Structural insulated panel

Abstract

The insulating core 20 has a cut resistant member 22. The cut resistant member may be a set of longitudinal bars and / or a metal sheet. The bars may be 5-20mm thick and the sheet may be a perforated sheet. The bars may be twisted members. The longitudinal elements may be arranged in a regular patter or an irregular pattern. The core may have an arrangement where the cut resistant members may be arranged closer to one face than the other to provide a more secure side. Also claimed is a SIP panel and a method of making an insulating core.

Description

Field This invention relates to structural insulated panels, also known as SIP panels. Background SIP panels are a type of building material used in construction. They are composed of a rigid foam insulation core sandwiched between two structural facings, such as two layers of structural board, typically oriented strand board (OSB). The panels are manufactured in a factory and can be shipped to a construction site, where they are cut to size and assembled into a final building structure, such as a building extension or conservatory or other such structure. One of the key advantages of SIP panels is their high level of thermal performance. The foam insulation core provides excellent insulation, helping to keep buildings warm in the winter and cool in the summer. This can result in significant energy savings and reduced heating and cooling costs. SIP panels are also strong and durable, and can be used as load-bearing walls, floors, and roofs. They are easy to install, and can be used to construct a wide range of building types, including single-family homes, multi-family dwellings, commercial buildings, and more. Overall, SIP panels are a versatile and energy-efficient building material that can provide significant benefits in terms of thermal performance, strength, and ease of installation. It is known to reinforce the foam core of a SIP panel (e.g. with materials such as steel or fiberglass), to increase its strength, stiffness and load-bearing capacity and to increase the strength-to-weight ratio to avoid undesired bending or warping of the SIP panel. The additional reinforcing material makes the SIP panel more suitable for use in load-bearing applications such as walls, floors, and roofs. It can also improve the panel's resistance to wind, snow, and other environmental loads, making it more suitable for use in areas with extreme weather conditions. Summary In a first aspect, the invention provides a SIP panel as claimed in claim 1. In a further aspect, the invention provides an external dwelling wall comprising the SIP panel of the first aspect. In a further aspect, the invention provides a method of making the SIP panel of the first aspect. In a further aspect, the invention provides building a wall, such as a new wall, using the SIP panel of the first aspect. In a further aspect, the invention provides making an existing wall more secure by retrofitting the SIP panel of the first aspect on an existing SIP panel. The inventors have realised that there is a need for a new SIP panel that can be used for more secure external wall building extensions. Traditionally, building extensions have a solid brick wall built around a timber-constructed dwelling. However, the inventors have realised that SIP panel structures are more vulnerable than a brick wall from a security point of view because it is relatively easy to e.g. drill four holes and cut (e.g. with a long reach reciprocal saw) a square hole out of a SIP panel that is large enough for a person to access the building. SIP panels can be used for constructing building extensions / building add ons that could leave the main dwelling exposed to unauthorised access. The inventors have realised that there is a need for a new SIP panel, particularly for external walls. A benefit of the present invention is to provide better security, not necessarily a stronger panel. Prior SIP panels contain embedded meshes that enhance strength of the SIP panel; however, such embedded meshes are relatively flimsy compared to the cut-resistant members of this invention. Prior strengthened SIP panels with embedded meshes would not be resistant to attack via cutting, unlike the SIP panel of the present invention. SIP panels according to the present invention may be relatively heavy compared to their traditional unsecure counterparts, but are more secure against unauthorised attackers by, for example, an attacker attempting to saw through a SIP panel from the outside. The cut-resistant member is arranged to prevent lateral cuts (e.g. via sawing). The cut-resistant member is configured to prevent saw cutting, e.g. if the cut-resistant member comprises bars, then the bars must be thick enough; if the cut-resistant member is a sheet, then the sheet must be thick enough for this purpose. The precise sufficient thickness may dependent on the material used to make the cut-resistant member. Preferably, the cut-resistant member (e.g. bars or sheet) is not flexible. The cut-resistant member may be made from hardened, high tensile steel, which is difficult to cut. The cut-resistant member may be in the form of one or more bars, sheet or mesh. The cut-resistant member is arranged to prevent cutting a large hole through the core. A large hole is one that can be used to gain access to the other side of the SIP panel, e.g. a hole of more than 15cm or 20cm or 25cm diameter or width. Other objects, advantages and features of the present invention will become apparent from the following specification. The present technology provides an improved SIP panel that cannot easily be attacked by cutting from the outside. As a result, the present technology both provides the advantages associated with SIP panels and