WO1996032552A1

WO1996032552A1 - Method and facade element for repair building

Info

Publication number: WO1996032552A1
Application number: PCT/FI1996/000187
Authority: WO
Inventors: Reino Parkkila; Jarmo Pirhonen
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-04-13
Filing date: 1996-04-10
Publication date: 1996-10-17
Anticipated expiration: 1997-10-13
Also published as: AU5335896A

Abstract

The invention relates to a method for repair building, whereby preferably the outer surface structure (1) of a building or a like is repaired by arranging an essentially stiff structured facade element (2), such as a casing sheet, plate, thin-shell panel or a like, in connection with the same, that covers the original outer surface and which is supported at a distance (e) apart from the outer surface of the surface structure (1). A substance (v) in liquid state is led between the facade element (2) and the surface structure (1), wherein the solidification of the substance (v) into solid state, at least partly causes the installed facade element (2) to stay in place essentially supported by the original surface structure (1). Particularly in connection with a reinforced concrete structure (1; 1'), such as a sandwich element or a like, a substance (v; v') comprising at least an alkaline component, such as mortar, cement or like, is led into the space between the surface structure (1; 1') and facade element (2), which after solidification forms an alkalising intermediate layer (v1) between the facade element (2) and the surface structure (1; 1'). The invention relates to a facade element, also.

Description

Method and facade element for repair building

The invention relates to a method for repair building, whereby preferably the outer surface structure of a building or a like is repaired by arranging an essen¬ tially stiff structured facade element, such as a casing sheet, plate, thin-shell panel or a like in connection with the same, that covers the original outer surface and that is supported at a distance apart from the outer surface of the surface structure. A substance in liquid state is led between the facade element and the surface structure, wherein the solidi¬ fication of the substance into solid state, at least partly causes the installed facade element to stay in place essentially supported by the original surface structure.

The method according to the invention is applicable for repairing of facades made of most heterogeneous materials. The invention has a particular meaning in repairing of reinforced concrete structures. A parti¬ cular characteristic of such structures comprising usually a so called sandwich composition is so called carbonation. Carbonation is caused by carbon dioxide that drifts inside the reinforced concrete structure, whereby the shrink steels inside the concrete get rusty, which is due to the neutralisation of the concrete surrounding the same. By influence of the internal pressure effect caused by formation of rust, it is usual, that particularly the steels situated close to the outer surface of the concrete split loose concrete above the same from the wall structure, whereby certain parts of the same become totally visible. The phenomena in question is particularly harmful in the sense of esthetics, in addition to which the phenomena is harmful considering strength of materials, also, because corrosion of steel due to the carbonation may significantly embrittle the structure. When the steels in the concrete are uniformly surroun¬ ded by alkaline concrete, the type of phenomena due to corrosion described above may not occur.

To prevent or eliminate actual carbonation it is known to use for example electric methods, whereby by means of an electric field arranged in connection with the reinforced concrete structure it is possible to prevent/eliminate neutralisation of the concrete in the reinforced concrete structure for example by adapting a so called cathodic protection, whereby electric voltage is arranged to affect the steels in the structure, or by adapting electric current by means of which for example sodium is led inside the basic structure from a treatment mass that is spread on the surface of the reinforced concrete structure, whereby formulation of sodium carbonate causes alka- lisation. After the treatment the treatment mass and the electric arrangements are removed. An other type of method for eliminating the above problem caused by carbonation is based on that, that the outer surface of the structure being carbonated is coated with an alkalising mass. For this purpose most heterogeneous chemical compositions have been developed to achieve the desired effect.

The electric methods described above are very compli¬ cated and expensive to carry out, and there are not enough long term experiences about the efficiency for example of the cathodic protection. In addition to that a condition for the functioning of the same is always adequate dampness of the reinforced concrete structure so, that the above methods are of no use for example in repairing structures weathered by freezing. The latter method requires for its part thorough protecting measures so, that the taken actions are directed towards right points as desired. Naturally the effect of the latter method is one-off natured, whereby the influence of the taken actions depends on the density of the mass to be sprayed on the surface as well as on one hand of the thickness and on the other hand of the composition of the mass being used. Thus all the methods above are based on expensive and difficult special measures and mass as well as high professional skill particularly when aiming at long term efficiency.

