WO2012114122A2

WO2012114122A2 - Construction panel

Info

Publication number: WO2012114122A2
Application number: PCT/GB2012/050426
Authority: WO
Inventors: Ian John PRITCHETT; Mark PATTEN; David MAYLE; Thomas EASDOWN; Max BURBIDGE; David Ledger; Luke Whale; Stuart Edwards
Original assignee: Lime Technology Limited
Priority date: 2011-02-24
Filing date: 2012-02-24
Publication date: 2012-08-30
Also published as: WO2012114122A3; GB2488436A; GB201203243D0; GB201103217D0

Abstract

A construction panel comprises: a first frame member; a second frame member disposed adjacent to the first frame member; the first and second frame members being connected together around their perimeters by one or more connecting members; wherein at least one connecting member is positioned to extend between said first and said second frame members so as to form a recess in a side of the panel. The recess allows adjacent panels to be located against other building structures and to be connected to one another by inserting a connection member into the cavity formed by two adjacent recesses and connecting the adjacent panels to the connection member. The panel may be filled with a vegetable based aggregate and the panel may be clad with a plant fibre based board to provide good thermal insulation. A panel is also provided which comprises a main panel body formed from a vegetable based aggregate based bio-composite and clad on one or more sides with a plant fibre based board. Also provided is a method of forming a construction panel comprising a frame structure filled with a filler material, comprising: assembling the frame structure; filling the frame structure with filler material; waiting for a first period of time after filling has taken place, sufficient to allow the filler material to solidify; then waiting for a second period of time, sufficient for the filler material to achieve a predetermined level of set; and then waiting for a third period of time, sufficient to dry the filler material to an equilibrium moisture content, wherein heat and/or dry moving air is applied to the panel during the third time period.

Description

Construction panel

The invention relates to construction panels, particularly construction panels for modular building and more particularly to panels which are environmentally friendly and provide good thermal insulation.

It is generally known to construct buildings in a modular fashion from a number of panels fixed together. However there are a number of problems associated with such panels. Many panels are made from non-environmentally friendly materials and/or have poor thermal characteristics. Modern building regulations are placing stricter requirements on the thermal characteristics of new buildings or

modifications to older buildings. There are similar concerns regarding the carbon footprint of materials used in construction. However at the same time, construction panels need structural strength and need to be capable of supporting the weight of panels above them as well as the weight of intermediate floor structures and/or roofs. Some panels are designed for structural capabilities like these, whilst others are designed as cladding for an existing building structure or building framework. Cladding panels require less structural strength. Construction panels and cladding panels are generally rectangular units which need to be connected together along their edges so as to form a larger surface or wall. To position the panels in the correct locations, they need to be lifted and manoeuvred into place, typically by a crane. The panels therefore also need to have the structural stability required for such lifting. Designing panels with the required stability, yet of a relatively simple construction is difficult.

Environmentally friendly thermal insulation materials are typically applied to building structures in a wet application process, e.g. by casting or spraying on site. This is typically the case for example for Tradical® Hemcrete® which is a mixture of lime binder and hemp shiv among other ingredients. The material provides high levels of insulation (low U-values) and also has a low carbon footprint. Additionally, the hemp is a sustainable material, it is easy to attain a high level of air tightness in buildings and the product is recyclable. Using Tradical® Hemcrete®, it is possible to build houses conforming to the UK Code for Sustainable Homes, levels 4, 5 and 6. However buildings constructed on site typically involve first building a timber frame with interior walls, then spraying or filling the timber frame with Tradical® Hemcrete® and then applying an exterior render to finish. This wet application process has certain disadvantages as follows. Working in the cold, especially in winter can lead to longer setting and drying times which can be inefficient. As the mixture dries it can shrink. As the mixture shrinks, in some extreme cases cracks may appear in the walls. These then need to be repaired before the render is applied. If the render is applied before the underlying mixture is dry, it can extend overall drying times and increase the risk of staining from the hemp. The thermal performance of the product is not maximised until the mixture is fully dry, i.e. until it has reached an equilibrium moisture content (typically around 5-10%). Drying to this level can take as much as 2-3 years in some cases.

Some Hemcrete® panels have been made off site which are then transported to site and used in building construction, but these have only been designed for attachment to a structural framework, i.e. they were suitable for cladding the framework, but were not strong enough to form a building structure in themselves.

According to a first aspect, the invention provides a construction panel comprising: a first frame member; a second frame member disposed adjacent to the first frame; the first and second frame members being connected together around their perimeters by one or more connecting members; wherein at least one connecting member is positioned to extend between said first and said second frame members so as to form a recess in a side of the panel. In this way, the overall panel structure is formed by the two adjacent frame members which define the perimeter of the panel. Each frame member defines a face of the panel (opposite faces) and the connecting member(s) form the other sides of the panel between those faces. Forming a recess in a side of the panel has a number of benefits. Firstly, the recess allows connection of one panel to another similar panel. By placing the recesses of the two panels adjacent to one another a hollow cavity is formed.

When a connection member is provided within this cavity, both panels can be connected to the connection member and can thereby be connected together. This process will be described in more detail below. A further benefit of the recess is in providing a means for locating the panel with respect to other building elements. For example a building foundation may be formed with a projection (or sole plate) shaped to be received in the recess, thus providing a means for locating a panel in the correct position on the foundations. This makes the building construction process easier and faster. The same applies for further building elements such as roof structures which can be quickly and easily located in a panel recess on the top of a constructed wall. The recess may be formed by positioning the connecting member(s) to extend from one frame member to the other frame member at a location which is radially inward from the perimeter of the frame members. The recess is thus formed by the opposing (i.e. inner) faces of the two frame members together with the outer face of the connecting plate. The terms "inner" and "outer" are used here with respect to the interior of the panel as a whole.

The depth of the recess, i.e. the position of the connecting member(s) with respect to the frame members may vary. It may be near to the outside of the panel if only a small recess is required. Alternatively, for a larger recess the location may be towards the radially inner side of the frame members. In some embodiments the location is around the centre point of the frame members, i.e. the connecting plate extends from a mid-point (in a generally radial direction) of the first frame member to the mid-point of the second frame member. In other embodiments an

asymmetric arrangement is preferred. The frame members and the connecting members together form an I-beam structure. This arrangement has high strength, in particular higher than sum of the strengths of the individual components.

An asymmetric I-beam profile provides a larger recess on one side and a smaller recess on the other side. In the present invention, the outer recess of the framework is for connection to other structures (e.g. other panels, roofs, floors, foundations, etc.) while the inner recess of the framework provides a key for insulation or filler material which can be added to the framework. An asymmetric arrangement allows the outer and inner recesses to be at different sizes. The outer recess is sized for an appropriately sized connection to other structures. The inner recess need not be so large. Therefore an asymmetric arrangement allows a smaller overall framework size than would be required for a symmetrical arrangement.

The panel may take any of a number of different shapes. For example, the panels could be triangular or hexagonal, but in most preferred embodiments they will be rectangular. The panels may be square. In preferred embodiments therefore the first and second frame members are rectangular.

