CA2173833A1

CA2173833A1 - Outer wall element for buildings, in particular wainscot panel for the breastwork area of the wall of a building

Info

Publication number: CA2173833A1
Application number: CA002173833A
Authority: CA
Inventors: Harald Schulz
Original assignee: Individual
Current assignee: Norsk Hydro ASA
Priority date: 1993-10-13
Filing date: 1994-10-12
Publication date: 1995-04-20
Also published as: GR3024317T3; HU9600968D0; ATE156254T1; SK46496A3; NO306577B1; FI961618A7; NO305772B1; PL313909A1; NO961261D0; GR3024237T3; FI961617A7; FI961617L; HUT76590A; HUT76589A; CZ107096A3; DE59403476D1; DK0720718T3; FI961618A0; FI961617A0; DE59403579D1

Abstract

The outer wall element has a transparent outer heat-insulating layer (30), located adjacent to the outer, radiation absorbing shell (10) and arranged between this outer shell (10) and an inner shell (20), whereby this inner shell (20) has at least one inner heat insulating layer (22) and the transparent outer heat insulating layer (30) is delimited at the side of the inner shell (20) by a radiation absorbing layer (21'). The g-value of the outer shell (10) is reduced to such an extent that no temperatures that would be destructive of materials can occur at the maximum expected insolation at the absorbing layer (21').

Description

' Outer wall element for buildings, in particular wainscot panel for the breastwork area of the wall of a buildinq The object of the invention is an outer wall element for buildings, in particular breastwork or wainscot panels in the breastwork area of a building wall, in accordance with Claim 1.
Façade claddings, which are used in the passive use of solar energy on the opaque parts of the building envelope, are known from W0-82/03 100 as the latest state of the art. In this source, using Fig. 1, an outer wall construction is described in which, between a transparent outer shell and the solid wall, a transparent outer heat insulating layer is provided adjacent to the outer shell and an insulating layer on the outer side of the wall. The latter is separated from the transparent outer heat insulating layer by a solar radiation absorbing layer. The heat created in the latter is conducted away by the insulating layer in the wall. In order to avoid overheating the absorbing layer and the insulating layer, the insulating layer consists of a material whose thermal conductivity can be changed considerably as a function of the temperature. For that purpose, the material contains a normally liquid heat transfer medium, which evaporates on the warm side of the insulating layer. The vapour is diffused through the pores of the material to the cold side of the layer and there releases its heat and condenses on the wall.
The condensate penetrates, for example by capillary action, back to the warm side of the layer thus creating a cycle in the heat transfer medium between the liquid to the vaporized state and transporting the heat principally from the outside to the inside. As the heat conductivity increases very rapidly and strongly with increasing solar radiation with a rise in temperature, a disproportionately greater quantity of heat is conducted through the insulation layer into the solid wall, so that the actual increase in the temperature of the absorbing layer is correspondingly lower, while the wall on the inside of the building may be warmer than is desired. In 1 2t~8~3 addition, an exterior cladding of similar design is known from EP-A-O 362 242. Here, in order to prevent the penetration of solar radiation into the interior of the outer wall structure from causing overheating that will damage materials, the inner heat insulating layer is designed to be somewhat translucent with a transmittance of less than 10% and a coefficient of absorption exceeding 15%, so that the absorption of the penetrating solar radiation within the heat insulating layer occurs over a relatively thick layer area. The heat insulating layer must be so thick overall that, when there is usable solar radiation, a temperature profile is created in the heat insulating layer whose maximum value inside the insulating layer is located between the inner and outer boundary surfaces of the layer. This can, particularly in the case of expected strong insolation, require a great thickness of the inner insulating layer and result in a construction thickness of the outer wall which is greater than that set by structural engineering requirements.
From CH-A-678 203, an outer wall design is known, in which an outer wall is insulated by an outer transparent insulating layer and protected by a superimposed weather protection sheet of transparent material. The outer wall has a solar absorbing dark cladding on the surface adjacent to the outer heat insulating layer. An inner heat insulating layer between this layer and the outer wall is not provided.
Excessive heat in the wall construction is avoided by the weather protection sheet, which owing to the manner in which it is mounted, allows more of the low winter sun to pass through than of the high summer sun. To that end, the surface of the weather protection sheet is arranged in relief fashion with two parts, oriented in opposed directions, one of which is transparent and the other is covered with an opaque paint layer, which results in a shading that varies with the incoming angle of the sunlight. A smooth outer glazing surface is not possible with this kind of weather protection sheeting.
From the literature, in an article entitled "Thermochromic Gels for Control of Insulation" in the magazine

2 1 73833 Solar Energy, Volume 50, number 5, May 1993, pages 407 - 414, an outer wall design is known in which the solid outer wall also has a solar absorbing dark cladding on the surface adjacent to the outer heat insulating layer, and there is also no inner heat insulating layer provided between this layer and the outer wall. The outer shell, which is separated from the absorbing layer by a transparent outer heat insulating layer, has thermochromic layers which affect the radiation transmission depending on the temperature, so that when a characteristic temperature is exceeded, the radiation transmission is actually reduced. Such layers are achieved by including a thermochromic gel in the narrow space between two glass panes. Such an outer shell design is actually more construction-intensive as a shell designed using traditional glazing.
A similar outer wall design as in W0-82/03 ioo is known from EP-A-0 473 859. Although the insulating layer in this instance does not have any changing thermal conductivity, there is, however, a space provided between the absorbing layer and the insulating layer in which there is a liquid heat transfer medium that circulates between the space and a piping system contained within the solid wall and thus transports the heat from the absorbing layer by convection directly into the solid wall.
The purpose of the invention is to design an outer wall structure in such a way that, under conditions of highest possible utilization of solar energy and assured comfort in the interior space, excessive temperatures that would damage materials will be avoided. The depth of the wall component is to be as narrow as possible and in particular not greater than the structural requirements for the load-bearing structure, especially, for example, the columns and beams.
In the outer wall structure in accordance with the invention, the absorption of incoming solar radiation is essentially in the absorbing layer delimiting the transparent outer heat insulating layer located adjacent to the inner heat insulating layer, on which thus generally the highest possible - 2 1 738~3 temperatures within the wall components occur. This layer can be very thin when it is impermeably only to solar radiation.
Although, the reduced g-value of the outer shell desired in accordance with the invention has a reduced absorption of solar energy in the outer wall element, it does however, ensure that with the highest possible insolation a maximum temperature in the absorbing layer is not exceeded, so that destruction of material by overheating cannot occur. The inner shell, that is, the inner heat insulating layer and the end layer, then need only be designed relative to their heat transfer resistance in such a way that at an allowable maximum temperature at the absorbing layer, the temperature occurring at the interior space side of the inner shell and that at the interior wall side of the interior air, are within temperature ranges determined by the thermal conductivity resistance, and are perceived by persons within the interior area as comfortable. This can be achieved through a comparatively thin thickness of the inner heat insulating layer. Higher values of the heat transfer resistance of the inner heat insulating layer are generally disregarded in the framework of this invention and would only unnecessarily increase the size of the inner heat insulating layer and/or the end layer and, consequently, also increase the design depth and the construction efforts and financial expenditures of the outer wall element in accordance with the invention overall.
The reduced absorption of solar radiation resulting from the desired reduction of the g-value of the outer shell through application of the invention, is used optimally by adapting the heat transfer coefficient k of this shell, when the correspondingly reduced k-value limits the outward heat loss of the absorbing layer and the outer shell. It is , therefore, desirable that the single pane glazing forming the outer shell, consists of an inner heat absorbing layer, particularly an L-E layer, and/or à solar screen layer.
Another very advantageous embodiment is one characterized by having the glazing consist of insulating glass elements of each two or three glass panes. In the latter case, the 2~ 73833 elements could have reduced spaces between the panes, in order to keep the expansion effect (pumping effect) of the air in the intervening spaces small when the air heats up. It is also recommended that the glass panes in the insulating glass components should be provided on individual, several or all sides (below they are also termed positions) with heat absorbing layers, in particular with L-E layers. In addition, it is useful to provide the insulating glass components or their glass panes with sun screen layers. Such sun screen layers should be optimized in such a way that the solar energy, in accordance with the invention, is used as much as possible without excessive temperatures occurring at the absorbing layer. Furthermore, the spaces between the panes of the insulating glass components can be filled with an inert gas, in order to serve to adjust the heat transfer -coefficients to the existing conditions and requirements, for example, lower g-values for south orientations of the outer wall structure, medium g-values for east/west orientations and high g-values for north orientations.
The outer shell can, however, also be composed of a specific design suitable for special systems, where these generally consist of two transparent glass panes and a prismatic or honeycomb structure in the intervening space approximately perpendicular to the plane of the panes.
A particularly advantageous embodiment of the invention is characterized by the fact that a heat retaining layer is located on the side of the interior shell inner facing the transparent inner heat insulating layer.
