Abstract:
A building construction unit and a method of constructing a building using wall and ceiling panel assemblies that are made up of traditional framing materials, such as studs and interior walls, coated with insulating foam, except that the typical exterior sheathing is optional. Because the panel assembly is structurally sound and thermally insulated, the only reason to install an exterior sheath or additional roofing material is for aesthetic or practical purposes.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to building construction methods, particularly to a method and unit that provides energy efficiency and structural soundness in buildings through a foam layer shell application. 
     Background Art 
     “Light framing” construction is a known construction mode using many small and generally closely spaced members that are assembled by nailing/screwing, and the mode includes balloon, platform and light-steel framing. Light framing building techniques are commonly used, especially in the USA, to erect residential, small commercial or light industrial structures. Light-frame construction using standardized dimensional lumber has become the prevailing light construction method in North America. Use of relatively minimal structural material allows builders to enclose a large area with minimal cost, while achieving a wide variety of architectural styles. 
     In light platform framing, each floor is framed separately, each floor level being framed as a separate unit or platform. Freed from the need to use heavy timbers (e.g., as with a post-and-beam system), platform framing offers ease of construction. Builders first fabricate a floor, which consists of wood joists and subflooring. The floor often serves as a working platform on which the stud wall frames are fabricated in sections and then lifted into place. A second floor, or the roof, is constructed atop the first-floor wall frame sections. The roof is formed of rafters (e.g., sloping joists) or wood trusses. The standard interior wall sheathing is gypsum board (drywall), which provides fire-resistance, stability, and a surface ready for interior finishing. Light framed structures traditionally have been constructed individually at each construction site; today many of the framing elements are mass-produced elsewhere and assembled on-site. 
     Modern light-frame structures typically obtain strength from rigid panels (plywood and/or other plywood-like composites such as oriented strand board (OSB) used to form all or part of wall sections). Until recent years, builders often employed any of several types of diagonal bracing techniques to stabilize framed walls. Diagonal bracing remains a vital interior part of many roof systems, and in-wall wind braces are required by building codes in many municipalities or by individual state laws in the USA. Special framed shear walls also are sometimes required to promote building structural strength, especially to foster compliance with earthquake engineering and wind engineering codes and standards. 
     Thus in commercial and residential construction, walls typically are framed up using vertical wooden or steel studs, to which an interior wall panel made of gypsum drywall (e.g., SHEETROCK® panel), fiberboard, traditional plaster, or the like is attached. Thereafter, exterior wall sheathing is used to enclose the wall and building and provide a surface for application of exterior finish materials, such as stucco, brick façade, shingles, aluminum or vinyl siding, etc. Insulating material, such as fiber glass, rock wool or cellulose, normally is sandwiched between the interior wall panel and exterior wall sheathing in order to thermally insulate the rooms and spaces of the building. Using this traditional method, there disadvantageously is little or no insulation present where the entire length of the vertical stud contacts the interior wall panel on one side, and exterior wall sheathing on the other side, providing a conduit for heat to readily escape the interior rooms, through the studs, to the outside environment. 
     The present invention solves this thermal insulation problem and also requires significantly less materials to achieve a highly energy efficient and structurally sound building. The presently disclosed method and system offers advantages of structural strength (potentially compliant with many building codes respecting wind and earthquake resistance) using fewer materials and less labor intensive methodology compared to fully conventional light framing construction. Less materials and ease of construction yields benefits of faster construction and reduced construction costs. 
     The present invention contemplates constructing a building using wall and ceiling panel assemblies that are made up of many traditional framing materials, but which are then coated with an insulating and strengthening foam. The foam layer initially is applied as viscous flowable foam, which may be sprayed in place. After controlled application, the foam layer then hardens into an enveloping shell which provides not only thermal insulation to the completed structure, but which also lends substantial structural strength. Moreover, because the foam shell substantially seals the interior of the structure against exterior weather, an exterior sheathing and an exterior façade are optional. A structure erected according to the present invention may be, if desired, substantially air tight and water tight (except where deliberately provided with doors, windows, vents, and the like). As the structure also is structurally sound and thermally insulated, the only reason to install an exterior sheath or additional roofing material is for aesthetic purposes. 
     While there are examples in the prior art of applied-foam insulating wall panels, none offer the advantages of the present invention. 
     SUMMARY OF THE INVENTION 
     The present invention is a unit and method of residential and commercial building construction. The construction unit is a structure comprised of closed cell polyurethane foam and portions of traditional light framing materials, such as studs, inner wallboard, roof trusses, and inner ceiling wall board. Standoffs are installed on a wall stud or roof truss that creates a gap between the stud/truss and the wall board which allows the foam to more completely coat the wall board. Once it is hardened, the wall board, standoff, stud/truss and foam become a structurally sound, highly insulated, building. The only purpose for the outside wall sheathing materials and roofing (e.g., shingles, tiles) are for aesthetic—not structural—reasons. 