In some particularly preferred embodiments, the panels are about 2.4 metres high and anything from 1 to 5 metres long. It will be appreciated that these sizes are given by way of example only and should not be construed as limiting.

Panels may have only a single recess on one side. Two such panels can then be joined by aligning the recesses as described later in this document. However in preferred embodiments the panel has a recess formed on more than one side of the panel. In some embodiments, recesses may be formed on two opposite sides so that the panel can be joined to additional panels on both sides. In other embodiments, the panel may have recesses formed on three or more sides for joining to panels either side as well as to panels above or below. Most preferably, the panel has recesses formed on all sides (e.g. all four sides for a rectangular panel) so that the panel can be joined to other panels or other structures on all sides. The recesses can also be used for aligning with other structures, e.g.

foundations as described elsewhere. In preferred embodiments the connecting members are connecting plates. These may extend the full length of the side of the panel. In other embodiments, there may be multiple plates per side, all being coplanar. These multiple plates may be abutted against one another or may be separated by some distance. In other embodiments the connecting members can be rods of low thermal conductivity, high strength material.

The first and second frame members may each be formed simply of peripheral members, i.e. extending around the periphery of the panel. This may provide strong enough structure for the panel. However preferably each of the first and second frame members comprises additional struts extending parallel to one of the sides of the frame members. These struts may extend along the longest or shortest side of the frame member, i.e. extending along the main face of the panel from one side of the panel to the opposite side of the panel. In use these struts may therefore extend horizontally or vertically. They provide additional structural support to the panel.

Preferably the struts of the first frame are parallel and adjacent to those of the second frame. Preferably the struts of the first frame are connected to the struts of the second frame by strut connecting members. Preferably the strut connecting members have low thermal conductivity so as to maintain the insulating properties of the panel. The strut connecting members provide additional strength to the framework by joining the two frame members together in many places. The strut connecting members may be connecting plates like those described above for the connecting members which connect the two frames together around their peripheries. The plates may be plywood webbing or other composite board material. However although this will provide great structural stability, it will not always be necessary. The strut connecting members may be any kind of connection such as screws, nails, bolts, brackets or other fixings. Alternatively the connecting members can be rods of low conductivity, high strength material. Strut connecting members may be applied at a plurality of locations along the length of each strut.

In preferred embodiments at least one reinforcement band is provided around the perimeter of the panel, between the first and second frame members and positioned within the or each recess. The reinforcement band provides additional strength in the form of tension around the perimeter. In particular, the

reinforcement band provides sufficient strength that the panel can be lifted by a crane without significant deformation. In some preferred embodiments, two parallel reinforcement bands are provided, one adjacent to the first frame member and one adjacent to the second frame member. The reinforcement bands may be made from any suitably strong material. They may for example be metal or plastic or they may be elastic. In preferred embodiments pallet banding or pallet wrap is used.

Preferably at least one corner of the panel is provided with a reinforcement structure comprising at least one triangular plate connecting the connecting member of one side to the connecting member of the neighbouring side. There may be two triangular plates formed on the opposing faces of each frame member and disposed radially inwardly of the or each connecting plate. Preferably a transverse member (e.g. a timber batten) extends between the two frame members in the region of said corner. Although a single such corner reinforcement may be used, preferably at least two are provided at opposite corners and more preferably one at each corner of the panel. Such corner reinforcements provide additional strength to the framework, which may be necessary particularly for larger panels to be lifted by a crane. The reinforced corner can act as a lifting point. The corner reinforcement(s) are particularly beneficial in combination with the reinforcement band(s) in this regard.

In some preferred embodiments, the first and/or second frame members of the panel may comprise diagonal reinforcement members extending from one corner to a diagonally opposite corner of the frame member. These diagonal reinforcement members provide additional structural support. They may be in the form of diagonal struts or they may be tension straps (e.g. formed from the same material as the reinforcement bands). Alternatively they may be rods or plates as described above. Preferably the first and second frame members are each formed from timber, but other materials could be utilized such as recycled plastics. Preferably they are joined together in such a way as to enhance their overall strength (i.e. the strength of the two joined components is stronger than the sum of the two individual components, e.g. as in the forming of an I-beam). These engineered components provide sufficient strength and can be made from renewably sourced materials.

The connecting members which connect the first and second frames may be plates formed from plywood, or other board of sufficient strength. Preferably composite board is used. Preferably the materials are sustainable. The triangular

reinforcement members may also be formed from plywood, or other board of sufficient strength.

The joint between the connecting plates and the frame members may take a number of forms. For example it may be a simple butt joint fixed in place with adhesive and/or dowel pins. In particularly preferred embodiments, the or each connecting plate extends from a groove in the first frame member to a groove in the second frame member. This forms a type of tongue in groove joint which holds the connecting plates securely in the desired position.

Preferably the interior of the panel is filled with a filler material. The filler material is preferably contained in the space formed by the first frame member, the second frame member and the peripheral connecting member(s). The filler material is preferably a thermal insulating material. The filler material may be a liquid or plastic state, solidifiable material which is cast or sprayed into the framework and then allowed to set and/or dry. In preferred embodiments the filler material is a mixture comprising organic aggregate(s), e.g. vegetable based aggregate(s) and mineral or organic binders e.g. hemp (or other cellulosic material), cement and lime. The mixture may in preferred embodiments be Tradical® Hemcrete®.

The filler material provides additional structural properties to the panel. As the filler material is placed around the frame structure of the panel, it fills all the gaps and provides support to the framework. The most common cause of failure for such panels is buckling and the filler material provides support against buckling. Thus a filled panel can have 2-3 times greater compressive strength than a non-filled panel.

The panel may have an internal lining board such as plaster board fixed to one side. The internal lining board may form an interior wall of the building. Other interior finishes may also be used. The internal lining board may be separated from the frame member by studs. The studs may be mounted to the struts discussed above. A service void may be formed between the internal lining board and the filler material of the panel. This service void may be used for services such as electrical and/or plumbing pipe work. The service void may contain a breathable vapour control layer (VCL) or membrane to control the amount of water vapour able to pass through the panel. This VCL/membrane may be fitted in the factory, or on site. The diffusion resistance of the VCL may be selected according to

circumstances, e.g. expected environmental conditions. It is desirable to allow water vapour to exit the building through the walls, but it is also important to ensure that any water vapour entering the walls from the inside can easily escape to the outside. A vapour control layer or membrane may be attached to the outer face of the panel to provide weather protection to the panel during construction and to control the amount of water vapour able to pass through. This VCL/membrane may also be fitted in the factory, or on site. The diffusion resistance of the outer VCL must be lower than that of the inner layer so as to ensure that water vapour does not get trapped inside the panel.

The panel may have wood fibre board fixed to one side. The wood fibre board provides extra insulation and acts as a base or carrier board on to which to apply render. The panel may be formed off site with internal liner board (e.g. plaster board) and wood fibre board attached. Alternatively these materials may be fixed to the panels on site after construction of the building. Other external finishes can be used.

According to another aspect, the invention provides a method of forming a construction panel comprising: forming a first frame member; forming a second frame member; disposing said second frame member adjacent to said first frame member; connecting said first and second frame members together around their perimeters by one or more connecting members; wherein at least one connecting member is positioned to extend between said first and said second frame members so as to form a recess in a side of the panel.

All of the preferred features discussed above in relation to the apparatus apply equally to the method. Therefore preferably the first and second frame members are rectangular. Preferably the panel has a recess formed on more than one side of the panel. Preferably each of the first and second frame members is formed with additional struts extending parallel to one of the sides. Preferably the struts of the first frame are connected to the struts of the second frame by strut connecting members. Preferably at least one reinforcement band is strapped around the perimeter of the panel between the first and second frame members and within the or each recess. Preferably the panel has at least one corner and the at least one corner of the panel is provided with a reinforcement structure comprising at least one triangular plate connecting the connecting member of one side to the connecting member of the neighbouring side. Preferably the corner reinforcement further comprises a transverse member extending between the two frame members in the vicinity of the corner. Preferably the frame members are constructed from engineered timber beams. Preferably the connecting members are plywood plates. Preferably the or each connecting member extends from a groove in the first frame member to a groove in the second frame member. Preferably the interior of the panel is filled with a filler material.

According to a further aspect, the invention provides a panel comprising a main panel body formed from a vegetable based aggregate based bio-composite and clad on one or more sides with a plant fibre based board. This combination of materials provides a panel/building system with excellent thermal properties due to the insulative properties of each of the vegetable based aggregate based bio-composite and of the plant fibre based board. Together these materials also provide a very stable structure which can easily be manoeuvred into position.

Preferably the vegetable based aggregate is hemp based aggregate. Preferably the plant fibre based board is wood fibre board. Preferably the plant fibre based board acts as a render carrier board. Preferably render is applied on the outside of the render carrier board.

The features described above in relation to the other aspects of the invention all apply equally to these aspects.

According to a further aspect, the invention provides a method of forming a construction panel comprising a frame structure filled with a filler material, comprising: assembling the frame structure; filling the frame structure with filler material; waiting for a first period of time after filling has taken place, sufficient to allow the filler material to solidify; then waiting for a second period of time, sufficient for the filler material to achieve a predetermined level of set, and then waiting a third period of time, sufficient to dry the filler material to an equilibrium moisture content, wherein heat and/or dry moving air (low relative humidity) is applied to the panel during the third time period.

Heat and/or moving dry air can only be applied to the panel after the chemicals within the filler material have set to a sufficient level, otherwise the filler material may lose its structural integrity and may crumble. The chemicals in many binders are dependent on water for their reactions, so force drying the panel too early can reduce the strength of the panel by reducing the set of the chemicals. However due to the structural strength provided by the framework, it is not necessary to achieve a full set of the chemicals in order to achieve sufficient overall panel strength.

Therefore the panel can be force dried after a certain filler material strength has been achieved. Once this set has been achieved, application of heat and/or dry moving air (low relative humidity) can greatly decrease the drying time to reach the equilibrium moisture content (e.g. 5 to 10%). Reducing the drying time avoids the problems associated with working in cold wet conditions, staining of the materials, shrinkage etc. Although shrinkage will still occur in a force dried panel, the cracks can simply be filled in the factory so that the panels are structurally sound and ready for use as soon as they reach the construction site. In order to determine when the filler material has achieved a sufficient set and therefore a sufficient strength and structural integrity, the panel is tested with a mechanical resistance device such as a penetrometer which measures the resistance of the material against a sprung probe. The strength which is deemed sufficient will depend on the materials of the panel as well as its intended use. A skilled person will be able to set an appropriate threshold for a particular situation.

Air may be applied to the panel (e.g. forcibly driven at or around the panel) during the third period of time in order to increase the drying rate. Once the filler material has set sufficiently, it is desirable to dry the panel is quickly as possible so as to increase the production rate of ready-to-use panels. In order to determine when a panel has reached the desired moisture content the moisture content can be tested, for example using an electrical resistance meter. Once the panel has reached the desired moisture level the forced air and/or heat can be stopped. A skilled person will again be able to determine an appropriate threshold moisture level according to the particular materials and circumstances.

As above, in preferred embodiments, the filler material may be a solidifiable liquid or plastic state material, preferably a mixture comprising lime and hemp, more preferably bio-composite material such as Hemcrete®. In preferred embodiments the filler material is a mixture comprising organic aggregate(s), e.g. vegetable based aggregate(s) and mineral or organic binders e.g. hemp (or other cellulosic material), cement and lime. The mixture may in preferred embodiments be

Tradical® Hemcrete®. Preferably the method further comprises a step of attaching one or more temporary face plates to the frame structure prior to the filling step to contain the filler material, and removing the temporary face plates after the first time period has elapsed (but preferably before the second time period has elapsed), i.e. after the filler material has solidified sufficiently that it will hold its shape.

The temporary plate(s) are required to contain the filler material until it has solidified and has bound to the framework. Once the mixture has adequately solidified, the temporary face plate(s) can be removed so as to allow a greater surface area of the filler material to contact the air and thus increase the drying rate.

Preferably the application of air and/or heat comprises cycling. Cycling of the air and/or heat can reduce the total energy used in the setting/drying process.

The first time period may be 1 to 5 days, preferably about 3 to 4 days.

The second time period may be 5 to 20 days, preferably about 10 to 15 days (this time period being in addition to that of the first time period).

The third time period may be 1 to 10 days, preferably about 5 days (again, this time period being in addition to the first and second time periods).

It will be appreciated that these time periods may vary with the materials and/or size of the panels as well as the environmental conditions. It is generally desired to reduce these time periods as much as possible without compromising the strength/integrity of the panel.

According to another aspect, the invention provides a method of joining a first construction panel and a second construction panel, wherein each panel comprises at least one recess, comprising: placing the first panel adjacent to the second panel such that a recess of the first panel is adjacent to a recess of the second panel so as to form a cavity; then positioning an elongate attachment member at least partly within the cavity; and fixing both the first panel and the second panel to the elongate attachment member. The elongate attachment member may have low thermal conductivity and may be made from a plurality of laminations to give a desired combination of strength and thermal conductivity. For example the elongate attachment member may have a core of material having low thermal conductivity which may be sandwiched between layers of stronger material which are suitable for receiving fixing members such as nails, screws, bolts, etc. The thermally insulating material used for the core is beneficial in reducing heat loss from within the building through the gaps between adjacent panels. However in general such materials do not have a good structure for receiving and holding fixing members such as nails, screws, bolts, etc. The stronger layers either side of the core layer provide this strength. Thus when fixing two panels together, the fixing members may be passed through the frame members of the panel and into the higher strength outer layers of the elongate attachment member. Such lamination based elongate attachment members provide adequate connection strength with improved insulation properties. Preferably the recess on each panel is a longitudinal recess. The longitudinal recess may extend along a full side length of the respective panels. The cavity formed by the combination of two such recesses may be a tubular cavity. The tubular cavity may be open at the ends so as to form a tunnel or through-hole. Preferably the elongate attachment member will extend from one recess into the other recess (i.e. it will be accommodated in both recesses) and more preferably will have a cross-section substantially matching that of the cavity. The connection may substantially fill the whole volume of the cavity for maximum connection strength between the panels.

