US20180216361A1

US20180216361A1 - Supporting structure for a Dome-Shaped Roof

Info

Publication number: US20180216361A1
Application number: US15/555,491
Authority: US
Inventors: Daniel Kerber
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-03-03
Filing date: 2016-03-03
Publication date: 2018-08-02
Also published as: EP3265628A1; CN107646061A; WO2016138992A1; DE102015002620A1

Abstract

DE 86 22 844 01 discloses a tent having a carrying framework and a tarpaulin arranged thereon, wherein the carrying framework is formed by a scissor type system of rods having the tarpaulin arranged thereon.

Description

The present invention relates to a supporting structure for a dome-shaped roof, comprising at least six arcuate supporting arms.
Dome-shaped buildings are to be found in advanced civilizations at any time in the history of mankind. They take many and diverse forms, ranging from the igloo to the Pantheon, to name just two examples. The advantages of this construction form can be found in their statics, economy of space (ratio of area to enclosed space), psychology (conveying feeling of security) and acoustics, in order to again list just a few examples.
Historico-culturally, the possibility of erecting safe, leakproof and warming buildings, dismantling them again and reconstructing them elsewhere has led to the development of tents in particular among nomadic peoples. Nowadays, this possibility plays an important role not least in development aid and in accommodating refugees, where, in addition to the simplicity of constructing and dismantling and transporting the buildings, the lasting stability of the construction is essential in both contexts. This is because the aim in these indicated contexts is increasingly not to locate the dwellings in temporary camps, but to use them to make settlements and villages which are fit for humane habitation as soon as possible.
The object of the present invention is to create a supporting structure for a dome-shaped roof which can be quickly and stably erected.
This object is achieved by an apparatus having the features of claim 1. Preferred configurations are indicated in the subordinate claims.
According to the invention, a supporting structure is provided for a dome-shaped roof. The roof membrane can then be configured as a tarpaulin, for instance made of synthetic fibers, preferably made of 100% cotton textile (for example, 200 g/m2 to 300 g/m2, particularly preferably 280 g/m2), but also—for instance depending on local availability and tradition—made of fur, wooden boarding, corrugated iron, plant fiber and/or leaf mesh, including in particular as a subsequent and/or additional and/or remedial covering. The supporting structure is particularly preferably adapted to support and hold a dome which is at least in the shape of a quarter circle, in particular hemispherical, and to allow said dome to be attached thereto. To this end, it spans such a dome-shaped area, in particular with its outer contour or at least with some of its body edges and/or surface points, which can then be suitably adapted to the fastening of a roof membrane for instance by means of eyelets, hooks or threads.
This spanning with both its outer and inner contour is particularly preferable: the supporting structure comprises at least six arcuate supporting arms, the body edges and/or surface points of which then span such a dome-shaped area on both the outside and the inside of the arc. This makes it possible to mount a rain-proof and wind-proof dome-shaped membrane on the outside, for example, and a heat-insulating layer on the inside. The intermediate space can then additionally be filled with loose material, for example for heat insulation such as, for example, wool, hay, straw and/or leaves, but also for example to provide sound insulation or even for storage purposes.
The supporting arms are each composed of rods (“scissor rods”) which cross each other in pairs—like scissors as it were—and are connected to each other by joints, and which can be extended and compressed by this configuration. At least two such articulated rods which cross each other are each also preferably articulated in the region of their ends with, in turn, preferably the end regions of at least two such articulated rods which cross each other and thus form a bar of a scissor-action lattice which can be extended and retracted.
The scissor rods are preferably made of hollow aluminum profiles, in particular with a rectangular (particularly preferably with a high rectangular) cross-section, but have also proved to be usable according to the invention as a multiplex and can, for example, also be made of wood, wood composites, recyclable plastic or glass-fiber reinforced plastic.
These supporting arms extend particularly preferably in a star pattern horizontally from a center part, about which they are preferably uniformly distributed on a horizontal circumference. They are preferably rigidly fixed to the center part in this horizontal orientation in a star pattern, in particular in that each at least one scissor rod of preferably each of the supporting arms is fastened in a non-twistable manner in particular at the end side to the center part about a vertical axis. In this case, said scissor rod can, however, be swiveled about a horizontal axis of a knee joint which is tangential to an imaginary circumference about the center part. The at least one scissor rod crossing another can be displaced upward and downward by means of a displaceable bearing (also in particular at the end side) preferably along a vertical rail (preferably a single rod) (and, in this case, can preferably also be swiveled about a horizontal axis which is tangential to an imaginary circumference about the center part). This pair of scissor rods is therefore opened to the maximum extent as scissors if the displaceable bearing is pushed away as far as possible by the knee joint (preferably downward). This segment of the supporting arm is then compressed and shortened to the maximum extent. According to the known principle of the “scissor-action lattice”, this scissor-action lattice “segment” also operates the other more external segments and shortens or lengthens the supporting arm—extends or compresses it—depending on the operating direction.