     The building construction unit and method of the present invention includes arranging two or more (normally a substantial plurality) panel assembly units adjacent to each other to form the walls, ceilings and floors of a building. This erection and arranging of panel assemblies is performed mostly according to known light framing techniques, but once the light framing is realized, the interior panels (e.g., gypsum board are attached to the inside of the framed walls/roof. The framed walls and roofs need not be provided with conventional exterior coverings such as brick or siding. Insulation such as fiberglass batting or blown-in cellulose need not be sandwiched between interior panels and exterior sheathing. Rather, the framed structure, including the installed interior panels, is covered with insulating foam. 
     Each panel assembly preferably is made of a number of studs with standoffs spaced along one side of the stud and an interior panel. For instance, where a panel assembly is being used as a wall, a number of studs are installed in the upright position a certain distance apart (this distance being calculated to provide adequate structural support for the building), and the standoffs are attached the studs so that the standoffs are between the studs and an interior wall panel. This creates gaps or spaces between the studs and the wall panel where the standoffs are not located. When the insulating foam is applied, it will fill these spaces providing more insulation for the room that is defined by the panel assembly than would be provided by the traditional method of attaching the wall panel directly to the studs. 
     Not only does the insulating foam provide thermal insulation, it also provides structural support so that an exterior wall panel or sheathing is not required. In a traditional building, an external panel would be attached to the exterior side of the stud, or the opposite side from the standoffs. This exterior panel would cover the studs and foam so that they could not be seen from outside the building, providing additional structural support to the building. In the present invention however, these exterior walls are not required since this method of construction provides enough structural support. Therefore, the exterior walls of a building using this method could have the appearance of insulating foam and the protruding exterior sides of the wall studs. Because this may be unattractive, the user of this method may desire to cover the exterior of the building with some material, but that material would not need to provide any structural support. The material would be for aesthetics only, for instance, the material could be made of solar panels, fabric, wood planks, reflecting material, anything, or nothing. 
     A combination of the studs with standoffs attached can be pre-fabricated. Further, the stud/standoff combination can be used in conventional construction methods. While not providing the structural support offered by the preferred embodiment of the present invention, the stud/standoff combination can be used such that the exterior sheathing is attached to the studs rather than an interior wall panel. Insulating foam is then sprayed on the interior side of the exterior sheathing so that the foam covers the sheathing and fills the gaps created by the standoffs prior to the installment of the interior wall panel. 
     In the preferred embodiment of the invention, the insulating foam is a closed-cell spray polyurethane foam (SPF) and is sprayed on such that when hardened, the foam layer is between about 2.0 inches and about 5.0 inches thick, and more preferably approximately 2.5 inches thick on wall panels and approximately 4.0 inches thick on ceiling panels. Preferably, the SPF layer hardens to a medium density (preferably between approximately 1.5 lbs/ft 3  and approximately 4.0 lbs/ft 3 , most preferably approximately 2.0 lbs/ft), and is closed-cell to provide structural strength. The SPF layer is applied to the arranged panel assemblies as continuously as practically possible, and so provides continuous coverage at the junction between panel assemblies. When panel assemblies are used as walls, the studs preferably are of 2×4 or 2×6 wood or steel construction. When panel assemblies are used as ceilings, the ceiling joists or roof trusses are of conventional design. A panel assembly preferably is constructed such that the space or gap between the exterior face of a panel (e.g., gypsum board) and the interior side of the stud is, preferably, a minimum of one-half inch, i.e., the depth of a standoff is at least 0.5 inch—although this dimension may vary depending upon particular design requirements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and form a part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings are only for the purpose of illustrating selected embodiments of the invention, and are not to be construed as limiting the invention. Further, all dimensions or proportions seen in the drawings are exemplary and not limiting of the scope of the invention. In the drawings: 
         FIG. 1  is a perspective view of a portion of a building construction unit erected according to the present invention; 
         FIG. 2  is an enlarged cross-sectional side-view of a portion of a building construction unit according to the present invention, taken in the vicinity of a juncture of a first panel abutting adjacent to a portion of a second panel where any two panel assemblies adjoin one another; 
         FIG. 3  is a perspective view of the exterior side of a single stud with standoffs, according to the present invention; 
         FIG. 4  is a perspective view of the interior side of the stud with standoffs; 
         FIG. 5  is a perspective view of a plurality of studs according to the present invention, showing the standoffs on interior sides of the studs; 
