Electrically heated wall element

Abstract

The disclosure relates to an electrically heated wall element (15) comprising a body sheet (20) comprising one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound and at least one heating element (10) on a first face of the body sheet -820). The at least one heating element (10) is formed as a heating element stack (25) and a surface layer (28) comprising one or more material layers covers the first face of the body sheet and the heating element stack. A heatable area of the electrically heated wall element is at least 0.15 m2. The heatable area is configured to be heated by a single heating element or by a plurality of heating elements, each of the plurality of heating elements configured to heat an area of at least 0.01 m2. The patterned conductive element of the single heating element or the plurality of heating elements covers 20% to 60%, preferably 40% to 50% of the heatable area.

Description

[0001] ELECTRICALLY HEATED WALL ELEMENT

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to the field of construction materials, and particularly to wall elements that are electrically heated.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] There are a few known efforts to provide electrically heated heater devices for walls, however with technical problems. Printed resistive heaters and decal type heaters require high operating voltages, which limits available heating area and increases risk of fire and electric shock. Available wall heating systems that include pre-formed cable mats, bronze mesh or carbon films are typically bulky and expensive.

[0006] A problem is that there are no resistive heaters available that are integrated directly to the construction materials and cover a wide area so that they enable effective and safe drying or heating the respective space or surface.

[0007] WO2022 / 234189 discloses an improved roll-to-roll processing method and an object manufactured by such method. This enables manufacturing conductive structures with metallic characteristics covering wide areas. Such conductive structures can be laminated on various carriers or inside laminate materials used in construction of buildings, interiors structures or surface materials.

[0008] BRIEF DESCRIPTION OF THE DISCLOSURE

[0009] An object of the present disclosure is to provide an electrically heated wall element so as to solve the above problem. The wall element is provided with one or more heating elements, which may be individually controllable.

[0010] The object of the disclosure is achieved by an electrically heated wall element, characterized by what is stated in the independent claims. Some embodiments of the disclosure are disclosed in the dependent claims.

[0011] According to an embodiment, an electrically heated wall element is provided. The wall element comprises a body sheet comprising one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound. The wall element comprises at least one heating element on a first face of the body sheet. The at least one heating element is formed as a heating element stack comprising a first adhesive layer, at least one patterned conductive element made of a metal foil and attached on a first face of the body sheet with the first adhesive layer. Optionally, the heating element stack comprises a carrier layer on attached on top of the at least one patterned conductive element or between the first adhesive layer and the at least one patterned conductive element. The wall element comprises a surface layer comprising one or more material layers, the surface layer covering the first face of the body sheet and the heating element stack. The surface layer is attached to the body sheet and to the heating element stack by a second adhesive layer.

[0012] A heatable area of the electrically heated wall element is at least 0.15 m2. The heatable area is configured to be heated by a single heating element or the heatable area is configured to be heated by a plurality of heating elements, so that each of the plurality of heating elements configured to heat an area of at least 0.01 m2.

[0013] Area of the patterned conductive element of the single heating element or the plurality of heating elements cover 20% to 60%, preferably 40% to 50% of the heatable area of the electrically heated wall element.

[0014] According to some embodiments, thickness of the patterned conductive element is between 2 pm and 50 pm, more preferably between 5 pm and 20 pm, most preferably between 9 pm and 18 pm.

[0015] According to some embodiments, wherein total thickness of the heating element stack is between 30 pm and 100 pm, preferably between 40 pm and 70 pm.

[0016] According to some embodiments, cross-section of the patterned conductive element is essentially rectangular. Width of the patterned conductive element is 10 times to 1000 times, preferably 100 to 500 times the height of the patterned conductive element. According to some embodiments, the patterned heating element is a patterned metal foil made of any one of aluminum, copper, zinc and nickel, or an alloy of these.

[0017] According to some embodiments, the patterned conductive element is configured to be heated into a comfort temperature using a DC operation voltage that is not more than 120V, preferably between 12V and 50V, or an AC operation voltage that is less than 50V.

[0018] According to some embodiments, the at least one surface layer visually hides the heating element stack.

[0019] According to some embodiments, each heating element is patterned as meandering line within respective heatable area.

[0020] According to some embodiments, total thickness of all the at least one surface layer combined is less than 2 mm, preferably less than 1,3 mm.