mitigates disadvantages. Brief Description of Drawings Embodiments will now be described by way of example only with reference to the accompanying schematic drawings, in which: Figure 1 shows a view from one side of a SIP panel according to an embodiment of the invention; Figure 2 shows a section view of a SIP panel of another embodiment; Figure 3 shows a section view of a SIP panel of another embodiment; Figure 4 shows a view from one end of a SIP panel of another embodiment; Figure 5 shows a section view of a SIP panel of another embodiment; Figure 6 shows a view from one end of a SIP panel of another embodiment; Figures 7a to 7d show a view from one side of SIP panels of other embodiments; Figures 8a to 8c show a view from one side of SIP panels of other embodiments; Figure 9 shows a section view of a SIP panel of another embodiment; Figure 10a shows a view from one side of a SIP panel of another embodiment; Figure 10b shows a section view of a SIP panel of another embodiment; Figure 11 shows a view from one side of a SIP panel of another embodiment; Figure 12 shows a view from one end of a SIP panel of another embodiment; and Figures 13a to 13c show a view from one end of a SIP panel of other embodiments. Description of Embodiments The exemplary embodiments described in the detailed description and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the described subject matter. Various embodiments are described. The specific embodiments are not intended as an exhaustive description or as a limitation to the broader discussed and claimed aspects. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s). Protection afforded by applying any applicable doctrine of equivalents is retained to its fullest extent. A facesheet is typically a thin layer of material that is laminated to the surface of a SIP panel to provide additional structural support (e.g. to provide additional strength, stiffness, or durability to the panel) or to protect the panel from external damage. Facesheets can be made from materials such as oriented strand board (OSB), plywood, fibreglass sheet, plastic sheet, plasterboard, cement board composite board, magnesia board. In some examples, the SIP panel is a bare SIP panel; that is, in such examples, there is no facesheet - the core is strong enough in itself to provide a SIP panel according to the invention. In such examples, a fascia may be clad or glued on to the core, e.g. foam core, directly. In such examples, the inventive core alone can be considered to be the SIP panel. In other examples, the SIP panel may comprise only one of the front facesheet or back facesheet. In one example SIP panel, plasterboard is provided on the back facesheet and the panel is bare on its front. In some examples having a front facesheet, the front facesheet is a planar sheet. In some examples having a back facesheet, the back facesheet is a planar sheet. The front and back facesheets may be parallel to each other. A foam core is typically made from a lightweight, rigid foam material to provide insulation within the SIP panel. The foam core can be at least any one or combination of: PIR (polyisocyanurate), PUR (Polyurethane), EPS (expanded polystyrene), mineral wool, fibreglass, plastic fibres, cellulose, natural fibres, phenolic and straw. Other suitable materials will also be apparent. The terms core, insulating core and SIP core are used interchangeably in this specification. A typical SIP panel is about 2.5m long and 600mm to 1800mm wide. In an embodiment of the invention, there is provided a SIP panel as shown schematically in figure 1. In this example, the SIP panel includes an insulating core 10 having located therein three cut-resistant members, in the form of metal bars 12. In other examples, a different number of cut-resistant members may be provided. In this example, the core comprises a rectangular core block profile having a top, a bottom, a left and a right side (for installation). In use, the block is usually arranged with its bottom resting on a floor surface in a known manner as will be apparent to the skilled person. The core block also has front and back sides arranged to face outwardly (e.g. towards a relatively insecure direction, such as towards outdoors, in use) and inwardly (e.g. towards a relatively secure direction, such as towards a secure building, such as a house, in use) respectively. The SIP panel is about 2.5m long and 600mm in this example. Typically, SIP panels have a depth of around 130mm. Different configurations will be apparent to the skilled person. E.g. SIP panels according to this invention of around 40mm depth may be provided for retrofitting as external cladding in order to address the same problem. The skilled person will realise that many different SIP panel depths may be provided in conjunction with this invention. In this example, the metal bars have a longitudinal profile, a circular cross-section and are 10 mm thick. In other embodiments, the metal bars may be of any other suitable thickness, e.g. between 5 mm and 20 mm thick. As a result the SIP panel of figure 1 cannot easily be attacked by cutting. In other embodiments, the metal bars may have any other suitable cross-section - for example, a starshaped, square, rectangular, triangular or other straight-edged cross-section. In other embodiments, the metal bars may have a curved-edge cross-section - for example, they may be circular or oval in crosssection. In some examples, the metal bars all have the same cross-section. In other examples, the metal bars may have different cross-sections. For example, figure 2 shows a schematic section view through a SIP core 20 (similar to the core 10 of figure 1) having four cut-resistant metal bars located therein, the metal bars having a circular-shaped 22a, a