Patent Application
20100088981
The present invention relates generally to building structures and particularly to a structural insulated panel for a foundation wall and to a foundation wall incorporating the same.
Structural insulated panels (“SIPs”) are an increasingly common material used in the construction of residential homes and other structures. Conventional SIPs have a sandwich-type structure, and comprise two sheets typically of a wood-based material, such as plywood or oriented strand board (“OSB”), that are bonded to an inner slab or foam insulation. Expanded polystyrene (“EPS”) is typically used for the insulation, with extruded polystyrene and polyurethane foam sometimes being used. The bonded sandwich structure of SIPs has been demonstrated to provide comparable strength to conventional walls consisting of a lumber stud frame filled with slabs of fiberglass insulation. SIPs are typically fabricated as sheets of a standard size (e.g. 4 feet×8 feet), which can then be cut to size on-site as needed prior to installation.
A key advantage of SIPs over conventional fiberglass/lumber stud walls is the superior thermal insulating performance offered by the closed cell structure of expanded polystyrene, which consists of a network of closed pockets of air trapped in the polystyrene. This closed cell structure results in the foam insulation being both airtight, which is beneficial for thermal insulation, and impermeable to moisture, which prevents the occurrence of water-related damage such as rotting and mould growth that could otherwise occur in “open cell” insulation materials such as fiberglass.
A number of SIP designs have been considered. For example, U.S. Pat. No. 6,279,287 to Meadows discloses a prefabricated building panel that includes first and second side panel members. A thermally insulating core is disposed between the panel members. A first panel end surface includes a pair of spaced projections defining a channel-way, while a second panel end surface includes a pair of spaced channels separated by a plug. Two adjacent building panels may be interconnected by engaging the pair of projections at the first end with the pair of channels and plug at the second end.
U.S. Pat. No. 6,599,621 to Porter discloses a flat structural panel for building construction that includes an inner insulating core of plastic foam and a pair of opposed outer facings, or sheets, bonded to the insulated core. One of the outer facings is of gypsum composite, or gypsum fiberboard, while the other outer facing is of a special plastic-impregnated OSB. The gypsum and OSB facings form the inner and outer surfaces of the panel. The facings provide high tensile strength, with the gypsum composite or fiberboard facing also providing resistance to fire and insects.
U.S. Patent Application Publication No. 20060117689 to Onken et al. discloses an insulated structural panel formed with a rigid foam core, a plurality of vertical hat channels on either face of the rigid foam core, and horizontal top and bottom L-channels on either face of the rigid foam core. The plurality of vertical hat channels on opposing faces of the rigid foam core is connected so as to compress the rigid foam core, thus adding structural strength to the insulated structural panel.
While more commonly used for above-ground walls of residential structures, the high strength and impermeability to moisture also render SIPs suitable for use as foundation walls. In these applications, a portion of the wall is below grade (i.e. below the ground surface), and the base of the foundation wall is typically placed upon a footing, which can either comprise a solid surface, such as a concrete pad, or a hard particulate bed, such as compacted gravel.
Although the axial and bending strengths of SIPs are known to be high, conventional SIPs typically require additional support along both their top and bottom surfaces. This support is typically provided by either one or more longitudinal strips of lumber secured to the top and bottom surfaces of the SIPs (commonly referred to as a “plates”), or U-shaped, longitudinally extending bands secured to the top and bottom surfaces of the SIPs. While the plates and bands contribute to the overall strength of the SIPs, they add to the quantity of material used in their construction and thereby increase cost.
It is therefore an object to provide a novel structural insulated panel and a foundation wall incorporating the same.
Accordingly, in one aspect there is provided a foundation wall comprising: a plurality of abutting, generally upright structural insulated panels, each of the panels comprising a slab of insulation sandwiched between first and second sheets and a top plate adjacent the top of said panel aid overlaying said insulation, the lower end of said panel being devoid of a bottom plate.
In another aspect, there is provided a structural insulated panel comprising: a first sheet; a second sheet; and insulation sandwiched between and bonded to the first and second sheets, wherein the first and second sheets and insulation are configured to define a generally planar, bottom surface of said panel.
In still another aspect, there is provided a structural insulated panel comprising: a first and second sheet each bonded to a respective first and second side of a slab of insulation, the sheets and insulation being configured to define generally planar, side surfaces of said panel.