Each of the supporting arms is preferably the same length—in particular, identical to each other with regard to the distances of the scissor-action lattice hinge points. The quarter-circle geometry of the supporting arms preferably results from the fact that all of the scissor rods are the same length, all having the same distance of their end joints from each other, but with the respective scissor hinge point for all scissor rod pairs offset by the same distance from the center between the end joints of each of the scissor rods (with the respective longer legs (between the scissor hinge and end joint) on the outside of the curvature of the extended scissor-action lattice bar). This offset is preferably between 1% and 5% of the distance of the end joints.
While extended, the supporting arms extend from the center part downward in a vertical plane in the shape of a quarter circle (that is, in particular with their scissor hinge points and/or surface points of in particular their outer and/or inner contour substantially on a quarter-circle line). In particular, since the supporting arms also have a spatial extent laterally, this means that they incorporate an (imaginary) vertical plane in their downward course in the shape of a quarter circle.
Each supporting arm therefore preferably comprises a plurality of (preferably four) pairs or “segments” of at least two scissor rods which cross each other in an approximately central hinge joint (“scissor hinge”). Preferably, one of these two scissor rods which cross each other additionally has a parallel scissor rod mirror-symmetrically identically (at least in kinematic terms) on the opposite side of the other scissor rod of the pair. The other scissor rod of the pair is therefore rotatably arranged as an individual scissor rod of the pair between the one of the scissor rods and its mirror-symmetrically parallel scissor rod about the scissor hinge. In addition, each of the two ends, namely, on the one hand, the end of the one scissor rod of the pair together with its mirror-symmetrically parallel scissor rod and, on the other hand, the end of the other individual scissor rod, is articulated to the two ends of the adjacent segment (namely the pair of scissor rods) by means of one knee hinge joint (the “end joint”) each and indeed such that the end of the individual scissor rod (the first-mentioned segment) between the ends of the one scissor rod and its mirror-symmetrically parallel scissor rod of the adjacent pair (segment) is rotatably arranged about the one end joint (connecting these), and the ends of the one scissor rod and its mirror-symmetrically parallel scissor rod (of the first-mentioned segment) hold between them the end of the individual scissor rod of the adjacent pair (segment) rotatably arranged about the end joint (connecting these).
When the supporting arm is extended, the distance of the two end joints can be positively fixed at the ends of each pair (segment) by a rod-shaped securing element or by a base part. To this end, the securing element is preferably swivelably fastened to the supporting arm about one of the two end joints, and can be locked (at the distance to be locked from this swivelable fastening by means of a suitable fastening apparatus on the securing element) in particular in the other of the two end joints, in particular can be caught there. This lockable distance (in particular in the case of identical scissor rods and their above-mentioned offset of the scissor hinge point for all scissor rod pairs from the center between the end joints of between 1% and 5% of the distance of the end joints) is preferably between 15% and 25% of the distance of the end joints of a scissor rod.
The supporting arms are articulated to a horizontal (preferably plate-shaped) base part by means of their bottommost scissor rods.
In each case at the lower end of the extended supporting arm, the bottommost scissor rod which is oriented downward and inward comprises coplanarly (in a plane in which it therefore lies itself and which is, in addition, located at right angles to the vertical plane, in which the supporting arm in the shape of a quarter circle is oriented), at least on one of its two sides, a lateral base supporting rod which also ends articulated to the base part (which is horizontal when the supporting arm is extended). This considerably promotes the stability of the individual supporting arm (and then also of the supporting structure according to the invention as a whole) laterally on the preferably plate-shaped horizontal base part, namely in particular having a planar footprint as a footprint on a level subsurface. If the base part is preferably configured in each case simply as a plate, the bottommost scissor rods of the respective supporting end articulated on the top side thereof.

Other advantages, configurations and details of the invention are described below in the description of embodiment examples with reference to the attached figures, wherein:

FIG. 1 shows a spatial view of a supporting structure according to the invention,

FIG. 2 shows a spatial view of a supporting structure according to the invention having a roof according to the invention,

FIG. 3 shows a spatial view of a supporting arm of the apparatus according to FIG. 1 in various phases of the compression,

FIG. 4 shows a spatial view of a center part of the apparatus according to FIG. 1,

FIG. 5 shows a spatial view of a segment of a supporting arm of the apparatus according to FIG. 1 in various stages of the locking,

FIG. 6 shows a spatial view of a base part of a supporting arm of the apparatus according to FIG. 1 in various stages of the locking, and

FIG. 7 shows spatial views of supporting structures according to the inventions made of supporting arms in accordance with FIG. 1 in various stages of the construction and reconstruction of buildings made therefrom.

The figures show a supporting structure 2 for a dome-shaped roof 4. FIG. 2 shows an igloo-type building 6 having the supporting structure which is not visible under the roof 4 made of a polyester fabric. The roof membrane 4 is configured as a tarpaulin which is attached to the supporting structure 2 and fastened in place with connectors 13 (see also FIG. 5e ). Depending on local availability and tradition, the roof membrane can be supplemented, replaced and/or repaired with layers and/or elements made of cotton, fur, plant fiber and/or leaf mesh.
The hexagonal ground plan of the building 6 together with the tent wall 8 having a tunnel-shaped entrance 9, which tent wall can be mounted on each of the six walls (other tent walls 11 comprise, for example, window openings), ensures that a plurality of such buildings 6 can be connected to form one building by means of the tunnel entrances 9 which can be fastened aligned with one another to form a uniform network oriented to one another at 60° to form a larger village community as it were with enclosed, protected connecting paths between the dwellings (FIG. 7f and FIG. 7g , further details will be provided below).
The supporting structure 2 is adapted to support and hold the hemispherical dome 4 and to allow said dome to be attached thereto. To this end, it spans such a hemispherical area, in particular with respect to FIG. 1 with its outer contour 14, namely with some of its surface points 10—the end joints 36 on the outside of the scissor rods 12, which are explained below—which hemispherical area is then suitably adapted to the fastening of the roof membrane 4 by means of rod-shaped securing devices with securing caps 13 (FIGS. 5e and f ).
This spanning is possible both with its outer contour 14 and inner contour 16: the supporting structure 2 comprises six arcuate supporting arms 18, the end joints on the outside of which span such a dome-shaped area as surface points 10 on the outside of the arc 14 and the end joints on the inside of which span such a dome-shaped area as surface points 20 on the inside of the arc 16. This makes it possible to mount the rain-proof and wind-proof dome-shaped membrane 4 on the outside and, for example, a heat-insulating layer (not shown) on the inside. The intermediate space can then additionally be filled with loose material (not shown) for example for heat insulation such as, for example, wool, hay, straw and/or leaves, but also for example to provide sound insulation or even for storage purposes.
The supporting arms 18 are, in particular with respect to FIGS. 1, 3 and 5, each composed of scissor rods 22 which cross each other in pairs and are connected to each other by joints, and which can be extended and compressed by this construction. At least two such articulated rods 22 which cross each other are each also articulated at their two ends with, in turn, the ends of at least two such articulated rods 22 which cross each other. They therefore form a bar 18 which can be extended and retracted in the manner of a scissor-action lattice.
These supporting arms 18 now extend, in particular with respect to FIGS. 1 and 3, in a star pattern horizontally from a center part 24 or connector 24, about which they are uniformly distributed on a horizontal circumference. They are rigidly fixed to the upper center part 24′ (having a ventilation opening 26 in the center, which aligns with a vent opening 28 in the apex of the roof membrane 4) in this horizontal orientation in a star pattern about a vertical axis, in that in each case the innermost top scissor rod 22′ (here the two parallel innermost top scissor rods 22′) of each of the supporting arms 18 is fastened in a non-twistable manner at the end side to the upper connector 24′ about a vertical axis (does not have this degree of freedom). In this case, said scissor rod can, however, be swiveled about a horizontal axis of a knee joint 30 which is tangential to an imaginary