METHOD FOR MANUFACTURING BUILDING ELEMENT WITH WOODEN FRAME, BUILDING ELEMENT WITH WOODEN FRAME, AND BUILDING ELEMENT SYSTEM

Abstract

“A method for manufacturing a building element with a wooden frame, the method comprising forming the frame of the element of wooden panels, filling the space inside the frame with insulation material, coating the wooden panels) which define the outer surfaces of the frame of the building element to be substantially air-tight, filling the space inside the frame with expanded perlite, and applying vacuum in the space inside the building element by a vacuum pump connected to the element. The invention also relates to such a building element with a wooden frame, as well as a building element system consisting of a plurality of such building elements with a wooden frame.”

Marked up version of the abstract:

A method for manufacturing a building element with a wooden frame, the method comprising forming the frame of the element of wooden panels, filling the space inside the frame with insulation material, coating the wooden panels which define the outer surfaces of the frame of the building element to be substantially air-tight, filling the space inside the frame with expanded perlite, and applying vacuum in the space inside the building element by a vacuum pump connected to the element. The invention also relates to such a building element with a wooden frame, as well as a building element system consisting of a plurality of such building elements with a wooden frame.

Claims

1. A method for manufacturing a building element with a wooden frame, the method comprising: forming a frame of wooden panels for the element, coating the wooden panels which define the outer surfaces of the frame of the building element to be substantially air-tight, filling the space inside the frame with expanded perlite, and applying vacuum in the space inside the building element by a vacuum pump connected to the element.

2. The method according to claim 1, wherein the edges of the panels of the building element are provided with bevels, at which the panels are joined together by a glued joint.

3. The method according to claim 1, wherein supporting pieces are inserted in the inside space delimited by the panels of the building element, to connect the largest panels of the element.

4. The method according to claim 3, wherein the supporting pieces are rod-like and/or plates equipped with openings, and the supporting pieces are made of a wood material.

5. The method according to claim 1, wherein the wooden panels of the building element are plywood sheets, and wherein the supporting pieces of the building element are also made of plywood or laminated veneer lumber.

6. The method according to claim 1, wherein glass panes and/or rubber sheets and/or metal sheets are attached onto the outer surfaces of the wooden panels of the building element, to achieve substantial air tightness, the attachment being preferably made by applying an elastic fixing layer.

7. The method according to claim 1, wherein a filter is installed between the inner space of the building element and the vacuum pump, to prevent removal of insulation material from the inside of the element.

8. A building element with wooden frame, comprising a wooden frame and insulation material inserted in the frame, wherein wooden panels defining outer surfaces of the frame of the building element are coated to be air-tight, the inner space in the frame is filled with expanded perlite, and a vacuum pump is connected to the element, for applying a vacuum in a space inside the frame.

9. The building element according to claim 8, wherein the vacuum pump connected to the element is used for adjusting the vacuum in the space inside the frame of the building element.

10. The building element according to claim 8, wherein edges of the panels of the element are provided with bevels, at which the panels are joined together by a glued joint, and wherein the wooden panels are preferably plywood sheets.

11. The building element according to claim 8, wherein the space inside the frame is equipped with supporting pieces connecting largest outer panels of the element, the supporting pieces being preferably rod-like and/or sheets provided with openings and being preferably made of a wooden material.

12. The building element according to claim 8, wherein glass panes and/or rubber sheets and/or metal sheets are attached onto outer surfaces of the wooden panels of the building element, to achieve substantial air tightness, the attachment being preferably implemented with an elastic fixing layer.

13. The building element according to claim 8, the building element being provided with a filter in connection with the connection of the vacuum pump, to prevent removal of insulation material from the inside of the element.

14. The building element according to claim 8, wherein a thickness of the element is 10 to 150 cm a width of the element is 120 to 320 cm, and the a length of the element is 120 to 1500 cm.

15. A building element system comprising a plurality of building elements according to claim 8, all of the building elements of the plurality of building elements being connected to one and the same vacuum pump.

16. The building element according to claim 14, wherein the thickness of the element is 15 to 30 cm. 6

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In the following, the invention will be described in more detail by way of example with reference to the appended figures, in which

[0027] FIG. 1 shows schematically a structure of a part of a building element according to the invention,

[0028] FIGS. 2A to 2D show schematically some edge joints of panels of a building element according to the invention,

[0029] FIGS. 3A and 3B show schematically some supporting pieces for the space inside a building element according to the invention,

[0030] FIGS. 4A to 4C show schematically a plate-like reinforcement for a building element according to the invention, separately and attached to a panel, as well as an alternative embodiment for the reinforcement,

[0031] FIGS. 5A to 5D show schematically some embodiments of reinforcements for flank panels of a building element according to the invention,

[0032] FIG. 6 shows schematically an alternative embodiment of reinforcements for flank panels, in two different projections, and

[0033] FIG. 7 shows schematically a cross-sectional view of a building element according to the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0034] FIG. 1 schematically shows a part of the structure of a building element 1 according to the invention.

[0035] In the embodiment of FIG. 1, the structure of the building element 1 consists of panels and bottom plates 2, flank panels 3 of the element, and supporting bars 4. In the embodiment of FIG. 1, the flank panels 3 are also provided with reinforcements 5.

[0036] FIGS. 2A to 2D schematically show an embodiment for the edge joint between the panels 2 and the flank panels 3 of the building element according to the invention, and variants of the edge joint.

[0037] In this embodiment, a bevel of 45 degrees is worked on all edges of the panels 2 and the flank panels 3. At these bevels, the panels 2 and the flank panels 3 are joined together by glued joints 6.

[0038] These bevels are used to minimize elongation of the glued joints 6 between the flank panels 3 and the panels 2 of the element, which are preferably plywood sheets, due to dimensional changes caused by vacuum drying of the plywood sheets. This is based solely on the naturally orthotropic material properties of wood; that is, the dimensions of wood, and thereby also plywood, are changed by changes in the moisture content, in different ways depending on the direction of viewing the material. With these bevels of 45 degrees, the effects of the moisture content on the glued joint 6 can be minimized.

[0039] In the example of FIG. 2A, the bevel extends over the whole thickness of the sheets 2 and 3 to be joined, whereas the example of FIG. 2B shows a joint with incomplete bevels. In the example of FIG. 2C, the outer edge of the joint is worked to be rounded, and in the example of FIG. 2D, the outer edge of the joint is worked to have a bevel whose plane is substantially perpendicular to the glued joint 6. The edge shapes shown in FIGS. 2C and 2D facilitate the coating of the outer surface of the element to become airtight.

[0040] FIGS. 3A and 3B schematically show some reinforcing pieces 7 and 8 for the space inside the building element according to the invention.

[0041] The reinforcing pieces 7 and 8 are designed to have a rod-like shape with sections widening at the ends. Being an orthotropic material, wood withstands loads in different ways, depending on the direction of the load. To conduct as little heat as possible through the building element, and not to be cut under the pressure loading through the panels of the element, the supporting elements 7 and 8 have to be shaped wider at their ends than in their middle sections.

[0042] In the embodiment of FIG. 3A, the supporting piece 7, which is shown in both side and end projections in FIG. 3A, is made by lathing, and the material used is plywood or laminated veneer lumber.

[0043] In the embodiment of FIG. 3B, the supporting piece 8 is designed to have an angular shape and is made of a plywood board or a plywood beam by sawing, milling or laser cutting.

[0044] FIGS. 4A and 4B schematically show a plate-like reinforcement 9 for a building element according to the invention, separately and connected to a panel 2, and FIG. 4C schematically shows an alternative embodiment 9′ of a plate-like reinforcement for a building element according to the invention.

[0045] In the embodiment of FIGS. 4A and 4B, the plate-like reinforcement 9 corresponds, in practice, to a uniform row of angular supporting pieces of FIG. 3B, connected to each other at their ends. This embodiment provides an alternative for separate single supporting pieces. Such a plate-like structure facilitates the manufacture of the supporting structure of the building element according to the invention, and its attachment to the panels 2 of the element. In this embodiment, a compromise is sought between the manufacturing costs and the thermal insulation capacity. The plate-like reinforcement 9 is preferably made of a plywood board by milling.

[0046] FIG. 4B illustrates an implementation of the internal supporting structure of the building element according to the invention, with plate-like reinforcements 9.

[0047] In the embodiment of the plate-like reinforcement of FIG. 4C, the openings in the plate-like reinforcement 9′ are formed by drilling, wherein cost-efficiency is achieved in the formation of the openings.

[0048] FIGS. 5A to 5D schematically show some embodiments of reinforcements for flank panels 3 of a building element 1 according to the invention.

[0049] In the building element according to the invention, the shaping of the flanks can be enhanced by optimizing the design of the flank of the element. Thus, the flank structure of the element is made by gluing a rectangular plywood sheet (flank panel 3) made of thin veneers and having an even thickness to a flank reinforcement structure made of plywood and worked to shape (FIG. 1, reinforcements 5). In this way, a lower thermal transmittance coefficient is obtained for the element than for an element having flank structures with a completely uniform thickness.

[0050] In the embodiment of FIG. 5A, the reinforcement structure 5a of the flank panel is formed of perpendicular reinforcements. In this reinforcement structure 5a, the reinforcements are perpendicular to the longitudinal direction of the flank panel, and the reinforcement structure is made of a plywood sheet by milling.

[0051] In the embodiment of FIG. 5B, the reinforcement structure 5b of the flank panel is formed of reinforcements forming a grid-like structure. In this reinforcement structure 5b, the reinforcements are oblique with respect to the longitudinal direction of the flank, forming a grid structure, and the reinforcement structure is made of a plywood sheet by milling.

[0052] In the embodiment of FIG. 5C, the reinforcement structure 5c of the flank has the geometry of a perforated structure which can be made by drilling instead of milling. Thus, the U value of the element is not fully optimized, but the manufacturing costs of the element can be reduced.

[0053] In the embodiment of FIG. 5D, the reinforcement structure 5d of the flank is provided with openings in different sizes and locations, wherein the size and the location of the openings are used to improve the U value of the element in a cost-efficient way with respect to a flank structure with a uniform thickness.

[0054] FIG. 6 shows a further developed embodiment of a reinforcement structure for flank panels, both in a lateral projection and in a cross-sectional view. The figure shows a flank panel 3 glued onto a reinforcement structure 5e.

[0055] In the building element according to the invention, the reinforcement structure of the flank can be optimized further in view of a better thermal transmittance coefficient of the element, by providing the reinforcements of the reinforcement structure with T-shaped shoulders by milling. This is illustrated in FIG. 6 for the case of transverse reinforcements according to FIG. 5A.

[0056] The inner corners of the T-shaped shoulders may also be rounded. The solution may be applied to perpendicular reinforcements (FIG. 5A), reinforcements having a grid structure (FIG. 5B) as well as reinforcements having a perforated structure (FIGS. 5C and 5D). In perforated structures, the openings have to be worked by milling. T-shaped reinforcements increase the bending stiffness of the reinforcement structure compared with a reinforcement structure having the same cross-sectional area without shoulders. Thus, the flank structure of the element can be made in the form of a structure having a lighter weight, and less heat will be conducted along the flank structure through the element.

[0057] FIG. 7 schematically shows the cross-section of a building element 1 according to the invention.

[0058] In this embodiment, the building element 1 consists of panels 2, flank panels 3, supporting rods 4 for the inner space of the element, a reinforcement structure 5 for the flank panels, expanded perlite 10 used as insulation material, a glass coating 11 on the panels, a rubber sheet coating 12 on the flanks, an elastic fastening layer 13 on the panels, a sealing seam 14 at the edges of the coating sheets, a connection to a vacuum pump 15, a filter 16, and a vacuum pump 17.

[0059] In this embodiment, the air-tight coating of the panels 2 of the building element 1 is implemented as a glass coating 11 by using window glass panes, and the air-tight coating of the flank panels 3 is implemented as a rubber sheet coating 12 by using EPDM rubber sheets, the sheets being fastened with an elastic fixing layer 13 by using Liquid Rubber HBS200 material. Metal sheets, such as aluminium sheets, may also be used as the air-tight coating.

[0060] The connection 15 for the vacuum pump 17 is provided with a filter 16 to prevent removal of expanded perlite 10 from the space inside the element. A metal filter gauze with a micro mesh size is used as the filter 15.

[0061] The parts of the frame of the building element 1 are joined together by gluing with a polyurethane glue.

[0062] The thickness of the building element 1 may vary between 10 cm and 150 cm. In most uses, the thickness of the element varies between 15 cm and 30 cm, but in applications where a minimum U value is sought, the element may have a thickness even greater than one meter. The width of the element may vary between 120 cm and 320 cm. In most uses, the width of the element will be between 280 cm and 320 cm. The length of the element may vary between 120 cm and 1500 cm. In most uses, the length of the element will be between 600 cm and 1500 cm. In an element longer than 300 cm or wider than 150 cm, scarfed plywood is used as the material for the panels and the flank panels.

EXAMPLES

[0063] In a first example, an element having a size of 120 cm×120 cm×23.6 cm is examined at an average temperature of 10 C., i.e. about 283 K. The density of expanded perlite is 60 kg/m.sup.3, and the average pore size of a layer is assumed to be 100 micrometres. Further, a pressure of about 0.1 millibar is maintained in the element. Under these conditions, the thermal conductivity of air is estimated to be about 0.0025 W/(m.Math.K). The thermal conductivity transmitted by the solid substance of the perlite layer and thermal radiation is estimated to have a value of about 0.006 W/(m.Math.K). Consequently, the total value determined for the thermal conductivity of the perlite layer will thus be 0.0085 W/(m.Math.K).

[0064] The panels of the element examined consist of birch plywood having a thickness of 18 mm, and they are placed 20 cm apart from each other. At the flanks of the frame structure, reinforcements 5a according to FIG. 5A are used, as well as 49 supporting rods 7 made of glued laminated wood and shown in FIG. 3A. All the veneers of the glued laminated wood are aligned, to achieve the best compression strength. The optimized radius of the tapered middle section of the supporting rod is thus 10 mm, and the radius of the widened ends, in turn, 20 mm. One flank of the element comprises six reinforcements transverse to the longitudinal direction of the flank. These reinforcements have a width of 15 mm and a thickness of 21 mm. The distance between the reinforcements is 135 mm, and the thickness of the thin veneer plywood glued onto the reinforcement structure of the flank is 6.5 mm.

[0065] The thermal conductivity of glued laminated wood in the direction of the veneer is found to be 0.22 W/(m.Math.K), and the thermal conductivity of birch plywood, in the direction of the veneer, is estimated to be 0.17 W/(m.Math.K). Thus, the proportion of the transmittance coefficient of heat transmitted along the frame, obtained with the above presented geometry, is about 0.040 W/(m.sup.2.Math.K). The proportion of the perlite layer, in turn, can be determined to be 0.041 W/(m.sup.2.Math.K). Finally, by summing up the proportions of the perlite layer and the frame structure on the thermal transmittance coefficient, a U value of 0.081 W/(m.sup.2.Math.K) is obtained for the element.

[0066] Examining a larger size of the element, the relative proportion of heat transferred along the flanks of the elements of the thermal transmittance coefficient of the element decreases; the ratio between the cross-sectional area of the flanks and the total cross-sectional area of the element decreases. In another example, the size of the element is 3 m×1.5 m×23.6 cm. Thus, the proportion of heat transferred along the frame of the element of the thermal transmittance coefficient of the element decreases to the value 0.027 W/(m.sup.2.Math.K), and a calculated U value as low as 0.068 W/(m.sup.2.Math.K) would be achieved for the element. From this, the thermal transmittance coefficient can be decreased even further by making the element thicker, by optimizing the geometry of the frame in the direction of FIGS. 5A and 6, and by developing a barrier layer with a higher density, whereby an ever lower internal pressure can be achieved in the element.

[0067] In a third example, a case according to the first example is examined, but with the exception of maintaining the internal pressure of the element at about 3 millibar. Thus, the total thermal conductivity of the perlite layer can be estimated to have an approximate value of 0.020 W/(m.Math.K). Thus, a value of 0.10 W/(m.sup.2.Math.K) can be calculated for the proportion of the perlite layer of the thermal transmittance coefficient of the element, and the U value calculated for the element will be 0.14 W/(m.sup.2.Math.K). Under these conditions, measurements of the thermal transmittance coefficient of a test specimen of an element were taken by Hot-Box equipment of Eurofins Expert Service (previously VTT Expert Service) in September 2018. The measured U value was 0.28 W/(m.sup.2.Math.K). The difference between the theoretical and measured U values is probably due to a too large granular size of expanded perlite.

[0068] With respect to the embodiments of the invention shown in the figures and described above, it should be noted that they are not intended to limit the invention in any way. A person skilled in the art will know how to and can amend these embodiments in a number of obvious ways within the scope of the appended claims. Consequently, the invention is not limited to the above described embodiments only.