Embodiments will now be described more fully with reference to the accompanying drawings in which:
a and 2b are cross-sectional side views of a base of the foundation wall of
a and 3b are cross-sectional top views showing a lumber spline joint and a SIP spline joint, respectively, formed between two adjacent SIPs in the foundation wall of
a,
4
b, and 4c are isometric, cross-sectional top, and isometric views, respectively, showing a corner configuration formed between two adjacent SIPs in the foundation wall of
a and 6b are cross-sectional top views showing a lap joint formed between two adjacent SIPs in a foundation wall;
a and 7b are cross-sectional side views of a frost wall comprising abutting SIPs supported by concrete and compacted gravel footings, respectively; p
a to 9f are cross-sectional views showing temporary lateral supports used with the butt joint of
Turning now to
Each SIP 20 has a generally sandwich-type structure that provides high strength both axially (i.e. along the vertical and horizontal axes) and in bending. In particular, each SIP 20 comprises an interior sheet 34, which faces interior 22 of the residential structure and an exterior sheet 36, which faces exterior 24. The materials used for interior sheet 34 and exterior sheet 36 are selected according to local building and construction codes for preserved wood foundations (e.g. CAN/CSA S406-M92, “Construction of Preserved Wood foundations”, a standard required by the 1995 National Building Code of Canada). In this embodiment, exterior sheet 36 is either preserved spruce/pine/fir (“SPF”) or preserved oriented strand board (“OSB”) plywood, and interior sheet 34 is non-preserved OSB. Occupying the volume between and bonded to sheets 34 and 36 is a layer of expanded foam insulation 38. In this embodiment, insulation 38 is expanded polystyrene (“EPS”), which is a material known to have “closed-cell” structure, meaning it comprises a structure of generally unconnected air pores within a matrix of polystyrene. As is known in the art, closed-cell materials such as EPS are impermeable to moisture and liquids, as no route exists for moisture to travel through the material. Similarly, closed-cell materials are airtight, and consequently provide superior thermal insulating properties as compared to fiberglass, which has what can be described as an “open cell” structure and which is therefore not inherently airtight.
SIPs 20 may be used with a moisture barrier covering one or both sheets 34, 36, depending on the requirements of local building and construction codes. In the embodiment shown in
Each SIP 20 also comprises a recess formed in the upper surface of insulation 38 that is sized to accommodate a top plate 46, as shown in
As shown
Rather than supporting the SIPs 20 on a concrete footing 30, the SIPs 20 may alternatively be supported on a footing of a compacted gravel bed 72, as shown in
A variety of joints may be used to join abutting SIPs 20 of the foundation wall 18 and
b shows a SIP spline joint in which a SIP spline 54 is accommodated within vertical recesses formed in facing sides of the insulation 38 of two adjacent SIPs 20. SIP spline 54 has a similar cross-sectional structure to each SIP 20, and comprises a volume of expandable foam 39 sandwiched between two appropriately-sized sheets 35. As sheets 35 are exposed to interior conditions only, the material used for each of the sheets 35 is either oriented strand board (“OSB”) or plywood. Strips of caulking 52 are provided along the seams formed between the abutting interior sheets 34 and the abutting exterior sheets 36 of the SIPs 20. Moisture barriers 40 cover the interior sheets 34 and exterior sheets 36 of both SIPs. Caulking 52 and moisture barriers 40 serve to block the passage of moisture through the joint formed between SIPs 20.
A foundation corner configuration formed by two abutting SIPs 20 is illustrated in
Also shown in
One or more SIPs 20 forming the foundation wall 18 can be configured to accommodate an opening, such as for a door or a window.
While the vertical sides of the insulation 38 of the SIPs 20 are typically recessed to accommodate an end plate or spline, as shown for example in
In addition to being used in a foundation wall, the SIPs can also be used in a frost wall.
Each SIP 720 has a generally sandwich-type structure that provides high strength both axially (i.e. along both the vertical and horizontal axes) and in bending. Unlike SIPs 20, SIPs 720 are surrounded by gravel backfill 744 on both sides, as depicted in
Each SIPs 720 also comprises a recess formed in the upper surface of insulation 38 that is sized to accommodate a top plate 746. Similar to top plate 46, top plate 746 comprises one or more horizontally-oriented lumber boards having a width commensurate with the thickness of insulation 738. In the embodiment shown, top plate 746 has a double plate configuration and comprises two such horizontal boards. Top plate 746 serves two functions, namely to provide a lumber surface to which abutting lumber may be fastened, and to also provide support at the top of SIP 720 to evenly distribute vertical loads both along the length and across the thickness of SIP 720. In the embodiment shown, top plate 746 distributes the vertical load imposed by floor 726 and upper outer wall 728 evenly upon the length and thickness of SIP 720.
The inherent strength of the SIPs 720 allows them to be used in the absence of a bottom plate. The base of each SIP 720 can be placed upon a concrete footing 730, as shown in
As the vertical sides of the SIPs 720 are flush and free of recesses, butt joints are used to join adjacent SIPs 720, as depicted in
During construction of a frost wall using SIPs 720, it may be useful to provide some temporary support at the base of each butt joint between adjacent SIPs 720. For example, some lateral support applied at the base of each SIP 720 can aid in the alignment and the support of the assembled frost wall prior to backfilling.
While a butt joint is described as being used between adjacent SIPs 720 forming the frost wall, it will be appreciated that a similar butt joint may be used to join structural insulated panels in other applications. Similarly, while a lap joint is described as being used between adjacent SIPs 620 in a foundation wall, a similar lap joint may be used to join SIPs in other applications.
While the material used for the sheets of the above embodiments is referred to as being plywood, preserved plywood, oriented strand board, or preserved oriented strand board, those of skill in the art will appreciate that the material used for the sheets may be of any suitable material known in the art.
While the insulation of the above embodiments is referred to as being EPS, those of skill in the art will appreciate that the insulation may be any of expanded polystyrene, extruded polystyrene, and/or polyurethane foam, or any other suitable insulating foam having similar mechanical, structural, and/or thermal properties known in the art.
Although embodiments have been described above with reference to the accompanying drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.
