Abstract:
Prefabricated building panels combine new and unexpected element dimensions and materials with the effect of reducing overall weight and depth while simultaneously improving panel performance such as thermal insulation. As compared to former panels, prefabricated building panels according to exemplary embodiments of the invention generally include thinner concrete slabs, wider separations between concrete and support framing, and new material choices for anchors connecting slabs with framing. Exemplary panels are compliant with energy codes such as the latest ASHRAE and IECC.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention generally pertains to prefabricated building panels and, more particularly, energy code compliant panels with performance improvement and cost and material reductions. 
       BACKGROUND 
       [0002]    Prefabricated building panels are a popular implement in today&#39;s construction industry, especially for commercial applications. Labor time and costs associated with welding and bolting, for example, significantly increase the cost of traditional construction whereby individual materials (e.g., external siding, insulation, support framing, etc.) are generally arranged and assembled at the job site. Mixing concrete at the job site includes labor costs as well as down time to permit the concrete to set. These and similar costs have been somewhat reduced in recent years by the development and increased use of precast concrete and, in particular, prefabricated building panels which combine precast concrete with other materials such as insulation and support framing. These panels are generally built and assembled at an off site location and then transported to the construction site, ready for installation. At the job site, the panels are hoisted and moved into position on the incomplete building structure. Once in position, construction workers may then bolt and/or weld the panels to the building frame and/or floor and to one another to fix them in their final locations. 
         [0003]    Despite the advantages identified above, known prefabricated building panels are far from ideal. Existing panels tend to be very heavy, typically in the range of 90 lbs per square foot, and in all cases require heavy machinery such as cranes to lift and maneuver at the job site. In general, the design of prefabricated building panels is a challenging puzzle of inseparable pros and cons. For example, in order to support the weight of itself and potentially other building elements (e.g., roofing, neighboring panels, etc.), the concrete must be quite thick, generally  6  or more inches. The height of many present day commercial buildings means wind speeds also become a critical consideration and further require increased material thicknesses for greater strength. While thicker concrete improves the strength of a panel, it obvious greatly increases the weight and volume of the panel, both effects being highly undesirable. 
         [0004]    Newer energy codes for buildings, especially renovations and new construction, continue to set more stringent performance criteria. As new codes go into effect, the construction industry is faced with a need for new alternatives which strike the difficult balance of such factors as weight, size (e.g., panel thickness), thermal insulation, strength (e.g., as measured in psi or maximum incident wind speed), and material costs. 
       SUMMARY 
       [0005]    New energy codes such as the latest ASHRAE and IECC are met by prefabricated building panels which combine materials with unexpected specifications (e.g., material thicknesses) and performance. These new panels represent a new class of panels with performance characteristics which only emerge from the combination of their constituent parts. 
         [0006]    According to an exemplary embodiment, a prefabricated building panel comprises a concrete slab having a thickness equal to or less than 2 inches; a plurality of stainless steel anchors permanently imbedded in the concrete slab; framing permanently secured to the concrete slab by the plurality of stainless steel anchors for structural reinforcement, the plurality of stainless steel anchors maintaining a spacing between said concrete slab and said framing of 0.5 to 3 inches; and a continuous insulation which fills at least 0.5 to 3 inches of the spacing between the concrete slab and the framing. Other exemplary embodiments with alternative or additional features are also disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a side profile section view of a prefabricated building panel; 
           [0008]      FIG. 2  is an isometric view of the prefabricated building panel shown in  FIG. 1 ; and 
           [0009]      FIG. 3  is a view of an inner face of a prefabricated building panel. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Prefabricated building panels are discussed herein as having two opposite and substantially parallel faces. For panels ultimately installed as part of a building exterior, an “outer face” refers to the side of a panel which faces outward from the building after installation. 
         [0011]    For most panels, the “outer face” will comprise concrete or a façade behind which is concrete. An “inner face” refers the side of the panel which faces inward toward the building interior after installation. These terms are nominal only and are not intended to limit the applications or use of the panels described herein. Panels having an “outer face” and “inner face” may be installed on a building exterior or in interior spaces of a building, where interior spaces of the building are to both sides of the panel. 
         [0012]    Referring now the drawings, and in particular  FIGS. 1 and 2 , there is shown a prefabricated building panel (i.e. “panel”)  100 . At a minimum, an exemplary panel  100  comprises at least one concrete slab  101 , framing  102 , anchors  103  which connect and maintain a fixed spatial relationship between the concrete slab  101  and framing  102 , and insulation  104 . 
         [0013]    At a broad level, a panel  100  differs significantly from existing prefabricated building panels such as that which is disclosed by U.S. Pat. No. 5,699,644 for a number of combined features, including but not limited to: a comparatively thinner concrete slab, a comparatively wider spacing between the concrete slab and the framing, and anchors which are made of stainless steel. 
         [0014]    In some exemplary embodiments, concrete slab  101  preferably has a thickness  110  equal to or less than 2 inches, and most preferably equal to or less than 1.5 inches (see  FIG. 1 ). The thickness  110  may be in the range of 1.5 to 2 inches, including the particular sizes of 1.5 or 2 inches. To persons of ordinary skill in the art, such thicknesses to concrete slab  101  would be prohibited on account of their reduced strength as compared to known slab thicknesses for prefabricated building panels. However, the reduction in concrete slab thickness according to the present application has the advantageous effect of reducing the weight of the panel and thus the maximum load capacity the panel  100  must be equipped to support. In some embodiments, it is furthermore advantageous for concrete slab  101  to comprise an unusually high fiber content (e.g., glass fiber, synthetic fiber, etc.). These fiber loads are greater than fiber loads for existing prefabricated building panels. The high fiber content of concrete slabs  101  of panels  100  provides improved crack control and resistance to wind forces. 