square-shaped 22b, an oval-shaped 22c and a star-shaped 22d cross-section. These metal bars are of a similar thickness to the bars 12 shown in figure 1. In other embodiments, the metal bars may be of different sizes. For example, figure 3 shows a schematic section view through a SIP core 30 (similar to the core 10 or core 20) having three cut-resistant metal bars located therein, the metal bars 32a, 32b, 32c all have circular shaped cross-sections, but are of different diameters. According to another embodiment, figure 4 illustrates a SIP panel comprising a core 40 having embedded therein metal bars 42 that are twisted along their length. Figure 4 is a schematic side view of the SIP panel 40. The metal bars 42 have a square-shaped cross-section and are longitudinal in form, i.e. they are twisted star-shaped cross-section metal bars. In this example, the bars are twisted during manufacture using standard techniques for twisting metal bars. The end result is a twisted longitudinal star cross-section bar as seen schematically in figure 4. The skilled person will appreciate that other cross-section shapes may also be twisted for example, twisted star, twisted rectangular, twisted oval cross-section shapes. The skilled person will also realise that in other examples the metal bars may be untwisted. One benefit of a twisted bar profile is that it can be more difficult to cut through because an attacker would need to cut on to an angled edge (rather than a simpler, flat edge). Therefore, advantageously with a twisted profile bar, there is less certainty / accuracy of cutting, and therefore more difficulty, for the attacker. Some shapes are more difficult to cut than others. E.g. a twisted star shape leads to a spiral profile that is more difficult to cut because an attacker needs to cut on to an angled edge. This can be especially difficult when cutting 'blind' (the cut-resistant members are embedded / contained in the opaque core). In the examples described in this specification, the core is opaque. Although, with any of the examples, the opaque core can be substituted with a transparent or partly-transparent core, It will be apparent to the skilled person that different suitable configurations of cut-resistant member are envisaged in this invention, e.g. any different combinations of one or more of the cross-section shape, thickness and untwisted / twisted profile previously mentioned can be used to form an inventive SIP panel. Referring to the previously-described examples, there are gaps between the cut-resistant members 12; 22a, 22b, 22c, 22d; 32a, 32b, 32c; 42. In this case, none of the gaps between the bars are greater than 200 mm. in some examples, the gap may be no more than 250mm, or preferably no greater than 200mm if the bars are aligned only in one direction (e.g. only vertical, or only horizontal, or only at some other angle, in use). In other examples, wider gap spacings, e.g. up to 300mm may be provided, e.g. if horizontal and vertical bars are located together or near each other. As a result holes that are large enough to provide easy access for a person through the SIP core (e.g. into a building) can not be easily cut. Figure 5 schematically shows a section view through another example of a SIP panel core 50, which is 1200mm wide, and has six cut-resistant members, in the form of circular-section metal bars 52, parallelly spaced regularly therethrough. The metal bars are spaced by 200mm in this example. In the previously-described examples, the bars are located substantially equidistant from the front and back faces of the inventive SIP panel. In other examples, the bars may be located closer to the back face than the front face. Advantageously, an attacker would need a longer blade to reach the cut-resistant members. Further, control of the cutting or sawing motion may be reduced at a longer distance as the cutting location would be further from the handle of the saw. Figure 6 is a schematic side view of a SIP panel comprising a core 60 having a cut-resistant member 62 located closer to one (back, in use) face than the other (front, in use) face. In the previously-described examples, the metal bars are provided in a regular pattern. They are parallel, vertical, and evenly spaced. Other suitable examples will be apparent to the skilled reader. For example, the bars may be parallel, horizontal, and evenly spaced in any of the examples. The regularly configured SIP panels are thereby relatively easy to manufacture. Other configurations will also be apparent to the skilled person. For example, there may be any combination of horizontal and parallel spaced (e.g. evenly-spaced in both directions) bars. In some examples, the metal bars may be provided in a crisscross or lattice format. For example, with bars in one orientation, e.g. horizontal, being provided in a first vertical plane and bars in another orientation, e.g. vertical, being provided in another nearby plane potentially abutting each other, or nearby to each other such that a person attempting to soar through would encounter both the horizontally- and vertically- oriented (or otherwise orientated in other examples) metal bars. Any of these arrangements may be inclined such that the bars are not horizontal or vertical in use, but maybe at an angle relative to horizontal or vertical (e.g. they are not aligned with the sides of the rectangular SIP panel block). In examples where the bars are in a crisscross or lattice arrangement, the bars may be: -vertical and horizontal in criss-cross at 90 degrees to each other but square on; or - laid diagonally such as in a diamond-shaped lattice (90 degrees to each other but skewed by 45 degrees relative to sides of the rectangular SIP panel); or - a first set of vertical bars with a second set of relatively