On the other hand for repairing of esthetically wounded facades it is known to use covering by so called thin-shell precasts, which kind of method is represented by the facade system marketed by Partek Betonila Oy. In this case on the outer surface of the wounded surface a new casing element made of concrete is attached at a distance apart from the original wall surface. This kind of a casing element must always be rested on a supporting construction element that is for example on the inner construction element of a so called sandwich element. This is due to that, that the hairpins binding the inner and outer construction elements of the reinforced concrete together are not able to carry any additional concrete structures mounted outside the facade. The top edge of such a casing element is attached with binders, that transmit both horizontal and vertical forces to the supporting structure. The binders being adapted at the bottom edges of each element transmit horizontal forces only. Normally for example a M 16 chemical anchor is appli- cable as a binder to be mounted on the supporting concrete structure. Accordingly the fixing of the bottom edge may normally be carried out for example by a M12 cotter bolt.

When adapting the above method thus all attachments of the casing elements are rested on the supporting construction elements. In case an original exterior structure is being left in place in a facade repairing site, necessary cuttings must be done to the same, to enable the above attachments. In addition to that the attachment of the original exterior surface must be secured for example by means of separate binders. So the method described above is very troublesome, because it requires quite a lot discharging measures directed to the facade to be covered, that is total removal of the outer construction element or making openings to the same. Furthermore it is obvious, that by adapting the above method it is not possible to affect in any way directly the actual carbonation, so that in principle it may go on further between the new casing element and the original wall structure, because there is a space for ventilation between these structures.

The above method naturally improves the appearance of the facade, but it contains, however, further the original problem that is the factors causing the weathering of the facade. In this case there is thus a risk involved with the method in question, that inside the new repaired facade there may proceed harmful processes, which in a way or another for example in the long run require further new repair activities.

The principle of using a solidifying substance in liquid form as an attachment mass led between the facade element and the surface structure particularly when treating a facade of a building, is previously known for example from patent documents DK 145428, CH 645 952 and GB 2 097 457. The solution presented in patent document DK 145 428 is based on that, that new facade elements to be installed at a distance apart from the facade to be repaired are attached by a thermally isolating attachment mass. From the patent document CH 645 952 it is furthermore known to attach so called decorative elements to the facade being repaired by adapting a solidifying attachment mass. The method represented further in the patent document GB 2 097 457 is based on that, that to form a facade of a building or to repair the same, molds suitably shaped are being used, either separate ones or ones to be attached to the wall to be treated so, that after fulfilling of the casting mold an outer surface with desired patterning is achieved to the wall. The solutions represented in this connection are thus meant particularly for facade maintenance by improving thermal insulation of the same or to achieve a desired decorative appearance of the facade to be repaired. It is not possible with these solutions either to improve the situation particularly for the part of car- bonisation of reinforced concrete structures or the like.

It is the aim of the method according to this inventi¬ on to achieve a decisive improvement in the problems presented above and thus to raise substantially the level of knowledge in the field. To achieve this aim, the method according to the invention is primarily characterized in, that particularly in connection with a reinforced concrete structure, such as a sandwich element or a like, a substance comprising at least an alkaline component, such as mortar, cement or like, is led into the space between the surface structure and facade element, which after solidification forms an alkalising intermediate layer between the facade element and the surface structure.

Simplicity and reliability of facade repairing enabled by the method according to the invention may be men¬ tioned as the most central advantages of the same. Thanks to the method according to the invention the most important thing, when keeping in mind parti¬ cularly the above reinforced concrete structures, is however, that it is possible to eliminate the effects of carbonation. The alkalising substance being adapted acts thus as an intermediate layer, also, that glues the new facade element and the old surface structure to each other, thanks to which a reliable enough attachment of the facade element is achieved. To carry out the method according to the invention is very simple, because the new facade element may be supported by simple arrangements directly to the outer construction element of the original surface structu- re, in which case it is not necessary to remove the original structures as a whole or partly to enable attachments; naturally in this connection mass of the new facade element must be considered so, that for example the bearing capacity of the original hairpins is not exceeded. In this connection it is thus advan¬ tageous to adapt casing elements having for example a so called metal cassette structure or exterior surface elements formed of an organic first base material, for example based on wood, pressed straws or like, and of an inorganic second base material for example based on stone, preferably by adapting cement as binder mate¬ rial, which do not increase significantly loads of the original structures. When adapting such structures, improving of the thermal insulation of the original wall structure simultaneously with the repair work is enabled, also, by utilising in an integral manner thermally insulated repair elements.

