Patent Application
20230193628
The present invention relates to the design and utilization of structures, in particular structural members used in building construction.
Historically, the construction of structures such as walls and partitions in a building such as a house has been accomplished by assembling a frame having vertical members (“studs”) attached to horizontal header (aka, top plate) and footer members. Monolithic sawn wood of industry-standardized nominal dimensions frequently has been used for framing walls (for example, a nominal “2x4” piece of lumber has nominal dimensions of 1.5 inches by 3.5 inches, and a “2x6” piece of lumber has nominal dimensions of 1.5 inches by 5.5 inches). Typically the larger dimension has been arranged perpendicular to the planar surfaces of the wall. The surface of the wall facing inward toward the space defined by the wall typically is sheathed in a continuous sheet material, such as drywall or a paneling material, as is well known in the art.
Because the framing members are conventionally solid wood, the passage of utilities such as plumbing pipes, electrical conduits, network cabling, etc. has required substantial builder effort to drill passages through the relatively thick and dense wood of every vertical member of the wall in the case of utility runs parallel to the floor, and through often double-thickness header and footer members in the case of utility runs between floors. The tooling and labor required to create these multiple apertures in the vertical and horizontal directions substantially increases costs and slows construction.
The conventional approach to building such walls also has the disadvantage of creating thermal “bridging” paths between one side of the wall and the opposite side. Wood structural members typically have relatively poor insulation values. As a result the locations on the surface of the wall directly in front of the vertical studs and the header and footer are pathways for heat transfer, effectively bypassing any inter-wall insulation placed inside the wall between the studs. These localized areas can significantly reduce the effective insulation value of the entire wall. For example, in a situation where the wall is intended to provide insulation between a warm living space and a colder outside environment, “cold spots” or “cold corners” may be discerned where the wood framing members allow passage of heat from the inside to the outside environment and is a drain on natural resources.
Another disadvantage of the conventional solid-wood framing approach is that it is resource-intensive, i.e., the volume of the increasingly costly solid wood members required for construction of a wall is relatively large relative to the loads carried by the wood members.
These and other disadvantages are addressed by the insulated structural member of the present invention. In this engineered structural member, substantially less solid wood is needed, and insulating material may be added to provide resistance to heat transfer between the inner and outer surfaces of the wall into which the engineered structural member is incorporated.
In one embodiment of a 2x6 member, a conventional solid 2x4 is rip-cut along its longitudinal centerline, resulting in two narrower length wood flange sections. Each of these cut flanges are provided with a longitudinal slot in their 1.5″ wide faces, sized to receive a relatively rigid thin sheet of material. This “web” member in turn is sized such that when the slots in the flanges are located over the opposite edges of the thin sheet, the overall width of the composite structural member is 5.5″ wide, i.e., a “2x6” is generated. Preferably, the web material is formed from cost-stable web material with superior moisture resistance as compared to osb and plywood, and uses recycled material (for example, 94% post-consumer recycled content & fibers).
The present invention’s structural member accordingly uses substantially less solid wood, with commensurate reduction in the cost and weight of the engineered “2x6” (on the order of 40% less by volume and 60% less by weight in a 2x6 embodiment, depending on the moisture content of the wood), and reduces the demand for harvesting natural resources.
The thermal conductivity of the structural member in the 5.5″ direction is reduced by the insulating effect of the very small heat conduction cross-section of the thin sheet web between the slots. The insulation effect is enhanced by including foam insulation in the recesses between the opposing wood flanges on one or both sides of the web. The foam insulation reduces both radiant heat transfer from one wood flange to the other, and radiant and convective heat transfer to the engineered 2x6 structural member from the interior space between adjacent engineered 2x6 structural member of the wall. The foam also acts to prevent thermal bridging of fasteners used to secure exterior sheathing and cladding.
In addition to the cost and material reductions associated with the inventive engineered structural member itself, the present invention may reduce in-situ labor costs by presenting only a relatively thin and easily penetrated web for an installer to cut through when passing utility runs through the wall. This would be the case with both horizontal utility runs and vertical utility runs through headers and/or sill plates arranged with their web sections parallel to the floor.
The engineered structural member also has the advantage of being lighter, stronger and more dimensionally stable than solid lumber (i.e., less susceptible to twisting, warping and shrinking), despite having a smaller cross sectional area. This stability may help minimize “nail pops,” where nail heads are pushed out above the surface of a drywall sheet. In addition, the additional load capacity may enable design of lighter, less costly structures (for example, by allowing greater spacing of vertical members, or the use of smaller-dimensioned headers and/or footers). The present approach may also minimize the effect of “thermal bridging” through fasteners that occur with solid lumber use with exterior rigid foam and sheathing installations.
Depending on the overall insulation effectiveness of a structure built from the present invention’s engineered structural member, it may be possible to meet prescriptive energy code requirements for continuous insulation and fenestration values that are not achievable using solid wood framing members, and eliminate the need for expensive exterior rigid foam insulation and spray foam within the wall cavity.
The above example is merely representative. Other sizes of engineered structural members embodying the present invention, such as 2x8s, may be formed using appropriately sized flanges, webs and optionally inter-flange insulating material such as rigid foam or spray foam material. Further, the present invention is not limited to a single web member between flanges, but may include multiple webs and additional insulation between the webs. Moreover, the present invention is not limited to flanges and/or webs produced solely by cutting apart dimensional lumber or otherwise homogeneous wood, but may be produced from other materials such as plywood, osb, and/or engineered lumber.
The present invention’s engineered structural member has many applications, including use as sill plates, headers, cripples, jacks studs, splines, columns, etc., and may be used wherever equivalent-sized solid lumber is used. For example, appropriately arranged, the inventive structural member may be used to form a continuous insulated “thermal break” within a wall cavity. Those familiar with structure construction will recognize that there will be other applications in which the engineered structural member may be used to replace conventional lumber. For example, depending on the application, different sizes of engineered structural members may be used together, such as using 2x6 vertical studs with a nominal 4x6 header or sill plate where additional load capacity is desired. Different lengths may also be used, including lengths that are standard in the industry such as 8-foot, 9-foot and 10-foot lengths, as well as extended (e.g., 22-foot) or shorter lengths.
The present invention is not limited to being sized to correspond to nominal size lumber, but may be constructed to any desired width and depth combination which meets a desired application, such as a wall with a desired custom depth.
In another embodiment of the present invention, the web between the flanges may be non-continuous. For example, relatively short web sections may be spaced apart from one another along the length of the engineered structural member, thereby further reducing weight and material cost, with only a small, or even no, reduction in structural strength.
A further embodiment uses conventional nail plates, i.e., reinforcing metal plates that are installed alongside joints to increase the joint’s strength, in place of the web or web sections. As which the previous embodiment, insulation also may be added in the gaps between nail plates to increase the effectiveness of the thermal break.
In another embodiment of the present invention, multiple webs may be used to link multiple flanges, for example, to create an extended in-line structural panel or to create a structural member with flanges at an angle to one another to form a portion of, or a complete, column member. Examples, of which angled structural members include, but are not limited to, an “L″-shaped corner, a square column or a hexagonal column.
The present invention thus provides the wood framed construction industry a lighter, more dimensionally stable alternative to solid wood framed wall construction, while still being able to meet code-required continuous insulation values by providing a continuous insulated thermal break within a wall cavity. This engineered structural member further is compatible with any type of insulation within the wall cavity, and has insulation performance that permits avoiding the disadvantages associated with the use of spray foam insulation within a wall cavity.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.
The assembled engineered structural member 10 includes flanges 11, 12, a web 13 engaged in slots 14, 15 in the flanges 11, 12, and insulation elements 16, 17 spanning the open spaces (“bays”) between the opposing faces of the flanges 11, 12 on the exposed faces 18, 19 of the web 13. At a nominal 2x6 lumber size, the engineered structural member uses approximately 40% less wood than a solid 2x6 piece of lumber of equivalent length. The engineered structural member may be used for vertical wall studs, headers and footers.
In this embodiment, the slots 14, 15 have a depth of 0.5 inches and a width of 0.125 inches. The web 13 has a width of 3.5 inches. The combination of the two 1.5 inch flanges 11, 12, the two 0.5 inch deep slots 14, 15, and the 3.5 inch web 13 result in an assembled structure with the nominal dimensions of a 2x6 (i.e., 1.5 inches by 3.5 inches) and a gap 2.5 inches wide between the flanges.
An efficient and cost-effective approach to producing the flanges 11, 12 in this embodiment is shown the cross-section view in
If the kerf 22 of the saw blade cut is 0.125 inches width, the resulting dimensions of the flanges 11, 12 are 1.5 inches wide by 1.6875 inches deep ((3.5″-0.125″)/2). Also shown in
Preferably, during assembly of the engineered structural member an adhesive, preferably waterproof, is placed into the slots 14, 15 and/or onto the opposing edges of the web 13 before or during the insertion of the web 13 into the slots. The assembled structural member may be clamped during curing of the adhesive to ensure consistent dimensions of the assembled member (i.e., avoiding one flange being slightly rotated about its longitudinal axis relative to the other flange), or alternatively may be left to cure without support if the resulting product is dimensionally suitable for the intended application. Optionally, heat may be used to enhance the adhesive curing process. Once cured, the engineered structural member is ready for any necessary precision dimensioning such as length trimming, then packaging and shipment. Alternatively or in addition, the web may be secured in the slots by mechanical fasteners such as nails, staples, screws, etc.
The materials of the inventive engineered structural member may include, for the flanges, specially-source lumber of suitable species and/or grade for the intended application. For example, visually graded douglas fir larch #2 may be desirable for cost, cutting ease and/or load capacity reasons.
The web member is preferably a thin sheet material with minimal weight but sufficient rigidity to support the opposing flanges at least until the engineered structural member is incorporated into a structure such as a wall. For example, lightweight, extrusion-coated cellulosic fiber boards may provide high strength, durability and superior moisture resistance compared to plywood where the strength characteristics of plywood are not needed, while being composed of fibers with ecologically-friendly post-consumer recycled content (e.g., 94% recycled content).
In embodiments in which additional insulation is to be located between the flanges at the exposed sides of the web, a preferred insulation material is ¾″x2-½″ XPS rigid foam, having an insulating value of 12.5. Other forms of lightweight insulating material may be used without departing from the present invention. Preferably the insulating material is adhered to the web and/or flanges with a waterproof adhesive, so that the insulation remains in place during handling and subsequent in-place service.
The adhesive used to bond the flanges and web together preferably is a liquid phenol-resorcinol resin adhesive, which is a two-part system which provides a waterproof, strong structural bond. For example, Aerodux 185® with HRP 155® hardener, when fully cured, is resistant to acids, weak alkalis, solvents and boiling water. Aerodux 185® is also suitable for bonding a wide range of materials to porous substrates, including wood (including improved or densified woods), mineral fiber reinforced boards, brick, concrete, unglazed porcelain, rigid expanded plastics (e.g., expanded polystyrene, polyurethane, PVC), industrial and decorative laminates (phenolic resin-based or phenolic resin backed), leather, cork, linoleum and nylon.
The
Alternatively,
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Because such modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
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