inclined crossing bars at 45 degrees to the first set of vertical bars. Advantageously, because cutting down or across vertically or horizontally relative to the SIP panel is how most attackers would approach cutting a hole in the SIP panel, which would mean having the cutting blade encounter the relevant bar at an angle, increasing the difficulty of gaining purchase on the bar and presenting more distance to cut through i.e. overall more difficult to cut. In any of the described examples having cut-resistant bars inclined relative to the sides of the rectangular SIP panel core, the inclination angle may be 45 degrees, or may be any other suitable angle, e.g. a more acute angle than 45 degrees. E.g. at an angle of at least 25 degrees to the vertical, or at least 30 degrees to the vertical, and optionally about 45 degrees. Figures 7a to 7d schematically illustrate some examples of such inventive SIP cores 70a, 70b, 70c, 70d having metal bars provided in a regular pattern. Any of the described examples may comprise irregular instead of regular patterns of cut-resistant members. For example, there may be uneven spacing between adjacent bars (whether horizontal or vertical or otherwise inclined). Figures 8a to 8c schematically illustrate some examples of such inventive SIP cores 80a, 80b, 80c having metal bars provided in an irregular pattern. Whether irregularly or regularly patterned, it is beneficial that no single space or gap between adjacent cut-resistant members (which are bars in the above-described examples, but may have any other suitable form) should be big enough to easily access for an attacker. Therefore, in most of the arrangements, there is no gap of 300 mm or more. In some examples the SIP panel is symmetrical from front to back or from back to front, (i.e. the cutresistant members are located substantially equidistant from the front and back faces of the SIP panel core block). In other examples, there is asymmetry (e.g. see the example of figure 6). The SIP panel has a front side and a back side. The front side is arranged to be outwardly facing after installation. The back side is arranged to be inwardly facing towards a relatively secure area compared to the front side. For example, the back side faces inwardly towards a home or dwelling or other building, whereas the back side is arranged to face outdoors. A benefit of having such asymmetry is that an attacker has a greater distance to reach out when sawing to reach the cut-resistant member(s) from the back side of the SIP panel, and may have less control or less power or less accuracy in their sawing motion when using the sawing tool (or other tool to cut or break the cut-resistant members). In some examples, the cut-resistant member is in the form of a cut-resistant (e.g. metal) sheet rather than bars. For example, see figure 9, which shows an example embodiment of a SIP panel comprising a SIP core 90 having a cut resistant member in the form of a cut-resistant sheet 94 located in the core. The core is formed around the sheet 94. In this example, the cut-resistant sheet is planar and is arranged substantially parallel to the front and rear surfaces of the core (which are also parallel to each other in this example). In some examples, the cut-resistant sheet may be located closer to the back than the front of the core (as previously described in relation to other examples for further security benefit). In this example, the thickness of the sheet is 7 mm and is uniform across the sheet. In other examples, the thickness of the sheet may be 1 mm to 10 mm. In this example, there are no bars. The sheet is uniform in this example. There are also substantially no holes or gaps in the sheet. The sheet alone provides an effective barrier to cutting due to its strength, stiffness and material. In another example embodiment, a SIP panel is shown schematically in figure 10a. In this example, the SIP panel includes a core 100 (similar to types previously described) having located therein three cutresistant members, in the form of cylindrical metal bars 102, along with a cut-resistant sheet 104 (of the type previously described in relation to figure 9). A schematic section view through the SIP panel 100 shown in figure 10b. As can be seen the bars 102 are configured in a first plane, and the sheet 104 is configured in a second plane - the two planes do not intersect within the bounds of the SIP panel (in fact, in this example, the planes happen to be parallel to each other and also happen to be parallel to the front and back faces of the SIP panel in this example). In any examples in which more than one set of cut-resistant members is provided (e.g. horizontal bars and vertical bars, or horizontal bars and sheet, or sheet and vertical bars, or any other arrangement, e.g. as previously described (see figures 7 and 8), different sets of cut-resistant members may be offset from each other (i.e. such that their planes do not intersect within the bounds of the SIP panel) - this allows for easier manufacture. In some examples, the sheet may be perforated. For example, see figure 11, which schematically shows a SIP panel similar to that shown in figure 9, i.e. comprising a SIP core 110 having a cut resistant member in the form of a cut-resistant sheet 114 located in the core. In this example, unlike the example of figure 9, the sheet 114 has perforations 116. The perforations are relatively small and form a regular pattern across the sheet. The perforations are relatively small, as are the gaps between the perforations, in comparison to any gap that would be needed for easy sawing (or other attack) of the cut-resistant sheet. In other cases, the perforations may be larger, but may comprise no more than 50% of the area of the sheet. In this example, the