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Multilayered structural insulated panel

Title: Multilayered structural insulated panel.
Abstract: A structural insulated panel includes an internal foam (EPS) core, oriented strand board (OSB) faces on the core, and a sheet of magnesium oxide (MagOx) on one or both of the faces for environmental purposes of either weather resistance and/or fire protection. The outer faces incorporate interior and exterior surfaces that need little more than a finish top coat paint. The combination of core, oriented strand board, and outer sheets provide a thermally efficient insulating structure that is a fully nationally code approved building structure. ...

USPTO Applicaton #: #20090313931 - Class: 523094 (USPTO) -
Inventors: William H. Porter

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The Patent Description & Claims data below is from USPTO Patent Application 20090313931, Multilayered structural insulated panel.

This application claims benefit under 35 U.S.C. §119(e) of provisional application Ser. No. 61/075,054, filed Jun. 24, 2008, entitled MULTILAYERED STRUCTURAL INSULATED PANEL, the entire contents of which are incorporated herein in its entirety.


The present invention relates to structural insulated panels useable in buildings.

The building industry continues to be challenged by increasing costs of construction, including material and labor. Large structural insulated panels (e.g., 8 foot×24 foot panels) can help by reducing the number of components and pieces that must be handled during construction, and further by reducing energy costs in the buildings once constructed. However, further improvements are desired to reduce on-site work and reduce components costs, and to reduce the risk of poor assembly/construction. For example, insulating systems are known for use with studded wall constructions (e.g., fiberglass batting, cellulose, and/or sprayed urethane products), however these systems are prone to have gaps that allow drafts and/or they can be squeezed thin such that they do not provide the insulative “R” value advertised.

In particular, it has been challenging to make structural insulated panels (SIPs) that meet cost, weight, code, environmental and structural requirements. Oriented strand board (OSB) by itself can potentially meet cost, structural and weight requirements, but it does not meet environmental needs for weather or code requirements for fire unless it is further covered or treated. Structural products made of foam are advantageous since they have low weight, but foam by itself potentially lacks strength. Further, when a fire occurs in a room lined with bare foam, the room heats up very quickly to a point where the foam may explode in flames. Because of this, residential building codes require that the plastic foam be separated from the inside of an enclosed area with the equivalent of ½ inch drywall. Notably, it is not acceptable to simply construct a structural insulated panel using a foam core covered with oriented strand board, since fire codes are not met. Further, substantial secondary finishing and/or covering layers must be added. However, available materials might include cementous materials or intermessent paints that, when they are machined in the factory or later cut in the paint, produce fine particles of silicon dust which are a health hazard (silicosis) or are destructive to cutting machines.


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In one aspect of the present invention, a structural insulated panel includes an internal foam (EPS) core, oriented strand board (OSB) faces of the core, and at least one thin sheet of non-cementous, fire retardant material (such as magnesium oxide (MagOx)), on one of the faces.

In narrower aspects, magnesium oxide sheet is attached to one or both of the faces with an adhesive.

In another aspect of the present invention, a method comprises steps of providing a foam core with oriented strand board faces, and applying a thin layer of magnesium oxide sheet over the faces.

In another aspect of the present invention, a structural insulated panel includes a structural insulated panel (SIP), and at least one thin layer of fire retardant material such as magnesium oxide (MagOx) on at least one of the faces of the structural insulated panel.

An object of the present invention is to provide an improved structural insulated panel that is energy efficient and insulative (e.g., 50% more energy efficient over conventional “stick” wood-stud-built construction), goes up quickly, and incorporates interior and exterior surfaces that need little more than a finish top coat paint . . . and which are fully nationally code-approved structures.

An object of the present invention is to provide an improved structural insulated panel of large size (e.g. 8 feet×24 feet), and which can be custom cut (e.g., by using CNC-type equipment) to match a building plan.

An object of the present invention is to provide a large panel having a highly insulative value and hence excellent energy efficiency, but competitive price when compared to other products (including their required on-site construction work such as the cost and labor and secondary processes required when using studs).

An object and function of this invention is to provide a light, smooth, thin layer of material over the OSB that will meet the fire code requirements and interior surface finish requirements.