In preferred embodiments the first and second panels are each fixed to the elongate attachment member by one or more fixing members extending through a frame member of the panel and into the elongate attachment member. The fixing members may be driven into position and held in place by friction, e.g. nails or screws or the fixing members could be held in place by adhesive or welded into position or they could be secured by retaining means, e.g. a bolt and a nut (optionally a captive nut). Any method of securing the panels to the elongate attachment member may be used. Preferably a plurality of fixing members are used for fixing each panel to the elongate attachment member.

Although the fixing members are preferably arranged perpendicular to the face of the panel, this may only be achievable with large enough frame members, large enough recesses and large enough elongate attachment members so that there is enough overlap between the elongate attachment members and the frame members to allow perpendicular fixing. Therefore in other embodiments, the or each fixing member may be applied at an angle to the surface of the panel so that the fixing members pass securely through both the frame members and the elongate attachment member. In some embodiments the angle may be around 45 degrees. The different fixing members may be applied at the same angle or at different angles depending on the circumstances.

The panels may be adjoined so that they share a common side, i.e. so that one panel lies fully adjacent to the other panel. However in some preferred

embodiments the recess of the first panel and the recess of the second panel may be offset so that the cavity is formed between a part of the first longitudinal recess and a part of the second longitudinal recess. A third construction panel having a recess may be positioned adjacent to the first panel so that a cavity is also formed by the recess of the first panel and the recess of the third panel. Again, this third recess is preferably a longitudinal recess and preferably forms a tubular cavity. The elongate attachment member may extend through both cavities, i.e. through the cavity formed by the recesses of the first and second panels and through the cavity formed by the recesses of the first and third panels. All three panels may be fixed to the elongate attachment member as described above. In this way, rows or columns of panels may be spatially offset with respect to one another which provides better structural linkage between the panels and greater stability to the structure as a whole.

In some preferred embodiments the elongate attachment member may extend from the cavity between the first and second panels and into a similar cavity formed by a third panel and a fourth panel, and the third panel and the fourth panel may also be fixed to the elongate attachment member by one or more fixing members. Fixing many panels to a single elongate attachment member also increases the linkage and the strength and stability of the structure.

The panels used in these methods may be any of the panels described above, optionally including some or all of the preferred features.

The invention also extends to a building constructed from a plurality of panels as described above. When assembled into a building, the cavities may extend substantially vertically or substantially horizontally. Preferably cavities are formed in both the vertical and horizontal directions and panels are joined together in the manner described above in both horizontal and vertical directions. Corner junctions in a building can be formed by fixing an additional strut to the face of one panel. The additional strut may have a raised profile so as to act as an elongate attachment member for a second panel mounted to it at 90 degrees or the additional strut may lie flush with the face of the panel, but serve as a mount point to which an elongate attachment member may be mounted. In this way another panel can be connected at 90 degrees to the first panel. Other angles may be achieved by appropriate shaping and angling of the elongate attachment member attached to the first panel.

The invention also extends to a method of constructing a building comprising joining a plurality of panels according to any of the apparatuses and/or methods described above.

It will be appreciated that the above preferred features are applicable alone or in combination. The skilled person will readily be able to apply the apparatus features to the methods and vice versa. Preferred embodiments of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 shows a panel according to a first embodiment of the invention in a partial cut-away view;

Fig. 2 shows two panels joined together in a straight line;

Fig. 3 shows a panel mounted on building foundations;

Fig. 4 shows two panels joined together to form a corner;

Fig. 5 shows a top view of a window section of a wall;

Fig. 6 shows a mounting arrangement for an intermediate floor;

Figs. 7a-c show details of a corner reinforcement;

Figs. 8a-b show the use of pallet banding as reinforcement;

Fig. 9 shows an elongate attachment member having a laminate construction; and Figs. 10 and 1 1 illustrate methods of attaching a plurality of panels together.

The basic construction of a construction panel 100 of a first embodiment is shown in Fig. 1. The panel 100 comprises two frame members 102 and 104. Each frame member 102, 104 is rectangular in shape and is constructed from 4 engineered timber beams joined with mitred joints at their ends (although it will be appreciated that in other embodiments, more or fewer beams could be used and they may be joined in any way). The two rectangular frame members 102, 104 are positioned adjacent to one another and in parallel so that the two frames together define a cuboid box frame for the panel 100.

The frame members 102, 104 are joined together around their perimeters by plates (made of plywood or other composite board material) 106 which extend

perpendicular to both frame members 102, 104 and extend along the length of the side of the panel 100. Plates 106 are provided on each of the four long, narrow sides of the panel 100, thereby forming a rectangular perimeter of the panel 100 with its two largest faces still open.

The plates 106 are not located at the outermost position between the frame members 102, 104. That is, they are not flush with the outermost edge of the frame members 102, 104. Instead, the plates 106 are set back from the edge so as to form a recess in each of the long, narrow sides of the panel 100. The profile of the recess is a square U shape with its sides formed from the opposing faces of the engineered timber beams of frame members 102 and 104 and with its bottom formed from the outer face of the plate 106. The plates 106 shown in the embodiment of Fig. 1 are symmetrically located with respect to the studs of the frame members, that is the plates 106 extend from the mid-point of the side of one timber stud (e.g. of frame member 102) to the mid-point of the opposing side of the other timber stud (e.g. of frame member 104). Therefore together the timber studs and the plate 106 form an I-beam (that is the side of the panel framework has a cross-section in the shape of an I). In other embodiments the plate 106 may be located off-centre, that is the profile of the I-beam may be asymmetrical with the plate 106 located more towards the inside of the panel 100 for a deeper recess or more towards the outside of the panel 100 for a shallower recess. A corresponding recess is formed by the opposite part of the I-beam, i.e. on the interior of the panel. This recess provides a key to be filled by filler material which thereby provides greatly increased rigidity and resistance to buckling. Hence the panel as a whole has greatly increased strength.

As shown in Fig. 1 , a number (three in this case) of additional support struts 108 are provided in each frame member 102, 104. The support struts 108 of the first frame member 102 are parallel to and adjacent to those of the second frame member 104 so that they may be readily joined together along their length by perpendicular connecting members 1 10. The struts 108 extend parallel to one of the sides of the rectangular frame members 102, 104. The struts 108 provide additional structural support and stability to the panel 100 as a whole. The struts 108 also provide attachment points for further structural or decorative components to be attached to the panel. For example, further insulation boards, render carrier boards, plasterboard or other interior decorative board or additional stud work can be attached to the struts 108. The struts 108 are provided at regular intervals along the largest faces of the panel 100. The connecting members 1 10 which join the struts 108 of one frame member 102 to those of the opposite frame member 104 are made from a material with low thermal conductivity so as to hinder the transfer of heat across the panel. The connecting members shown in Fig. 1 are connecting rods. A plurality of such rods 1 10 are provided along the length of each pair of struts 108 so as to connect them together in a plurality of places. The panel 100 is filled with filler material 1 12. The filler material 1 12 in this embodiment is Tradical® Hemcrete® which is a mixture of predominantly hemp shiv and lime binder. In other embodiments the filler material 1 12 is other blends of organic aggregates and mineral or organic binders. The filler material provides additional structural support to the panel 100. The filler material 1 12 is applied in a wet form, e.g. filled or sprayed into the panel 100 and then allowed to set and dry. The filler material 1 12 thus binds to the framework of the panel 100 (i.e. the frame members 102, 104, the plates 106, the struts 108 and the connecting rods 1 10), thus binding the whole panel structure together. The filler material also makes the panel 100 solid. The filler material 1 12 provides rigidity to the framework and prevents it from buckling. This provides a large increase in structural strength. The filler material 1 12 is thermally insulating and preferably has a low thermal conductivity. The filler material 1 12 also has a large mass and therefore a large thermal inertia which slows down the changes in temperature which may occur within a building constructed from such panels 100.

On the exterior of the panel 100 shown in Fig. 1 (i.e. the side which will face the exterior of a building formed from such panels and which will be open to the elements), various additional layers are applied for additional insulation, weather protection and for improved appearance. First, a plurality of wood fibre boards 1 14 are fixed onto the frame member 102 and its struts 108. The wood fibre boards 1 14 may be fixed by nails, screws, staples etc. or they may be attached with adhesive. On top of the wood fibre boards 1 14, a layer of render basecoat 1 16 is applied. The render basecoat 1 16 is applied with an alkali resistant glass fibre mesh 1 18 for additional structural support. On top of the render basecoat 1 16, a render topcoat 120 is applied for the final exterior finish. If desired, the topcoat 120 could also be painted. The render coatings 1 16, 120 are breathable so as to allow moisture within the panel to escape to the outside. Preferably the render coatings contain lime among other ingredients.

On the interior of the panel 100 of Fig. 1 (i.e. the side which will face the interior of a building formed from such panels 100 and can therefore form the interior walls thereof), additional structures may be formed. Internal studs 122 are fixed to the struts 108 of the frame member 104. Plasterboard 124 is then fixed to the studs 122. The studs 122 serve to space the plasterboard 124 from the filler material 1 12 and thus create a service void 132 (not shown in Fig. 1 ) therebetween which can be used for electrical work or pipe work. Additionally, breathable vapour control layers (membranes) may be fitted to either or both of the interior and exterior sides of the panel 100 so as to control the flow of moisture through the panel 100. On the interior side, a vapour control layer 128 (not shown in Fig. 1 ) may be placed adjacent to the filler material 1 12, between the struts 108 and the studs 122. On the exterior side of the panel 100, a vapour control layer (not shown) may be placed adjacent to the filler material 1 12, between the struts 108 and the wood fibre board 1 14. The exterior vapour control layer must have a diffusion resistance less than that of the interior vapour control layer so that moisture entering the panel from the inside is not significantly impeded from escaping to the outside.

It will be appreciated that, although the panel 100 shown in Fig. 1 is shown in a fully pre-constructed form, i.e. with all layers applied in a factory before transport to the construction site, the panels 100 could be formed in a more basic form in the factory, e.g. with just the framework 102, 104, 106, 108, 1 10 and the filler material 1 12. The additional layers of insulation, render and interior and exterior surface layers may be applied on site after the panels 100 have been assembled together to form a building. In this way these interior and exterior layers may bridge the gap between panels 100, thus adding to the weatherproofing and creating a smoother finish. The layers need not then be restricted in extent to a single panel size, but may be applied across whole building walls at once. For example, the external render layers may be sprayed over the whole building in a single application, bridging all joins in the process. Likewise, the internal walls of rooms of the building may be bridged by the internal boards and plaster may be applied over all joins for a smooth finish. This may be a full depth plaster layer or just a skim finish. If the vapour control layers are applied in the factory, they provide some protection to the panel 100 during transport. At the site, the vapour control layers of adjacent panels 100 may be joined with tape to seal the gap between the panels.

Fig. 2 illustrates a join between two panels 100a and 100b. The engineered timber beams 102a, 104a (and the connecting plate 106a between them) of the first panel 100a are located adjacent to the engineered timber beams 102b, 104b (and plate 106b) of the second panel 100b. Thus the longitudinal recess of the first panel (formed by 102a, 106a, 104a) is positioned adjacent to the longitudinal recess of the second panel (formed by 102b, 106b, 104b). Together these two recesses form a hollow longitudinal cavity of rectangular cross section between the two panels 100a, 100b.

To join the two panels 100a, 100b together a longitudinal (elongate) attachment member 134 is slotted into this cavity and substantially fills the cavity. That is, the attachment member 134 is a longitudinal beam with a rectangular cross section substantially matching that of the cavity. Each panel 100a, 100b is then fixed to the attachment member 134 by screws 136 (although it will be appreciated that other fixing members such as nails, staples, bolts, etc. may also be used, or adhesive). The screws 136 are applied through the timber studs of the frame members 102a, 102b on the outside and the timber studs of the frame members 104a, 104b on the inside, and they extend into the attachment member 134, thus securely fixing both panels 100a, 100b to the attachment member 134, and thereby fixing both panels 100a, 100b to each other. The screws 136 are applied at an angle (i.e. not perpendicular to the face of the panels) so that they pass through the frame member 102, 104 and into the attachment member 134. The screws 136 are applied at different angles. In the embodiment shown in Fig. 2, they are all directed towards the centre of the attachment member 134. It will however be appreciated that the screws 136 may be applied perpendicular to the surface if there is sufficient overlap between the frame members 102, 104 and the attachment member 134.

Studs 122 are fixed (e.g. by nails, screws, etc. or adhesive) to the internal frame members 104b and internal struts 108. Plasterboard 124 is fixed to the studs 122, thus forming a service void 132 between the plasterboard 124 and the filler material 1 12 of the panels 100a,b. A vapour barrier 128 is positioned adjacent to the filler material 1 12 and between the struts 108 and the studs 122 so as to limit movement of moisture through the panel 100a,b. The plasterboard 124 has been skimmed for a smooth finish. On the opposite side of the panels 100a,b wood fibre board 1 14 is fixed to the struts 108 and/or the frame members 102, 104 and is covered by a layer of render 120. It can be seen that the interior and exterior layers shown in this embodiment are not coterminous with the panels 100a,b. In this embodiment, the interior and exterior layers 1 14, 120, 128, 122 and 124 have been fixed to the panels on site after the panels 100 have been fixed together to form a wall or building. In other embodiments, they may be attached to the panels 100 in the factory before being transported to site.

