists or consist of silicate glass.

9. A composite panel according to any of the preceding claims, in which the second panel has throughout the colour of the part thereof affording that face of the second panel which faces towards the first panel.

10. A composite panel according to claim 9, in which the second panel has a grey colour throughout.

11. A composite panel according to any of claims 1 to 8, in which the second panel consists of a pane of transparent material which supports a pigmented coating.

12. A composite panel according to claim 11 in which the pigmented coating is grey.

13. A composite panel according to claim 11 or claim 12, in which the pigmented coating is situated on the side of the pane of transparent material which is distal with respect to the inter-panel space.

14. A composite panel according to claim 11 or claim 12 in which the pigmented coating is situated on the side of the pane of transparent material which is nearest to the inter-panel space.

15. A composite panel according to any of the preceding claims, including an insulating layer of low thermal conductivity situated on the side of the opaque second panel which is distal with respect to the inter-panel space.

16. A composite panel according to claim 15, including a closing panel disposed on the side of the insulating layer which is distal with respect to the second panel.

17. A composite panel according to claim 16, in which the closing panel consists of a metal plate.

18. A composite panel according to claim

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

aluminium foil so that the transfer of heat through the charging gas in the chambers 43 is caused only by thermal conduction, convection being eliminated by the close spacing of the bulkheads. Since the aluminium foils nearly completely inhibit the exchange of radiation between the bulkheads, it follows that each of the chambers has a high thermal transfer resistance. SF6 may be used as charging gas as in the illustrated embodiment, and the distances between bulkheads 41 may be between 1 mm and 5 mm.

In the embodiment illustrated in Fig. 9, the distance between the outer panel 10 and the inner panel 16, i.e. the thickness of the inter-panel space 14, is 1 mm. The spacer 40 has a thickness, perpendicularly to the plane of the panels 10, 16 of 16 mm. It will be clear to those skilled in the art how the thermal transfer resistance of the panel may be calculated. It should be noted that the inter-panel space 14, which is filled with the same gas as that used for the chambers 43 in the embodiment of Fig. 9, must be included in the calculation. In the other embodiments in which the inter-panel space 14 is sealed in gas-tight manner with respect to the insulating layer 20, as illustrated in Figs.

10, 11 and 13, a different kind of calculation will naturally apply. It is particularly advantageous in these embodiments that a gas of low thermal conductivity can be used for the insulating layer 20 as already mentioned, while a charging gas of high thermal conductivity, as is desired for good heat dissipation to the external atmosphere, can be used for the inter-panel space 14.

As may be seen by reference to Figs. 10 to 14 an edge closure 46 of plastics compound or the like can be provided in all embodiments.

WHAT WE CLAIM IS:-

1. A composite panel for use as a facade element for cladding wall portions of buildings which are disposed between window openings and are glazed by insulating glass panes. the panel comprising a first trans parent panel and a second, opaque panel parallel with the first panel and spaced therefrom to define therewith an inter-panel space, the edges of the panels being supported by an edge structure, said inter-panel space being filled with a gas, the nature of the gas and the width of said inter-panel space, corresponding to the gap between said first and second panels, being such that the resistance to heat flow across said inter-panel space, between said first and second panels, is no greater than would be the case if said gas were air and the width of said space were 3 mm.

2. A composite panel according to claim 1 wherein said inter-panel space is filled with a gas which has a thermal conductivity higher than that of air and wherein the width of said inter-panel space is no greater than 5 mm.

3. A composite panel according to claim 1 wherein said inter-panel space is filled with air and has a width no greater than 3 mm.

4. A composite panel according to claim 3, in which the thickness of the inter-panel space is 1 mm.

5. A composite panel according to any of the claims 1 to 4, in which the opaque second panel is a thermally insulating panel.

6. a composite panel according to any of the preceding claims, in which a heatreflecting coating is disposed on the side of the first panel nearest to the inter-panel spnce.

7. A composite panel according to any of claims 1 to 5, in which a heat-reflecting coating is provided on the side of the second panel which is nearest to the inter-panel space.

8. A composite panel according to any of the preceding claims, in which the first panel and/or the second panel consists or consist of silicate glass.

9. A composite panel according to any of the preceding claims, in which the second panel has throughout the colour of the part thereof affording that face of the second panel which faces towards the first panel.

10. A composite panel according to claim 9, in which the second panel has a grey colour throughout.

11. A composite panel according to any of claims 1 to 8, in which the second panel consists of a pane of transparent material which supports a pigmented coating.

12. A composite panel according to claim 11 in which the pigmented coating is grey.

13. A composite panel according to claim 11 or claim 12, in which the pigmented coating is situated on the side of the pane of transparent material which is distal with respect to the inter-panel space.

14. A composite panel according to claim 11 or claim 12 in which the pigmented coating is situated on the side of the pane of transparent material which is nearest to the inter-panel space.

15. A composite panel according to any of the preceding claims, including an insulating layer of low thermal conductivity situated on the side of the opaque second panel which is distal with respect to the inter-panel space.

16. A composite panel according to claim 15, including a closing panel disposed on the side of the insulating layer which is distal with respect to the second panel.

17. A composite panel according to claim 16, in which the closing panel consists of a metal plate.

18. A composite panel according to claim

16 or 17, in which the closing panel is provided with flange projections and recesses complementary thereto for the attachment of fastening means such as screw fasteners or the like.

19. A composite panel according to any of the preceding claims, in which the first and second panels are bonded to each other in the region of the edge of the composite panel.

ne. 4 composite panel according to any of claims 1 to 18, in which the first and second panels are joined to each other by means of an edge section which surrounds the panel perimeter.

21. A composite panel according to claim 20, in which the two panels are bonded to the edge section.

22. A composite panel according to any of claims 16 to 21, in which the perimeter edge of the first panel projects to a greater extent from the component plane than the corresponding edge of the second panel and of the insulating layer.

23. A composite panel according to any of claims 16 to 22, in which, at its peripheral edge, the second panel projects beyond the peripheral edge of the insulating layer.

24. A composite panel according to claim 22 or 23, including a spacer which grips around the insulating layer, is connected to the closing panel, more particularly by soldering or adhesive joining, and projects from said closing panel towards the first and second panels.

25. A composite panel according to claim 24 when dependent on claim 26 in which the side of the spacer which is distal with respect to the closing- panel is bonded to the second panel.

26. A composite panel according to claim 24 when dependent on claim 22, in which the side of the spacer which is distal with respect to the closing panel is bonded to the first panel.

27. A composite panel according to any of claims 16 to 26 in which the edge region of the closing panel is curved towards the first panel and is then bent to produce an edge flange parallel with the plane of the first and second panels.

28. A composite panel according to claim 30 when dependent on claim 25 in which the flange is bonded to the first panel.

29. A composite panel according to claim 27 when dependent-on claim 23 in which the flange is bonded to the second panel.

30. A composite panel according to claim 27 when dependent on any of claims 24 to 26 in which the flange is bonded to the spacer.

31. A composite panel according to any of the preceding claims, including an edge closure of plastics or the like.

32. A composite panel according to any of the preceding claims including a desiccant for the inter-panel space.

33. A composite panel according to claim 32, in which the desiccant is situated within the inter-panel space between the first and second panels.

34. A composite panel according to claim 32 when dependent on any of claims 24 to 26 or 30, in which the desiccant is disposed within the spacer, the interior thereof communicating with the inter-panel space.

35. A composite panel according to claim 32 when dependent on any of claims 28 to 30, in which the insulating layer is solidly constructed and its outer edge nearest to the closing panel is chamfered, and that the desiccant is disposed in the space provided between the chamfered surface of the insulating layer and the closing panel, the said space communicating with the interpanel space.

36. A composite panel according to claim 32, in which the desiccant is embedded in the insulating layer, which communicates with the inter-.panel space.

37. A composite panel according to any of claims 16 to 36, in which the insulating layer comprises a gas-filled space situated between the second panel and the closing panel the said space being subdivided into a plurality of chambers by at least one intermediate bulkhead which is parallel with the second panel and the closing panel.

38. A composite panel according to claim 37 in which the gas filled space forming the insulating layer is provided with two bulkheads and therefore has three chambers.

39. A composite panel according to claim 37, in which the gas filled space forming the insulating layer has three bulkheads and therefore four chambers.

40. A composite panel according to claim 37, in which the gas filled space forming the insulating layer has four bulkheads and therefore five chambers.

41. A composite panel according to any of claims 37 to 40 in which the bulkheads have a maximum thickness of lmm.

42. A composite panel according to any of claims 37 to 41, in which both sides of each of the bulkheads are heat-reflecting.

43. A composite panel according to claim 42, in which each of the bulkheads are covered on both sides by metal foil.

44. A composite panel according to claim 43, in which the core of each of the bulkheads which is covered by metal foil consists of fire-retardant material such as asbestos.

45. A composite panel according to claim 42 in which the bulkheads themselves consist of metal foil under tension.

46. A composite panel according to any of claims 37 to 45, in which each of the chambers has a width of 3 to 5 mm.

47. A composite panel according to any of claims 37 and 46 in which at least the chamber which adjoins the closing panel is sealed in gas tight manner with respect to the other chambers and communicates ";ith the outer atmosphere.

48. A composite panel according to any of the claims 37 to 46 in which the chambers communicate with each other near the panel edges.

49. A composite panel according to claim 48, including ports which are provided in the bulkheads for connecting the chambers.

50. A composite panel according to claim 15 or any of the claims 16 to 49 when dependent thereon, in which the insu1ating layer is filled with a gas of low thermal con ductility.

51. A composite panel according to claim 53, in which the insulating layer is filled with a gas which is heavier than air.

52. A composite panel according to claim 51 in which the insulating layer is filled with CO2, SFG or a gaseous fluorocarbon or fluorohydrocarbon compound.

53. A composite panel according to claim 15 or any of claims 16 to 52 when dependent thereon in which the gas-filled inter-panel space situated between the first panel and the second panel communicates with the insulating layer, more particularly by means of a pressure equalizing port situated near the edge.

54. A composite panel according to any of the claims 15 to 52 in which the gas-filled inter-panel space situated between the first panel and the second panel is sealed in gastight manner with respect to the insulating layer.

55. A composite panel according to claim 54, in which the inter-panel space is filled with a gas whose thermal conductivity is greater than that of air.

56. A composite panel according to claim 55, characterised in that the inter-panel space is filled with helium.

57. A composite panel substantially as hereinbefore described with reference to and as shown in any of the accompanying drawings.