[0021] The disclosure is based on the idea of using wall elements with laminated conductive structures with conductive metal patterns as resistive heaters. An advantage of electrically heated wall elements of the disclosure is that resistive heaters integrated into wall elements can be installed in a space as an integral part of the walls themselves, which reduces cost of installation of heating systems in a room or any other space or surface to be heated. This also enables drying the space and surfaces by means of heating. When the heating system is an integral part of the walls, no separate heating appliances are needed, which increases freedom of interior design. Heating by such integrated resistive heaters is energy efficient, since heating elements can be configured to be individually controllable; this enables switching off heating elements that are covered by bulky furniture like sofas, pianos or bookshelves, or any other obstacles.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which:

[0024] Figure 1 illustrates a room; Figure 2 illustrates a cross section of a wall element according to a first embodiment;

[0025] Figure 3 illustrates a cross section of a wall element according to a second embodiment;

[0026] Figure 4 illustrates a cross section of a wall element according to a third embodiment;

[0027] Figure 5 illustrates a cross section of a wall element according to a fourth embodiment;

[0028] Figure 6 illustrates heating elements in an electrically heated wall element.

[0029] DETAILED DESCRIPTION OF THE DISCLOSURE

[0030] The disclosure relates to wall elements, particularly to wall elements with laminated, resistive heating elements that are primarily used for heating and / or drying interior spaces, such as rooms, as well as for heating and / or drying surfaces of the wall elements.

[0031] Figure 1 illustrates a room 100 with walls covered by electrically heated wall elements 15. Each electrically heated wall element 15 comprises one or more heating elements 10, which may be individually controllable as illustrated by coloured and white heating elements 10: coloured heating elements 10 illustrate active heating elements that are used for heating the room, and white heating elements 10 illustrate inactive heating elements. By having controllable heating elements 10, any heating elements 10 that are behind an obstacle 21, such as the table or bookshelf, or for instance a sofa or piano, can be switched off, thus saving energy.

[0032] Each electrically heated wall element 15 is a layered structure. A body sheet comprising one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound forms the main structural support. The body sheet can be basically of any known type of wall element material typically used for interior walls, and the body sheet may have a plurality of layers to provide desired mechanical characteristics. At least one heating element comprising a heating element stack is attached on the body sheet. The heating element stack comprises a first adhesive layer and at least one patterned conductive element comprising patterned metal foil. The patterned conductive element is attached on a first face of the body sheet with the first adhesive layer.

[0033] According to some embodiments, the heating element stack comprises an additional carrier layer on attached on top of the at least one patterned conductive element. Such carrier layer improves mechanical characteristics of the heating element stack during manufacture and enables for example laminating the heating element to the body sheet from roll, which enables mass production.

[0034] Figure 2 illustrates layers of the wall element according to a first embodiment. Drawing is not in scale. The body sheet 20 comprises one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound forms the main structural support. The body sheet can be basically of any known type of wall element material typically used for interior walls, and the body sheet 20 may have a plurality of layers to provide desired mechanical characteristics.

[0035] Heating element 10 in form of a heating element stack 25 is attached on a first face of the body sheet 20. In the first embodiment, the heating element stack comprises portions of a first adhesive layer 22 and at least one patterned conductive element 24 comprising a patterned metal foil. The heating element stack 25 is marked in the drawing with a dotted line on the left side of the drawing. Marking of the heating element stack 25 is omitted on the right side for clarity. The patterned conductive element 24 is attached on the first face of the body sheet 20 with the first adhesive layer 22. In the first embodiment, the first adhesive layer 22 covers essentially the entire face of the body sheet 20 or at least partially covers areas between portions of the patterned conductive element 24 and / or portions between different patterned conductive elements 24.

[0036] There are several alternatives for manufacturing the heating element stack according to the first embodiment. For example, the entire area of the first face of the body sheet 20 may be covered with a layer of first adhesive layer 22, and a uniform, thin metal foil is attached thereto. The metal foil may be provided from a roll, or it may be provided as in form of a sheet or sheets. The metal foil is thereafter patterned by a pervasive method, such as laser cutting, die-cutting or kiss-cutting to pattern the metal foil to generate the one or more patterned conductive elements 24. Patterning of the metal foil can also be made by milling or knife cutting. Using pervasive methods for patterning the metal foil involves a risk of harming the body sheet 20. Milling may remove not only portions of the metal foil that are not part of the one or more patterned conductive elements 24, but also at least part of the first adhesive layer 22 in areas between different portions of a patterned conductive element 24 or between mutually separate patterned conductive elements 24.

