The composite log module can have an elongated structural shell having a first set parallel walls rigidly interconnected with a second set of parallel walls perpendicular to the first set of parallel walls, the interconnected walls enclosing an elongated cavity housing a core having thermal insulation material, and two opposite mating outer surfaces associated with the first set of parallel walls for stacking identical ones of the composite log, and two sides associated with the second set of parallel walls, the walls each having a structural engineered material.

BACKGROUND 
       [0001]    Modular building construction has attracted much interest over the last decades. The perspective to be able to build your own home out of relatively easy to assemble components is appealing when considering the hourly rates of skilled construction workers. 
         [0002]    Although some former modular building concepts have been satisfactory to a certain degree, there remained room for improvement. 
       SUMMARY 
       [0003]    Some of the main factors which will affect the commercial success of a modular building concept include the level of skill required to complete the assembly, the amount of skilled worker hours required, the manoeuvrability of the components (weight) vs. the amount of components; the durability of the components, the overall appeal of the finished construction, and at least in northern climates, the insulation strategy. 
         [0004]    Increasing the size of the wall components is a way to reduce the amount of components. However increasing the size tends to increase weight, which should be limited to a certain reasonable extent. One aim is to provide walls which are formed of elongated composite logs having at least 8 feet in length, a satisfactory height, a satisfactory structural resistance, and a satisfactory thermal insulation, while being light enough to provide handling by two average persons. It is aimed that the weight of the composite logs be maintained below 80 lbs if possible, for instance. 
         [0005]    In a concept of logs formed of a structural shell with an insulating core, the main structural materials are typically much denser than insulation materials and should thus be used strategically, in an engineered manner, to limit the overall structural component volume vs. the volume of insulation. 
         [0006]    In accordance with another aspect, it was found that using solid foam components in the core as thermal insulation can be beneficial, because although the structural resistance of solid foam components is typically low when compared to that of engineered structural materials, it remains non-negligible and can contribute to overall structure. It was found that using an adhesive to adhere solid foam components inside the shell to the engineered structural components of the shell allowed to better harness the structural resistance of the solid foam components in the overall structure, and therefore reduce the required amount (weight) of engineered structural materials. 
         [0007]    In accordance with another aspect, it was found that using a separator panel intersecting the cavity can be a strategic way to add structure to significantly improve the structural characteristics with a relatively low cost in weight. The advantages of a separator panel are even further increased when solid thermal insulation components are adhered to it. 
         [0008]    It was also found that using engineered materials such as manufactured wood panels instead of wood in the structural components can reduce weight, because the mechanical resistance of engineered materials are typically better known than that of wood and a lesser excess material safety buffer is required. 
         [0009]    Henceforth, in accordance with another aspect, there is provided a composite log having an elongated structural shell having a first set parallel walls rigidly interconnected with a second set of parallel walls perpendicular to the first set of parallel walls, the interconnected walls enclosing an elongated cavity housing a core having at least one block of rigid plastic foam insulation adhered to inner faces of the walls by an adhesive, and two opposite mating outer surfaces associated with the first set of parallel walls for stacking identical ones of the composite log, and two sides associated with the second set of parallel walls, the walls each having at least one board of manufactured wood. 
         [0010]    In accordance with another aspect, there is provided a method of assembling a composite log having a first set of parallel walls having grooves with a second set of parallel walls perpendicular to the first set of parallel walls and interconnected therebetween and engaged into the grooves, and a core having at least one block of rigid plastic foam insulation; the method comprising in sequence : stacking the core onto a first one of the parallel walls of the first set, with an adhesive applied therebetween; engaging a first end of the parallel walls of the second set into the grooves of the first one of the parallel walls of the first set, with an adhesive between the core and the parallel walls of the second set; folding the parallel walls of the second set onto opposite sides of the core; lowering the second one of the parallel walls of the first set onto the core, thereby engaging the second end of the parallel walls of the second set into the grooves of the second one of the parallel walls of the first set; and applying a predetermined pressure in compression respectively between both sets of parallel walls and allowing the adhesive to set. 