Advantageous embodiments of the method according to the invention are presented in the dependent claims directed to the method.

The invention relates to a facade element applied for in connection with the method, also, that is represen- ted in more detail as two alternative embodiments in the preambles of the independent claims directed to each one of them. The primary characteristics of the facade element are represented in the characterizing parts of the corresponding claims.

Simplicity of construction, manufacturing as well as installation of the facade element according to the invention may be mentioned as the most important advantages of the same. A crucial advantage of the facade element according to the invention is particu¬ larly the lightness of the same, which enables even repairing of facades being in a very bad shape by attaching the new facade to the casing part of the original sandwich element by an alkalising mass. When adapting a suitable substance as the alkalising mass, it is also possible to minimize casting pressures further so, that during the installation stage signi¬ ficant loads will not either be directed towards the facade to be fixed. By adapting advantageously casing elements including metal cassette structures, it is also possible to construct the casing elements so, that barrier structures existing therewith act as the edges of the molding surfaces, which for its part makes the attachment casting of the casing elements a lot easier, because there is no need to fill up the edges. On the other hand, when adapting for example exterior surface elements including a base material made of wood or pressed straw, in practice very strongly built, but however very light constructions are achieved, whereby it is possible to gain loads corresponding nearly to those of the type of casing elements made of metal described above. By utilising a facade element according to the invention it is also possible to improve the thermal insulation of the original wall by adapting thermal insulation arrange¬ ments existing integrally within the casing element or totally built-in with the exterior surface element. In the following description, the invention is illu¬ strated in detail with reference to the appended drawings. In the drawings,

Fig. 1 shows as a principle an embodiment of the method applied for particularly in connection with a usual reinforced concrete structure or a so called sandwich element,

Fig. 2 shows an advantageous embodiment of the method according to the invention, whereby a thermally isolated casing element has been adapted as the facade element,

Fig. 3 shows an alternative embodiment of the method according to the invention, whereby a ther¬ mally isolated exterior surface element has been advantageously adapted as the facade element,

Fig. 4 shows a exterior surface element according to fig. 3 seen from above,

Fig. 5 shows a three-dimensional cross section of the exterior surface element according to fig. 3, and

Fig. 6 shows further an advantageous exterior surfa¬ ce element being utilized in the method according to the invention as a perspective view.

The invention relates to a method for repair building, whereby preferably the outer surface structure 1 of a building or a like is repaired by arranging an essen¬ tially stiff structured facade element 2, such as a casing sheet, plate, thin-shell panel or a like in connection with the same, that covers the original outer surface and which is supported at a distance e apart from the outer surface of the surface structure 1. A substance v in liquid state is led between the facade element 2 and the surface structure 1, wherein the solidification of the substance v into solid state, at least partly causes the installed facade element 2 to stay in place essentially supported by the original surface structure 1. Particularly in connection with a reinforced concrete structure 1; 1' , such as a sandwich element or a like, a substance v;v* comprising at least an alkalising component, such as mortar, cement or like, is led into the space between the surface structure 1;1' and facade element 2, which after solidification forms an alkalising intermediate layer vl between the facade element 2 and the surface structure 1;1^• .

With reference particularly to fig. 1 it is advanta¬ geous when adapting the method to utilize also a mechanical attachment arrangement 3, such as bindings, supports and/or the like, that rests at least partly on the original surface structure 1. As shown in fig. 1 as the attachment arrangement 3 fasteners have been used that support the facade element 2 to the surface structure 1 essentially in the horizontal direction by the opposite edges of the same, due to which the width e of the space between the structures 1, 2 is adjusta¬ ble. Thus with reference to fig. 1 of principle for supporting of the facade element 2 fasteners 3 are used having a frame part 3a", that is attached essen¬ tially to the surface part l'c of the surface structu¬ re 1, into which a support part 3a' going through the intermediate layer vl is movably attached for example by a screw joint as shown in the presented applicati- on.

