Static structures (e.g. – buildings) – Facer held by stiffener-type frame – Back-to-back facers spaced by concealed framing
Reexamination Certificate
2002-03-27
2004-04-06
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
Facer held by stiffener-type frame
Back-to-back facers spaced by concealed framing
C052S223100, C052S309100, C428S317100, C428S537100, C428S537500, C428S105000, C428S113000
Reexamination Certificate
active
06715249
ABSTRACT:
TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION
The present invention relates generally to insulated sheathing for use in building construction or the like and, more particularly, to an insulated sheathing having enhanced structural properties.
BACKGROUND OF THE INVENTION
In constructing a building, and in particular a house, a relatively thin panel board of is commonly used to cover the structural framework of exterior walls. The board is typically fabricated from a low-cost, lightweight material having enhanced insulating properties, such as for example polystyrene or polyurethane foam. Usually, the boards are sized for use in conjunction with conventional frame sections (that is, frames with wooden studs on 16 inch (40.64 cm) or 24 inch (60.96 cm) centers). The boards may also have varying thicknesses and compositions, depending on, among other considerations, the desired resistance to heat flow. In the case of foams, additional layers of materials, called “facings,” are also commonly laminated on or affixed to one or more of the surfaces to create a vapor barrier, increase the stiffness, durability, or resistance, as well as to possibly prevent the release of blowing agents.
While insulating boards fabricated solely of foam or the like provide the desired thermal insulation value, they simply do not have sufficient strength to resist the various wind and other racking type loads created in a typical building. For example, when secured to the frame using typical mechanical fasteners, such as nails or staples, the insulating material is unable to withstand the local tensile and compressive stresses created as the result of in-plane shear forces acting on the frame. The fasteners may tear the insulating panel. As a result, the loads are not controlled and the building integrity is compromised. To prevent this, a common practice is to install metal or wood braces on the boards to handle these loads. However, this increases the overall construction cost and effort required.
Another common practice is to attach a layer of plywood or oriented strand board (OSB) to the frame to provide the desired structural enhancement. However, neither plywood nor OSB provides the desired degree of resistance to heat loss. To maintain thermal integrity with this practice, a layer of insulation board may be placed on the plywood or OSB board. However, this practice significantly increases the overall cost of construction. Also, it increases the wall thickness to the point where special jamb extensions are required to finish out the wall.
In an effort to reduce construction costs without compromising the integrity of the resulting building, others in the past have proposed a reinforced insulating material in the form of a sheathing designed to eliminate the need for adding a separate structural layer, such as plywood, to the frame. For example, U.S. Pat. No. 5,345,738 to Dimakis discloses a structurally enhanced sheathing comprised of a layer of insulating foam in combination with opposing facing layers of a treated cellulosic (paper) material. While this composite sheathing is somewhat stronger than the foam insulation alone, there are shortcomings. First of all, the outer layers are essentially formed of paper, and thus may not provide the desired level of moisture imperviousness and strength. Additionally, forming and laminating facings comprised of several distinct layers add to the manufacturing expense. Of course, cost is a key consideration in the design of structural sheathing, since the builder is trying to keep costs as low as possible to not only increase profits, but also to remain competitive in the market.
Accordingly, a need is identified for an improved sheathing for use in insulating and strengthening a building or the like. The sheathing should be sufficiently strong to avoid the past need for attaching additional layers of wood or the like to the frame to provide at least a minimum level of structural enhancement. The sheathing should also be easy to manufacture at a relatively low cost, such that it results in a significant advance in terms of structural performance per unit cost as compared to prior art proposals.
SUMMARY OF THE INVENTION
A structurally enhanced sheathing for use in insulating a building or the like is disclosed. The structural enhancement comes from the use of a structural layer of material in conjunction with an insulating layer of material. The structural material may comprise a plurality of fibers extending in first and second biased directions, and thus, defining a grid having a plurality of openings. The openings are capable of receiving an adhesive for attaching the sheathing to a stable mounting structure, such as a wall frame. Preferably, the fibers forming the structural material are biased relative to a common axis, such as a centerline of the insulating material. Alternatively the structural material may be formed of a polymer film. Preferably the polymer film is a multilayer film adding sufficient mechanical properties to the insulating layer.
In accordance with a first aspect of the present invention, a sheathing for insulating and structurally enhancing a stable mounting structure is provided. The sheathing comprises a first layer of insulating material and a second layer of structural material attached to the insulating material. The structural material includes a plurality of fibers extending in first and second biased directions such that the fibers form a grid having a plurality of openings for receiving a first adhesive for securing the sheathing to the stable mounting structure.
In one embodiment, the insulating material may be selected from the group consisting of extruded polystyrene foam, expanded polystyrene foam, polyurethane foam, polypropylene foam, polyisocyanate foam, polyisocyanurate foam, and combinations thereof. However, it is also possible to form the insulating material of wood, paper, waxed cardboard, and combinations thereof. The insulating material is usually in the form of a rectangular board, but can be of any shape, such as a square, circle, or the like.
To enhance the ability of the structural material to withstand tensile stresses acting on the wall frame to which the sheathing is attached, the fibers may be oriented at any included angle between 0 and 90 degrees. Preferably, the fibers are oriented at first and second biased directions at an included angle of substantially 30 to 60 degrees relative to a common axis, such as a centerline of the insulating material (preferably the longest centerline, such that in the case of a rectangular sheathing, the fibers span from the top corner at one side to the opposite, bottom corner). Double-biasing the fibers at a 45-degree angle relative to a common axis, such as the centerline, is preferred for the majority of building applications. However, the angles of each direction may be different (for example, the first direction is 35 degrees and the second direction is 55 degrees), or the fibers extending in the same direction may be oriented at different angles, depending on the particular types of loading encountered or the degree of racking strength required for a particular application.
Each fiber is preferably comprised of a material selected from the group consisting of glass fibers, polymer fibers, carbon fibers, natural fibers, mineral fibers, metals, polymer films or tapes, or combinations thereof. The fibers may be singular or may be divided into a plurality of bundles or strands. In the case of polymers, the fibers may consist of polyester, nylon, polypropylene, poly-paraphenylene terephthalamide, and other low-elongation polymers. Also, it should be appreciated that the fibers in each plurality may be of different types, weights, lengths, or comprised of different materials in order to meet the anticipated racking load resistance requirements. Preferably, the fibers are continuous or elongated, but it is also possible to use random length, non-continuous fibers.
The selected fibers may be interwoven, layered, or stitched at the proper orientation. In a
Devalapura Ravi K.
Rusek Stanley J.
Amiri Nahid
Barns Stephen W.
Eckert Inger H.
Friedman Carl D.
Gasaway Maria C.
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