FIRE-RATED ROOFING SYSTEM
1. A fire-resistant composite comprising:
- a first layer comprising a flexible polymeric sheet; and
a second layer, the second layer comprising a first carbon fiber sheet and a second carbon fiber sheet with an inert fiber mat positioned between the first carbon fiber sheet and the second carbon fiber sheet.
A fire-resistant polymeric membrane includes a polymer layer such as PVC, TPO, or EPDM affixed to a carbon fiber composite. The carbon fiber composite includes one or two layers of non-woven carbon fibers and at least one of an inert fiber mat or a metal foil layer, wherein the metal foil layer has a melting temperature of at least about 660° C. The present invention also provides an underlayment, wherein the underlayment is formed from one or more fibrous carbon layers affixed to at least one of an inert fiber mat or a metal foil having a melting temperature greater than 660° C.
- 1. A fire-resistant composite comprising:
a first layer comprising a flexible polymeric sheet; and a second layer, the second layer comprising a first carbon fiber sheet and a second carbon fiber sheet with an inert fiber mat positioned between the first carbon fiber sheet and the second carbon fiber sheet.
- View Dependent Claims (2, 3, 5)
- 6. A fire-resistant roofing underlayment comprising:
at least one carbon fiber layer; and at least one of an inert fiber mat or a metal foil layer being coextensive with the carbon fiber layer, the metal foil layer having a melting temperature greater than about 660°
wherein the at least one carbon fiber layer has a basis weight of at least 3 ounces per square yard.
- View Dependent Claims (7)
- 8. A roof structure comprising:
a roof deck covered with a fire-resistant composite membrane comprising; a first layer comprising a flexible polymeric sheet; and a second layer affixed to the first layer, the second layer comprising at least one carbon fiber sheet and at least one of an inert fiber mat or a metal foil, the metal foil having a melting temperature above about 660°
- View Dependent Claims (9)
This application claims priority to and is a divisional application of U.S. patent application Ser. No. 15/227,274, filed Aug. 3, 2016, which in turn claims priority to U.S. Provisional Application No. 62/281,352, filed Jan. 21, 2016. This application also claims the benefit of U.S. Patent Application Publication U.S. 2017/0210100, the entirety of which is hereby incorporated by reference.
Commercial roofs are rated based on fire resistance. The fire rating is based on the ability of the roof'"'"'s surface to withstand one or more tests. To obtain a Class A over wood deck fire rating, a roofing system must pass ASTM E 108 (hereinafter, this is simply referred to as a Class A fire rating). In this test, combustible material is placed on the roof surface, ignited and allowed to burn. If the roof'"'"'s structure does not sustain a flame, meets structural integrity requirements after the test is complete, and does not have holes larger than a certain size after the test, the roof system passes the test. A comparable test method is UL 790. Built-up roofs which are formed from bituminous material can pass this test by using multiple layers of a glass matting. The glass mats provide an inorganic barrier layer that prevents the fire from extending through the surface of the built up roof.
Membrane roofs which are formed from polymeric sheet membranes and, in particular, non-bituminous polymeric sheets, can achieve a UL Class A over wood deck rating. But the roof system is much more expensive. It requires a fireproof material such as gypsum board or fiberglass facers over an intumescent coating. The added expense often makes such roofs cost-prohibitive.
Embodiments of the present invention are premised on the realization that a roofing structure capable of achieving a Class A fire rating can be formed with a composite membrane. The composite membrane is formed from a non-bituminous polymeric sheet or membrane affixed to a carbon fiber composite. The carbon fiber composite includes one or two layers of a carbon fiber fabric affixed to at least one of an inert fiber mat or a flexible metal foil, wherein the metal foil has a melting temperature sufficiently high to prevent the roof deck from igniting. Generally a foil formed from a metal having a melting temperature of greater than 660° C. is suitable for use in embodiments of the present invention.
In particular, the carbon fiber composite can be formed with two layers of the carbon fiber fabric with the inert fiber mat and/or the metal foil positioned in between the two layers. Tufting fixes all three layers together. This structure is then affixed to the polymeric sheet.
The inert fiber mat can be, for example, glass scrim, woven glass fibers, asbestos, elastinite, basalt, and so on. The metal foil can be, for example, stainless steel, iron, galvanized iron, galvanized steel, titanium, aluminum, and so on.
Further, an alternate embodiment of the present invention encompasses an underlayment sheet formed from the carbon fiber layers affixed to a metal foil having a relatively high melting temperature. The structure can be used as an underlayment to achieve a fire-resistant roof wherein the underlayment is then covered with a waterproof layer, such as a polymeric sheet or even a bituminous layer.
The objects and advantages of present will be appreciated in light of the following detailed descriptions and drawings in which:
According to one embodiment of the present invention, with reference to
The composite roofing membrane 10 includes an upper layer 14 intended to be exposed to the elements and a lower layer 16 intended to rest on the roof deck 12. Layers 14 and 16 are generally coextensive with each other except on one edge as explained hereinafter. The upper layer 14 is a polymeric sheet material or membrane. Typically, these have a nominal thickness of 45 to 80 mils. However, thinner, as well as thicker, membranes will function. The polymeric membrane 14 can be formed from any typical polymer used as a roofing membrane. These include polyvinyl chloride (PVC), thermoplastic polyolefin (TPO), ethylene propylene monomer rubber (EPM), ethylene propylene diene monomer rubber (EPDM), chlorosulfonated polyethylene, such as Hypalon brand, flexible acrylics as well as others. Bituminous materials are not included within the definition of polymeric membranes.
Typically, the polymeric membrane 14 is actually two plies affixed together, an upper ply 18 and a lower ply 20 as shown in
The lower layer 16 of composite 10 is a composite including at least one carbon fiber sheet or layer and at least one of a metal foil or an inert fiber mat. With reference to
With reference to
The carbon fiber layer(s) have a combined basis weight effective to provide sufficient thermal insulation to prevent a fire from igniting the roof deck. Generally, for use in embodiments of the present invention, the combined weight of the carbon fiber layers should be at least 3 ounces per square yard (oz/yd2) (100 gsm), or 6 oz/yd2 (200 gsm), more precisely 9 to 20 oz/yd2 (300 to 667 gsm or higher), and, in particular, 9 to 15 oz/yd2 (300 to 500 gsm). In an embodiment where the composite includes two carbon fiber layers, one of the carbon fiber layers may have a weight that is greater than the weight of the other of the carbon fiber layers. For example, with reference to
The carbon fibers can be formed in any manner. In particular, carbon fibers formed by reducing polymeric fibers to form carbon are particularly suitable for use in embodiments of the present invention, in particular, fibers formed from polyacrylonitrile. However, carbon fibers formed from other polymers will work in embodiments of the present invention. The carbon fiber can be any fire-resistant carbon fiber. These include ox fibers, such as oxidized polyacrylonitrile fiber. They can also be fully oxidized carbon fibers. Further, they can be graphite fiber. The ox fibers are less expensive and provide adequate fire resistance and insulation.
Further, the carbon fiber layer can include other inert or fire-resistant fibers such as mineral fibers (e.g., basalt), glass fibers, or aramid fibers. Thus, the percentage of carbon fibers in the carbon fiber layer may vary. The percentage of carbon fibers in the carbon fiber layer may be, for example, greater than 25%, greater than 50%, greater than 60%, or greater than 70%. But the carbon fiber layers should have a sufficient amount of carbon fibers to prevent ignition. One commercially available carbon fiber web is Pyron brand available from Zoltek Incorporated. Notably, the thickness of the carbon fiber layer may increase as the percentage of carbon fibers decreases. Further, the carbon fiber layer, or another layer in the composite, may include organic or inorganic flame retardant additives.