thickness of the sheet is 7 mm and is uniform across the sheet. In other examples the thickness of the sheet may be 1 to 10 mm. In this example, the cut-resistant sheet is substantially planar and is arranged substantially parallel to the front and rear surfaces of the core (which are also parallel to each other in this example). In some example, the cut-resistant sheet may be located closer to the back than the front of the core (as previously described in relation to other examples for further security benefit). In any of the examples, the cut-resistant member(s) may be arranged parallel to (front and back) faces of the SIP core as previously described. In other examples (e.g. see figure 12), this may not be the case. Figure 12 is a schematic side view of a SIP panel comprising a core 120 having cut-resistant members in the form of cylindrical metal bars 122 that are inclined relative to the front and rear faces of the SIP core 120. The same principle can be applied to examples with cut-resistant sheets. In use, an inventive SIP panel may be used to construct new buildings or extensions to buildings. In other examples, an inventive SIP panel maybe retrofit over existing SIP panels (which are relatively insecure) to provide added security compared to traditional SIP panels. In such retrofit examples, the SIP panel can be installed abutting or nearby the existing SIP panel. In examples where the inventive SIP panel is asymmetric as previously described, the back side of the inventive SIP panel is installed facing towards a relatively insecure side, e.g. towards outdoors and the front side is installed facing towards a relatively secure side, e.g. indoors towards a building. In one example, the inventive SIP panel core is formed by forming a body of the insulating core around at least one cut-resistant member (of the type previously described, e.g. bars or sheet). In any of the described examples, one way of forming the inventive SIP panel is to arrange the cut-resistant member(s) in a desired configuration and then to form the SIP core around the pre-arranged cut-resistant member(s) to form the inventive panel. In combination with any described examples, the SIP core can be used bare (without any further sheets attached (as previously described). Or one or more further sheets (such as a front facesheet or back facesheet or both) can be attached to the front, the back, or both surfaces of the core in a known manner. Figures 13a to 13c schematically show three examples of SIP panels in which a SIP core 130 has cutresistant bars 132 embedded in it, and having either: a front facesheet 136F (figure 13a); a back facesheet 136B (figure 13b); or both front 136F and back 136B facesheets (figure 13c). As previously discussed, the SIP’s front face is arranged to face externally and the SIP’s back face is arranged to face internally towards a secure building in use. This can be important in examples where the SIP panel is asymmetric - it is generally advantageous to make the panel more difficult to attack from an external side than an internal (secure) side. In any examples having cut-resistant members (e.g. sets of bars or sheet or other cut-resistant members) near to each other (e.g. the above-described crisscross arrangement with a set of vertical bars in one plane near a set of horizontal bars in a nearby plane), there may be a gap between the planes such that the bars do not abut in use. Advantageously, this gap allows foam material to flow unimpeded between nearby bars as the core is being formed around the cut-resistant members. Various modifications may be made to the present invention without departing from its scope. These will be apparent to the skilled reader. The invention's scope is defined in the claims and accompanying description. For example, apart from metal other materials having cut-resistant properties may be used to form the cut-resistant members. These materials will be apparent to the skilled person. The inventive SIP panel may include cut-resistant members formed wholly or partly of metal (or another cut-resistant material instead of metal). The, each or any cut-resistant member of any example may comprise a cut-resistant coating or cut-resistant core instead of being formed entirely of metal (or other cut-resistant material). The, each or any cut-resistant member of any example may be substantially solid (i.e. not hollow). In some examples, the, each or any cut-resistant member may have weight-saving features such as perforations. SIP panels come in a variety of sizes. For example, typical sizes include panels having thickness 95mm, 145mm or 170mm, and 1220mm (height) x 2440 mm (length), or 1220 mm (height) x 6000 mm (length), or 2.5m long and 600mm to 1800mm high. The skilled person will understand that suitably dimensioned panels can be created for bespoke requirements. In most of the above-described examples, the or each cut-resistant member (bars or sheet) protrudes from the core. In other examples, preferably the or each cut-resistant member is cut to be level with any one or more of the top, bottom or side of the SIP core or panel. For example, a SIP panel similar to that shown in figure 1 may have an identical SIP core having located therein three cut-resistant members, in the form of metal bars that do not protrude from the core. Similarly examples in relation to other described embodiments will be apparent to the skilled reader. In some examples, during the manufacturing process, the cut-resistant member(s) may protrude from the core and may then subsequently be trimmed or cut to 5 be level with the core. In other examples, during the manufacturing process, the cut-resistant member(s) and core may be formed substantially level without the need for such further trimming or cutting.