circumference about the center part 24. The one scissor rod 22″ crossing another is (together with the respective scissor rod 22″ of the other arms 18) articulated to a second connector 24″ (also at the end side) and can be displaced upward and downward with respect to the upper connector 22′ (and can, in this case, also be swiveled about a horizontal axis about the center part which is tangential to an imaginary circumference). This pair of scissor rods 22′, 22″ is therefore opened to the maximum extent as scissors if the lower connector 24″ is pushed away to the greatest possible extent downward by the upper connector 24′. This segment 22′, 22″ of the supporting arm 18 is then compressed and shortened to the maximum extent (according to FIGS. 3e and 5f ). According to the known principle of a scissor-action lattice, this scissor-action lattice segment 22′, 22″ also operates the other more external segments 22 and shortens or lengthens—extends the supporting arm 18 or compresses it—depending on the operating direction (see in particular FIGS. 3 and 5).
Each of the supporting arms 18 is the same length—and, in particular, identical to each other with respect to the distances of the scissor-action lattice hinge points 36, 38. The quarter-circle geometry of the extended supporting arms 18 results from the fact that all of the scissor rods 22 are the same length, all having the same distance of their end joints 36 from each other (see in particular FIG. 3a ), and with the respective scissor hinge point 38 for all scissor rod pairs 22 offset by the same distance from the center between the end joints 36 of each of the scissor rods 22 (with the respective longer legs (between the scissor hinge 38 and end joint 36) on the outside of the curvature of the extended scissor-action lattice bar (supporting arm) 18).
While extended, the supporting arms 18 extend from the center part 24 downward in an imaginary vertical plane in the shape of a quarter circle (that is, in particular with their scissor hinge points 38 and end points 36 as surface points of their outer contour 14 and inner contour 16 substantially on a quarter-circle line).
Each supporting arm therefore comprises a plurality of (in this case four) pairs or “segments” of in this case three scissor rods 22 which cross each other in an approximately central hinge joint (“scissor hinge”) 38. As shown (see in particular FIG. 5a ), one of these two scissor rods 22 a of a segment which cross each other always additionally has a parallel scissor rod 22 b mirror-symmetrically identically (including in kinematic terms) on the opposite side of the other scissor rod 22 c of the pair. The other scissor rod 22 c of the pair is therefore rotatably arranged as an individual scissor rod of the pair between the one 22 a of the scissor rods and its mirror-symmetrically parallel scissor rod 22 b about the scissor-type articulation 38. In addition, each of the two ends 36, namely on the one hand, the end of the one scissor rod 22 a of the pair together with its mirror-symmetrically parallel scissor rod 22 b and, on the other hand, the end of the other individual scissor rod 22 c, is then articulated to the two ends of the adjacent segment (pair of scissor rods) by means of one knee hinge joint 36 (the “end joint”) each and indeed such that the end 36 of the individual scissor rod 22 c (of the first-mentioned segment) between the ends of the one scissor rod 22 a′ and its mirror-symmetrically parallel scissor rod 22 b′ of the adjacent pair (segment) is rotatably arranged about the one end joint 36 (connecting these), and the ends 36 of the one scissor rod 22 a and its mirror-symmetrically parallel scissor rod 22 b (of the first-mentioned segment) hold between them the end 36 of the individual scissor rod 22 c′ of the adjacent pair (segment) rotatably arranged about the end joint 36 (connecting these).
When the supporting arm 18 is extended, the distance 40 of the two end joints 36′ can be positively fixed at the ends of each pair (segment) by a rod-shaped securing element 42 or by a base part 44 (this will be dealt with presently). To this end, the securing element 42 is swivelably fastened (see in particular FIG. 5) about one of the two end joints 36, and can be locked (at the distance 40 to be locked by means of a suitable fastening apparatus 46 on the securing element 42; see in particular FIG. 5b ) in the other of the two end joints 36″, namely can be caught there and secured by a block 48 which can be screwed in). To ensure that the fork-shaped fastening apparatus 46 on the securing element 42 threads in reliably on both sides about the scissor rod 22 on the end joint 36″, a wedge-shaped guide rail 49 is located there (and on each of the securing elements 42).
The supporting arms 18 are articulated to the horizontal (preferably plate-shaped) base part 44 by means of their bottommost scissor rods 22 (see in particular FIG. 6), which base part is bolted and/or screwed to the bottommost outer end joint 36′″ (which functions like a securing element 42) only in the extended condition of its supporting arm 18.