The carbon fibers can be held together to form sheets using various well-known methods. In particular, tufting can be employed to fix the fibers together. This method does not incorporate adhesives into the carbon fiber layer(s) that could ignite during a fire. Further, tufting can be used to bind the carbon fiber layer(s) and any intervening layers (e.g., a metal foil and/or an inert fiber mat) together. In an embodiment, threads are woven through the lower layer of the composite to hold all of the layers together.
The metal foil (e.g., metal foil 34 or 42) for use in embodiments of the present invention has a melting temperature high enough to prevent a fire which burns through the polymeric membrane 14 from igniting the roof deck. Any metal foil which has a melting temperature greater than about 660° C. should be suitable for use in embodiments of the present invention. Metal foils having higher melting temperatures, such as at least 800° C., 900° C., 1000° C., 1100° C., 1200° C., or 1300° C. or higher, provide added protection. Such metals includes, for example, aluminum, cast iron, chromium, Inconel, iron, manganese, nickel, stainless steel, high carbon steel, medium carbon steel, low carbon steel, titanium, copper, and tungsten. A galvanizing coating may be required over iron or steel to prevent rusting. This list of metal foils is exemplary and any metal foil that has the requisite melting temperature and can be formed into a foil is suitable for use in embodiments of the present invention. The metal foil must be thin enough to be flexible and thick enough to protect the roof surface. The thickness of the metal foil may vary depending at least in part on the type of metal used for the foil. Generally, the metal foil may be relatively thin having a thickness of 0.0003″ (0.0075 mm) to 0.004″ (0.1 mm), in particular 0.002″ (0.05 mm). Additionally, the metal foil may be relatively thick having a thickness between 0.04″ (1 mm) and 0.06″ (1.5 mm).
The fiber mat (e.g., inert fiber mat 35) for use in embodiments of the present invention is an inert, inorganic fiber mat. The fiber mat may be, for example, woven or spun-bond. The fiber mat may be formed from a number of materials including a glass scrim, woven glass fibers, asbestos, elastinite, and basalt. The weight of the fiber mat may range from, for example, 10 to 200 grams per square meter (g/m2) or more. Various embodiments may include an inert fiber mat having a weight of 10 g/m2, 20 g/m2, 30 g/m2, 45 g/m2, or 70 g/m2. However, thinner, as well as thicker, fiber mats will function. Further, the fiber mat may be made of one or more layers of inert, inorganic material.
The composite roofing membrane 10 can be formed by bonding together the polymeric membrane 14 to lower layer 16. For example, a thermoplastic membrane can be heat-bonded to lower layer 16. An exemplary method of bonding a polymeric sheet to a fibrous web is disclosed, for example, in Venable U.S. Pat. No. 5,456,785.
As shown in
The composite roofing membrane 10 is fixed to the roof deck by any well known method, such as by an adhesive (not shown) between the bottom surface of membrane 10 and the top surface of roof deck 12 or by use of mechanical fasteners (not shown). Basically, any method of maintaining a membrane in position on a roof deck can be utilized in embodiments of the present invention.
An alternate embodiment of the present invention is shown in
Lower layer 16 or underlayment 44 can be modified yet still be within the scope of the present invention. Various configurations of carbon fiber layers, inert fiber mat layers, and/or metal foil layers can be used. For example, one carbon fiber layer could be affixed to two metal foil layers, one on one side and one on the other side. Three or more carbon fiber layers could be affixed together, separated by two or more inert fiber mat layers and/or metal foil layers. Two or more different metal foils could be used, for example, one made of stainless steel and one made of titanium.
In an alternate embodiment, a composite roofing membrane is shown in
To test an embodiment of the present invention, a composite roofing membrane as shown in
Embodiments of the present invention described herein permit one to form a Class A fire rated roof structure. Further, the structure, even when formed with a polymeric membrane, is cost-effective and competitive with fire-rated built-up roof structures.
This has been a description of embodiments of the present invention along with the preferred method of practicing embodiments of the present invention. However, the invention itself should only be defined by the appended claims wherein we claim: