Patent Publication Number: US-8973310-B1

Title: Ventilated roof system and method

Description:
I. STATEMENT OF RELATED APPLICATIONS 
     This application is entitled to priority from U.S. Provisional Patent Application 61/788,427 by John C. Henderson filed Mar. 15, 2013. Provisional application 61/788,427 is incorporated by reference as if set forth in full herein. 
    
    
     II. BACKGROUND OF THE INVENTION 
     A. Field of the Invention 
     The invention relates to roofing and specifically to roofing ventilation. The ventilated roof system and method of the Invention provides full ventilation of the underside of the roof deck, prevents blinding of ventilation intakes by attic insulation, provides a secondary barrier to water intrusion into the living space of the building, allows elimination of soffits in roof construction, and allows escape of water vapor from the interior of the building. 
     B. Statement of the Related Art 
     The portion of a building roof that is exposed to the elements is protected by a durable, weather-resistant surface, such as shingles. As used in this document, the term ‘shingle’ means tab shingles, architectural shingles, cementatious shingles, metal shingles, slate, sheet metal, tar paper, underlayment, roll roofing, ceramic tile roofing, wood shakes, synthetic versions of any of the above and any other weather proofing product that may be applied to a pitched roof. 
     The shingles are supported by a roof deck. As used in this document, a ‘roof deck’ means the generally planar structural covering the upper side of a building and providing support for shingles. The ‘roof deck’ usually is composed of wood in the form of plywood sheets or dimensioned lumber. The term ‘roof deck’ also may include other roofing materials previously applied to the plywood or dimensioned lumber, such as tar paper or other underlayment, ice and water shields, and shingles. 
     The roof deck has a pitch from the eave (lower edge) of the roof to the ridge of the roof so that water and snow will fall from the roof. As used in this document, the term ‘ridge’ means a high location on a roof, such as where the roof deck intersects another roof deck for a gable or hip roof or intersects a vertical wall for a shed roof. 
     To apply shingles to a roof deck, the roof deck is first covered by underlayment. The course of shingles proximal to the lower edge of the roof is then nailed to the deck over the underlayment. Each subsequent course of shingles proceeding from the lower edge to the ridge of the roof overlaps the preceding course and is nailed to the roof deck so that water running from each shingle flows onto the top of the adjacent downhill shingle. The underlayment and shingles cooperate to form a composite surface that is tight to rain water, snow melt and water vapor. 
     The roof deck is supported by rafters that extend from the eave to the ridge of the roof. The ends of the rafters at the eave are covered by a fascia board. As used in this document, the term ‘attic’ refers to an attic and also refers to any other air space under a roof assembly, such as the space between a ceiling or insulation and a roof deck of a structure equipped with a cathedral ceiling. 
     Moisture in the form of water vapor is released into the air inside a structure by the occupants of the structure, by the building plumbing systems and by the soil underneath the structure. If that water vapor is trapped under the impermeable shingle roof, the resulting condensation can damage the roof, can damage the remainder of the structure and can promote growth of mold within the attic. To avoid these effects, the space underneath the roof must be ventilated. Ventilation also serves to allow air heated by solar gain to escape from the space under the roof, reducing the cooling load on the building. During daylight hours, the sun shining on the roof warms the roof deck, causing the roof deck to be warmer than the ambient air. The warm roof deck warms the air immediately below the roof deck. During cold weather, heat within the inhabited space of the structure will leak into the attic space, which also warms the air in the attic space. The air within the attic that is warmed by the sun or by escaped building heat expands, becomes buoyant, and tends to rise. Because the roof is pitched, the warm air rises along the roof deck toward the ridge of the roof. The warm air can be released from the ridge by a ridge vent or at the gable from a gable end vent. 
     Warmed air escaping from the ridge vent will place the attic space at a lower air pressure than the ambient pressure outside the attic. For effective ventilation, eave vents are provided to allow make-up ambient air to enter the area under the roof. A roof equipped with eave and ridge vents acts as a large, low-pressure air pump, pumping air out through the ridge vent and in through the eave vents. The power input to the roof air pump system is heat energy generated either by sunlight shining on the roof deck or by heat leaking into the attic from the heated living space of the structure. If any portion of the roof is starved for ventilation air, then the lack of air flow through the air-starved attic space may cause the problems associated with excess moisture. 
     Any roof ventilation system must deal with building insulation. Insulation may be applied between joists of an attic space or may be applied between rafters supporting a roof deck. If the insulation blocks the flow of air along the underside of the roof deck, the evils of inadequate ventilation will occur. A problem location in prior art roof ventilation systems is the area of the eaves of the roof. Insulation installed proximal to the eave may block the air intakes, preventing the flow of ventilation air through the attic. Insulation applied between the rafters also may block ventilation air and may be separated from the underside of a roof deck by a baffle, frequently composed of styrofoam. Any improper installation of the baffle or of the insulation can block the flow of air, resulting in excess moisture and condensation. Ventilation air also may be blocked by anything that gets in the way of the air, including the building structure or building debris. 
     The present invention is not taught by the prior art. 
     III. BRIEF DESCRIPTION OF THE INVENTION 
     The Invention is a system for construction of a roof that provides complete ventilation of the underside of the roof deck while allowing water vapor to escape from the structure and avoiding any interference with the ventilation of the roof deck due to blockage of air flow by insulation or by other building materials such as wood, dry wall, metal beams, masonry, or any other structural components or construction debris that may block the flow of air under the roof deck. 
     The roof ventilation system includes a pitched sub-deck installed on the rafters of a structure. The sub-deck is composed of plywood sheet, dimensioned lumber or oriented strand board and covers the rafters. The sub-deck must be strong enough to support a worker during installation of the roofing system and strong enough not to sag excessively after construction is completed. Once the roof is completed, the structural duties of the sub-deck are minimal and so the sub-roof deck may be light in weight. Plywood having a thickness of ⅜″ has proven suitable in practice for the sub-deck. Where the ventilated roofing system of the invention is retrofitted to an existing roof, the deck of the existing roof becomes the sub-deck of the ventilated roofing system of the Invention. The ends of the rafters below the sub-deck are covered by a sub-fascia. Where the ventilated roofing system of the Invention is retrofitted to an existing roof, the prior art fascia board of the existing roof becomes the sub-fascia of the ventilated roofing system. 
     A barrier fabric composed of a liquid water-impermeable and water vapor-permeable flexible non-woven fabric is installed over the top of the sub-deck. An example of such a fabric is Tyvek® Home Wrap® by DuPont. A second example is Tyvek® Attic Wrap, which features a reflective layer. A third example is Typar® House Wrap by Polymer Group, Inc. The barrier fabric is permeable to water vapor, so water vapor penetrating through the structure is not stopped by the barrier fabric and can pass through the barrier fabric. Liquid water, however, cannot pass through the barrier fabric under the pressures that the fabric will experience on a roof. The fabric barrier drapes over the edge of the sub-deck and the sub-fascia at the eave of the roof and may be attached to the sub-fascia. 
     Furring strips are installed on top of the barrier fabric and are attached to the sub-deck and the rafters. A ‘furring strip’ is one or more elongated members, such as dimensioned lumber, that are disposed on top of the barrier fabric and that run from proximal to the eave to the ridge of the roof. Each furring strip is located above a rafter and is nailed through the barrier fabric to the rafter. The top of the furring strip is in a spaced-apart relation to the top of the barrier fabric. A separation between the top of the barrier fabric and the top of the furring strip of about 1.5 inches has proven suitable in practice. 
     The roof deck is composed of plywood, dimensioned lumber or oriented strand board and spans the adjacent furring strips. The roof deck provides the structural support for the weather-resistant surface of the roof. Underlayment and shingles cover the roof deck in the conventional manner, providing a water-impermeable composite surface to the roof deck. The roof deck is in the spaced-apart relation to the barrier fabric and the sub-deck. The separation between the roof deck and the barrier fabric also serves to protect the barrier fabric from nail penetrations by nails used to install the shingles to the roof deck. 
     The space between the barrier fabric and the underside of the roof deck and between each pair of adjacent furring strips defines a ventilation channel to provide a flow of air to the underside of the roof deck. The exit to the ventilation channels is any suitable exhaust vent located so as to exhaust air from a ventilation channel. The exhaust vent may be a ridge vent or may be a vent installed at the intersecting planes of a hip roof. The exhaust vent may be installed proximal to the top of a shed roof or may be installed at any intermediate location on a roof deck requiring ventilation; for example, below an architectural feature such as a skylight that otherwise would block the flow of air through the ventilation channel. 
     The intake to the ventilation channels is any suitable soffit or eave intake vent. An intake vent that has proven suitable in practice is a corrugated plastic intake vent attached to the sub-fascia. The barrier fabric overlaps the sub-deck and sub-fascia at the eave and is disposed between the intake vent and the sub-fascia, securing the barrier fabric to the sub-fascia. The corrugated plastic intake vent has an inlet side and an exhaust side. The inlet side of the plastic intake vent is exposed to the ambient air outside the structure. The exhaust side of the corrugated plastic intake vent is disposed within the ventilation channel, so that the corrugated plastic vent communicates between the ambient air outside the structure and the ventilation channel. The corrugated plastic vent is covered by a fascia that blocks access to the ventilation channels other than through the corrugated plastic intake vent. A gutter to control water flowing from the roof may be attached to the fascia. 
     The corrugated plastic vent prevents entry of insects, animals, debris and water into the ventilation channels. The disposition of the plastic corrugated vents assures that blowing rain or snow cannot enter the intake vents. An overflowing gutter at a roof edge is a common location for entry of water into a structure. Any water overflowing on the building side of a gutter mounted to the fascia is prevented from entering the structure by the barrier fabric. 
     The ventilation channels provide protected ventilation for the roof that cannot be blocked by insulation, allowing insulation to be packed into the attic in a quantity and manner that would otherwise block conventional ventilation. The barrier fabric serves as secondary containment for any water that may penetrate the weather-resistant surface of the roof deck or enter through the ridge vent. Rather than entering the occupied portion of the structure, the water is conveyed to the roof edge and discharged through the corrugated plastic intake vent to the outside of the structure. The barrier fabric is not exposed to sunlight or to weather, and so should last indefinitely. The water vapor-permeable barrier fabric also allows the water vapor that otherwise would condense on the sub-deck to pass through the sub-deck and to be exhausted from the building. 
     If a barrier fabric with a reflective surface is used, the reflective surface reduces radiant heat gain or loss through the barrier fabric and hence through the roof. 
     The installation of any roofing product presents obvious hazards to the installers because of the potential for falls. The use of the sub-deck in the roofing system of the Invention allows installation of the barrier fabric and the remainder of the roof system by an installer who can physically stand upon the sub-deck, which promotes safety—a major consideration in any roofing installation. 
     The ventilated roof system of the invention may be retrofitted to an existing roof with little or no work conducted within the building. The ventilated roof system also provides a thermal break from the conditioned air inside the building, aiding energy efficiency of the building. To fully realize the energy savings of the ventilated roofing system in a retrofit of an existing roof, existing openings into the attic are closed, such as existing gable end vents, existing ridge vents and existing intake vents. 
     Roofing product makers, such as shingle makers, frequently limit warranties of the installed roofing products to roofs that have adequate ventilation. The superior ventilation of the roof system of the Invention will preserve rights under those warranties. Because the superior ventilation, the ventilated roof system of the invention will last longer than a conventional roof, saving the building owner the expense of replacement and saving roofing contractors the costs of warranty claims. The sub-deck protects the barrier fabric during the life of the roof from damage from below, as by a homeowner moving things about in the attic. 
    
    
     
       IV. BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross section of a ventilated roof system of the Invention from a gable end. 
         FIG. 2  is a detail side view of the ventilated roof system of the invention. 
         FIG. 3  is a detail cross section side view of the eave of the ventilated roof system. 
         FIG. 4  is a detail cutaway perspective view of the eave of ventilated roof system. 
         FIG. 5  is a detail cross section view of the ventilated roof system viewed parallel to a rafter. 
         FIG. 6  is a detail cross section side view of the ridge of the ventilated roof system. 
     
    
    
     V. DESCRIPTION OF AN EMBODIMENT 
       FIGS. 1 through 6  illustrate the construction and operation of the ventilated roof system  2  of the Invention.  FIG. 1  presents an overview of the ventilated roof system  2  in cross section from a gable end. A building  4  has a plurality of rafters  6  that support the ventilated roof system  2 . The building  4  and ventilated roof system  6  defines an attic  8 . The attic  8  includes insulation  10  to slow heat transfer between the interior of the building  4  and the outside air  12 . Because of the ventilated roof system  2  of the Invention, the insulation may be packed into the eave  14  without blocking ventilation of the ventilated roof system  2  and without damage to the building  4 . The rafters  6  have a pitch between the eave  14  and the ridge  16 . The pitch of the rafters  6 , and hence of the ventilated roof system  2 , causes rain water, snow and debris to tend to run off of the ventilated roof system  2 . 
     The ventilated roof apparatus  2  includes a sub-deck  18  that is attached to and supported by the rafters  6 , generally by nails penetrating through the sub-deck  18  and extending into the rafters  6 . The sub-deck  18  is composed of plywood, oriented strand board or dimensioned lumber that sheathes the top surface of the rafters  6 . 
     The sub-deck supports a sheet of barrier fabric  20  that covers the sub-deck  18 . The barrier fabric  20  is composed of a non-woven polymer that is permeable to water vapor  22  ( FIG. 2 ) but is not permeable to liquid water under the conditions that the barrier fabric  20  can reasonably be expected to encounter. Examples of suitable barrier fabric  20  are Tyvek® Home Wrap®, Tyvek® Attic Wrap, both by Dupont, and Typar® House Wrap by Polymer Group, Inc. Tyvek® Attic Wrap includes a reflective coating that assists in slowing the movement of heat between the outside air  12  and the building interior. 
     Furring strips  24  are attached to the barrier fabric  20 , sub-deck  18  and the rafter  6 , generally by nails penetrating the furring strips  24 , barrier fabric  20 , sub-deck  18  and extending into the rafters  6 . The furring strips  24  extend from the eave  14  to the ridge  16 . The furring strips  24  may be composed of any suitable material, but 2×3 or 2×4 dimensioned lumber has proven suitable. 
     The deck  26  is attached to the furring strips  24 . The deck  26  is composed of plywood, oriented strand board or dimensioned lumber. Shingles  28 , as defined above, are attached to the top surface of the deck  26  and provide a barrier to weather. The furring strips  24  separate the sub-deck  18  and the deck  26  so that the deck  26  and sub-deck  18  are in a spaced-apart relation  30 . Where the furring strips  24  are 2×3 or 2×4 dimensioned lumber, the deck  26  and sub-deck  18  are separated by 1.5 inches, which has proven suitable in practice. Any other suitable thickness for the furring strips  24  and hence the spaced-apart relation  30  of the deck  26  and sub-deck  18  may be used, provided that the separation is large enough to allow adequate ventilation of the deck  26  and is small enough to avoid an unpleasant appearance of the ventilated roof system  2 . 
     The spaced-apart relation  30  of the deck  26  and sub-deck  18  defines ventilation channels  32  extending from the eve  14  to the ridge  16 . A suitable intake vent  34  allows ambient air  12  to enter the ventilation channels  32  proximal to the eave  14 . A suitable exhaust vent  34  allows air to exit the ventilation channels  32  proximal to the ridge  16 . While any intake  30  may be used, the RafterVent by DCI Products, 415 South Penn Street, Clifton Heights, Pa. 19018 has proven suitable in practice for the intake vent  34 . While any exhaust vent  36  may be used, the SmartRidge I and SmartRidge II exhaust vents by DCI Products are suitable for the exhaust vent  36 . 
       FIG. 2  illustrates the operation of the ventilated roof system  2  for control of water vapor  22  from the interior of the building  4 . Water vapor  22  escapes into the air  12  on the interior of the building from the building occupants, from plumbing systems, from cooking and bathing, and from the soil underneath the building  4 . If the water vapor  22  is not controlled, it will condense and promote mold growth and damage to the building  4 . The water vapor  22  penetrates the walls, floors and ceilings of the building  4  and will be present in the attic  8 . The water vapor  22  in the attic penetrates the sub-deck  18  and the barrier fabric  20  and enters the ventilation channels  32 . The water vapor  20  laden air  12  is exhausted through the exhaust vents  36 , avoiding condensation within the building and the consequences of inadequate ventilation. 
     As shown by  FIG. 2 , the barrier fabric  20  also serves as a secondary barrier to the intrusion of water through the shingles  28  and deck  26  and into the interior of the building  4 . If liquid water from rain or snow manages to penetrate the shingles  24  and the deck  26 , the liquid water encounters the barrier fabric  20  through which it cannot pass. The liquid water flows on top of the barrier fabric  20  downward to the eave  14 , where the liquid water is discharged outside the building  4 . The presence of the barrier fabric  20  thus protects the building  4  from intrusion by liquid water should the shingles  28  be damaged due to mishap or age. 
     The construction of the ventilated roof system at the eave  14  is illustrated by  FIGS. 3 and 4 .  FIG. 4  is a cross section of the ventilated roof system  2  at the eave  14 .  FIG. 5  is a partial perspective cutaway of the ventilated roof system  2  at the eave  14 . From  FIGS. 3 and 4 , the sub-deck  18  terminates at the end of the rafter  6 , where it meets a sub-fascia  40 . The sub-fascia board  40  covers the end of the rafters  6 . The sub-fascia  40  and the soffit  42  in cooperation define a closed eave. Where the ventilated roof system  2  of the Invention is retrofitted to an existing roof, the sub-fascia  40  may be the fascia board of the existing roof. The barrier fabric  20  on top of the sub-deck  18  extends beyond the lower edge of the sub-deck  18  to define an overhang  44  that drapes over the sub-fascia  40 . The overhang  44  prevent liquid water, for example liquid water from an overflowing gutter, from entering the building  4  through the junction of the sub-fascia  40  and the sub-deck  18 . 
     The intake vent  34  is attached to the sub-fascia  40 , with the overhang  44  disposed between the intake vent  34  and the sub-fascia  40 . The intake vent  34 , in this instance a RafterVent by DCI Products, allows air  12  to pass through many small channels defined by the intake vent  34 . The air  12  moves as indicated by arrows  38 . The air  12  moves through the intake vent  34  due to solar heating of air  12  within the ventilation channels  32  or due to warming of the air within the ventilation channels  32  due to escaped building heat. The warmed air  12  is less dense than cooler air  12  outside of the building  4  and tends to rise toward the ridge  16 , where the air discharges from the exhaust vent  36 . 
     Also from  FIGS. 3 and 4 , the lower end of the ventilation channels  32  are closed by a fascia  46 , which also covers the intake vent  34 , hiding the intake vent. Flashing  48  prevents liquid water from entering the building  4  at the junction of the fascia  46  and the deck  26 . 
       FIG. 5  illustrates the operation of the furring strips  24  and is an end view of the ventilated roof system  2  in section. From  FIG. 5 , the furring strips  24  have a height that defines the spaced-apart relation  30  of the deck  26  and the sub-deck  18 . The height of the furring strips  24  also prevents nails securing the shingles  28  to the deck  26  from damaging the barrier fabric  20 . 
       FIG. 6  illustrates the ventilated roof system  2  at ridge  16 . The ridge  16  is a high location on the ventilated roof system  2  and air  12  moves through the ventilation channel  32  and discharges through the exhaust vent  36 . The exhaust vent  36  illustrated is a SmartRidge I by DCI Products, but any suitable exhaust vent  36  may be used. 
     From  FIG. 6 , the barrier fabric  20  extends over the entire surface of the sub-deck  18  and extends over the ridge  16 . If the ventilated roof system  2  of the invention is installed on an existing roof, the sub-deck  18  is defined by the original roof deck of the roof being replaced. That original roof deck may define openings at the ridge for ventilation. The extension of the barrier fabric  20  over those openings in the original roof deck ensures that liquid water cannot enter the building through the openings. 
     LIST OF NUMBERED ELEMENTS 
     
         
         ventilated roof system  2   
         a building  4   
         rafter  6   
         attic  8   
         insulation  10   
         outside air  12   
         eave  14   
         ridge  16   
         a sub-deck  18   
         a barrier fabric  20   
         water vapor  22   
         furring strips  24   
         a deck  26   
         shingles  28   
         a spaced apart relation  30   
         a ventilation channel  32   
         an intake vent  34   
         an exhaust vent  36   
         arrows  38  indicating movement of air 
         sub-fascia  40   
         soffit  42   
         an overhang  44   
         fascia  46   
         flashing  48