         FIG. 6  is a perspective view of a plurality of studs, showing the exterior sides of the studs; 
         FIG. 7  is a perspective view of a representative panel assembly according to the present invention, the exterior face of a panel being visible, with standoffs defining spaces between the panel and the interior sides of the studs; 
         FIG. 8  is a perspective view of the representative panel assembly seen in  FIG. 7 , after a layer of insulating foam has been applied to the exterior face of the panel and filling the spaces defined by the standoffs and between the interior sides of first studs and the exterior face of the panel; 
         FIG. 9  is a perspective view of a second stud in the form of, or included within, a roof truss; 
         FIG. 10  is a perspective view of the building construction unit according to the present invention, in which second studs are in the form of roof trusses; 
         FIG. 11  is a perspective view of a portion of a self-supporting building construction unit according to the present invention, in which a vertical third panel assembly is provided parallel to a vertical first panel assembly and with a second panel assembly disposed horizontally and perpendicularly between the first and third panel assemblies; 
         FIGS. 12A-D  are perspective views of a construction unit as it appears at successive stages of erection according to the present invention; 
         FIG. 13  is an enlarged view of the construction unit seen in  FIG. 12C , showing an arrangement of three panel assemblies in a possible juxtaposition according to the present invention; 
         FIG. 13A  is an enlarged view of a portion of the construction unit depicted in  FIG. 13 , the portion generally identified at “A” in  FIG. 13 ; 
         FIG. 13B  is an enlarged view of a portion of the construction unit depicted in  FIG. 13 , the portion generally identified at “B” in  FIG. 13 ; and 
         FIG. 13C  is an enlarged view of a portion of the construction unit depicted in  FIG. 13 , the portion generally identified at “C” in  FIG. 13 . 
     
    
    
     Like label numerals are used to denote like or similar elements throughout the various views. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     There is disclosed hereafter a method for erecting a structure, and a construction unit erected thereby. Initial steps of erection may be similar to known techniques, including for example the provision of foundation components such as reinforced poured concrete footings and/or stem walls. The method and structure of the inventive method also may be practiced upon conventional concrete masonry unit (CMU) substructures. Conventional subflooring may be installed generally according to known techniques, including the pouring of concrete slab-on-grade, and/or the installation of truss-supported subflooring upon supporting substructure. The present invention exploits and then improves upon basic processes borrowed from light framing construction. 
     As used herein, certain terms have the following definitions: 
     A “stud” is a metal or wood post used in the framework of a structure for supporting interior wall panels such as wallboard or similar material. A stud also provides structural support for a ceiling panel or roof top in the form of a ceiling joist, rafter, roof truss, or the like. 
     A “panel assembly” is a portion of the building construction unit, namely, a plurality of studs, and standoffs, and a panel attached to the studs, as shown generally in  FIG. 7 . 
     Where the subscript “n” is used, “n” equals a positive integer and refers to the “nth” element of the apparatus and system that includes a plurality of such elements of indefinite number “n,” (e.g., “nth” wall panel assembly in a construction unit having a plurality of panel assemblies). 
     The disclosed method, and a construction unit according thereto, is intended to provide an airtight envelope that completely surrounds the habitable spaces within residential structures and/or temperature and environmentally controlled portions of commercial structures, including high rise buildings. The airtight characteristic of the envelope is subject mainly to deliberate apertures and openings in the envelope, such as doors, vents, stacks, windows, and the like, which may be disposed through/in the envelope. 
     Reference first is made to  FIGS. 1, 4, and 7 , showing an example portion of a building construction unit  12  ( FIG. 1 ) and a simple panel assembly  42  ( FIG. 7 ) erected according to an embodiment of the present invention. There is provided a plurality of first studs  13 ,  13   n  which in a preferred embodiment are disposed substantially vertically. Each of such first studs has an interior side  14 ,  14   n  ( FIGS. 4, 7 ) and an exterior side  15 ,  15   n  (also shown in  FIG. 7 ). The studs  13 ,  13   n  may be composed of metal or preferably wood, generally according to conventional light frame construction. 
     A plurality of first standoffs  16 ,  16   n  are attached (e.g., with adhesive or nails) to the interior side  14  of each first stud  13 . The first standoffs  16  may be composed of wood, plastic, or composite, but preferably constitute a generally rigid yet thermally insulating material. Each panel assembly according to this disclosure includes a panel, and panel assembly  42  features first panel  17 . The panels of panel assemblies, including the first panel  17 , have a first (e.g., upper) end  18 , and second (e.g., lower) end  19 , an interior face  20  (see  FIGS. 1, 2 ) and an exterior face  21 . The exterior face  21  of the first panel  17  is attached to the first standoffs  16  to define spaces  22  between the exterior face  21  of the first panel  17  and the interior side  14  of the first studs  13 . 