         [0011]    In accordance with another aspect, there is provided a composite log having an elongated structural shell having a first set parallel walls rigidly interconnected between a second set of parallel walls, the interconnected walls enclosing an elongated cavity housing a core having thermal insulation material, and two opposite mating outer surfaces associated with one of the first set and second set of parallel walls for stacking identical ones of the composite log, and two sides associated with the other one of the first set and second set of parallel walls, the walls each having a structural engineered material. 
         [0012]    Many further features and combinations thereof concerning the present improvements will appear to those skilled in the art following a reading of the instant disclosure. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0013]    In the figures, 
           [0014]      FIG. 1  includes schematic views  1 A,  1 B and  1 C showing types of mechanical deformation which a composite log can suffer when subjected to stress; 
           [0015]      FIG. 2  is an oblique view showing an example of a composite log, fragmented; 
           [0016]      FIG. 3  is a cross-sectional view of the composite log, shown with additional optional components; 
           [0017]      FIG. 4  includes  FIGS. 4A to 4C  which schematically depicts successive steps of an exemplary method of assembling a composite log. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows different types of mechanical stresses to which an elongated composite building module (herein after referred to as a composite log) can be subjected to, and examples of resulting deformation. In  FIG. 1A , the composite log  10  is subjected to compression which causes buckling. In  FIG. 1B , the composite log  10  is subjected to compression which causes torsion. In  FIG. 10 , the composite log  10  is subjected to compression which causes bending. The structure in the composite log  10  is engineered to withstand pre-established thresholds of such stresses which can be well above the maximum stresses which can normally be expected. 
         [0019]    Turning now to  FIG. 2 , an example of a composite log  10  is shown. The composite log  10  can be seen to generally include a structural shell  12  having two pairs, or sets, of opposite walls  14 ,  16 . In this example, the walls in each given pair  14 ,  16  are parallel to each other and perpendicular to the walls of the other pair  14 ,  16 . Further, each one of the walls of each pair includes an engineered structural material. In this particular example, the engineered structural material is in the form of panel(s) of manufactured wood. Plywood is the preferred type of manufactured wood in this example. In this example, it can be seen that the upper wall  18  and lower wall  20  each include two wide plywood panels  22 ,  24 . Further, plywood boards  26 ,  27  are adhered to the two plywood panels  22 ,  24  in a manner to form mating surfaces  28 ,  30 . More particularly, the mating surfaces  28 ,  30  in this case are of the tongue and groove type, the spacing between the boards  26  of the upper panel  18  being adapted to the width of the boards  27  of the lower panel  20 , and vice-versa. Other examples of manufactured wood can be veneer based, particle based, or fiber based, and can include wood-plastic composite or oriented strand board for instance. It will be noted that in this example using structural panels, grooves are defined in the side walls  32 , into which the structural panels  22  of the upper and lower walls  18 ,  20  can be engaged. The presence of this mating engagement can significantly improve structural resistance. The walls can be interconnected in any suitable manner such as by adhesion, fastening, etc. In this example adhesion was preferred. It will be noted here that other engineered materials than manufactured wood can be used in alternate embodiments, such as fiber cement or instance. Further, alternately to being assembled, the walls of the shell can be integral such as by forming an extruded shell of a plastic material, for instance. 
         [0020]    In this example, the side walls  34 ,  36  each have three parallel and interspaced spacer boards  38  adhered to a full plywood panel  40 . The spacer boards  38  form air space channels  42  therebetween. It will be noted here that in alternate embodiments, the air space channels can be oriented vertically rather than horizontally. 
         [0021]    A core  50  is housed inside the structural shell  12 . The core  50  includes thermal insulation. In this particular example, the thermal insulation includes solid plastic foam. Outer surfaces of the solid plastic foam thermal insulation the core  50  are fully adhered to the structural panels  16 ,  14  via an adhesive  52 , a feature which can significantly improve the structural resistance of the composite log. In alternate embodiments, adhesion can be provided without an adhesive, such as by using the naturally occurring adhesion characteristics of some sprayed foam insulation (such as sprayed polyurethane) for instance. In this particular example, the solid plastic foam is extruded expanded polystyrene, but it will be understood that any other suitable insulation materials can be used, even loose fill insulation for instance, in some alternate embodiments. Blocks of insulation can be formed of a stack of smaller components if desired. In this specification, the expression thermal insulation refers to materials having a thermal conductivity above 0.35 m 2 .K/(W.in) or an R-Value above 2, and preferably above 52 m 2 .K/(W.in) or a R-Value above 3. For instance, low-density extruded expanded polystyrene panels can have an R value between R-3.6 and R-4.7. 
         [0022]    In this example, one separator board  54  is used and interconnects the side walls  16  and the thermal insulation includes two blocks  56 ,  58  of rigid plastic foam, one on each side of the separator board  54 . Each one of the lateral, upper and lower surfaces of the blocks  56 ,  58  of rigid plastic foam are fully adhered to a corresponding one of the side walls, upper wall  18 , separator board  54  and lower wall  20 . This configuration can significantly improve the structural resistance of the composite log to deformation such as illustrated in  FIG. 1A , for instance. Further, the presence of a separator board  54  which intersects the cavity, especially when the rigid thermal insulation is adhered to the separator board using an adhesive, can significantly enhance the structural resistance. It will be noted here that in an alternate embodiment, the separator can be oriented obliquely with blocks having a triangular cross-section for instance, and/or there can be more than one separator used. 
         [0023]    Turning now to  FIG. 3 , further details are shown. In this particular example, the mating engagement between the opposite surfaces  28 ,  30  is provided with a tongue and groove engagement. More particularly, a double tongue and groove engagement as shown was preferred in this example, with both tongues  60  and both grooves  62  being interspaced from one another. Each one of the grooves  62  can include an adhesive bead (not shown) which is compressed and activated when successive composite logs are stacked against one another. Further, in this particular case, each one of the grooves  62  houses a weather strip  64  to impede air infiltration. In this particular embodiment, given that the bottom wall  20  and upper wall  18  are made of pieces of plywood having the same thickness, the grooves  62  are provided with an elongated recess  66  which houses the weather strip  64  and into which the weather strip  64  can be compressed upon installation. 
         [0024]    Further, in this embodiment, the composite log  10  can optionally include any one of various types of interior finishing panels  70  and/or exterior facing panels  72 . When both panels are provided, the wall can automatically have two finished sides once completed, which is very appealing in terms of efficiency of assembly. The panels  70 ,  72  can enclose the air space channels. In this particular example, the exterior facing panel  72  can be fibro cement, and the interior finishing panel  70  can be wood, for instance. It will be noted that the air space channels  42  can be used to house technical components such as water conduits or electrical wires, for instance. 
         [0025]    The composite logs can be stacked into a wall. More particularly, the end of the core  50 , upper and lower walls  18 ,  20  of the composite logs  10  can be placed in abutment against an upstanding pole, and the sidewalls  16  project lengthwisely from the end of the core  50  to overlaps onto a portion of the pole, to which it can be secured. It will be noted that in an alternate embodiment, the composite log can be used in roof structure rather than wall, for instance. 
         [0026]    Turning now to  FIG. 4 , it will be understood how the example composite log described above and illustrated can be manufactured. First, each one of the four walls can be assembled from corresponding manufactured wood pieces. A first one of the lateral walls  16 A is positioned, and the core  50 , including foam insulation blocks  56 ,  58  and separator board  54  is stacked above it. Two perpendicular walls  18 ,  20  can be engaged in the grooves  32 . The two perpendicular walls  18 ,  20  can then be folded onto the core and pressure applied to satisfactorily activate the adhesive between the two perpendicular walls and the core. This step can also align the ends of the two perpendicular walls  18 ,  20  with grooves  32  in the last panel  16 B, which can be lowered into place to form the engagement. Finally, pressure can also be applied in the perpendicular direction to activate the adhesive so that the adhesive is activated in both perpendicular directions. Many alternate manufacturing methods can be used, and the particular manufacturing method can be adapted to the particular configuration of the composite log. 
         [0027]    As can be seen therefore, the examples described above and illustrated are intended to be exemplary only. The scope is indicated by the appended claims.