Thanks to the arrangements above an originally uneven facade may be easily repaired even by the new facade covering the same. Depending on one hand on the shape of the original surface structure 1 and on the other hand of the material of the facade element 2 being used, it naturally possible to support the facade element 2 to the inner or supporting part la' of the concrete element 1' for the sake of safety as shown in fig. 1 with lines of dots and dashes by means of for example straight-through bolting 3b. This is necessary at sites, where there exists uncertainty whether the hairpins s binding the inner part l'a and the outer part 1'c of the reinforced concrete element 1' toget¬ her are able to carry the additional loads, caused by the new facade element 2 and the substance v. In fig. 1 the reference letters t refer to the shrink steels of the reinforced concrete and l'b refer correspondin¬ gly to the original thermal insulations of the ele¬ ment.

As an advantageous embodiment of the method according to the invention, because of the reasons described above, a casing element 2' is being used, that is essentially lighter by the specific weight than concrete, advantageously as the one shown in fig. 2, that is coated by metal, plastics and/or like. In the advantageous embodiment the casing element 2' includes a thermal insulation 2'a and joint organs 4 placed at the top, at the bottom and depending on the installa¬ tion conditions advantageously also at the sides of the element to enable attachment of the same to another element.

According to the advantageous embodiment shown in fig. 2, when leading the substance v into the casting space between the said structures 1, 2' , in addition to the above structures 1, 2' a barrier structure at one or several edges of the casing element 2' is used as the edges of the molding surfaces, that closes the edge of the casting space between the structures 1, 2' . Further as an advantageous alternative embodiment of the method according to the invention with reference to the applications shown for example in figs. 3 - 6 essentially non-metallic and sheet like, plate like and/or a like exterior surface elements are used as the facade element 2, that may be installed in place, being settled inside adjacent exterior surface ele¬ ments, by utilizing joint organs 4 as described above. Furthermore as an advantageous embodiment, in this connection exterior surface elements are used having a surface polishing 13 particularly for finishing the appearance of the same, such as a surface patterning, painting and/or a like, the surface polishing 13 being preferably prefabricated essentially integrally in connection with the manufacturing of the exterior surface elements. In this connection exterior surface elements 2" at least partly made of an organic first base material 2a, for example based on wood, vegetable and/or like, and of an inorganic second base material 2b, for example based on stone, plastics, glass, rubber, metal and/or like, are used as the facade element 2 preferably by adapting cement as binder material.

Further as an advantageous embodiment simultaneously with the repair work of the facade also the thermal insulation of the original wall structure is improved by utilizing the kind of exterior surface elements 2" described above, in which there has been arranged a thermal insulation arrangement 6 essentially built-in in connection with the manufacturing of the same, in other words in which the thermal insulation arrange¬ ment is being placed essentially inside the same advantageously by casting techniques. In this connec- tion particularly with reference to fig. 3, the thermal insulation arrangement 6 comprises for example a perforated isolation plate, and as shown in fig. 5 a truss-like x, y thermal insulation layer 6a. The purpose of the type of arrangements above is naturally to eliminate cold spots of the structures and on the other hand to enable adequate natural metabolic of the exterior surface element 2" as well as to anchor the opposite walls of the same to each other.

When utilizing the type of casing elements 2' or exterior surface elements 2" described above, the method may be adapted in most sites for example as shown in figs. 1 or 3 so, that they are rested for example on the outer part 1'c of the concrete element 1' , only.

According to the advantageous embodiment shown in fig. 1 in the space between the surface structure 1 and the casing element 2' there has been used a binding and/or reinforcing structure x to support the intermediate layer vl, v2, such as a grate, net or a like, that has been fixed before the actual installation advanta- geously to the surface structure 2 and/or to the attachment arrangement 3. Further as an advantageous embodiment shown for example in fig. 2 the facade element 2 or the casing element 2' is arranged venti¬ lated by means of air cavities.

The facade element according to the invention is intended as described above for repair work preferably of a facade or a like of a building, which comprises thus as shown in fig. 2 an essentially stiff structu- red casing element 2' , coated by metal and/or plastics and being preferably thermally insulated, that is intended to be installed in place by casting a subs¬ tance v in liquid state between the same, being supported at a distance e apart from the outer surface of the surface structure 1, and the surface structure 1, that solidifies into solid state. To ease the installation of the casing element 2' it includes joint organs 4, to be settled inside one or several adjacent casing elements 2' and a barrier structure, such as an edge strip, scuff plate 2'c or a like, at one or several edges of the casing element 2' to form the edges of the molding surfaces of the casting space between the facade element 2 and the surface structure 1.

An alternative embodiment of the facade element according to the invention comprises a exterior surface element 2", that is at least partly made of an organic first base material 2a, for example based on wood, vegetable and/or like, and of an inorganic second base material 2b, for example based on stone, plastics, glass, rubber, metal and/or like, preferably by adapting cement as binder material. In this case as an advantageous embodiment in an integral manner thermally insulated exterior surface element 2" inclu¬ des a, preferably throughout therewith built-in thermal insulation arrangement 6 forming for example a trusslike x, y, a perforated structure or a like at the same level. As an advantageous embodiment the exterior surface element 2" in question includes further a surface polishing 13 for finishing the appearance of the same, such as a surface patterning, painting and/or a like, the surface polishing 13 being also preferably prefabricated essentially integrally in connection with the manufacturing of the exterior surface element.

The type of exterior surface element 2" particularly as shown in figs. 3 -6 comprises further advantageous¬ ly female 4a and male joints 4b that is edge grooves and edge flanges. Particularly in the embodiments shown in figs. 3, 4 and 6 the above male edge flanges are formed of isolation sheets 6a' being fixed in the edge grooves 4a of the exterior surface element 2 " , that are arranged advantageously during the manufactu¬ ring of the same, whereby two edge grooves 4a at two sides of the exterior surface element 2" act as female joints when connecting the exterior surface elements together.

Further with reference to fig. 3 the attaching point 8 of the exterior surface element 2", that is to be connected at least partly by means of a mechanic attachment arrangement, such as by mounting bolts, is arranged advantageously essentially in connection with joint organs 4 that is in the edge flanges 4b. Further as an advantageous embodiment particularly with reference to fig. 3, at the back surface of the exterior surface element 2" there has been arranged connecting organs 9, such as recesses, grips and/or the like to secure attachment of the exterior surface element 2" to the surface structure 1.

It is obvious that the invention is not limited to the embodiments presented or described above, but it can be modified within the basic idea even to a great extent. This is firstly due to that, that the method according to the invention may be adapted in very many ways technically, in most heterogeneous circumstances and in connection with most heterogeneous structures. Thus the directive drawings represent general princi¬ ples, only, however in maybe most general contexts.

Claims

1. Method for repair building, whereby prefer¬ ably the outer surface structure (1) of a building or a like is repaired by arranging an essentially stiff structured facade element (2), such as a casing sheet, plate, thin-shell panel or a like in connection with the same, that covers the original outer surface and which is supported at a distance (e) apart from the outer surface of the surface structure (1), and whereby a substance (v) in liquid state is led between the facade element (2) and the surface structure (1) , wherein the solidification of the substance (v) into solid state, at least partly causes the installed facade element (2) to stay in place essentially supported by the original surface structure (1) , characterized in, that, particularly in connection with a reinforced concrete structure (1;1' ) , such as a sandwich element or a like, a substance (v;v' ) comp- rising at least an alkaline component, such as mortar, cement or like, is led into the space between the surface structure (1;1' ) and facade element (2) , which after solidification forms an alkalising intermediate layer (vl) between the facade element (2) and the surface structure (1;1' ) .

2. Method according to claim 1, whereby a mechanical attachment arrangement (3) , such as bin¬ dings, supports and/or the like, that rests at least partly on the original surface structure (1) and that supports the facade element (2) to the surface struc¬ ture (1) essentially in the horizontal direction, is used to fasten the facade element (2), characterized in, that the width (e) of the cast space between the surface structure (1) and the facade element (2) is adjusted during the installation by adapting fasteners (3), the width of which is adjustable, to support the facade element (2) to the surface structure (1).

3. Method according to claim 2, characterized in, that for supporting of the facade element (2) fasteners (3) are used having a frame part (3a"), that is attached essentially to the surface part (l'c) of the surface structure (1) , into which a support part (3a') going through the intermediate layer (vl) is movably attached for example by a screw joint or accordingly.

4. Method according to any of the claims 1 - 3 above, characterized in, that casing elements (2'), coated by metal and/or plastics and being preferably thermally insulated are used as the facade elements (2), that are installed in place preferably by means of joint organs (4) to be settled inside one or several adjacent casing elements (2') and by adapting a barrier structure, such as an edge strip (2'c) or a like, at one or several edges of the casing element (2') as the edges of the molding surfaces of the casting space between the facade element (2) and the surface structure (1) .

5. Method according to any of the above claims 1 - 3, wherein essentially non-metallic and sheet like, plate like and/or a like exterior surface elements are used as the facade element (2), that are installed in place preferably by means of joint organs (4) to be settled inside one or several adjacent exterior surface elements and/or that include a surface polishing (13) particularly for finishing the appearance of the same, such as a surface patterning, painting and/or a like, the surface polishing (13) being preferably prefabricated essentially in an integral manner in connection with the manufacturing of the exterior surface elements, characterized in, that exterior surface elements (2") at least partly made of organic first base material (2a), for example based on wood, vegetable and/or like, and of an inorganic second base material (2b), for example based on stone, plastics, glass, rubber, metal and/or like, are used as the facade element (2) preferably by adapting cement as binder material.

6. Method according to claim 5, in connection of which simultaneously with the repair work also the thermal insulation of the surface structure (1) , such as a facade or a like is improved, whereby in connec- tion with the exterior surface element there has been arranged preferably in an integral manner during the manufacturing of the same a thermal insulation arran¬ gement (6), characterized in, that as the facade element (2) exterior surface elements (2") are used, in which the thermal insulation arrangement (6) is arranged built-in essentially in connection with the manufacturing of the same.

7. Method according to claim 6, characterized in, that as the facade element (2) exterior surface elements (2") are used, in which the thermal insulati¬ on arrangement (6) is arranged preferably by adapting casting techniques or accordingly as an essentially internal thermal insulation layer (6a) forming for example a truss-like (x, y), a perforated structure or a like at the same level.

8. Method according to any of the above claims 1 - 7, characterized in, that the facade element (2), such as the casing element (2') or the exterior surface element (2") during the manufacturing of the same, and/or the intermediate layer (vl) during the installation of the facade element (2) is arranged ventilated by means of air grooves, cavites (i), pipes and/or the like.

9. A facade element, that is intended for repair work preferably of an outer surface structure (1) of a building or a like, which, essentially stiff structured facade element (2), such as a casing sheet, plate, thin-shell panel or a like, is intended to be installed in place by casting a substance (v) in liquid state between the facade element (2) , being supported at a distance (e) apart from the outer surface of the surface structure (1) , and the surface structure (1) , wherein the solidification of the substance (v) into solid state at least partly causes the installed facade element (2) to stay in place essentially supported by the original surface structu¬ re (1), characterized in, that the facade element (2) comprises a casing element (2'), coated by metal and/or plastics and being preferably thermally insula- ted, that includes joint organs (4), arranged there¬ with for the installation of the same, to be settled inside one or several adjacent casing elements (2') and a barrier structure, such as an edge strip (2'c) or a like, at one or several edges of the casing element (2') to form the edges of the molding surfaces of the casting space between the facade element (2) and the surface structure (1) .

10. A facade element, that is intended for repair work preferably of an outer surface structure (1) of a building or a like, which, essentially stiff structured, non-metallic and essentially sheet like, plate like and/or a like facade element (2) is to be installed in place preferably by means of joint organs (4) to be settled inside one or several adjacent facade elements (2) and/or that includes a surface po¬ lishing (13) particularly for finishing the appearance of the same, such as a surface patterning, painting and/or a like, the surface polishing (13) being prefe- rably prefabricated essentially in an integrate manner in connection with the manufacturing of the facade element, and whereby the facade element (2) is inten¬ ded to be installed in place by casting a substance (v) in liquid state between the facade element (2), being supported at a distance (e) apart from the outer surface of the surface structure (1) , and the surface structure (1) , wherein the solidification of the substance (v) into solid state at least partly causes the installed facade element (2) to stay in place essentially supported by the original surface structu¬ re (1), characterized in, that the facade element (2) comprises a exterior surface element (2"), that is at least partly made of an organic first base material

(2a), for example based on wood, vegetable and/or like, and of an inorganic second base material (2b), for example based on stone, plastics, glass, rubber, metal and/or like, preferably by adapting cement as binder material, whereby preferably in an integral manner thermally insulated exterior surface element (2") includes a, preferably throughout therewith built-in thermal insulation arrangement (6) forming for example a truss-like (x, y) , a perforated structu- re or a like at the same level.