     Combined reference is made to  FIGS. 1 and 2 . For illustrative purposes in  FIGS. 1 and 2 , the first panel assembly is shown in the vertical plane and the second panel assembly is shown in the horizontal plane, the first panel assembly being attached at a right angle to the second assembly. Despite this illustrative representation, any number of panel assemblies, connected or arranged at any of various angles (but most typically orthogonally), are contemplated and their arrangement in various constructive configurations is within the capability of a person skilled in the art. 
       FIG. 2  is a vertical cross section of portions of adjoining first (e.g. vertical) and second (e.g., horizontal) panel assemblies, in the vicinity where they come together, showing single first stud  13  and single second stud  53 . There thus also are provided a plurality of second studs  53 , the second studs  53  having an interior side  54  and an exterior side  55 . The second studs are similar in general configuration to first studs  13 , but may serve as beams/joists and thus more preferably and likely have larger moments of inertia, or are integrated as the bottom chord in a truss (see stud  53   n  in  FIG. 9 ). The second studs  53  thus may be disposed substantially horizontally and may be, or be a part of, a roof joist system. A plurality of second standoffs  56  are attached to the interior side  54  of each second stud  53  of the plurality of second studs, similarly as described and shown for the first studs  13 . 
       FIGS. 1 and 2  also illustrate that a second panel  57  (similar to panel  17 , such as a gypsum board) is arranged adjacent to the first panel  17 . The second panel  57  has a first end  58 , a second end  59 , an interior face  60  and an exterior face  61 . The exterior face  61  of the second panel  57  is attached to the second standoffs  56  to define spaces  62  between the exterior face  61  of the second panel  57  and the interior side  54  of the second studs  53 . A first end  58  of the second panel  57  preferably is in contact with a portion of an upper edge of the first panel  17 . A layer of insulating foam  30  is applied to cover the exterior face  61  of the second panel  57  and the exterior face  21  of the first panel  17 , filling the spaces  22  defined between the exterior face  21  of the first panel  17  and the interior side  14  side of the first studs  13 , also filling the spaces  62  defined between the exterior face  61  of the second panel  57  and the interior side  54  of the second studs  53 . The foam layer  30  thus contacts and adheres to both the exterior faces  21 ,  61 , as well as to the interior sides  14 ,  54  of the studs to constitute a shell-like layer incorporating the studs. 
       FIG. 2  offers an enlarged, cross-sectional, diagrammatic view of the connection of a first panel assembly (including first studs  13 , first standoffs  16 , first panel  17 , and first spaces  22 ), with a second panel assembly (including second studs  53 , second standoffs  56 , second panel  57 , and second spaces  62 ), with the layer of insulating foam  30  also shown. This corner connection is at the joist band area of a framed construction, where the ends of roof joists (e.g., second studs  53 ) rest atop the top plate (not shown for sake of simplicity of illustration) that typically runs horizontally along the top ends of vertical wall studs (e.g., first studs  13 ). 
       FIG. 3  illustrates that multiple standoffs  16   n  preferably are attached to the interior side  14  of a representative single first stud  13   n , where n equals a positive integer and refers also to the nth element in a multiplicity of studs usable in a building construction unit according to this disclosure; description of a single stud serves substantially to describe a plurality of similar studs. The exterior side  15  is the side to which a first panel  17  is affixed.  FIG. 4  shows the single first stud  13   n  with standoffs  16   n  attached the stud&#39;s interior side  14 . The standoffs may be composed of polymers, wood, high density expanded polystyrene, or a wood-polymer composite. Each first stud  13   n  has a top end  68  that ordinarily connects to a top plate (not shown, but generally according to light framing convention), and a bottom end  69  that connects to a toe plate (not shown, but also generally according to convention).  FIG. 5  illustrates that there is a plurality of the single first studs  13   n  (with standoffs  16   n  on the studs&#39; interior sides  14   n ) while  FIG. 6  is a view of the plurality of studs  13   n  with standoffs  16   n  extending from the studs&#39; exterior sides  15   n . Each panel assembly (e.g. assembly  42  in  FIG. 7 ) includes a plurality of spaced studs  13   n . 
     Specific reference is made to  FIG. 7 , which depicts a representative panel assembly  42  according to the present disclosure. A plurality of panel assemblies are interconnected and juxtaposed as walls and roofs to erect a construction unit (e.g., unit  12  of  FIG. 1 ) having two or more walls and a roof. Doors and windows can be defined as desired in any given panel assembly. Any particular panel assembly  42  preferably includes a panel  17   n , with the exterior face  21  of the panel attached to standoffs  16 , which standoffs are in turn attached to the interior sides  14  of a plurality of studs  13   n . Space  22   n  is defined in one direction between adjacent standoffs, and (in a second direction) between the exterior face  21  of the panel  17   n  and the interior side  14   n  of the studs  13   n . 
     Attention is invited to  FIG. 8 , showing the representative panel assembly  42   n  seen in  FIG. 7 , but after the application of a layer of insulating foam  30  to cover the exterior face  21   n  of a panel  17   n  and also to fill the spaces  22   n  defined between the exterior face  21   n  of the panel  17   n  and the interior sides  14   n  of the studs  13   n . The foam layer  30  preferably is polymer foam (e.g., an aromatic isocyanate) that is applied by spraying. The layer  30  preferably is sprayed into place (using known spray application systems) as viscous foam, but cures to a hard layer of medium density (e.g., approximately two pounds per cubic foot).  FIG. 8  also indicates that the foam layer  30  contacts and adheres to the lateral sides of the studs  13   n , as well as to the interior sides of the studs. There accordingly is defined a structural shell that includes a structural integration of the studs  13   n  with a panel  17   n , with the standoffs and spaces  22   n  enhancing thermal insulation between the studs and panel without compromising structural integrity. The polymer foam preferably is applied so as to compile a layer that cures substantially integrally, preferably to define a layer  30  that is generally continuous over the exterior face  21  of a single panel assembly (but between the studs  13   n ), as well as wrapping around the junctures (near/along wall corner stanchions, and near/along wall top plates) between adjacently juxtaposed panel assemblies. 
     A person skilled in the art recognizes that the mutual orientation of the studs and panel can be substantially reversed, that is, to turn the arrangement “inside out” with the studs on the inside of the construction unit and the panel on the outside. In such an alternative embodiment, the interior face of a panel faces outward with respect to the interior of the construction unit, and the spaces are defined by the spacers between the panel and the studs, whose interior sides also face inward toward the enclosed space of the structure. Thus the representative panel assembly  42   n  seen in  FIG. 7 , is merely flipped, and the layer of insulating foam is applied to cover the exterior face  21   n  of the panel  17   n  (but now facing the opposite direction) also to fill the spaces  22   n  defined between the exterior face  21   n  of the panel  17   n  and the interior sides  14   n  of the studs  13   n . 
       FIG. 9  depicts a single second stud  53   n  in the form of, or being a chord of, a roof truss, with multiple second standoffs  56   n  attached to the interior side  54   n  of the second or roof truss stud  53   n .  FIG. 9  is best considered in combination with  FIG. 10 , illustrating a building construction unit  12  according to this disclosure and as suggested by  FIG. 1 . The construction unit  12  of  FIG. 10  is shown covered with the foam layer  30  and having second studs  53  arranged the form of a roof truss. 
     Taking reference to  FIG. 11 , it is seen that an example self-supporting building construction unit  32  according to this disclosure features a unit similar to the unit  12  of  FIG. 1 . The construction unit  32  provides a third panel assembly disposed, for example, as a wall parallel to the first (wall) panel assembly and perpendicular to the second (roof) panel assembly. However, it is to be understood that a third panel assembly could be disposed or arranged orthogonally with respect to the first and second panel assemblies, i.e., to “close” the open end of the structure of  FIG. 11 , with all three panel assemblies mutually perpendicular in three dimensions to define a 3-D corner. A foam layer  30  is in such a case applied to substantially integrate into a structural shell all three juxtaposed panel assemblies. 
     The third panel assembly includes a plurality of third studs  73 , each of the third studs  73  having an interior side and an exterior side, a plurality of third standoffs attached to the interior side of each third stud  73 , generally in accordance with those elements and features as described hereinabove for first plurality of studs  13  and second plurality of studs  53 , as well as the first and second panels  17 ,  57 . Likewise, a third panel  77  is provided, the third panel  77  having a first upper end, a second lower end, an interior face  80  and an exterior face, the exterior face being attached to the third standoffs in a manner like unto that previous described above for the first and second panels. There also are side or lateral end edges to the third panel. Spaces are defined between the exterior face of the third panel  77  and the interior side of the third studs  73 . The first or upper end of the third panel  77  is adjacent to, preferably abuts, at least a portion of the second end  59  of the second panel  57  (see also  FIG. 1 ). 
     And again, as seen in  FIG. 11  a layer of insulating foam  30  is provided on the exterior face of the third panel  77 , the layer  30  substantially covering the exterior face of the third panel  77 , and filling the spaces defined between the exterior face of the third panel  77  and the interior sides of the third studs  83 .  FIG. 11  thus depicts three of the representative panel assemblies  42  of  FIG. 7  arranged as two parallel walls and a roof. There is a substantially continuous layer of insulating foam  30 , the layer  30  covering the exterior faces of all the panels, and filling the spaces defined between the exterior faces of the panels and the interior sides of all the studs, and bonding together the studs and panels. 
     It accordingly is understood that, although not depicted, according to the disclosed method two panel assemblies  42  may have their respective side ends placed together and with the planes of the panels disposed to define an angle (typically 90 degrees) between them, so to define two walls of a construction unit. The side ends of the panel assemblies may be connected structurally at a corner stanchion according to known principles of light framing. However, the respective side edges of the panels (e.g., a pair of panels  17 ) of the respective panel assemblies preferably are adjacent, preferably abutted together, to define a vertical juncture that can be covered with an applied foam layer  30 . 
     A construction unit  32  according to the present disclosure can be self-supporting, even with only the three panel assemblies depicted in  FIG. 11 , due to the structural integrity and enhancement provided by the cured foam layer  30 —potentially even in the absence of diagonal bracing within the walls and at the corners of two walls, as commonly required in the art. The foam layer  30  adheres securely to all the panels and all or substantially all the studs and, when cured, with the studs and panels defines a generally integrated thermally insulating shell or envelope of the construction unit. 
     Still referring to  FIG. 11 , it is noted that there is a first juncture  90  defining the corner (generally in the vicinity of the joist band) whereat the first panel  17  and the second panel  57  come substantially adjacently together or in actual abutment. Similarly, the construction unit  32  of  FIG. 11  has a second juncture  91  (in the vicinity of the joist band) along a corner defined where the second panel assembly  57  and the third panel assembly  77  preferably abut adjacently together. Referring also to  FIG. 2 , and as described further hereinafter, a construction unit  32  according to the present disclosure has the advantageous feature that the layer of insulating foam  30  is applied to wrap continuously over the outside of the junctures  90 ,  91 , to cover that juncture and all other junctures similarly defined between other panels throughout a construction unit. The insulating layer  30  is applied substantially continuously between the first studs  13 , and between the second studs  53 , and between the third studs  73  as well as over the junctures  90 ,  91  running perpendicular to the studs. As mentioned, the insulating foam  30  also is applied so to fill all the spaces (provided by the use of the standoffs, e.g.,  16 ,  56 ) defined between the exterior faces (e.g.,  21 ,  61 ) of the several panels (e.g.,  17 ,  57 ,  77 ) and the interior sides (e.g.,  14 ,  54 ) of the studs  13 ,  53 ,  73 . When a plurality of panel assemblies are joined to erect a construction unit (typically to enclose a hollow interior habitation special volume), the application of the insulating foam layer  30  thereby constitutes a mostly continuous, unbroken (i.e., accounting yet for doors, windows, and other intended structural and functional openings) envelope which seals the interior of the structure from significant penetration by weather, including moisture and air. 
     It is readily understood by a person skilled in the art that fourth and fifth panel assemblies (substantially the same as those described) could be arranged with and against the first three panel assemblies seen in  FIG. 11 , to close the open ends of the structure, and thereby to compose a five-sided construction unit enclosing an open hollow interior, the overall construction unit defining a generally parallelepiped shape. All the junctures (including, e.g., junctures  90 ,  91 ) at the abutments of adjacent panels of adjoining panel assemblies preferably are covered with the layer of foam  30 . The layer  30  thus is essentially seamless where adjacent panel assemblies come together (i.e., at and along wall corner stanchions where to wall panel assemblies are connected, and along joist bands at the top plates where wall panel assemblies connect to a roof panel assembly. 
       FIGS. 12A through 12D  serve to illustrate further a method of erecting a construction unit structure in accordance with the present disclosure. It is noted that some initial steps of the method are similar to erecting a structure according to known light framing construction techniques, such as conventional frame-on-slab construction. Known techniques may be adapted to accommodate the more specific disclosure of the inventive method as described herein. 