In each case at the lower end of the extended supporting arm 18, the bottommost scissor rod which is oriented downward and inward additionally comprises coplanarly (in a plane in which it therefore lies itself and which is, in addition, located at right angles to the vertical plane, in which the supporting arm 18 in the shape of a quarter circle is oriented), at least on its two sides, a lateral base supporting rod 50 which also ends articulated to the base part 44 (which is horizontal when the supporting arm 18 is extended). This considerably promotes the stability of the individual supporting arm 18 (and then also of the supporting structure 2 according to the invention as a whole) laterally on the preferably plate-shaped horizontal base part 44, namely in particular having a planar footprint 54 as a footprint on a level subsurface 52. The bottommost scissor rods 22 of the respective supporting arm end articulated on the base part 44 which is simply configured as a plate, on the upper side thereof (see in particular FIG. 6).
FIG. 7 then initially shows again how the supporting structure 2 is erected (FIG. 7b ) from a supporting arm 18 of the supporting structure 2 (FIG. 7a ), and indeed on a tent floor (FIG. 7c ) having an upward facing edge (in which the outer edges of the six base parts 44 of the supporting arms 18 can be radially supported outwardly). The igloo-shaped building 6 in accordance with FIG. 2 is initially erected by assembling, first of all, the roof membrane in the shape of a quarter circle (FIG. 7d ) and then a second roof membrane in the shape of a quarter circle and two tunnel entrances (FIG. 7e ) on the supporting structure.
Initially, three such igloos 6 (FIG. 70 and then seven such igloos 6 (FIG. 7g ) are then connected to form one building by means of the tunnel entrances which can be fastened aligned with one another to form a uniform network oriented to one another at 60° to form a larger village community as it were with enclosed, protected connecting paths between the dwellings.
In accordance with FIG. 7h , another building is in addition erected, which is now made up of only four arcuate supporting arms 18 in the shape of a quarter circle, two each of which together form a hemispherical arc. In this case, both hemispherical arcs span a tunnel having a hemispherical cross section in parallel to each other and are covered with a suitably sized roof membrane so that a tunnel is created, both sides of which are open.
Two other buildings in the shape of a quarter circle can be erected (FIG. 7i )—again made up of only four arcuate supporting arms 18 in the shape of a quarter circle, which however now extend again, as in the case of the igloo 6, in a star pattern horizontally from a center part and are distributed uniformly on a horizontal (but now only hemispherical) circumference about the center part.
Placing such a construction in accordance with FIG. 7i at the two sides of the tunnel in FIG. 7h creates a closed long house (FIG. 7j ).
The buildings in the shape of a quarter circle (FIG. 7i ) can also be produced—by recycling elements as it were—in that two parts of the building are rebuilt according to FIG. 7d (from, for example, two elements of a damaged igloo which might not be required such as that in FIG. 7e ), namely by removing the two surplus supporting arms (which are not required for supporting the roof membrane in the shape of a quarter circle) from the construction according to FIG. 7d . Thus, the elements required for fixing (to the long house in accordance with FIG. 7j ) can also be obtained in that the (as many as four) surplus supporting arms of the construction not required for fixing as shown in FIG. 7d can be omitted.
By interposing a second tunnel in accordance with FIG. 7h the long house can also be subsequently further extended (FIG. 7k ) with a correspondingly enlarged supporting structure (FIG. 7l ). In the case of the tunnel in accordance with FIG. 7h , incidentally, the arcuate supporting arms in the shape of a quarter circle are fixed horizontally and laterally to a central beam made up of an upper and a lower connector the length of the beam (and the tunnel) (FIG. 7m and FIG. 7n ).
Building parts such as for example the two sides of tunnels (such as that in accordance with FIG. 7h of any length) can be erected as a new building: for example, added to a tunnel having a cross-section in the shape of a quarter circle (FIG. 7o and FIG. 7p ) against a (for example already existing) wall—or, for example, as a roof vault having a cross-section in the shape of a quarter circle (FIG. 7q and FIG. 7r ) on a (for example already existing) circular wall. To this end, appropriate elements of the supporting structure according to the invention and of the roof membrane are dismantled, for example, from a building which might otherwise be damaged (for example according to FIG. 7k ) and thus re-erected to create a new building.