Fig. 3 illustrates the attachment of a panel 100 to a building foundation 150. Fig. 3 shows the lower portion of a panel 100 with the lower engineered timber beam of the frame members 102 and 104 mounted on top of the building foundations 150. A damp proof course (DPC) or damp proof membrane (DPM) 142 is shown, extending from the area underneath the floor 146 over the raised foundation blocks (e.g. thermal insulating blocks 146) in a known fashion. Above the DPC 142, a timber base plate 140 is mounted. The timber base plate 140 provides the connection point for the panel 100 above it. The base plate 140 is wide enough to support the whole width of the panel 100. The frame members 102 and 104 rest on top of the base plate 140. The recess formed in the bottom of the panel 100 (formed by the frame members 102, 104 and the connecting plate 106 between them) lies above the base plate 140. An additional locating plate 152 is mounted on top of the base plate 140 and is sized so as to match the dimensions of the recess of the panel 100. The locating plate 152 provides an easy means to locate the panel 100 accurately on the foundations 150. The locating plate 152 also provides support for the panel by closely matching the shape of the panel, specifically the longitudinal recess in the bottom side of the panel 100. It will be appreciated that in other embodiments the base plate 140 and the locating plate 152 could be formed as a single piece having an upper surface shaped to match the profile of the panel 100 including its recess.

The panel 100 can be attached to the foundations by fixing the frame members 102 and 104 to the base plate 140 and/or to the locating plate 152. The fixing means (not shown in Fig. 3) may be any of those described above, e.g. screws, nails, bolts, staples or adhesive. Although the fixing means are not shown in Fig. 3, they are applied in a similar manner to that illustrated in Fig. 2.

Fig. 4 shows two panels 100a and 100b joined together to form a corner. The corner shown here is at 90° but it could be at a different angle. Both panels 100a and 100b are of the type described earlier with frame members 102a,b and 104a,b, connected by connecting plates 106a,b and filled with filler material 1 12. However, as will be described in more detail below, panel 100a has an additional strut 160 to assist with the corner mounting.

To form the corner joint, panel 100b is aligned so that its outer face (that of frame member 102b) is flush with the peripheral faces of frame members 102a and 104a. Thus the outer frame member 102b of panel 100b is placed adjacent to the inner frame member 104a of panel 100a. Outer frame member 102b could thus simply be fixed to inner frame member 104a by a fixing means 136 as described above. However in order to provide additional strength and security of the joint, the inner frame member 104b also needs to be securely connected to panel 100a.

Therefore, to provide a joint surface for both inner frame member 104b and outer frame member 102b, the frame 100a is provided with an additional corner strut 160 located adjacent to inner frame member 104a. The corner strut 160 is connected to inner frame member 104a by any suitable means, e.g. by screws, nails, bolts, etc. or by adhesive. The corner strut 160 must be formed as part of the panel framework before the filler material 1 12 is added. Corner mounting plate 162 is attached to corner strut 160 and has a profile corresponding to the recess formed in the end of panel 100b by frame members 102b, 104b and connecting plate 106b.

Corner mounting plate 162 also acts as a locating plate and is thus positioned so as to ensure that the panels 100a and 100b are mounted flush with each other as described above. Panel 100b may then be securely attached to panel 100a by fixing the frame members 102b and 104b to the corner mounting plate 162. This attachment may be via fixing means 136 as described above, e.g. by screws, nails, bolts, adhesive, etc. It will be appreciated that the corner strut 160 and corner mounting plate 162 may be two separate members or they may be a single member formed into the appropriate shape. A single member has the benefit of extra stability and simplicity, but a two part design allows disconnection of the corner mounting plate 162 so as to allow use of the panel 100a in other circumstances.

It will be seen that the panel 100a in Fig. 4 is a short panel, provided only for the purpose of forming the corner joint. Short panel 100a in this case has no intermediate struts 108 as these are unnecessary for such a short panel. Panel 100a is however otherwise similar to the panel design previously described and in particular it can be seen that it is joined to a third panel 100c in the same way as described in relation to Fig. 2 using an elongate attachment member 134 located in the cavity formed by the adjacent recesses of panel 100a (formed by frame member 102a', 104a' and connecting plate 106a') and of panel 100c (formed by frame member 102c, 104c and connecting plate 106c). In other embodiments, the corner joint may be formed by two full size panels or two short panels. As in previous embodiments, the interior of the corner joint illustrated in Fig. 4 is provided with a vapour control layer 128, studs 122, plasterboard 124 (with skim layer on top) on the interior side and wood fibre board 1 14 and render system 120 on the exterior side. At the interior corner, a double stud is formed from stud 122 and stud 122' so as to provide an appropriate mounting point for the interior board work.

Fig. 5 shows a window 200 positioned between two panels 100a and 100b. The panels 100a and 100b are located horizontally either side of the window 200. The panels 100a and 100b have a similar construction to those of other embodiments except that at the end adjacent to the window they have a double stud construction to from a cripple stud capable of supporting a lintel above the window. Additional studs 202a, b and 204a, b are attached to the frame members 102a,b 104a,b respectively. The additional studs 202a, b, 204a, b are joined by connecting members 206a, b. The additional studs 202a, b 204a, b and connecting member 206a, b form an I-beam in the same way as the frame members 102, 104 and connecting member 106. The cavity between the additional studs and the frame members is filled with insulation material 208. The window 200 is then inserted into the gap between panels 100a and 100b and is sealed in place in conventional fashion, e.g. with expanding tape 210 and/or various sealing beads. The interior and exterior panels 1 14, 120, 124 may also be fitted up to the window in conventional fashion.

Fig. 6 shows a floor 300 supported by a wall formed from two panels 100a and 100b. Fig. 6 shows a portion of a wall formed from panel 100a mounted on top of panel 100b. It can be seen that these two panels are joined in a similar fashion to the joint shown in Fig. 2, i.e. with both panels 100a and 100b mounted to an elongate attachment member (e.g. an elongate timber batten) 134 which fits within the cavity formed by the recesses of each panel (respectively formed from frame members 102a, 104a and connecting plate 106a and frame members 102b, 104b and connecting plate 106b).

The intermediate floor 300 (which forms the ceiling of one storey and the floor for the storey above) is connected to the wall structure in the following manner. A floor support block 302 is fixed to the inner frame members 102a and 102b of both panels 100a and 100b. The attachment may be by means of screws 136 as shown, but may be any other fixing means as described elsewhere. The floor support block 302 has a height equal to half the height of a floor panel 300 (excluding any cladding thereon). The intermediate floor 300 is also formed from a panel with similar construction to that of the constructions panels 100, but with light weight insulation material 306 instead of the heavy weight filler material 1 12. The floor panel 300 is clad with suitable flooring boards 308 and ceiling boards 310. Floor panel 300 has frame members 312 and 314 joined by connecting plate 316 so as to form a recess in the same manner is with the construction panels 100. Also in a similar manner to the corner mounting arrangement of Fig. 3, a floor mounting plate 318 is inserted into the recess formed by floor frame members 312, 314 and floor connecting plate 316. The floor mounting plate 318 has substantially the same cross-section as the recess so that it lies flush with the end of the floor frame members 312, 314. A floor hanging block 320 is fixed to both the upper floor frame member 312 and the floor mounting plate 318 by means of screws 136 or similar attachment means. The floor hanging block 320 has a height equal to half the height of a floor panel 300 (excluding any cladding thereon). Therefore to mount the floor panel 300 onto the wall, the floor hanging block 320 is simply rested on top of the floor support block 302. Together the floor support block 302 and the floor hanging block 320 make up a height equal to that of the floor panel 300.