An object and function of the present invention is to provide layering of a smooth layer of fire resistant material over the OSB that allows the SIP panels to meet the common code requirements for a thermal barrier or over the foam core of the SIP.

These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.


FIG. 1 is a perspective view of a multilayered panel of the present construction.

FIG. 2 is an enlarged transverse cross section through FIG. 1.


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A structural insulated panel 20 (SIP) (FIGS. 1-2) includes an internal foam (EPS) core 21, moisture-resistant oriented strand board (OSB) faces 22 on the core 21, and thin outer sheets 23 of non-cementous, fire retardant material, such as magnesium oxide (MagOx) adhered to the exposed faces of the oriented strand board. The thicknesses and sizes can be varied as necessary (see FIGS. 1-2) for particular building code requirements and particular builder preferences. By making the sheets 8 feet×24 feet, building efficiencies can be achieved that were not previously possible using structural insulated panels. Further, it is contemplated that the large panels of 8 feet×24 feet can be cut to match customer plans by using CNC machines, such as by cutting door, window, and outlet openings into the large panels.

In ASTM E84 fire testing, it takes about 15 minutes for the back side of drywall to raise in temperature from ambient to above 250 degrees Fahrenheit. I refer to this as the “15 minute rule” for thermal barrier.

I have found that magnesium oxide sheet can be advantageously applied to exposed surfaces of oriented strand board adhered to the inner and outer faces of a foam core in order to pass the “15 minute rule” for thermal barrier of a building wall. More specifically, the magnesium oxide sheets as a face permit the arrangement to meet the environmental requirements for a building wall for weather and code requirements for fire. I have found that since magnesium oxide does not burn, it keeps enough heat off of the wood oriented strand board so that the laminar arrangement meets the 15 minute thermal test. An optimal approximate thickness of the oriented strand board is about 7/16 inch and the magnesium is about 2 mm. However, it is contemplated that a scope of the present inventive concept includes a internal foam (EPS) core that is at least about 3½ inches thick up to several inches thick, and the oriented strand board (OSB) faces can be about ½ inch to 1 inch thick, and the at least one sheet of magnesium oxide (MagOx) can be about 5 mm thick, or more preferably about 3 mm thick.


Notably, thin magnesium oxide sheets only come in 4 foot×8 foot sheet sizes. However, using the present inventive concepts, thin magnesium oxide sheets can be readily used to make big panels, such as 8 feet×24 feet, by applying 4 foot×8 foot sheets of magnesium oxide to the big oriented strand board. This is a significant advantage for builders, since it makes for a more efficient and quicker building construction. It also has advantages since, by doing this at a factory, tighter tolerances and joints can be made. It is noted that the smaller 4′ wide panels of magnesium oxide would take much longer to install individually at a construction site, and also would be much less structural than when they are integrally bonded to form part of a larger 8 foot×24 foot laminar arrangement. Further, separately attached 4 foot×8 foot magnesium oxide sheets would result in more junctions and hence more air infiltration to a building . . . as well as more “crease” locations (if not tightly abutted at joints) potentially resulting in hot spots that permit fire intrusion. For this reason, in my opinion it has been counterintuitive to make the presently-proposed laminar arrangement. This explains, at least in part, why it has not previously been done.

In addition to using the present arrangement on an inside wall surface, the exterior wall surface gains advantages using magnesium oxide over “bare” oriented strand board. Here, the magnesium oxide can act as a weather resistant surface. Also, in areas where fire is likely to occur on the outside, the magnesium oxide provides an “external” resistance to fire that is desirable. The fire resistance can also be provided in cellulose or other materials by impregnating it with ammonium phosphate or with phenolic or with another fire retardant material, or by including in a paint or adhesive a fire resistant material.

It is noted that national codes approve panels made with oriented strand board faces on foam. This makes passing of fire testing a key requirement for product sales to the housing and building industry. Hence, the present invention is highly advantageous and very important for product sales to the housing and building industry for structural insulated panels.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise.

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stats Patent Info
Application #
US 20090313931 A1
Publish Date
Document #
File Date
Other USPTO Classes
5230915, 527941, 523093
International Class

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Fire Protection
Magnesium Oxide

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