Patent Application
20080313985
1. Field of the Invention
The present invention relates to a method and structural member for securing a roof or an outer wall of a building against wind forces tending to lift the roof or outer side wall off the building.
2. Description of the Related Art
It is well known that high wind forces from storms and hurricanes exert significant uplift forces and tend to lift roofs and remove side walls from a building structure. Wood, wood composite, or equivalent structures predominate in residential construction, and when wood framing is employed the structure must be protected from forces developed by high winds. Houses in the Caribbean or southeast coastal regions of the United States are situated in the pathway of annual hurricanes and as such, encounter hurricanes and/or tornadoes from time to time. Such houses in the Caribbean area are typically constructed of cement blocks with a wooden top plate fastened to the top of cement block walls, for attaching a side walls and a wooden roof. In the case of upward loads, the roof is generally tied to the walls using a variety of steel connectors that connect the top plate to the walls. Due to house locations in a susceptible high wind area, some building codes require that houses built with wooden roof support beams have a hurricane ties in place on every rafter. The installation of such ties slows the foundation and framing stages of construction, which in turn increases labor costs. From the foregoing, it is apparent that there is a need for a strong side wall and roof tie system that provides for uplift loads which is cost effective and easy to install.
The primary failure locations on buildings during hurricanes are at the roof to wall connection, or at the wall to floor connection. Decks of sloped roofs in residential buildings are particularly vulnerable to damage caused by wind uplift. When a roof is removed in a storm, rain enters the building, often resulting in a total loss of the building and its contents. The causes of wind uplift damage to roof decks can be from improper nailing techniques, wrong nails, wrong nail spacing, or poor workmanship when nails miss the structural members below or by use of an overdriven fastener. There are existing means to remediate this problem. During roof replacement, fasteners can be added. In lieu of roof replacement, adhesive caulks can be used on the attic side to improve the attachment bond strength between the roof deck and the structural members. U.S. Pat. No. 6,931,813 provides a roof-tie bracket system for bracing a wood framed roof of a building. The structure is reinforced against the destructive wind forces by high strength brackets attached to every rafter where it joins the ceiling plates. The roof-tie bracket is connected to the structure by way of a plurality of fasteners, such as nails or lag bolts. U.S. Pat. No. 6,725,623 provides a method for controlling uplift on a roof with a plurality of clamps and transverse bars. The transverse bars have a series of downward extending brackets each of which has a flexible foot to press down on the flat panels of the roof, thereby providing a structural brace to hold the panels down in a heavy wind. U.S. Pat. No. 6,427,392 provides a method of roof reinforcement against hurricanes by placing an anchor assembly into a cavity in a wall and securing the anchor assembly to wall coverings enclosing the cavity around an anchorage area and then tying the anchor assembly to the roof structure. These are all point to point mechanical anchoring systems. U.S. Pat. No. 5,890,327 teaches a method of reinforcing or retrofitting building roof structures against hurricane force winds by applying a thin stream of a liquid polymer foam adhesive under pressure upwardly along the intersections of the rafters or support members and the roof panels to provide a filleted connection. The liquid polymer foam adhesive is only effective in corner regions formed at the intersections between said support members and interior surfaces of the roof panels.
The present invention provides a solution to the above and other problems by providing improved reinforcing and anchoring of a roof and side walls to a building structure, wherein a greater hold down force is applied to the roof and side walls to counter the uplift and horizontal forces generated by high winds.
This has been accomplished according to this invention by providing a roof panel or outer wall panel, comprising spaced apart beam members, and a sheathing attached to and spanning a space between adjacent beam members; and spraying and adhering a layer of a foamable polymer adhesive composition such as a polyurethane or polyisocyanurate adhesive composition, which foamable polymer adhesive composition is preferably present in the form of foamable liquid, onto substantially the entirety of the beam members and substantially the entirety of the inner side of the sheathing such that the layer on the sheathing and the beam members is preferably substantially continuous. By substantially continuous it is meant that there are substantially no breaks or spaces in the layer, across the area on which it is deposited. A closed cell spray polyurethane or polyisocyanurate foam is applied at a uniform depth under a roof deck or side wall sheathing between the structural beams to provide additional bonding strength. This is different from filleted adhesive caulks in that it provides additional bonding strength and also significant insulation under the roof deck or side walls. This creates a conditioned attic or side wall space and seals soffit areas to deter the intrusion of wind driven rain. This also provides a significant energy savings.
This invention uses such improved roof and side wall panels to help secure the roof to the side walls and the side walls to the flooring, and stiffens the roof and side walls to distribute wind loads to the roof and side wall framing. The present invention can be incorporated during initial construction of a structure, or may be retrofitted into existing structures.
The invention provides a method of securing a roof or an outer wall of a building against wind forces, which comprises:
The invention also provides a structural member for a roof or an outer wall of a building comprising:
a) a roof panel or outer wall panel, said roof panel or outer wall panel comprising a plurality of spaced apart beam members, and a sheathing having an inner side and an outer side, the sheathing spanning a space between adjacent beam members and being attached to the beam members such that the inner side of the sheathing is in juxtaposition with the beam members; and
b) a layer of a rigid, closed cell foam comprising a polymer adhesive composition on at least a portion of side walls of said beam members and substantially the entirety of the inner side of the sheathing such that the layer on the sheathing and the beam members is substantially continuous, and adheres the sheathing to the beam members.
The invention further provides a structural member comprising:
The invention still further provides a structural member comprising:
Roofs and side walls in residential and light commercial buildings comprise two main elements: beams such as wood, wood composite, metal or combinations thereof as framing and rafters, and a sheathing. A sheathing is a layer of boards or of other wood or fiber materials applied to the outer studs, joist, and rafters of a building to strengthen the structure and serve as a base for an exterior weatherproof cladding. Sheathing is typically plywood, oriented strand board (OSB) fibrous cement, fiberglass reinforced gypsum, insulated sheathings, such as expanded and extruded polystyrene, or polyisocyanurate, but can also be foam board and combinations of these materials. Beams are typically dimensional lumber made from softwood species of wood, engineered woods or formed steel. These have nominal cross sections of 2″×3″, 2″×4″, 2″×6″, 2″×8″, 2″×10″ or 2″×12″. These beams can be built as prefabricated truss assemblies or site-built as rafters or side framing. Sloped residential roofs and side walls are constructed by spacing the beams at regular intervals, typically 12″, 16″ or 24″, most commonly 24″. Sheathing is typically available in 4 ft.×8 ft. sheets and is placed and fastened to a face of the beam with such fasteners as nails, screws or clips. Application of these fasteners is not always done properly in both new and existing homes, and can be a main cause of roof or side wall failure. Roofing materials, including underlayment and shingles are then attached to the outside surface of the sheathing.
According to this invention, a uniform thickness of a closed cell spray polyurethane or polyisocyanurate foam adhesive insulation (ccSPF) is then applied on the underside of the roof deck or side wall sheathing and maintains a continuous contact with at least a portion of the two opposite sides of the sides of the beams, preferably at least half of the width of the two opposite sides of the sides of the beams, and more preferably substantially the entirety of the two opposite sides of the beams which are perpendicular to the sheathing. The closed cell spray polyurethane or polyisocyanurate foam adhesive, because of its inherent strength and stiffness, and its ability to form a tenacious bond to other construction materials such as wood and steel, acts as an adhesive. The closed cell spray polyurethane or polyisocyanurate foam adhesive acts to uniformly distribute the wind load from the sheathing to the beams, thus increasing the uplift load considerably. Testing has shown that typical uplift loads increase from approximately 70 pounds per square foot to approximately 240-285 pounds per square foot after the application of about 3″ thickness of a closed cell spray polyurethane or polyisocyanurate foam adhesive. Considering that roofs of homes in coastal hurricane areas can be subjected to wind uplift loads of from about 100 to about 130 psf, this increase is significant. In addition to providing uplift resistance, an application of about 3″ thickness of a closed cell spray polyurethane or polyisocyanurate foam adhesive can provide additional insulation, on the order of R19. Since closed cell spray polyurethane or polyisocyanurate foam adhesive is water resistant, it can also be used to strengthen soffit areas against wind damage and prevent intrusion of wind driven rain in these areas. Closed cell spray polyurethane or polyisocyanurate foam adhesive may also provide a measure of corrosion protection to mechanical fasteners and brackets in roof structures.
Closed cell spray polyurethane or polyisocyanurate foam adhesives are well known in the art and are generally commercially available. In general, polyurethane or polyisocyanurate foams are prepared by combining an isocyanate, a polyol or mixture of polyols, a blowing agent or mixture of blowing agents, and other materials such as catalysts, surfactants, and optionally, flame retardants, colorants, or other additives. Methods of producing polyurethane and polyisocyanurate foams are generally known and consist in general of the reaction of an organic polyisocyanate (including diisocyanate) and a polyol or mixture of polyols in the presence of a volatile blowing agent, which is caused to vaporize by the heat liberated during the reaction of isocyanate and polyol. This reaction can be enhanced through the use of amine and/or other catalysts as well as surfactants. The catalysts ensure adequate curing of the foam, while the surfactants regulate and control cell size. Flame-retardants are traditionally added to rigid polyurethane or polyisocyanurate foam to reduce its flammability. Fluorocarbons act not only as blowing agents by virtue of their volatility, but also are encapsulated or entrained in the closed cell structure of the rigid foam and are the major contributor to the low thermal conductivity properties of rigid polyurethane foams. The use of a fluorocarbon as the preferred commercial expansion or blowing agent in insulating foam applications is based in part on the reduced thermal conductivity, or k-factor associated with the foam produced. K-factor is defined as the rate of transfer of heat energy by conduction through one square foot of one inch thick homogenous material in one hour where there is a difference of one degree Fahrenheit perpendicularly across the two surfaces of the material. Since the utility of closed-cell polyurethane-type foams is based, in part, upon their thermal insulation properties, it would be advantageous to identify materials that produce lower k-factor foams. It is convenient in many applications to provide the components for polyurethane or polyisocyanurate foams in pre-blended foam formulations. Most typically, the foam formulation is pre-blended into two components. The isocyanate or polyisocyanate composition comprises the first component, commonly referred to as the “A” component. The polyol or polyol mixture, surfactant, catalysts, blowing agents, flame retardant, and other isocyanate reactive components comprise the second component, commonly referred to as the “B” component. While the surfactant, catalyst(s) and blowing agent are usually placed on the polyol side, they may be placed on either side, or partly on one side and partly on the other side. Accordingly, polyurethane or polyisocyanurate foams are readily prepared by bringing together the A and B side components for spray applied foams, froths, and the like. Optionally, other ingredients such as fire retardant, colorants, auxiliary blowing agents, water, and even other polyols can be added as a third stream to the mix head or reaction site. Most conveniently, however, they are all incorporated into one B component. The foam is a preferably applied at a thickness of from about 2.5 cm to about 15 cm. The foam may be applied as single or multiple layers.
Any organic polyisocyanate can be employed in polyurethane or polyisocyanurate foam synthesis inclusive of aliphatic and aromatic polyisocyanates. Preferred, as a class is the aromatic polyisocyanates. Preferred polyisocyanates for rigid polyurethane or polyisocyanurate foam synthesis are the polymethylene polyphenyl isocyanates, particularly the mixtures containing from about 30 to about 85 percent by weight of methylenebis(phenyl isocyanate) with the remainder of the mixture comprising the polymethylene polyphenyl polyisocyanates of functionality higher than 2. Preferred polyisocyanates for flexible polyurethane foam synthesis are toluene diisocyanates including, without limitation, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, and mixtures thereof.
Typical polyols used in the manufacture of rigid polyurethane foams include, but are not limited to, aromatic amino-based polyether polyols such as those based on mixtures of 2,4- and 2,6-toluenediamine condensed with ethylene oxide and/or propylene oxide. Another example is aromatic alkylamino-based polyether polyols such as those based on ethoxylated and/or propoxylated aminoethylated nonylphenol derivatives. These polyols are generally preferred in spray applied polyurethane foams. Another example is sucrose-based polyols such as those based on sucrose derivatives and/or mixtures of sucrose and glycerine derivatives condensed with ethylene oxide and/or propylene oxide.
Typical polyols used in the manufacture of flexible polyurethane foams include, but are not limited to, those based on glycerol, ethylene glycol, trimethylolpropane, ethylene diamine, pentaerythritol, and the like condensed with ethylene oxide, propylene oxide, butylene oxide, and the like. These are generally referred to as “polyether polyols”. Another example is the graft copolymer polyols, which include, but are not limited to, conventional polyether polyols with vinyl polymer grafted to the polyether polyol chain. Yet another example is polyurea modified polyols which consist of conventional polyether polyols with polyurea particles dispersed in the polyol.
Examples of polyols used in polyurethane modified polyisocyanurate foams include, but are not limited to, aromatic polyester polyols such as those based on complex mixtures of phthalate-type or terephthalate-type esters formed from polyols such as ethylene glycol, diethylene glycol, or propylene glycol. These polyols may be blended with other types of polyols such as sucrose-based polyols, and used in polyurethane foam applications.
Catalysts used in the manufacture of polyurethane foams are typically tertiary amines including, but not limited to, N-alkylmorpholines, N-alkylalkanolamines, N,N-dialkylcyclohexylamines, and alkylamines where the alkyl groups are methyl, ethyl, propyl, butyl and the like and isomeric forms thereof, as well as heterocyclic amines. Typical, but not limiting, examples are triethylenediamine, tetramethylethylenediamine, bis(2-dimethylaminoethyl)ether, triethylamine, tripropylamine, tributylamine, triamylamine, pyridine, quinoline, dimethylpiperazine, piperazine, N,N-dimethylcyclohexylamine, N-ethylmorpholine, 2-methylpiperazine, N,N-dimethylethanolamine, tetramethylpropanediamine, methyltriethylenediamine, and mixtures thereof.
Optionally, non-amine polyurethane catalysts are used. Typical of such catalysts are organometallic compounds of lead, tin, titanium, antimony, cobalt, aluminum, mercury, zinc, nickel, copper, manganese, zirconium, and mixtures thereof. Exemplary catalysts include, without limitation, lead 2-ethylhexoate, lead benzoate, ferric chloride, antimony trichloride, and antimony glycolate. A preferred organo-tin class includes the stannous salts of carboxylic acids such as stannous octoate, stannous 2-ethylhexoate, stannous laurate, and the like, as well as dialkyl tin salts of carboxylic acids such as dibutyl tin diacetate, dibutyl tin dilaurate, dioctyl tin diacetate, and the like.
In the preparation of polyisocyanurate foams, trimerization catalysts are used for the purpose of converting the blends in conjunction with excess A component to polyisocyanurate-polyurethane foams. The trimerization catalysts employed can be any catalyst known to one skilled in the art including, but not limited to, glycine salts and tertiary amine trimerization catalysts, alkali metal carboxylic acid salts, and mixtures thereof. Preferred species within the classes are potassium acetate, potassium octoate, and N-(2-hydroxy-5-nonylphenol)methyl-N-methylglycinate.
Dispersing agents, cell stabilizers, and surfactants may be incorporated into the blowing agent mixture. Surfactants, better known as silicone oils, are added to serve as cell stabilizers. Some representative materials are sold under the names of DC-193, B-8404, and L-5340 which are, generally, polysiloxane polyoxyalkylene block copolymers such as those disclosed in U.S. Pat. Nos. 2,834,748, 2,917,480, and 2,846,458.
Other optional additives for the blowing agent mixture may include flame retardants such as tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, tris(1,3-dichloropropyl) phosphate, diammonium phosphate, various halogenated aromatic compounds, antimony oxide, aluminum trihydrate, polyvinyl chloride, and the like. Other optional ingredients may include from 0 to about 5 percent of water based on the weight of the polyol blend, which chemically reacts with the isocyanate to produce carbon dioxide. The carbon dioxide acts as an auxiliary-blowing agent.
Also included in the mixture are blowing agents. Generally speaking, the amount of blowing agent present in the blended mixture is dictated by the desired foam densities of the final polyurethane or polyisocyanurate foams products. The polyurethane foams produced can vary in density from about 1.0 to about 6.0 pounds per cubic foot, more preferably from about 1.8 to about 4.0 pounds per cubic foot and most preferably 2 to 4 pound per cubic foot. The density obtained is a function of how much of the blowing agent, or blowing agent mixture, is present in the A and/or B components, or that is added at the time the foam is prepared.
When spray foam is applied, the A-side chemicals (e.g. polyisocyanate) and B-side chemicals are mixed in appropriate amounts, typically equal amounts by volume, and then atomized into a mist. The B-side contains polyols, the blowing agents, catalysts, fire retardants, etc. The blowing agent is in a liquid form in solution in the B-side. In the case of water as blowing agent, the water mixes with the polyisocyanate to form CO2 gas, it creates gas cells in the polyurethane. The component parts are mixed in the spray gun. The polyurethane is created as the two chemicals mix and hits the wall or roof surface.
Useful blowing agents non-exclusively include: hydrocarbons, methyl formate, halogen containing compounds, especially fluorine containing compounds and chlorine containing compounds such as halocarbons, fluorocarbons, chlorocarbons, fluorochlorocarbons, halogenated hydrocarbons such as hydrofluorocarbons, hydrochlorocarbons, hydrofluorochlorocarbons, hydrofluoroolefins, hydrochlorofluoroolefins, CO2 generating materials such as water, and organic acids that produce CO2 such as formic acid. Examples non-exclusively include low-boiling, aliphatic hydrocarbons such as ethane, propane and butane, normal pentane, isopentane and cyclopentane; ethers and halogenated ethers; trans 1,2-dichloroethylene, pentafluorobutane; pentafluoropropane; hexafluoropropane; and heptafluoropropane; 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124); and 1,1-dichloro-1-fluoroethane (HCFC-141b) as well as 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); 1-chloro 1,1-difluoroethane (HCFC-142b); 1,1,1,3,3-pentafluorobutane (HFC-365mfc); 1,1,1,2,3,3,3-heptafluoropropane (HCF-227ea); trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12); 1,1,1,3,3,3-hexafluoropropane (HFC-236fa); 1,1,1,2,3,3-hexafluoropropane (HFC-236ea); difluoromethane (HFC-32); difluoroethane (HFC-152a); 1,1,1,3,3-pentafluoropropane (HFC-245fa); trifluoropropenes, pentafluoropropenes, chlorotrifluoropropenes, tetrafluoropropenes including 1,1,1,3-tetrafluoropropene (HFO-1234ze), trans-1,1,1,3-tetrafluoropropene (trans-HFO-1234ze), 1,1,1,2-tetrafluoropropene (HFO-1234yf), 1,1,1,2,3-pentafluoropropene (HFO-1225ye), 1-chloro-3,3,3-trifluoropropene (HCFC-1233zd), and low-global warming hydrofluorocarbons such as hydrofluoroolefins and hydrofluoroethers. Combinations of any of the aforementioned blowing agents are useful.
The most preferred blowing agent is 1,1,1,3,3-pentafluoropropane (HFC-245fa) which is commercially available from Honeywell International Inc. as Enovate Blowing Agent. This latter molecule remains in solution until the heat generated by the polyurethane and/or the polyisocyanurate reaction vaporizes it and creates the gas in the cells of the polyurethane foam.
In one embodiment, the mixture comprises only one blowing agent. In another embodiment the mixture comprises a plurality of blowing agents, for example a combination of two blowing agents or combinations of three blowing agents. When combinations of two or more blowing agents are employed, each individual blowing agent may be present in an amount of from about 1 percent by weight to about 99 percent by weight, wherein the total amount of blowing agent is 100% by weight. In a two component combination of blowing agents, one blowing agent may be present in an amount of from about 1 percent by weight to about 50 percent by weight and the other blowing agent may be present in an amount of from about 50 percent by weight top about 99 percent by weight.
One useful combination of blowing agents comprises 1,1,1,3,3-pentafluorobutane and at least one fluorinated hydrocarbon selected from the group consisting of 1,1,1,2-tetrafluoroethane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3,3-hexafluoropropane and 1,1,1,2,3,3,3-heptafluoropropane. A particularly useful combination of blowing agents comprises from about 50% to about 99% by weight of 1,1,1,3,3-pentafluorobutane and from about 1% to 50% by weight of at least one fluorinated hydrocarbon selected from the group consisting of 1,1,1,2-tetrafluoroethane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3,3-hexafluoropropane and 1,1,1,2,3,3,3-heptafluoropropane.
Another useful combination of blowing agents comprises a) pentafluorobutane, and b) at least one further blowing agent selected from the group consisting of low-boiling, aliphatic hydrocarbons selected from the group consisting of ethane, propane and butane, normal pentane, isopentane, or cyclopentane; halogenated hydrocarbons; ethers and halogenated ethers; difluoromethane (HFC-32); difluoroethane; 1,1,2,2-tetrafluoroethane (HFC-134); 1,1,1,2-tetrafluoroethane (HFC-134a); pentafluoropropane; hexafluoropropane, and heptafluoropropane; particularly wherein the pentafluorobutane is 1,1,1,3,3-pentafluorobutane (HFC-365mfc), and the further blowing agent comprises at least one of 1,1-difluoroethane (HFC-152a), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,2,3,3,3-hexafluoropropane (HFC-236ea), 1,1,1,3,3,3-hexafluoropropane (HFC-236fa) or 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea). This is useful when comprising 10 to 70% by weight of HFC-365mfc and 90 to 30% by weight of the further blowing agent, and optionally further comprises 2 to 50% by weight of carbon dioxide.
Another useful combination of blowing agents comprises 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and 1,1,1,3,3-pentafluoropropane (HFC-245fa). Useful amounts may range from up to about 50 weight percent of HFC-365mfc and about 50 weight percent or more of HFC-245fa.
Another useful combination of blowing agents comprises 1,1,1,3,3-pentafluorobutane (HFC-365mfc) and 1,1,1,3,3-pentafluoropropane (HFC-245fa). Useful amounts may have an HFC-365mfc to HFC-245fa weight ratio range of from 40:60 to about 80:20.
Another useful combination of blowing agents comprises HFC-365mfc, HFC-227ea and one or both of HFC-245fa and HFC-134a. Preferably 65 to 85 parts by weight comprises HFC-365mfc and HFC-227ea of which percentage, 80 to 95 parts by weight are HFC-365mfc, and the remainder is HFC-227ea; and at least 15 parts by weight comprises one or both of HFC-245fa and HFC-134a.
The blowing agent compositions according to the invention may include other optional ingredients such as phosphorus compounds and catalysts.
A useful combination comprises from about 10 to about 20% by weight of a phosphorus compound, preferably triethyl phosphate or tris-chloroisopropyl phosphate; and a mixture of: a) HFC-365mfc, and b) HFC-134a, HFC-227ea or HFC-245fa.
A useful combination comprises HFC-365mfc and a catalyst which catalyses the polyol/isocyanate reaction and, optionally which catalyses the trimerization of isocyanates.
Closed-cell spray foams suitable for this application preferably have the following nominal properties:
Useful closed-cell spray foams are disclosed in U.S. Pat. Nos. 6,414,046; 7,214,294; 6,843,934, 6,806,247, 6,790,820; 6,784,150, among others, and which are incorporated herein by reference.
Useful closed-cell spray foams include Comfort Foam® FE178, FE158, CF178, CF158 commercially available from BASF Polyurethanes—Foam Enterprises (a division of BASF) of Florham Park, N.J.; BaySeal™ 2.0 commercially available from BaySystems (a division of Bayer) of Spring, Tex.; Corbond® commercially available from Corbond of Bozeman, Mont.; HeatLok Soy 0240 commercially available from Demilec USA of Arlington, Tex.; Styrofoam™ 2.0 commercially available from Dow Chemical Company of Midland, Mich.; PF-173, PF-193 commercially available from Gaco Western of Seattle, Wash.; Permax commercially available from Resin Technology Division (a division of Henry Co.) of Ontario, CA; Foam Lok™ FL-2000™ commercially available from Lapolla Coatings of Houston, Tex.; InsulStar® commercially available from NCFI Polyurethanes (formerly North Carolina Foam Industries) of Mt. Airy, N.C.; and DuraFoam-Duraseal™ 1.9 commercially available from Urethane Contractor Supply Company of Phoenix, Ariz.
In another embodiment of the invention, an elongated channel for the passage of ventilating air is fixed on the inner side of the sheathing between and separated from adjacent spaced apart beam members. In this case, a layer of the rigid, closed cell foam polymer adhesive composition is positioned on the side walls of the beam members, on the elongated channel, and on the inner side of the sheathing between the elongated channel and the spaced apart beam members. The layer of rigid, closed cell foam on the sheathing, the elongated channel and the beam members is substantially continuous, and adheres the sheathing to the beam members. As stated above, by substantially continuous it is meant that there are substantially no breaks or spaces in the layer, across the area on which it is deposited.
Some building product manufacturers, most notably certain asphalt shingle manufactures, require proper attic ventilation to avoid heat damage to the shingles. The generally accepted rule is to provide 1 ft2 of ventilation opening for every 300 ft2 of attic space. Many house designs employ cathedralized ceilings, where insulation is applied between the structural members in the vicinity of the roof deck. To achieve proper ventilation in this application, attic baffles are used along the entire when applying insulation under a roof deck in a conditioned attic or cathedralized ceiling.
The following non-limiting example serves to illustrate the invention.
This Example details the test procedure to determine the ultimate wind uplift load for roof/wall panels reinforced with a closed-cell spray polyurethane foam. It is based on a slightly modified version of ASTM E330-02 “Standard Test Method for Structural Performance of Exterior Windows, Doors, Skylights and Curtain Walls by Uniform Static Air Pressure Difference” using a test wind uplift test arrangement.
A structural member is formed according to the configuration shown in
The panel specimens were placed in an upside down position in a test frame. The approximate dimensions of the top opening of the test frame are about 5 ft×9 ft. When centered in the test frame the OSB sheet is suspended by the dimensional lumber, which spans across the 5 ft dimension of a test frame. A polyethylene sheet is then draped carefully across the test panel, and cut so that it is just even with the bottom of the test frame. The polyethylene sheet is then sealed to the bottom of the test frame with duct tape.
A vacuum pump is turned on, and a vacuum valve is opened slightly to evacuate the test frame. This pulls the polyethylene sheet over the test panel. Care is taken to be sure the polyethylene sheet drapes evenly over the test panel without excessive folding to prevent risk of leakage. Any leaks that may develop are sealed with duct tape. After an initial removal of air, a vacuum is applied at an even, controlled rate. At pre-defined pressure increments, the panel is allowed to sit for approximately 15-30 seconds before the pressure is increased to the next increment.
Vacuum pressure is controlled and monitored on a digital gage until failure. Failure is readily noticeable, producing a distinctly visual and audible sound at failure. Failure typically occurs by a failure of the connection between the OSB and dimensional lumber. At the point of failure, the maximum pressure recorded by the digital pressure gage is then recorded. This pressure (vacuum) is then converted to pounds per square foot, and becomes the measured wind uplift load.
In a typical failure of a no-foam specimen, the heads of the nails are pulled through the OSB sheathing, without the nails being pulled out of the truss itself. In at typical failure of the foam fillet test specimen, delamination occurs between the truss and foam occurs. Once this has occurred, the nail heads are immediately pulled through the OSB in a similar manner as a no foam specimen.
Two specimens of each type (no foam, filleted foam and uniform fill foam) were tested. On one of the uniform fill specimens, the nail heads were ground off to simulate removal of the nails. The table below contains a summary of the results.
The results show there are significant differences in ultimate failure capacities among the three groups of data with the full foam layer coverage producing the greatest increase in ultimate failure capacity over the non-retrofitted panels. Because only 5 full-foam samples were included in the sample results, the 95% confidence level for the mean failure capacity is relatively large as compared to the mean (20.3%). For the completed test sequence, the 95th percentile confidence level was 13.9% and 10.6% respectively, for the no foam and fillet samples.
Statistical T-tests showed sufficient evidence to reject the hypothesis that the mean failure loads of the three categories are the same at the 95th percentile level. Analysis of the results show that the application of the spray-applied polyurethane foam to roof sheathing samples produces a definite increase in the ultimate wind uplift capacity of these samples. Both methods of foam application (fillet and full foam coverage) significantly improve the performance of the roof sheathing to support connection. The results show a substantial improvement in wind resistance by the uniformly filled full foam coverage samples compared to the filleted samples.
While the present invention has been particularly shown and described with reference to preferred embodiments, it will be readily appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is intended that the claims be interpreted to cover the disclosed embodiment, those alternatives which have been discussed above, and all equivalents thereto.
This application claims the benefit of U.S. provisional patent applications 60/945,974 filed Jun. 25, 2007; and 60/948,269 filed on Jul. 6, 2007; and 61/036,579 filed Mar. 14, 2008, which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60945974 | Jun 2007 | US | |
| 60948269 | Jul 2007 | US | |
| 61036579 | Mar 2008 | US |