Claims

1. A supporting structure for a dome-shaped roof, the supporting structure comprising:

at least four arcuate supporting arms that are extendable and compressible;

wherein each arcuate supporting arm comprises a plurality of scissor rods which cross each other in pairs and are connected to each other by a plurality of joints; and

wherein, while extended, each arcuate supporting arm extends from a center part downward in a vertical plane in a shape of a quarter circle and is articulated to a horizontal base part by a plurality of bottommost scissor rods of the supporting arms.

2. The supporting structure of claim 1, wherein the supporting arms extend in a star pattern horizontally from the center part.

3. The supporting structure of claim 2, wherein the supporting arms are distributed uniformly on a horizontal circumference about the center part.

4. The supporting structure of claim 1, wherein a lower end of the bottommost scissor rods of the supporting arms is oriented downward and inward in a horizontal plane, wherein the horizontal plane is located at right angles to the vertical plane, at least on one of its two sides, and has a lateral base supporting rod which is articulated to the horizontal base part.

5. The supporting structure of claim 1, wherein the horizontal base part is configured as a plate, on the upper side of which the bottommost scissor rods are articulated.

6. The supporting structure of claim 1, wherein the plurality of scissor rods are a same length.

7. The supporting structure of claim 1, wherein:

each supporting arm comprises a first pair of two scissor rods and a second pair of two scissor rods, wherein the first pair comprises a first scissor rod and a second scissor rod and the second pair comprises a third scissor rod and a fourth scissor rod;

wherein the first scissor rod and the second scissor rod cross each other in an approximately central hinge joint, of which the first scissor rod comprises a parallel scissor rod mirror-symmetrically identically on the opposite side of the second scissor rod of the first pair so that the second scissor rod of the pair is rotatably arranged as an individual scissor rod of the pair between the first scissor rods and its mirror-symmetrically parallel scissor rod about the approximately central hinge joint; and

a first end of the first scissor rod of the first pair together with its mirror-symmetrically parallel scissor rod and a second end of the second scissor rod are articulated to two ends of the second pair of scissor rods by means of one knee hinge joint each, such that the first end of the second scissor rod is rotatably arranged between the ends of the third scissor rod and its mirror-symmetrically parallel scissor rod of the second pair about the one knee hinge joint, and that the ends of the first scissor rod and its mirror-symmetrically parallel scissor rod hold between them the end of the fourth scissor rod of the second pair rotatably arranged about the knee hinge joint.

8. The supporting structure of claim 7, wherein a distance of the two knee hinge joints at the ends of each pair can be positively fixed by a rod-shaped securing element or by the base part.

9. The supporting structure of claim 1, wherein each scissor rod is hollow.

10. The supporting structure of claim 1, wherein each scissor rod comprises a rectangular cross-section.

11. The supporting structure of claim 1, wherein each scissor rod comprises at least one of aluminum, wood, wood composites, recyclable plastic, and glass-fiber reinforced plastic.

12. An igloo, comprising:

an igloo floor comprising an upward facing edge;

a support structure comprising a plurality of arcuate supporting arms, wherein a base of each supporting arm radially supports the igloo floor;

a plurality of wall membranes extending from an igloo apex to the igloo floor, wherein each wall membrane is radially supported by two of the supporting arms; and

a plurality of tunnel entrances radially supported by two of the supporting arms.

13. The igloo of claim 12, wherein each supporting arm comprises a plurality of scissor rods and a plurality of joints, each joint connecting at least two of the scissor rods.

14. The igloo of claim 13, wherein each scissor rod is hollow and comprises a rectangular cross-section.

15. The igloo of claim 13, wherein the plurality of scissor rods have a same length.

16. The igloo of claim 12, wherein a shape of each wall membrane is a quarter circle.

17. The igloo of claim 12, wherein each wall membrane is a tarpaulin.

18. The igloo of claim 17, wherein each wall membrane comprises at least one of synthetic fibers, cotton textile, fur, wooden boarding, corrugated iron, plant fiber, and leaf mesh.

19. The igloo of claim 17, wherein an inner surface of each wall membrane comprises heat-insulating material.

20. The igloo of claim 12, wherein a first tunnel entrance is connected to a second tunnel entrance of a second igloo.