The other features of the panel such as studs 122, plasterboard (or other lining board) 124, wood fibre board 1 14 and render system 120 are all substantially the same as previously described. The vapour control layer 128 may run continuously from panel 100b to panel 100a, past the floor panel 300 by running around the floor support block 302 (between the floor support block 302 and the floor panel 300), between the floor support block 302 and the floor hanging block 320 and then around the floor hanging block 320 (between the floor hanging block 320 and the panel 100a).

It will be appreciated that floor panels 300 may have a similar structure and be connected together in a similar manner to the wall panels 100 described above. A floor support system as described above may be utilised at each edge of the floor in question so as to mount the floor to all available supporting walls.

It will be appreciated that other timber frame floor mounting systems may be used in other embodiments as are known in the art. It will be appreciated that in the above descriptions the elongate attachment member 134, the corner mounting plate 162, the locating plate 152 and the floor mounting plate 318 may all be longitudinal, elongate beams extending the full length of the respective panels or further (e.g. to join two or more panels together). However in other embodiments, these may be provided as a plurality of smaller members collectively extending in the same direction, but not formed as a single piece. This plurality of smaller members may abut each other end to end or there may be spaces formed between them.

Figs. 7a-c show in detail a reinforced corner according to one embodiment of the invention. Fig. 7a is a plan view of the reinforced corner, Fig. 7b is an illustration from the side showing filler material 1 12 present within the framework. Fig. 7c is a perspective view of the reinforced corner without filler material present.

The reinforcements comprise two triangular panels 400, each fitted to the opposing sides of the frame members 102 and 104, i.e. on the interior of the panel. The triangular panels 400 abut against the connecting plates 106. In Fig. 7a the connecting plate along the side is shown, but the connecting plate 106 on the top is omitted so that the reinforcement detail can be seen. The triangular panels 400 are mounted such that two sides of the triangle are connected to different arms (different studs) of a frame member (e.g. 102) either side of the corner to be reinforced. The third side extends from one arm of the frame member to the arm on the other side of the corner. Between the two triangular members 400, i.e. between the two frame members 102, 104, a rectangular timber batten 402 is provided. The batten 402 is fixed to the two triangular plates 400 at each end, e.g. by any of the aforementioned fixing means, and the triangular plates 400 are fixed to the frame members 102, 104, also by any of the aforementioned fixing means. This extra reinforcement provides additional structural stability to the panel as a whole.

In an alternative embodiment only a single triangular reinforcement member 400 may be used, centrally located between the frame member 102, 104 and connecting the connecting plate 106 of one side to the connecting plate 106 of the neighbouring side. The timber batten 402 extends through the single triangular member (e.g. the triangular member may be notched around it). Figs. 8a and 8b show a partial perspective view and a partial end view of a corner of a panel 100 in which pallet banding 500 has been applied around the panel, within the recess. The pallet banding 500 may be applied by a proprietary application tool. The pallet banding 500 provides additional structural stability to the panel as a whole and allows it to be lifted readily by a crane or other hoist.

Fig. 9 shows a cross section of a join between two panels 100a and 100b. A recess of panel 100a is formed from the frame members 102a, 104b and the connecting plate 106a. A recess of panel 100b is formed from the frame members 102b, 104b and the connecting plate 106b. The elongate attachment member 134 which is located in the cavity formed by the two recesses is of a laminated construction. The elongate attachment member 134 has a core 600 of thermally insulating material and two outer panels 602 which sandwich the core 600 between them. The panels 602 are of a stronger material such as plywood or other composite board which is capable of receiving fixing members such as nail, screws, bolts, etc. The panels 602 are laminated to the core 600. The elongate attachment member 134 is oriented such that the panels 602 face the inside and outside of the building, i.e. they face towards the frame members 102a, b 104a, b for receiving the fixing members passed therethrough. The panel 100 shown in Fig. 1 may be made as follows. The timber frame members 102 and 104 may be formed from engineered timber studs joined at their corners. Struts 108 may be mounted to the frame members 102, 104. The frame members 102 and 104 may then be connected together by means of connecting plates 106 and/or connecting rods 1 10. The connecting plates extend the full length of the sides of the frames and thus provide structural support as well as a solid wall capable of retaining the filler material 1 12. The connecting rods 1 10 are not full length connecting plates like those forming the perimeter of the panel 100 so that they allow flow of filler material within the main body of the panel 100. A temporary side structure (face plate) is attached to one side of the panel (e.g. the side of frame member 102) so as to form a box having five solid faces capable of containing filler material 1 12 and one open face for filling the box. Solidifiable filler material 1 12 is then poured into the box and placed up to the various frame structures 102, 104, 106, 108, 1 10. The box is filled to the brim so as to form a flat, level surface flush with the open side of the box (e.g. flush with the frame member 104). The solidifiable mixture is then allowed to solidify, set and/or dry as appropriate. Once the material has solidified, i.e. once the mixture has set hard enough that the panel 100 has enough structural stability to stand on its own without deformation, the temporary face plate can be removed. Uncovering this face of the panel 100 allows more air contact with the panel 100 to increase the drying rate. Once the chemicals in the panel have fully set, the moisture content of the panel can be reduced more rapidly through application of forced air and/or heat. These are applied in cycles so as to reduce the energy required for the drying process. Once the panel has achieved an equilibrium moisture content (typically 5- 10%), the forced drying can be stopped and the panel can be used or stored for later use. Any cracks in the filler material caused by shrinkage can be filled in the factory prior to transport to site.

The above setting and drying processes are applied before any of the other features of the panel, e.g. the interior and exterior layers (wood fibre, render, plasterboard) described above are applied.

In other embodiments, the external connecting plates 106 around the perimeter are not solid plates, but are thermally insulating connecting rods. In this embodiments in order to contain the filler material 1 12, additional temporary plates may be required around the perimeter in order to retain the filler material 1 12 until it has solidified.

It will be appreciated that, although all of the above embodiments are described with the framework (frame members 102, 104, connecting members 106, struts

108, studs 122, elongate attachment member 134, triangular plates 400 and batten 402) being made from various types of wood product, they could in other embodiments also be made from plastic, particularly recycled plastic. In one particularly preferred embodiment, the time required for solidifying is about 3-4 days, the time required for fully setting is about 10-15 days and the period required to reach equilibrium moisture content under forced drying is about 5 days. It will be appreciated that these time periods will depend upon the nature of the filler material 1 12, the size of the panel 100, the environmental conditions (temperature, humidity, etc.) in which the solidifying, setting and drying are carried out and the strength of the forced drying (air flow, air temperature, air humidity, etc.) amongst other things. The skilled person will be able to adapt the process according to the particular panels being dried. In one particular embodiment, air is applied at a temperature of about 50-70°C and the relative humidity is controlled to about 20%. However other drying techniques may be used.

Figs. 10 and 1 1 illustrate two ways of connecting multiple panels together. Fig. 10 illustrates four panels 901 , 902, 903, 904 all being connected to a single elongate attachment member 134. Panels 901 and 903 are in line and panels 902 and 904 are in line. Therefore the joins between them are in line. However all four panels are connected to the same attachment member 134. Panel 901 may be connected to panel 902 by a vertical elongate attachment member (not shown). Likewise for panels 903 and 904. Fig. 1 1 shows a similar arrangement, but with offset panel joins. Panels 905, 906, 907, 908 and 909 are again all joined to the same single elongate attachment member 134, but the joins between panels 905/906 and 906/907 do not align with the join between panels 908/909. Rather the joins are offset so that each panel is supported by two panels from the row beneath. It will be appreciated that these attachment schemes could also be applied vertical domain as well as the horizontal domain, i.e. with vertical elongate attachment members having multiple panels attached on each side.

Claims

1. A construction panel comprising:

a first frame member;

a second frame member disposed adjacent to the first frame;

the first and second frame members being connected together around their perimeters by one or more connecting members;

wherein at least one connecting member is positioned to extend between said first and said second frame members so as to form a recess in a side of the panel.

2. A construction panel as claimed in claim 1 , wherein the first and second frame members are rectangular

3. A construction panel as claimed in claim 1 or 2, wherein the panel has a recess formed on more than one side of the panel.

4. A construction panel as claimed in claim 1 , 2 or 3, wherein each of the first and second frame members comprises additional struts extending parallel to one of the sides.

5. A construction panel as claimed in claim 4, wherein the struts of the first frame are connected to the struts of the second frame by strut connecting members.

6. A construction panel as claimed in any preceding claim, wherein at least one reinforcement band is provided around the perimeter of the panel, between the first and second frame members and positioned within the or each recess.

7. A construction panel as claimed in any preceding claim wherein the panel has at least one corner and wherein said at least one corner of the panel is provided with a reinforcement structure comprising at least one triangular plate connecting the connecting member of one side to the connecting member of the neighbouring side.

8. A construction panel as claimed in claim 7, further comprising a transverse member extending between the two frame members in the vicinity of the corner.

9. A construction panel as claimed in any preceding claim, wherein the frame members are constructed from engineered timber beams.

10. A construction panel as claimed in any preceding claim, wherein the connecting members are plywood plates.

1 1 . A construction panel as claimed in any preceding claim, wherein the or each connecting member extends from a groove in the first frame member to a groove in the second frame member.

12. A construction panel as claimed in any preceding claim, wherein the interior of the panel is filled with a filler material.

13. A panel comprising a main panel body formed from a vegetable based aggregate based bio-composite and clad on one or more sides with a plant fibre based board.

14. A panel as claimed in claim 13, wherein the vegetable based aggregate is hemp based aggregate.

15. A panel as claimed in claim 13 or 14, wherein the plant fibre based board is wood fibre board.

16. A panel as claimed in claim 13, 14 or 15, wherein the plant fibre based board acts as a render carrier board and wherein render is applied on the outside of the render carrier board.

17. A method of forming a construction panel comprising:

forming a first frame member;

forming a second frame member;

disposing said second frame member adjacent to said first frame member; connecting said first and second frame members together around their perimeters by one or more connecting members;

18. A method of forming a construction panel comprising a frame structure filled with a filler material, comprising:

assembling the frame structure;

filling the frame structure with filler material;

waiting for a first period of time after filling has taken place, sufficient to allow the filler material to solidify; then

waiting for a second period of time, sufficient for the filler material to achieve a predetermined level of set; and then

waiting for a third period of time, sufficient to dry the filler material to an equilibrium moisture content,

wherein heat and/or dry moving air is applied to the panel during the third time period.

19. A method as claimed in claim 18, wherein the filler material is a bio- composite material such as Hemcrete®.

20. A method as claimed in claim 18 or 19, wherein the method further comprises a step of attaching one or more temporary face plates to the frame structure prior to the filling step to contain the filler material, and removing the temporary face plates after the first time period has elapsed.

21 . A method as claimed in claim 18, 19 or 20, wherein the application of air and/or heat comprises cycling.

22. A method as claimed in any of claims 18 to 21 , wherein the first time period is 1 to 5 days, preferably 3 to 4 days.

23. A method as claimed in any of claims 18 to 22, wherein the second time period is 5 to 20 days, preferably about 2 weeks.

24 A method as claimed in any of claims 18 to 23, wherein the third time period is 1 to 10 days, preferably about 5 days.

25. A method of joining a first construction panel and a second construction panel, wherein each panel comprises at least one recess, comprising:

placing the first panel adjacent to the second panel such that a recess of the first panel is adjacent to a recess of the second panel so as to form a cavity;

positioning an elongate attachment member at least partly within the cavity; and

fixing both the first panel and the second panel to the elongate attachment member.

26. A method as claimed in claim 25, wherein the first and second panels are each fixed to the elongate attachment member by one or more fixing members driven through a frame member of the panel and into the elongate attachment member.

27. A method as claimed in claim 25 or 26, wherein a plurality of fixing members are used for fixing each panel.

28. A method as claimed in claim 25, 26 or 27, wherein the or each fixing member is applied at an angle to the surface of the panel.

29. A method as claimed in claim 28, wherein the angle is about 45 degrees.

30. A method as claimed in any of claims 25 to 29, wherein the elongate attachment member has a cross section which matches the cross section of the cavity.

31 . A method as claimed in any of claims 25 to 30, wherein the recess of the first panel and the recess of the second panel are offset so that the cavity is formed between a part of the first recess and a part of the second recess.

32. A method as claimed in claim 31 , wherein a third construction panel having a recess is positioned adjacent to the first panel so that a cavity is also formed by the recess of the first panel and the recess of the third panel.

33. A method as claimed in any of claims 25 to 30, wherein the elongate attachment member extends from the cavity of the first and second panels and into a similar cavity formed by a third panel and a fourth panel, and the third panel and the fourth panel are also fixed to said elongate attachment member by one or more fixing members.

34. A building constructed from a plurality of panels as claimed in any of claims 1 to 16.

35. A method of constructing a building comprising joining a plurality of panels as claimed in any of claims 1 to 16.

36. A method of constructing a building comprising joining a plurality of panels according to the methods as claimed in any of claims 25 to 33.

37. A method as claimed in claim 36, wherein the or each panel is as claimed in any of claims 1 to 16.