[0037] A wall element 15 typically further comprises a surface layer 28 covering the first face of the body sheet 20 and the heating element stack 25. The surface layer 28 is attached to the body sheet 20 and to the heating element stack by a second adhesive layer 26. As known in the art, the surface layer 28 of a wall element 15 may comprise one or more layers, such as a decorative layer and one or more protective layers to achieve desired look for the walls as well as to have desired properties for the surface of the wall facing the room. For example, protective layers may be added on the first face of the body sheet 20 to make it washable and water impermeable, to protect the decorative layer from wear and tear and so on. Preferably, these surface layer covering the first face of the body sheet 20 and the heating element stack are significantly thinner than the body sheet 20. Preferably thickness of the surface layer 28 is between 0.5 and 2 mm, preferably between 0.9 and 1.3 mm. This applies to all embodiments. Thinness of the surface layer 28 also facilitates effective radiation of heat from the patterned conductive element 24 to the room when heated. Surface layer is not, as such, determining the inventive concept according to the disclosure.

[0038] After patterning the conductive elements 24 and / or the heating element stack 25, the first face of the body sheet 20 with the heating elements stack 25 is covered with the second adhesive 26, on which a surface layer 28 are placed, so that heating element stacks 25 are preferably hidden from sight and the final wall element has desired look, feel and technical characteristics. For example, surface layer 28 may comprise a decorative layer and / or a protective layer that makes the first face of the wall element to be washable and / or water resistant. Preferably, thickness of the layer of second adhesive 26 is sufficient to make the upper face of the wall element essentially flat before surface layer 28 is attached, so that the heating element stack 25 cannot be visually detected after the entire surface layer 28 is in place. Alternatively, or additionally, the surface layer 28 may be sufficiently stiff and / or thick that the heating element stack 25 is not visible on the top of the surface layer 28.

[0039] If the patterned conductive element 24 is cut from metal foil attached to the body sheet 20, portions of the metal foil that are not used as part of the patterned conductive element 24 may be removed mechanically or left in place, however mechanically separated from the patterned conductive element 24. Properties of the second adhesive 26 used for attaching surface layer may not be ideal for attachment to metal. Also heating of the patterned conductive element 24 when in operation may affect properties of the second adhesive 26, thus increasing risk of separation of surface layer 28 from the patterned conductive element 24 over time. However, by designing the patterned conductive element 24 such that they cover between 20% and 60% of the area of the body sheet, preferably as meandering patterns, risk areas for separation of the surface layer 28 are small enough not to become a major problem mechanically nor visually, when attachment of the surface layer 28 with the body sheet by the first 22 and / or second adhesive layer 26 is reliable on areas between portions of the patterned conductive element 24 and / or between patterned conductive elements 24.

[0040] Removing parts of metal foil that are cut off and not part of the heating elements may be a laborious task, which likely increases the cost of manufacturing the wall element 15. However, leaving additional, unused metal areas in the wall element structure likely increases the risk of unwanted separation of surface layer 28 from the body sheet 20, because it reduces the area on which the first 22 and / or second 26 adhesive layers directly couple the surface layer 28 to the body sheet 20, without any intermediate metal layers. Adhesion of the surface layer 28 with any remaining, unused metal areas may be improved by adding another adhesive layer between.

[0041] Figure 3 illustrates layers of the wall element according to a second embodiment. Drawing is not in scale. Like in all embodiments, the body sheet 20 comprises one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound forms the main structural support. The body sheet 20 can be basically of any known type of wall element material typically used for interior walls, and the body sheet 20 may have a plurality of layers to provide desired mechanical characteristics.

[0042] The heating element stack 25 is attached on a first face of the body sheet 20. The heating element stack 25 is marked with a dotted line on the left side, but marking is omitted on the right side for clarity. In the second embodiment, the heating element stack 25 comprises a first adhesive layer 22 and at least one patterned conductive element 24 made of a patterned metal foil. The patterned conductive element 24 is attached on a first face of the body sheet 20 with the first adhesive layer 22. In the second embodiment, shape of the first adhesive layer 22 is essentially the same with the patterned conductive elements 24.

[0043] During manufacturing, the patterned conductive element 24 may be provided from a roll or in form of individual sheets.

[0044] Like in all embodiments, total thickness of the heating element stack 25 should be small enough that upon adding the second adhesive layer 26 and the surface layer 28, the heating element stack 25 does not cause bulging of the outer surface of the wall element 15 on areas with the heating element stack 25, and thus the heating element stack 25 remains essentially invisible in the final product.

[0045] Like in the first embodiment, there is a higher possibility that surface layer 28 is separated from the body sheet 20 in areas with the heating element stack 25, either due to overall poorer adhesion of the second adhesive 26 to the metal surface of the patterned conductive element 24, or due to changes in adhesion due to heating of the heating element.

[0046] Figure 4 illustrates layers of the wall element according to a third embodiment. Drawing is not in scale. Like in all embodiments, the body sheet 20 comprises one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound forms the main structural support. The body sheet 20 can be basically of any known type of wall element material typically used for interior walls, and the body sheet 20 may have a plurality of layers to provide desired mechanical characteristics.

[0047] The heating element stack 25 is attached on the body sheet 20. In the third embodiment, the heating element stack 25 comprises a first adhesive layer 22 and at least one patterned conductive element 24 made of a patterned metal foil, and a carrier layer 27 that facilitates handling of the heating element stack

[0048] 25 during attachment of a pre-patterned heating element stack to the body sheet 20. The heating element stack 25 is marked with a dotted line on the left side, but marking is omitted on the right side for clarity. The heating element stack 25 with the patterned conductive element 24 is attached on a first face of the body sheet 20 with the first adhesive layer 22, the first adhesive layer forming a part of the heating element stack 25. In the third embodiment, shape of the first adhesive layer 22 as well as the shape of the carrier layer 27 is essentially the same as the shape the patterned conductive elements 24. The carrier layer 27 is included in the heating element stack when the manufacturing is implemented as disclosed in an earlier application WO2022 / 234189 by the same applicant. This embodiment is particularly practical for providing the patterned conductive element 24 from a roll, which facilitates effective mass production. Individual sheets with readily patterned heating element stacks 25 are also applicable, however not as practical for mass production.

[0049] In this embodiment, surface layer 28 is attached by the second adhesive layer

[0050] 26 that attaches primarily with the body sheet 20 and the carrier layer 27.

[0051] Figure 5 illustrates a fourth embodiment, in which the carrier layer 27 is disposed between the first adhesive layer 22 and the at least one patterned conductive element 24. This order of layers leaves the patterned conductive element 24 on the top of the heating element stack 25, thus having an interface between the metal sheet of the patterned conductive element 24 and the second adhesive layer 26. The patterned conductive element 24 is preferably formed as an elongated, meandering line. Shape of the line is a design option. Corners of the line may be rounded.

[0052] In all embodiments, cross-section of the patterned conductive element 24 is preferably rectangular, with thickness being significantly less than lateral dimensions thereof so that the patterned conductive element 24 does not significantly cause the heating element stack 25 to bulge from the first face of the body sheet 20. For example, thickness of the cross-section of the patterned conductive element 24 may be in level of 1 / 10, 1 / 50, 1 / 100 or 1 / 1000 of width of the respective cross-section of the patterned conductive element 24. Preferably, thickness of the cross-section of the patterned conductive element 24 is between 1 / 50 and 1 / 500 of width of the respective cross-section of the patterned conductive element 24. In other words, width of the patterned conductive element 24 is preferably at least 10 times, more preferably at least 50 times, most preferably at least 100 times the thickness of the patterned conductive element 24. Width of the patterned conductive element 24 is determined as line width, in other words across the longitudinal axis of a portion of the line.

[0053] In this context, a safe, low DC operating voltage is below 120 V, preferably between 12 V and 50 V. Operating current should not exceed 16 A. Likewise, a safe, low AC operating voltage should not exceed 50 V. Typical operating power of a heating element is between 50 W / m2and 400 W / m2.

[0054] The thin metal layer of the patterned conductive element 24 facilitates ease of design to achieve suitable resistance for each heating element so that safe operating voltages can be used. Non-limiting examples on dimensions of a patterned conductive element 24 that have resistance suitable for use in electrically heated wall elements:

[0055] - Copper resistivity is approximately 1.7*10'8Q / cm, which gives an exemplary, 0.02 mm (20 pm) thick, 2 mm wide and 1 m long patterned conductive element 24 a resistance of 0,425 ,

[0056] - An exemplary copper-zinc alloy resistivity is approximately 7*10'8 / cm, which gives a 0.02 mm thick, 2 mm wide and 1 m long patterned conductive element 24 a resistance of 1,75 . An exemplary copper-nickel-zinc alloy resistivity is approximately 2.8*10'8Q / cm, which gives a 0.02 mm thick, 2 mm wide and 1 m long patterned conductive element 24 a resistance of 7 .

[0057] For example, annealed copper has slightly higher resistivity than rolled copper - both can be used as material for patterned conductive elements 24. As known in the art, resistivity of alloys depends on proportions of metals in the alloy as well as applied manufacturing method.

[0058] In all embodiments, heating of the patterned conductive element 24 when in operation may affect properties of the second adhesive 26, thus increasing risk of separation of surface layer 28 from the patterned conductive element 24 over time as in the first, second and fourth embodiments, or from the carrier layer 27 in the third embodiment. Also, characteristics of the patterned conductive element 24 and the second adhesive as such may increase the risk of separation of the surface layer 28 in the area of the patterned conductive element 24.

[0059] In all embodiments, heating elements 10 preferably essentially cover majority of the area of the first face of the body sheet 20. Area of the one or more heating elements 10, which essentially corresponds to the area of the respective one or more heating element stacks 25 and the area of the respective patterned conductive element 24 is between 20% and 60% of the respective heatable area of the first face of the body sheet 20. 40% to 50% coverage of the heatable area by the heating elements is preferred to increase achievable heating efficiency. By limiting the relative coverage area of the heating element stack 25 and thus the relative coverage area of the patterned conductive elements 24 to maximum 60%, preferably to maximum 50% of the respective heated area of the wall element 15 ensures that even if the one or more surface layer 28 would not remain properly adhered on the heating element stack 25, the one or more surface layer 28 remain sufficiently attached by the second adhesive layer or the first and second adhesive layers to the body sheet 20 in areas between portions of the heating element stack 25 and, of course, between different heating elements 10, when the wall element 15 comprises more than one heating element 10. According to a preferred embodiment, the heating element 10 is patterned into meandering lines which enable frequent contact areas between portions of the heating element stack 25 for reliable attachment between the body sheet 20 and surface layer 28, thus reducing visual detectability of possible separation of attachment of surface layer 28 from the heating element stack 25.

[0060] In all embodiments, thickness of the metal foil and thus thickness of the patterned conductive element is between 2 pm and 50 pm, more preferably between 5 pm and 20 pm, most preferably between 9 pm and 18 pm. By manufacturing the patterned conductive element out of such thin metal foil of aluminum, copper, zinc and nickel, or an alloy of these, enables designing a patterned conductive element with resistance level that is suitable for heating a room into a comfort temperature with safe, low operating voltages. As known in the art, comfort temperature refers to an ideal comfort temperature for an average human, which is typically in the region of 20 to 22 degrees centigrade but varies geographically depending on the surrounding climate. Heating is typically needed only in relatively cool climates, where 20 to 22 degrees centigrade is a typical room temperature. Required heating power required from heating elements 10 depends on ambient temperature. Low operating voltages are important to ensure that even if the patterned conductive element was accidentally cut for example by knife or saw, or pierced by a nail or screw, or any hand tool, no life-threatening nor fire hazards are caused even if heating is on.

[0061] Total thickness of the heating element stack 25 should be between 30 pm and 100 pm, preferably between 40 pm and 70 pm. This range of thickness is thin enough that the second adhesive layer 26 can level the upper surface well enough so that the heating element stack 25 does not cause visible bulking of the outer surface of the wall element 15, while enabling keeping the overall thickness of adhesive layer or layers, heating element stack and surface layer thin enough to facilitate efficient radiation of heat from the patterned conductive elements 24 when heated by applying operating power thereto.

[0062] Figure 6 illustrates exemplary patterned conductive elements 24 in an electrically heated wall element 15. In this example, area of the electrically heated wall element 15 corresponds approximately to a heatable area, which in the shown example is configured to be heated by two mutually separate heating elements. Top layers are omitted that would preferably visually hide the entire heating element stack. This wall element 15 has two mutually separate patterned conductive elements 24, thus two mutually separate heating elements, which are to be coupled to a power source 55 for effectuating heating. Temperature of the patterned conductive element 24 may be controlled by adjusting the voltage fed to the patterned conductive element 24. Temperature may also be controlled by means of a thermostat that intermittently causes switching heating on an off.

[0063] For effective heating of a room, electrically heated wall element 15 comprises one or more heating elements that are configured to heat a relatively large area of the wall element 15, i.e. at least 0.15 m2, referred herein as the heatable area. The heatable area may be configured to be heated by a single heating element. Alternatively, the heatable area may be configured to be heated by a plurality of heating elements, each configured to heat an area of at least 0.01m2. For example, if the total area of the wall element shown in Figure 5 is 0.15 m2, both heater elements are configured to heat an area of approximately 0.075 m2. On the other hand, if the wall element 15 shown in Figure 6 would has an area of 0.5 m2, each heater element is configured to heat an area of approximately 0.25 m2.

[0064] Such large heatable areas are not achievable with safe, low levels of operating voltage and current with patterned conductive elements made from printed conductors generated using currently available conductive inks, such as silver inks, carbon inks or dielectric inks, because these conductive inks have too low conductivity, which significantly limits the available heatable area with safe operating voltages and currents. Only patterned conductive elements 24 made out of metal foils made of actual metal with good conductivity allow wide enough area to be heated by a single patterned conductive element 24. Preferred metals to be used as material of the patterned conductive elements 24 are aluminum, copper, zinc and nickel, or an alloy of these.

[0065] In the simplest configuration, heating operation by heating elements 10 comprising the patterned conductive element 24 may be controlled locally by a switching arrangement (not shown), which may also enable adjusting voltage for controlling temperature. Controlling may comprise a manual switch and / or a controller 58 that enables at least on-off switching, preferably also controlling temperature. Preferably, heating operation of each heating element 10 is individually controllable. Heating operation may be controlled remotely over a wireless or wireline connection towards the controller 58.

Claims

CLAIMS1. An electrically heated wall element comprising :- a body sheet comprising one or more of plasterboard, fibreboard such as plywood, plastic board, composite material, and sheet moulding compound,- at least one heating element on a first face of the body sheet, wherein the at least one heating element is formed as a heating element stack comprising a first adhesive layer, at least one patterned conductive element made of a metal foil and attached on a first face of the body sheet with the first adhesive layer, optionally a carrier layer on attached on top of the at least one patterned conductive element or between the first adhesive layer and the at least one patterned conductive element, and- a surface layer comprising one or more material layers, the surface layer covering the first face of the body sheet and the heating element stack, wherein the surface layer is attached to the body sheet and to the heating element stack by a second adhesive layer, characterized in that- a heatable area of the electrically heated wall element is at least 0.15 m2, wherein the heatable area is configured to be heated by a single heating element or wherein the heatable area is configured to be heated by a plurality of heating elements, each of the plurality of heating elements configured to heat an area of at least 0.01 m2, and- area of the patterned conductive element of the single heating element or the plurality of heating elements cover 20% to 60%, preferably 40% to 50% of the heatable area.

2. The electrically heated wall element according to claim 1, wherein thickness of the patterned conductive element is between 2 pm and 50 pm, more preferably between 5 pm and 20 pm, most preferably between 9 pm and 18 pm.

3. The electrically heated wall element according to claim 1 or 2, wherein total thickness of the heating element stack is between 30 m and 100 p rn, preferably between 40 pm and 70 pm.

4. The electrically heated wall element according to any one of claims 1 to 3, wherein cross-section of the patterned conductive element is essentially rectangular, and wherein width of the patterned conductive element is 10 times to 1000 times, preferably 100 to 500 times the height of the patterned conductive element.

5. The electrically heated wall element according to any one of claims 1 to 5, wherein the patterned heating element is a patterned metal foil made of any one of aluminum, copper, zinc and nickel, or an alloy of these.

6. The electrically heated wall element according to any one of claims 1 to 5, wherein the patterned conductive element is configured to be heated into a comfort temperature using a DC operation voltage that is not more than 120V, preferably between 12V and 50V, or an AC operation voltage that is less than 50V.

7. The electrically heated wall element according to any one of claims 1 to 6, wherein the at least one surface layer visually hides the heating element stack.

8. The electrically heated wall element according to any one of claims 1 to 7, wherein each heating element is patterned as meandering line within respective heatable area.

9. The electrically heated wall element according to any one of claims 1 to 9, wherein total thickness of all the at least one surface layer combined is less than 2 mm, preferably less than 1,3 mm.

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