     There is installed a foundation generally according to convention, which may be footings with stem walls  40  (e.g. reinforced concrete) as shown in  FIG. 12A . A concrete slab  41  or other floor is provided.  FIG. 12A  shows that first studs  13  are provided, the first studs each having an interior side and an exterior side ( FIGS. 3 and 4 ), and may be provided vertically to define partially a wall. The first studs  13  with other framing elements may, according to convention, define window/doors, as suggested in  FIG. 12A . First standoffs ( FIGS. 5 and 6 ) are attached to the interior sides of the first studs  13 . Second studs  53  also are provided, the second studs likewise each having an interior side and an exterior side. In  FIG. 12A  the second studs  53  are disposed horizontally to define partially a roof, and optionally may be part of a roof trussing system ( FIGS. 9, 10 ). Second standoffs ( FIG. 9 ) are attached to the interior sides of the second studs  53 .  FIG. 12A  also shows that third studs  73  are provided, the third studs each having an interior side and an exterior side ( FIGS. 3 and 4 ); the third studs  73  may be provided vertically to define partially a wall. Third standoffs ( FIGS. 5 and 6 ) are attached to the interior sides of the third studs  13 . 
       FIG. 12B  shows that a first panel  17  is provided, the first panel having a first end, a second end, an interior face and an exterior face. The second panel  57  also is provided, the second panel having a first end, a second end, an interior face and an exterior face. A first panel assembly thus is provided by connecting the exterior face of the first panel  17  to the first standoffs on the first studs  13  to define spaces between the exterior face of the first panel and the interior sides of the first studs  13 . The first panel assembly may define a vertical wall, and includes the first studs  13 , the first standoffs, and the first panel  17 . Similarly, a second panel assembly is provided by connecting the exterior face of the second panel  57  to the second standoffs to define spaces between the exterior face of the second panel  57  and the interior sides of the second studs  53 . The second panel assembly thus may define a horizontal roof, and includes the second studs  53 , the second standoffs, and the second panel  57 . A plurality of third studs  73  preferably was provided. A third panel  77  accordingly is provided, the third panel likewise having a first end, a second end, an interior face and an exterior face. As with the provision of the first and second panel assemblies, a third panel assembly thus is provided by connecting the exterior face of the third panel  77  to third standoffs attached on the third studs  73  to define spaces between the exterior face of the third panel  77  and the interior sides of the third studs  73 . The third panel assembly may define a vertical wall, and includes the third studs  73 , third standoffs, and the third panel  77 . 
     Reference to  FIGS. 12B and 12C  indicate generally the step of adjoining together the first two panel assemblies (i.e., panel assemblies  42 ,  44  of  FIG. 13 ), of what may eventually be a plurality of panel assemblies that are positioned with ends adjacent and adjoined together. A first panel assembly (for instance, wall panel assembly including studs  13  and panel  17 ) and second panel assembly (for instance roof panel assembly including studs  53  and panel  57 ) are adjoined end to end. The adjoining may be by generally conventional means, such as by nailing or framing anchors, with/to a corner stanchion (between two wall panel assemblies) or a top plate (to join a wall panel assembly to a roof panel assembly). The step of adjoining two panels assemblies preferably includes placing the first end of a first panel  17  adjacent to the first end of a second panel  57  to define a first juncture  90 , and applying continuously the layer of insulating foam  30  over the first juncture. Application of the foam layer  30  includes covering the exterior face of the first panel  17  and covering the exterior face of the second panel  57 , and filling the spaces defined between the exterior face of the first panel  17  and the interior sides of the first studs  13 , and filling the spaces defined between the exterior face of the second panel  57  and the interior sides of the second studs  53 , and with the same continuous application also wrapping the layer of insulating foam  30  over the first end of the first panel and over the first end of the second panel to cover the first juncture  90 . 
     By these steps a sealing envelope comprised of the foam layer  30  covers the first panel assembly and the second panel assembly. The method also preferably includes placing the first end of the third panel  77  adjacent to a second end of the second panel  57  to define a second juncture  91 , as also seen in  FIG. 12C . Thereafter, the step of applying continuously the layer of insulating foam  30  preferably further comprises covering with the foam layer the exterior face of the third panel  77 , filling with the foam layer the spaces defined between the exterior face of the third panel  77  and the interior sides of the third studs  73 , and wrapping the layer of insulating foam over the first end of the third panel  77  and over a second end of the second panel  57  to cover the second juncture  91 . In this manner a sealing envelope or shell covers the first panel assembly, the second panel assembly, and the third panel assembly. This forgoing process can be successively or simultaneously repeated to juxtapose and join additional fourth, fifth, sixth or more panel assemblies (e.g. elements  42   n ,  44   n ,  46  of  FIG. 13 ) to erect a construction unit of practically any desired layout or configuration. 