The heat retaining layer has the advantage that, when the outer wall structure is in accordance with the invention, the solar energy received in the absorbing separation layer in front of it is stored partially in the solid storage mass of the heat retaining layer and is released again if the supply of solar energy has in the meantime diminished or should no longer continue to exist. Depending on the thermal capacity and heat insulating capacity of the storage and insulating materials forming the layers in the inner shell, the utilization of the solar energy supply can, depending on the thermal properties of the other parts of the wall structure, in particular the outer shell and the transparent outer heat insulating layer, be enhanced, notably with respect to the prevention of overheating in the wall component and delaying the release of the stored heat in relation to the actual solar energy radiation. For with other conditions remaining the same, the heat retaining layer creates a lower temperature on the absorbing layer, within the outer wall component in any case and on its inner wall surface, and this can be used to raise the g-value of the outer shell in order to use up the solar energy supply more completely without exceeding the permissible maximum temperatures. Moreover, the heat retaining layer should have the optimum heat capacity possible, in order to be able to absorb the solar energy supply as fully as possible, without any unnecessarily great temperature variances occurring. Particularly useful embodiments are characterized in that the heat retaining layer contains retaining materials of one or more mineral sheets, ceramic sheets, glass, natural or synthetic materials, particularly including gravel-based concrete. Storage materials which work as latent heat retainers can also be used, such as for example sodium sulfate. However, the retaining material of the retaining layer can also consist of synthetic material, particularly of one or more synthetic sheets, because synthetics possess as a rule about double the specific heat of concrete. This reduced density of the synthetic material as compared to the heavier retaining materials balances out, so that approximately equal storage capacities can be obtained with concrete and with synthetic material as the retaining mass, for example. The retaining materials mentioned above can, in accordance with the invention, be used either individually or mixed in combination with each other in the heat retaining layer.~
Further, it is recommended that storage materials of low thermal conductivity are selected for the heat retaining layer, so that the heat stored in it does not get given off to ~, quickly to the surrounding environment, even when there are heat insulating layers, when the temperature drops on both sides of the wall element. The heat retaining layer should, therefore, cool only slowly. For that reason, the inner heat insulating layer is arranged between the heat retaining layer and the end layer of the inner shell.
The inner heat insulating layer can in its simplest form, be made up of an air layer. Generally, however, the inner heat insulating layer contains certain insulating materials , such as PUR [polyurethane] foam, PS ~polystyrene] foam, glass fibres, mineral fibres, or similar materials. There is also the option of designing the inner heat insulating layer using multiple layers with air layers between 5 and 50 mm, preferably 20 mm. Greater thicknesses for these air layers should be avoided, so that heat convection through air circulating within this layer remains low and the heat insulation achieved by this air layer does not unnecessarily reduced. It may contain an end sheet of metal, particularly aluminum or steel. This end layer may also contain a retaining material, in particular concrete, which can be achieved in an especially simple manner by having the retaining material consist of the concrete breastwork of the building wall.
As regards the construction of the outer transparent heat insulating layer adjacent to the inner shell, there are several options in accordance with the invention. For example, this transparent heat insulating layer in its simplest form can again be an air layer between 5 and 50 mm, preferably 20 mm. The air layer can be located immediately next to the absorbing layer. Between the air layer and the absorbing layer, however, there can be a glass pane. However, the transparent outer heat insulating layer can also be composed of capillary sheets of transparent plastics with a honeycomb or chamber structure perpendicular to the layer, as is known from Bauphysik 13 (1991), H. 6, pages 217 - 224 entitled "Transparante Warme~7mm~7ng, Materialien, Systemtechnik und Anwendung" [Transparent heat insulation, materials, systems technology and application], and which requires no further discussion here for that reason. Furthermore, the outer transparent heat insulation layer can also consist of fibre glass and/or acrylic resin foam, either individually or in combination as the insulating material.
The absorbing layer, together with the deliberately reduced g-value of the outer wall element can aid in optimizing the external appearance of the latter, wherein lies another important advantage of the invention. That is because the small g-values considerably reduce the view through the outer shell, thereby making it more difficult to see through the outer wall elements behind the outer shell as well, thus making it easier to meet the aesthetic requirements of the appearance.
In the case of an outer wall element with a heat retaining layer adjacent to the absorbing layer, then a suitable embodiment of the glazing could be single clear glass panes or insulating glass elements consisting of two clear glass panes.
Examples are given below of embodiments of the invention which are explained by means of the drawings; the following are shown:

Fig. 1 section through the layer structure of a wainscot panel in accordance with the invention, shown schematically, 5 Fig. 2 another embodiment of the wainscot panel shown as in Fig. 1, Fig. 3 schematic diagram showing the layer structure of the outer shell only.

In the drawing the outer shell receiving solar radiation is generally labelled 10 and the inner shell is generally labelled 20. Between the two shells there is a transparent outer heat insulation layer 30 immediately adjacent to the outer shell 10, while the inner shell 20 consists of multiple layers with a heat retaining layer 21 and an inner heat insulating layer 22, whereby the heat retaining layer 21 is positioned on the side of the inner shell 20 facing the transparent heat insulating layer 30. The retaining material 5 of this heat retaining layer 21 may take various forms, for example, mineral sheets, ceramic sheets, glass or natural or artificial stone, in the latter case especially concrete, but may also be made of synthetic, especially one or more plastic sheets which, however, is not shown in detail in the drawing.
This inner shell 20 has an end layer 23 delimiting the outer wall element on the inner side, and its side facing the outer shell 10 a heat insulating layer 22 is provided which is located between the heat retaining layer 21 and the end layer 23. The heat insulating layer 22 may contain PUR
15 [polyurethane] foam or PS [polystyrene] foam, glass fibres, mineral fibres etc. as insulating materials. The heat insulating layer 22 may also contain one or more layers of air 10 to 50 mm, preferably 20 mm, thick. This is also not shown in detail in the drawing. End layer 23 itself should in any 20 case be vapour-proof and may consist of an end sheet of metal, such as aluminum or steel, but may also consist of solid storage material, in particular concrete.
The transparent heat insulating layer 30 can again be an air layer between 5 and 50 mm thick, preferably 20 mm.
25 However, the transparent outer heat insulating layer 30 can also be composed of capillary sheets of transparent plastics with a honeycomb or chamber structure perpendicular to the layer, which also is not illustrated in the drawings for reasons of simplicity. Furthermore, the outer transparent heat 30 insulation layer 30 can also consist of fibre glass and/or acrylic resin foam, either individually or in combination as the insulating material. The heat retaining layer 21 is - - positioned on the side of the inner shell 20 facing the transparent heat insulating layer 30, and is provided with a 35 . radiation absorbing, spectrally selective absorbent, if required, radiation-impermeable layer 21', which may be designed as a thin coating.

The outer shell 10 consists of glazing which may be provided with one or more sun screen coatings for the purpose of lowering the g-value. In the case of an outer shell 10 with a heat retaining layer 21 adjacent to the heat insulating layer 30, the glazing can consist either of individual clear glass panes or insulating glass components made of two or more clear glass panes. In general, the glazing is formed by individual glass panes 11, if necessary provided with an inner heat absorbing layer, in particular an L-E coating and/or sun screen coatings, which results in a lower k-value.
Furthermore, the glazing can consist of insulating glass elements made up of two or three glass panes 11, 12, 13, in which case the insulating glass elements may have spaces between the panes which are reduced. The glass panes 11, 12, 13 may also have heat absorbing coatings, in particular L-E
layers, on one, several or all sides of the panes in addition to the sun screen coatings, where the L-E layers on the open surfaces of the panes may be formed by pyrolytically applied layers of stannic oxide. In addition, there is the option that the insulating glass elements, or their glass panes 11, 12, 13, are provided with sun screen layers. The spaces between the panes can also be filled with an inert gas. In consequence, it is recommended in accordance with the invention that in practice, with a view to optimizing each adjustment of the k-value and the g-value to the existing requirements, that is, with respect to the maximum temperature occurring on the absorbing layer 21' the following combinations, explained in detail in Fig. 3, can be described as particularly useful:

1. Single glass pane with a heat absorbing and sun screen pane 11 with the sun screen layer in position 1 for a deliberately reduced g-value and an L-E layer in position 2, 2. Double insulating glazing consisting of two glass panes 11, 12 with a sun screen layer, for example, sun screen layer in position 2, heat absorbing layer (L-E) in position 3, or sun screen layer in position 2, heat absorbing layer (L-E) in positions 3 and 4, with the heat absorbing layer in position 4 consisting of a pyrolytically applied layer of stannic oxide, or sun screen layer plus heat absorbing layer in position 2, heat absorbing layer (K) in position 4, in each case with or without inert gas filling the spaces between the panes.

3. Triple insulation glazing made of glass panes 11, 12, 13 with sun screen layer in position 2, heat absorbing layer in position 3, heat absorbing layer in position 5, or sun screen layer in position 2, heat absorbing layer in position 3, heat absorbing layer in position 5, heat absorbing layer in position 6, or sun screen and heat absorbing layer in position 2, heat absorbing layer in position 5, or sun screen and heat absorbing layer in position 2, heat absorbing layer in position 5, heat absorbing layer in position 6, in each case with or without inert gas filling the spaces between the panes.

The outer shell 10 may also, in accordance with the embodiment in Fig. 2, consist of two transparent glass panes 11' and of a prismatic or honeycomb structure 11" in the intervening space approximately perpendicular to the plane of the panes.

Claims

Claims:

1. Outer wall element for buildings, in particular wainscot panel for the breastwork area of the wall of a building, which to use solar energy has a transparent outer heat insulating layer (30), located adjacent to an outer, solar radiation absorbing shell (10) consisting of glazing and arranged between this outer shell (10) and an inner shell (20), and where this inner shell (20) has an inner heat insulating layer (22) and a transparent outer heat insulating layer (30) which is delimited at the side of the inner shell (20) by an end layer (23), whereby moreover the inner shell (20) on its side facing the transparent heat insulating layer (30) is delimited by a absorbing layer (21') taking up solar radiation from the outer heat insulating layer (30), and whereby the total energy transmittance g of the outer shell (10) is reduced to such an extent that at the highest insolation to be expected at the installation site, a maximum temperature at the absorbing layer (21') is not exceeded, and whereby the heat transfer coefficient k of the outer shell (10) is adapted to the reduced g-value in such a way that the solar energy is used to the maximum extent possible.

2. Outer wall element as in Claim 1, characterized in that the glazing of an individual glass pane (11) consists, if necessary, of an-inner heat absorbing coating, in particular an L-E coating, and/or a sun screen layer.

3. Outer wall element as in Claim 1, characterized in that the glazing of each insulating glass component consists of two or three glass panes (11, 12, 13).

4. Outer wall element as in Claim 3, characterized in that the insulating glass components have reduced spaces between the panes.

5. Outer wall element as in Claim 3 or 4, characterized in that the glass panes (11, 12, 13) have in one, several or all positions (1 through 6) heat absorbing coatings, in particular L-E layers.

6. Outer wall element as in one of Claims 3 through 5, characterized in that the insulating glass components or their glass panes (11, 12, 13) are provided with sun screen layers.

7. Outer wall element as in one of Claims 3 through 6, characterized in that the spaces between the panes of the insulating glass components are filled with an inert gas.

8. Outer wall element as in Claim 1, characterized in that outer shell (10) consist of two transparent glass panes (11') and a prismatic and/or honeycomb structure (11'') in the intervening space approximately perpendicular to the plane of the panes in order to direct the incoming light current.

9. Outer wall element as in one of the Claims 1 to 8, characterized in that a heat retaining layer (21) is positioned on the side of the inner shell (20) facing the transparent heat insulating layer (30).

10. Outer wall element as in Claim 9, characterized in that the heat retaining layer (21) has a retaining mass consisting of one or more mineral sheets.

11. Outer wall element as in one of the Claims 9 or 10, characterized in that the heat retaining layer (21) has a retaining mass consisting of one or more ceramic sheets.

12. Outer wall element as in one of the Claims 9 to 11, characterized in that the heat retaining layer (21) has a retaining mass consisting of glass.

13. Outer wall element as in one of the Claims 9 to 12, characterized in that the heat retaining layer (21) has a retaining mass consisting of natural or artificial stone.

14. Outer wall element as in Claim 13, characterized in that the heat retaining layer (21) has a retaining mass consisting of concrete.

15. Outer wall element as in one of the Claims 9 to 14, characterized in that the heat retaining layer (21) has a retaining mass consisting of plastic, specifically one or more plastic sheets.

16. Outer wall element as in one of the Claims 9 to 15, characterized in that the heat retaining layer (21) consists of a retaining mass of low thermal conductivity.

17. Outer wall element as in one of the Claims 9 to 16, characterized in that the inner heat insulating layer (22) is placed between the heat retaining layer (21) and the end sheet (23).

18. Outer wall structure as in one of Claims 1 through 17, characterized in that the heat insulating layer (22) consists of PUR [polyurethane] foam or PS [polystyrene] foam, glass fibres, mineral fibres, etc.

19. Outer wall structure as in one of Claims 1 through 18, characterized in that the inner transparent heat insulation layer (30) consists of one or more layers of air between 10 and 50 mm, preferably 20 mm thick.

20. Outer wall structure as in one of Claims 1 through 19, characterized in that the end sheet (23) is constructed to be vapour proof.

21. Outer wall structure as in Claim 20, characterized in that the end sheet (23) has a sealing sheet of metal (aluminum or steel).

22. Outer wall structure as in one of Claims 20 or 21, characterized in that the end sheet (23) contains a retaining mass, in particularly concrete.

23. Outer wall structure as in one of Claims 1 to 22, characterized in that the transparent heat insulating layer (30) is formed by an air layer between 10 and 50 mm, preferably 20 mm thick.

24. Outer wall structure as in one of Claims 1 to 22, characterized in that the transparent outer heat insulating layer (30) is composed of capillary sheets of transparent plastics with a honeycomb or chamber structure perpendicular to the layer.

25. Outer wall structure as in one of Claims 1 to 22, characterized in that the transparent outer heat insulating layer (30) is composed of glass wool as the insulating material.

26. Outer wall structure as in one of Claims 1 to 22, characterized in that the transparent outer heat insulating layer (30) is composed of acrylic resin foam.

27. Outer wall structure as in one of Claims 1 to 26, characterized in that an outer wall element with a heat retaining layer (21) adjacent to the absorbing layer (21') the glazing preferably consists of individual panes or of insulating glass elements of two clear glass panes each.