Claims

1. An insulating core for a SIP panel having at least one cut-resistant member located therein.

2. The insulating core of claim 1, wherein the or each of the at least one cut-resistant member comprises a metal cut-resistant member.

3. The insulating core of any preceding claim, wherein the cut-resistant member comprises one or a combination of:a sheet; anda plurality of longitudinal cut-resistant members, such as bars.

4. The insulating core of claim 3, wherein the longitudinal cut-resistant members have a thickness or diameter of at least 5 mm thick, and optionally up to 20 mm.

5. The insulating core of claim 3 or claim 4, wherein the sheet is at least 1 mm thick, and optionally up to 10 mm thick.

6. The insulating core of any of claims 3 to 5, wherein the sheet comprises a perforated sheet, and optionally wherein at least 50% of the area of the sheet is unperforated.

7. The insulating core of any of claims 3 to 6, comprising the plurality of longitudinal cut-resistant members, wherein some or all of the longitudinal cut-resistant members comprise twisted longitudinal cutresistant members.

8. The insulating core of any of claims 3 to 7, wherein some or all of the longitudinal cut-resistant members have a circular, ovular, square, or star-shaped cross-section.

9. The insulating core of any of claims 3 to 8, wherein longitudinal adjacent cut-resistant members are arranged no more than 300mm apart.

10. The insulating core of any preceding claim comprising a plurality of cut-resistant members arranged in a regular pattern.

11. The insulating core of claim 10, wherein the regular pattern comprises any one or combination of:• a plurality of parallel metal bars, such as a plurality of evenly-spaced parallel metal bars;• a plurality of parallel metal bars, such as a plurality of vertically-configured metal bars;• a plurality of parallel metal bars, such as a plurality of horizontally-configured parallel metal bars;• a plurality of parallel metal bars, such as a plurality of inclined parallel metal bars; and• a lattice or criss-cross arrangement of metal bars, optionally an inclined lattice or criss-cross arrangement of metal bars.

12. The insulating core of any of claims 1 to 9 comprising a plurality of cut-resistant members arranged in an irregular pattern, such as any one or a combination of:• an irregular array of metal bars;• a plurality of unevenly-spaced parallel metal bars;• a plurality of divergently-inclined metal bars; and• an irregular lattice or criss-cross arrangement of metal bars, optionally an irregular inclined lattice or criss-cross arrangement of metal bars.

13. The insulating core of any preceding claim having: a back face arranged, in use, to face towards a relatively secure side; and a front face arranged, in use, to face towards a relatively insecure side, such as towards outdoors, and optionally wherein the at least one cut-resistant member is arranged closer to the back face than the front face.

14. The insulating core of claim 13, wherein the front face and the back face are parallel to each other.

15. The insulating core of claim 13 or claim 14, wherein the or each of the at least one cut-resistant member is arranged parallel to the front face.

16. The insulating core of any of claims 3 to 15, wherein the core comprises a rectangular insulating core and the longitudinal cut-resistant members are angled relative to sides of the core, such as at an angle of at least 25 degrees to the vertical, or at least 30 degrees to the vertical, optionally about 45 degrees.

17. A SIP panel comprising the insulating core of any preceding claim and further comprising one or both of:• a front facesheet attached to a front face of the insulating core; and• a back facesheet attached to a back face of the insulating core.

18. A building extension made of: one or more insulating cores as claimed in any of claims 1 to 16; or one or more SIP panels as claimed in claim 17, wherein the front face is arranged to face externally and the back face is arranged to face internally towards a secure building.

19. A method of making an insulating core according to any preceding claim comprising:forming a body of the insulating core around at least one cut-resistant member.

20. The method of claim 19 further comprising attaching to the insulating core one or both of:• a front facesheet; and• a back facesheet.

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