         [0015]    In exemplary embodiments, framing  102  may be, for example, galvanized steel studs or similar supporting members. C-shaped studs or beams are well suited for this application, but other alternatives supplying the same supportive functionality may occur to those of skill in the art and are likewise employable in the practice of the invention. In exemplary embodiments, individual studs or beams of framing  102  are assembled using automobile assembly spot-welding. Unique to panel  100  over prefabricated building panels known in the art is the feature that framing  102  comprises a plurality of parallel beams which may be spaced apart by spacing  120  at least as large as 4 feet. Older panels such as that which is disclosed by U.S. Pat. No. 5,699,644 necessitated adjacent parallel beams be spaced apart no more than 2 feet. In the older panels, separation exceeding 2 feet would generally compromise the required structural integrity of the overall panel; the reduced amount of framing would be insufficient to support the weight of the comparatively very thick concrete slabs. In light of the thinness and resulting lightness of concrete slabs  101  in panel  100 , spacing  120  between adjacent beams of framing  102  may exceed 2 feet, 2.5 feet, 3 feet, 3.5 feet, up to at least 4 feet. As compared to existing panels such as that which is disclosed by U.S. Pat. No. 5,699,644, a panel  100  may also have studs or beams of framing  102  which are smaller in width  150 . Width  150  of framing  102  may be 6 inches or less, 5 inches or less, or 4 inches or less. Width  150  may be in the range of 4 inches to 6 inches. 
         [0016]    Framing  102  is permanently secured to concrete slab  101  by a plurality of anchors  103  which, in exemplary embodiments, are stainless steel. As shown in the drawings, some exemplary embodiments of a panel  100  are manufactured such that a head of each anchor  103  is permanently imbedded in the concrete of slab  101 . The opposite end of each anchor  103  is welded to framing  102 . In an assembled state, a panel  100  has a spacing  130  between the concrete slab  101  and the nearest framing  103  of 0.5 inch to 3 inches. In some exemplary embodiments, spacing  130  is at least 1.5 inches. In still further exemplary embodiments, spacing  130  is preferably at least 2 inches or most preferably at least 2.5 inches or more. Spacing  130  is fixed and maintained by the anchors  103 , these being imbedded in the concrete slab  101  and welded to framing  102 . 
         [0017]    Known prefabricated building panels have anchors, bolts, or screws which are generally made of regular steel (i.e., not stainless steel). The provision of stainless steel anchors  103  in exemplary embodiments of the present invention is particularly advantageous over the existing art for at least the reason that stainless steel is approximately 38% less thermally conductive as compared to regular steel. As a result, there is less heat transfer between the inner face and outer face of the panel  100 . 
         [0018]    Insulation  104  is arranged between concrete slab  101  and framing  102 . In exemplary embodiments, insulation  104  is a continuous insulation. The through penetration of anchors  103  through insulation  104  does not disqualify it from being accurately described as “continuous”. Insulation  104  fills at least some of the spacing  130  and, in most exemplary embodiments, fills an entirety of the spacing  130 . Geometrically, the thickness of insulation  104  within spacing  130  cannot exceed the span of spacing  130 . However, the thickness  140  of insulation  104  (see  FIG. 2 ) may exceed the span of spacing  130  where the insulation is partially disposed to a side of a beam (e.g., between adjacent beams) of framing  102 . In  FIG. 2 , thickness  140  of insulation  104  is clearly greater than spacing  130 , which in the illustrated embodiment is substantially filled by insulation  104 . Thickness  140  may be as large as the sum of the span of spacing  130  and framing width  150 . 
         [0019]    The span of spacing  130  is unexpectedly large in contrast to existing panels such as that which is disclosed by U.S. Pat. No. 5,699,644. Owing to insulation  104  being of a thickness equal to or greater than the span of spacing  130  in exemplary embodiments, weightbearing support of the panel  100  is provided in part by the thick rigid volume of insulation  104 . This reduces the maximum load which concrete slab  101  is required to bear, permitting the concrete slab to be even thinner than would be permitted with insulation having a comparative small thickness (e.g., 1 inch or less). 
         [0020]    For some embodiments, a panel  100  may further include furring or hat channels  106  and/or gypsum board (i.e. drywall)  107 . Traditional panels have an inner face consisting of only insulation and framing, and materials such as gypsum board must be installed on the job site after the panels have been maneuvered and fixed into their final positions on the building structure. In contrast, some embodiments of the present invention include channels  106  and gypsum board  107  (as is indicated by the dashed portion of the curvy bracket associated with reference numeral  100  in  FIG. 1 ) to reduce the installation time and thus costs associated with work at the job site. 
         [0021]    Panels  100  may take a variety of dimensions, including different widths  160  and heights  170  (see  FIG. 3 ). A particular advantage of a panel  100  is its depth  180 . Generally, depth  180  is determined as the sum of the concrete slab thickness  110 , the span of spacing  130 , and the framing stud width  150 . If, for example, these were 1.5 inches, 2.5 inches, and 4 inches, respectively, the depth  180  of the panel  100  would be 8.0 inches. 
         [0022]    While an exemplary application of panels  100  is for exterior walls, some panels  100  or variations thereof may also be used for other purposes including but not limited to interior walls, flooring, or roofing. 
         [0023]    While exemplary embodiments of the present invention have been disclosed herein, one skilled in the art will recognize that various changes and modifications may be made without departing from the scope of the invention as defined by the following claims.