       FIG. 12D  illustrates that any of a variety of suitable exterior sheathings  33  may optionally then be installed, e.g., to the exterior sides of the various studs, to aesthetically cover the structure and/or provide a surface for application of exterior finish materials, such as stucco, brick façade, shingles, aluminum or vinyl siding, etc. However, the installation of exterior sheathings in the inventive method and structure is optional, and primarily for aesthetics; the sealing envelope provided by the application of the continuous foam layer  30  in the process described provides for a sealing of the space within the structure against the weather, sound, vermin, etc. 
     The method of the present disclosure is further explained by reference to  FIG. 13 , which is an enlarged view of the construction unit of  FIG. 12C . A construction unit completed according to the basic steps of the inventive method includes a plurality of panel assemblies arranged and connected to comprise the construction unit; there are at a minimum a first panel assembly  42 , a second panel assembly  44 , and a third panel assembly  46  erected and configured as explained hereinabove, and as seen in  FIG. 13 . Fourth and fifth panel assemblies are not depicted in  FIG. 13  for the sake of simplicity, but may be provided to close the sides appearing to be open in the figure. The panel assemblies  42 ,  44 ,  46  are adjoined end-to-end and situated on the foundation  40 . The foam layer is visible in all three panel assemblies  42 ,  44 ,  46  on the exterior faces of the first panel  17  between the first studs  13 , and on the exterior face of the second panel  57  between the second studs  53 . Although not explicit in  FIG. 13 , it is readily understood that the foam layer also coats the exterior face of the third panel  77  between the third studs  73 . 
       FIG. 13A  is an enlarged vertical sectional view of a portion, designated generally at “A” in  FIG. 13 , of a construction unit according to a substantially completed method of the present disclosure.  FIG. 13A  is similar to  FIG. 2 , but offers additional detail regarding advantageous features of the method and system of the invention. The  FIG. 13A  configuration typifies the connections between wall panel assemblies (e.g., panel assemblies  42 ,  46  of  FIG. 13 ) and associated roof panel assemblies (e.g., panel assembly  44  of  FIG. 13 ) throughout a construction unit according to the present disclosure. Perceived instead as a horizontal sectional view,  FIG. 13A  also suffices to illustrate generally the configuration at the connections between adjacent vertically oriented wall panel assemblies (i.e. at a wall corner stanchion where two wall panel assemblies  44  are adjoined) in this construction unit. 
       FIG. 13A  shows a first stud  13 , with a couple of its first standoffs  16  attached to its interior side. The exterior face of the first panel  17  is attached to the first standoffs  16  to space the panel  17  apart from, but about parallel to, the first stud  13 . Spaces  22  are between the interior side of the first stud  13  and the exterior face of the first panel  17 .  FIG. 13A  also indicates a second stud  53  resting atop the top end of the first stud  13  (e.g., with top plate there between). The exterior face of the second panel  57  is attached to the second standoffs (not seen in  FIG. 13A ) to space the second panel  57  apart from, but about parallel to, the second stud  53 . A space thus also is between the interior side of the second stud  53  and the exterior face of the second panel  57 . 
     The top edge of the first panel  17  is closely adjacent to and preferably abuts an edge of the second panel  57  at the first juncture  90 . The foam layer  30  is applied substantially continuously to the exterior faces of panels  17 ,  57 , so to fill the spaces defined between the panels and the studs  13 ,  53 . Significantly and as shown in  FIGS. 13A and 13B , the foam layer  30  also wraps around the exterior side of the juncture  90  where the panels abut, thereby provided a seamless seal where the panels come together. So doing at all junctures between adjoining panels provides a sealing envelope which substantially encases the exterior faces of all the panel assemblies of the construction unit to supply benefits of the invention.  FIG. 13B , for example, illustrates that the foam layer  30  is seamless and continuous as it covers both a vertical first panel and a horizontal second panel as it envelopes the junction of the panels. A third panel assembly adjoining the first two seen in  FIG. 13B  likewise is enveloped seamlessly and continuously by the same application of the foam layer  30 . 
     The foundation  40  seen in  FIG. 13  is seen in the enlarged view of  FIG. 13C . In an embodiment of the invention, the foundation includes a vertical stem wall  92  having an exterior face. In this alternative embodiment, the foam layer  30  is applied substantially continuously to coat and cover not only the exterior face of a first panel on the studs  13 , but also the top of a toe or sole plate  93  and the face  94  of the stem wall as well, thereby to seal and encapsulate the connection between the first panel assembly (e.g., panel assembly  42 ) and the foundation of the construction unit structure. 
     Whereas the figures and description have illustrated and described the concept and preferred embodiment of the present invention, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without affecting the scope thereof. The detailed description above is not intended to limit the broad features or principles of the invention, or the scope of patent monopoly to be granted. Thus although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents.