US20180058072A1

US20180058072A1 - Venturi Ridge Vent

Info

Publication number: US20180058072A1
Application number: US15/677,280
Authority: US
Inventors: John C. Henderson; Stephen C. Henderson
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-08-24
Filing date: 2017-08-15
Publication date: 2018-03-01
Also published as: CA2977091A1

Abstract

A venturi ridge vent has an air-permeable vent body configured for mounting at the ridge of a pitched roof. The vent body defines a first opening and an opposing second opening and defines a flow path for air moving between the first and second openings. The first and second openings are disposed on opposing sides of the ridge when the vent body is mounted to the roof. The flow path defines a throat intermediate to the first and second openings. The throat area is less than the first or second opening areas to define a venturi. The attic is in fluid communication with the flow path proximal to the throat when the vent body is mounted to the roof.

Description

I. STATEMENT OF RELATED APPLICATIONS

This application claims priority from U.S. Provisional Patent Application 62/378,985 filed Aug. 24, 2016 by John C. Henderson, which 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 to roofing ventilation. The Invention is a venturi ridge vent for use at the ridge of a pitched roof. The Invention utilizes the venturi effect to reduce the air pressure at the ridge to draw more air from under the roof deck than would otherwise be the case.

B. Statement of the Related Art

As used in this document, the term ‘roof’ refers to the top portion of a building that separates the attic of the building from the outside air and that protects the building from the elements. The term ‘attic’ refers to an air space under a roof. ‘Attic’ also includes the air space between a ceiling and a roof deck of a building having a cathedral ceiling. A roof is protected by a durable, weather-resistant surface, such as shingles. As used in this document, ‘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-proof product that may be applied to a pitched roof.
A roof deck supports the shingles. As used in this document, a ‘roof deck’ means the generally planar structure 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 tarpaper 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 location on a roof where a roof deck intersects another roof deck and for which the included angle of the intersecting roof decks under the roof is less than 180 degrees. The ridge has a ‘ridge first side’ on one of the intersecting roof decks. The ridge has an opposing ‘ridge second side’ on the other of the intersecting roof decks.
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 so that water running from each shingle flows onto the adjacent downhill shingle. The underlayment and shingles cooperate to form a composite surface that is tight to rain water, snowmelt and water vapor.
Rafters extend from the eave to the ridge of the roof and support the roof deck. A ridge board extends along the ridge under the roof deck. The upper ends of the rafters are attached to the ridge board.
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 attic must be ventilated. Ventilation also serves to allow air heated by solar gain to escape from the attic, reducing the cooling load on the building.
For ventilation of a pitched roof at the ridge, the intersecting roof decks may include one or more ‘attic openings.’ For the purposes of this document, an ‘attic opening’ is an opening through the roof that provides fluid communication between the air in the attic and the air outside the building. The attic opening may be in the form of one or more slots at or adjacent to the ridge. A ridge vent may be interposed between the attic opening and the outside air to prevent entry into the attic by water, insects and debris while allowing air to exit the attic.
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 in volume under Charles' Law. The warm air is light and buoyant and floats on cooler, denser air entering the attic space through eave vents. Because the roof is pitched, the warm air rises along the roof deck toward the ridge of the roof. The warm, buoyant air can be released from the attic at the ridge by the ridge vents.
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 airflow through the air-starved attic space may cause the problems associated with excess moisture.
The present invention is not taught by the prior art.

III. BRIEF DESCRIPTION OF THE INVENTION

The venturi ridge vents of the invention utilizes the venturi effect to reduce the air pressure above the attic opening at the ridge to pull more air from the attic than would otherwise be the case. The source of energy for the venturi ridge vent is ambient air blowing across the ridge of the roof.
The venturi ridge vent includes a vent body that is air-permeable and that defines a first opening and a second opening. When the venturi ridge vent is installed on a roof at the ridge, the first opening is disposed on a first side of the ridge and the vent second opening is disposed on the opposing second side of the ridge. The two openings are in fluid communication with each other so that air blowing across the roof may enter the first opening, travel along a flow path defined by the vent body, and exit through the second opening.
Of course, depending on the wind direction the air can travel from the second opening to the first opening. For the purposes of explanation, this document will describe the flow of air from the first to the second opening. All statements herein apply equally to air flowing from the second opening to the first opening.
The vent body defines a throat in the flow path between the first and second openings. The first opening, the second opening, and the throat each defines a cross-sectional area. The area at the throat is less than the area of the first opening and the second opening. The throat therefore defines a venturi. From the principle of mass conservation, the velocity of the air will increase as the air travels from the relatively large first opening through the relatively small throat, and then will decrease as the air continues to the relatively large second opening. From the Bernoulli relation, the air pressure at the throat and transverse to the direction of air travel is reduced with the increase in velocity of air traveling along the flow path and through the throat. The attic opening communicating between the attic space and the venturi ridge vent coincides with the location of increased air velocity; namely, the throat of the venturi. The air within the attic therefore sees the reduced pressure at the throat. The higher ambient air pressure acting at the eave vents pushes the air within the attic through the attic opening at the ridge. In short, due to the venturi effect, wind blowing across the roof pulls air from the attic, even if the air is not heated and is not buoyant.
If the air within the attic space is somewhat warm and buoyant, the somewhat buoyant air further defines the throat of the venturi, restricting the size of the venturi at the throat and hence increasing the velocity of the air moving through the venturi from one opposing opening to the other. The increase in velocity results in a decrease in air pressure transverse to the throat, providing a greater air pressure gradient between the eave and the ridge to pull attic air from the attic space.
For decreasing wind speeds and increasing attic air temperatures, at some point the pressure differential caused by the buoyancy of the attic air overwhelms the flow of air between the first and second openings and reduces or stops the flow of air between the two openings. The air from the attic flows toward the one of the opposing first and second openings having the lowest pressure, which is the second opening.
With further increases in attic air temperatures and little or no wind, the hot, buoyant air from the attic space overwhelms the energy of the wind and flows out through both of the opposing first and second openings.
The venturi ridge vent may define a shingle support that is configured to support shingles in a spaced-apart relation to the two intersecting roof decks at the ridge and to allow air to flow between the roof decks and the shingle support. The venturi ridge vent may be attached to the ridge by a nail penetrating the shingle support and roof deck. The shingle support and the roof deck then define the first and second openings and the area of the first and second openings.
The cross-sectional area of the first and second openings and of the throat generally are defined by the height of the first and second openings and of the throat and by the length of the vent body. The vent body may be elongated and have a longitudinal axis. When the vent body is mounted to the roof deck, the longitudinal axis is oriented parallel to the ridge. The Invention contemplates any and all differences in cross-sectional area between the two opposing openings and the throat of the venturi that will increase the velocity of air in the venturi as the air travels between the first and second openings above the velocity that would be achieved without the venturi effect created by the difference in cross-sectional area.
The height of the vent body and hence the cross-sectional area of the flow path for air moving between the first and second openings may decrease in a tapered manner from the first and second openings to a minimum at the throat. For this embodiment, the shingles attached to the vent body are not parallel to the roof decks defining the ridge, which some persons may find to not be aesthetically pleasing. To cause shingles supported by the vent body to be parallel to the roof decks when the vent body defines a tapered flow path, the top side of the vent body may include a shim. The shim is disposed above the air flow path defined by the vent body so that the thickness of the vent, including the vent body and the shim, is substantially equal for all locations where the vent body is attached to the intersecting roof decks and so that the shingles supported by the shim are substantially parallel to the corresponding roof decks.
An air-permeable, non-woven fabric may cover the opposing first and second openings to prevent entry of insects, debris, water or snow into the attic space. The non-woven fabric may include a multiplicity of small perforations to increase the permeability to air of the non-woven fabric.
The vent body may be composed of any suitable material, such as corrugated plastic, a molded plastic, wood, paper, metal, a three-dimensional entangled web structure made of continuous monofilaments fused where the monofilaments intersect, or any other suitable material.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end view of the venturi ridge vent mounted to the ridge of a roof.

FIG. 2 is a perspective view of the venturi ridge vent mounted to a roof.

FIG. 3 is an end view of the venturi ridge vent.

FIG. 4 is an end view of the venturi ridge vent bent to conform to the ridge.

FIG. 5 is a perspective view of the underside of the venturi ridge vent.

FIG. 6 is a perspective view of the underside of the venturi ridge vent with non-woven fabric having perforations.

FIG. 7 is an end view of a second embodiment of the venturi ridge vent to achieve parallel shingle supporting surfaces and roof decks.

FIG. 8 is an end view of the venturi ridge vent.

FIG. 9 is a second end view of the venturi ridge vent.

FIG. 10 is a third end view of the venturi ridge vent.

V. DESCRIPTION OF AN EMBODIMENT

FIGS. 1-6 illustrate a first embodiment of the Invention. FIG. 1 is an end view of the venturi ridge vent 2 installed on a pitched roof 4 and FIG. 2 is a perspective view of the venturi ridge vent 2 on the roof 4. The roof 4 comprises rafters 6 that support opposing roof decks 8 that intersect at a ridge 10. A ridge board 12 is disposed between the rafters 6 at the ridge 10. The opposing roof decks 8 define an attic opening 14 that communicates with the attic 16 and the attic air 18 within the attic 16. The roof decks 8 are covered by shingles 20 to define weather-tight composite surfaces.
The venturi ridge vent 2 includes a vent body 22. The vent body 22 is mounted to the roof 4 at the ridge 10 by nailing the vent body 22 to the two opposing roof decks 8 or by any other suitable mechanism, such as screws or an adhesive. The vent body 22 defines a vent first side 24 and a vent second side 26. When the vent body is mounted to the roof 4 at the ridge 10, the vent first side 24 is disposed on the ridge first side 28 and the vent second side 26 is disposed on the opposing ridge second side 30. The vent body 22 defines a first opening 32 on the vent first side 24 and an opposing second opening 34 on the vent second side 26. The first and second openings 32, 34 are in fluid communication with each other and with the attic opening 14 when the vent body 22 is mounted to the roof 4 at the ridge 10.
FIG. 3 shows an end view of the venturi ridge vent 2 that is not yet conformed to a ridge 10. FIG. 4 is an end view of the venturi ridge vent 2 of FIG. 2, but with the venturi ridge vent 2 bent to conform to the ridge 10 of the roof 4. The venturi ridge vent 2 is elongated in the direction normal to the plane of the page of the end views of FIGS. 1, 3 and 4. The vent body 22 defines a longitudinal axis 36 in the elongated direction. The longitudinal axis 36 is oriented parallel to the ridge 10 when the vent body 22 is mounted to the roof 4 at the ridge 10. The venturi ridge vent 2 may include a shingle support 38 disposed between the vent body 22 and the shingles 20. The shingle support 38 provides even support for the shingles 20 and provides a nailing surface for attachment of the shingles 20 to the vent body 22 and the vent body 22 to the roof 4. The venturi ridge vent 2 may be rolled for convenience of transportation, handling and storage prior to installation on the roof 4.
When the venturi ridge vent 2 is mounted to a ridge 10 and as shown by FIG. 1, the roof decks 8 and the shingles 20 or shingle support 38 in cooperation define a flow path 40 for air 42 through the vent body 22 between the first opening 32 and the second opening 34. As shown by FIG. 3, the first opening 32 has a first opening height 44 and the second opening 34 has a second opening height 46. The first and second opening heights 44, 46 are the heights of the flow path 40 at the two openings 42, 34 that are available for air 42 to move through the vent body 22. The roof decks 8 and the shingles 20 or shingle support 38 in cooperation also define a throat 48 in the flow path 40 intermediate to the first and second openings 32, 34. The throat 40 has a throat height 50 that is less than the first opening height 44 and the second opening height 46.
The vent body 22 has a length 52 parallel to the ridge 10 when the vent body 22 is mounted to the ridge 10. The length 52 in combination with the first opening height 44 defines a first opening area 54. The length 52 in combination with the second opening height 46 defines a second opening area 56. The length 52 in combination with the throat height 50 defines a throat area 58. The first and second opening areas 54, 56 and throat area 58 define the cross-sectional areas through which air 42 travels when the air 42 moves along the flow path 40. The throat area 58 is less than the first opening area 54 and the second opening area 54.
When wind 60 blows across the roof so that a component of motion of the wind 60 is in a direction 62 transverse to the ridge 10 of the roof 4, a portion of the kinetic energy of the wind 60 is converted to air pressure energy on the roof deck 8 toward the wind 60. The first opening 32 in the venturi ridge vent 2, which faces the wind 60, experiences the increased air pressure of the roof 4 deck toward the wind 60. The second opening 34, which faces away from the wind 60, experiences a reduced air pressure. The difference in air pressure between the first and second openings 34, 38, combined with the kinetic energy of the wind 60 striking the first opening 32, causes air 42 to flow through the flow path 40 from the first opening 32 to the second opening 34.
As shown by FIGS. 1 and 3-6, the flow path 40 of the air 42 traveling through the vent body 22 narrows because the throat area 58 is less than the first opening area 54 and the second opening area 56. As the air 42 reaches the throat 48, the velocity of the air 42 increases as the pressure energy of the air 42 is converted to kinetic energy due to the principal of mass conservation. Past the throat 48, the kinetic energy of the air 42 is converted back to pressure energy as the area through which the air 42 must pass increases. The flow path 40 therefore defines a venturi.
From the Bernoulli relation, at the throat 48 where the velocity of the air 42 is increased, the air pressure transverse to the direction of airflow is reduced from what it otherwise would be. The throat 48 of the venturi ridge vent 2 coincides with the attic opening 14 defined by the intersecting roof decks 8 and communicating with the attic 16. The reduced air pressure at the throat 48 pulls the attic air 18 through the attic opening 14 and out through the second opening 34. The result is that the venturi ridge vent 2 more effectively exhausts attic air 18 from the attic 16 than would otherwise be the case, including attic air 18 that is not warmed and is not buoyant.
FIG. 5 is a perspective view of the underside of the venturi ridge vent 2 of FIGS. 1, 3 and 4 showing the tapered nature of the venturi ridge vent 2. The vent body 22 defines the flow path 40, shown by FIGS. 1 and 7. The flow path 40 has a flow path height 74, shown by FIG. 7. For the tapered embodiment, the flow path height 74 decreases in a tapered manner between the first opening 32 and the throat 48, and then increases in a tapered manner between the throat 48 and the second opening 34.
FIG. 6 is a perspective view of the underside of the venturi ridge vent 2 of FIG. 4 showing an air-permeable fabric 64 in place covering the first and second openings 32, 34 to prevent the entry of insects, water or debris when the venturi ridge vent 2 is installed on a roof 4. The air-permeable fabric 64 of FIG. 5 may include a multiplicity of small perforations 66 to increase the permeability of the air-permeable fabric 64. The permeability of the air-permeable fabric 64 may be adjusted to meet a particular application by selecting the size and density of the multiplicity of perforations 66.
FIG. 7 is an end view of another embodiment of the Invention. In FIG. 7 the venturi ridge vent 2 defines a vent thickness 72 that is substantially the same at each location at which the vent body 22 contacts the roof deck 8. As a result, the shingles 20 on either side of the ridge 10 are generally parallel to the corresponding roof deck 8. The reason for the parallel configuration is to avoid any negative aesthetic perception where the shingles 20 supported by the venturi ridge vent 2 and shingles 20 supported by the corresponding roof decks 8 are not parallel.
In the embodiment of FIG. 7, a barrier of reduced permeability 68 in cooperation with the roof decks 8 defines the tapered flow path 40 through the vent body 22. The barrier of reduced permeability 68 may be composed of air-permeable fabric 64, polymer, metal or any other suitable material. A shim 70 supports the shingle-supporting surface 18 above the barrier of reduced permeability 48. The shim and the barrier of reduced permeability 68 may be one and the same. The venturi ridge vent 2 may dispense with the shingle support 38 and the shingles 20 may be attached directly to the shim 70 and vent body 22.
FIG. 8 is an end view of one embodiment of the vent body 22. The vent body of FIG. 8 defines porous, air-permeable columns 76. The air permeable columns 76 of FIG. 8 support the shingles 20 or the shingle support 38 above the roof decks 8.
Air permeable fabric 64 may cover the first and second openings 32, 34 to prevent entry into the attic 16 of water, insects or debris. The air permeable fabric 64 is not required for the portion of the vent body 22 corresponding to the attic opening 14 to provide unobstructed flow of attic air 18 through the attic opening 14 to the venturi ridge vent 2.
The end views of FIGS. 9 and 10 present two additional profiles of the venturi ridge vent 2. The venturi ridge vent 2 of FIGS. 8, 9 and 10 is constructed and operates in the manner described in FIGS. 1 through 4 and as described herein. The dashed lines of FIGS. 9 and 10 represent areas where the air-permeable, non-woven fabric 64 is not located to allow attic air 18 unobstructed access to the venturi ridge vent 2 through the attic opening 14. The air-permeable, non-woven fabric 64 may be wettable or water-resistant and may be flame retardant.
The vent body 22, columns 76 of FIG. 8, or shim 70 of FIG. 7 may be composed of corrugated plastic, molded plastic, wood, metal, or any other suitable material.
Any of the components, features or configurations of any of FIGS. 1 through 10 may be applied to the features of any other of FIGS. 1 through 10 or otherwise described in this document.
Among the many materials from which the vent body 22, columns 76 and shim 70 may be composed is a three-dimensional entangled web structure made of continuous monofilaments fused where the monofilaments intersect. An example of the three-dimensional entangled web structure is Enkamat® ASV7010 available from Low & Bonar of 1301 Sandhill Rd, Ashville, N.C., US. The three-dimensional entangled web structure may be able to withstand roof temperatures of about 65 to 100 degrees C. The structure may include a thermoplastic material that may be, for example, a polyester polyolefin, or nylon. Exemplary materials for the entangled web structure include polypropylene, nylon 6 (or polyamide 6), polylactic acid, polycaprolactone, polyethylene, terephthalate, polybutylene terephalate, polytrimethylene terephalate, polyethylene naphthalate, vectran, high density polyethylene, and blends or copolymers thereof.
The polymer structure of the entangled web structure is formed by extrusion into a three-dimensional structure having a patterned configuration. For example, the entangled web structure may have a patterned configuration including pyramids, cones, waffles, cylinders, and the like. The patterned structure may create an air space. The air space may make up about 80% to about 99% of the entangled web structure. For example, about 85% to about 99%, or about 95% to about 98% of the entangled web structure is open air space. The entangled web structure may have a thickness on a range of from, for example, about 0.25 to about 4.0 inches, about 0.5 to about 3.0 inches, or about 0.75 to about 1.5 inches. The entangled web structure may have a basis weight in a range of from, for example, about 5 to about 25 ounces per square yard (osy), to about 10 to about 20 osy, or about 12 to about 18 osy. The entangled web may have a thickness of about 1.5 inches (38 mm) with a basis weight of about 15 osy. The thickness of filaments in the three-dimensional entangled web structure may be in the range of 0.1 to 2.5 mm, or in the range of 0.15 to 2.0 mm, or in the range of 0.2 to 1.5 mm, or in the range of 0.25 to 1.2 mm, or in the range of 0.25 to 0.75 mm. The patterned configuration may reduce in height from the first or second opening to the throat in order to achieve a venturi effect.
The following is a list of the numbered elements from the specification and drawings.

Venturi ridge vent 2
Pitched roof 4
Rafters 6
Roof decks 8
Ridge 10
Ridge board 12
Attic opening 14
Attic space 16
Attic air 18
Shingles 20
Vent body 22
Vent first side 24
Vent second side 26
Ridge first side 28
Ridge second side 30
First opening 32
Second opening 34
Longitudinal axis 36
Shingle support 38
Flow path 40
Air 42
First opening height 44
Second opening height 46
Throat 48
Throat height 50
Length 52
First opening area 54
Second opening area 56
Throat area 58
Wind 60
Direction 62 (transverse to the ridge)
Air-permeable fabric 64
Multiplicity of perforations 66
Barrier of reduced permeability 68
Shim 70
Vent thickness 72
Flow path height 74
Porous columns 76

Claims

I Claim:

1. A venturi ridge vent for mounting on a pitched roof, the pitched roof having a ridge and an attic opening communicating through said pitched roof proximal to said ridge, the venturi ridge vent comprising:

a. a vent body, said vent body being air-permeable, said vent body being configured to be mounted to the pitched roof at the ridge, said vent body having a configuration to support a shingle above said roof when said vent body is mounted to the roof at the ridge;

b. said vent body defining a vent first side and an opposing vent second side, said vent body being configured so that said vent first side is disposed on a ridge first side and said vent second side is disposed on an opposing ridge second side when said vent body is mounted to the pitched roof at the ridge;

c. said vent first side defining a first opening, said vent second side defining an opposing second opening, said first and said second openings being in fluid communication with one another and with the attic opening when said vent body is mounted to the roof at the ridge, said vent body defining a flow path for an air between said first opening and said second opening;

d. said first opening defining a first opening height and said second opening defining a second opening height, said flow path defining a throat proximal to said attic opening when said vent body is mounted to the roof at the ridge, said throat having a throat height, said throat height being less than said first opening height and said second opening height.

2. The venturi ridge vent of claim 1 wherein said vent body has a length, said length and said first opening height defining a first opening area, said length and said second opening height defining a second opening area, said length and said throat height defining a throat area, said throat area being less than said first opening area and said second opening area.

3. The venturi ridge vent of claim 2 wherein when said vent body is mounted to the roof at the ridge said air may pass along said flow path from a one of said first and second openings to another of said first and second openings, said air having a velocity, said velocity being greater at said throat than at said first opening and said second opening whereby said vent body defines a venturi.

4. The venturi ridge vent of claim 1 wherein said body is elongated, said body having a longitudinal axis, said longitudinal axis being parallel to the ridge when said body is mounted to the roof at the ridge and wherein said configuration of said vent body to support said shingle comprising: a shingle support, said shingle support being supported by said vent body, said shingle support being configured to receive a nail to secure said shingle support and said vent body to said roof, said shingle support in combination with the roof defines said first opening height, said second opening height and said throat height when said vent body is mounted to the roof at the ridge.

5. The venturi ridge vent of claim 1 wherein said vent body is elongated and defines a longitudinal axis, said vent body having a vent body height at each location between said first opening and said second opening, said vent body height narrowing in a tapered manner along said flow path between said first opening and said throat in a direction transverse to the ridge when said vent body is mounted to the roof at the ridge with said longitudinal axis parallel to the ridge, said vent body height increasing in a tapered manner along said flow path between said throat and said second opening in said direction transverse to the ridge when said vent body is mounted to the roof at the ridge with said longitudinal axis parallel to the ridge.

6. The venturi ridge vent of claim 5 wherein said configuration of said vent body to support said shingle comprises:

a. a barrier of reduced permeability, said barrier of reduced permeability being disposed between said vent body and said shingle when said vent body is mounted to the roof at the ridge, said barrier of reduced permeability and said vent body in combination defining said flow path; and

b. a shim, said shim being disposed between said barrier of reduced permeability and said shingle when said vent body is mounted to the roof at the ridge, said shim in combination with said vent body and said barrier of reduced permeability defining a vent thickness, said vent thickness being substantially equal for each location on said vent body that is in contact with the roof when said vent body is mounted to the roof at the ridge, whereby a shingle supported by said shim is generally parallel to the roof when said vent body is mounted to the roof at the ridge.

7. The venturi ridge vent of claim 6 wherein said shim and said barrier of reduced permeability are one and the same.

8. The venturi ridge vent of claim 6, said configuration of said vent body to support a shingle comprising: a shingle support, said shingle support being disposed between said shim and said shingle when said vent body is mounted on the roof at the ridge and said shingle is supported by said vent body.

9. A method of ventilating a pitched roof, the pitched roof having a ridge and an attic opening communicating through said pitched roof proximal to said ridge, the method comprising:

a. attaching a vent body to the roof at the ridge, said vent body being air-permeable, said vent body defining a first and an opposing second opening disposed on opposing sides of the ridge, said first and said second openings being in fluid communication with one another and with the attic opening, said vent body defining a flow path for an air between said first and said second openings, said flow path defining a throat intermediate to said first and second openings and proximal to said attic opening, said first opening defining a first opening height, said second opening defining a second opening height, said throat having a throat height, said throat height being less than said first opening height and said second opening height;

b. supporting a shingle by said vent body.

10. The method of claim 9 wherein said step of attaching said vent body to the ridge further comprises: providing that said first opening defines a first opening area, said second opening defines a second opening area and said throat defines a throat area, said throat area being less than said first or second opening area.

11. The method of claim 10 wherein an air may pass along said flow path through said vent body from a one of said first and second openings to another of said first and second openings in response to a wind transverse to the ridge, said air having a velocity, said velocity being greater at said throat than at said first opening and said second opening whereby said vent body defines a venturi.

12. The method of claim 10 wherein said step of attaching said vent body to the ridge further comprises: providing that said vent body is elongated and defines a longitudinal axis, said longitudinal axis being disposed parallel to the ridge of the roof, said vent body defining a shingle support, said shingle support being supported by said vent body, said shingle support receiving a nail securing said shingle, said shingle support and said vent body to said roof, said shingle support in combination with said roof defining said first opening height, said second opening height and said throat height.

13. The method of claim 10 wherein said step of attaching said vent body to the ridge further comprises: providing that said vent body defines a flow path height at each location between said first opening and said throat and between said throat and said second opening, said flow path height narrowing in a tapered manner between said first opening and said throat in a direction transverse to the ridge, said flow path height increasing in a tapered manner between said throat and said second opening in said direction transverse to the ridge.

14. The method of claim 10 wherein said step of attaching said vent body to the ridge further comprises:

a. providing a barrier of reduced permeability disposed between said vent body and said shingle, said barrier of reduced permeability and said vent body in combination defining said flow path; and

b. providing a shim, said shim being disposed between said barrier of reduced permeability and said shingle, said shim in combination with said vent body and said barrier of reduced permeability defining a vent thickness, said vent thickness being substantially equal for each location of said vent body that is in contact with the roof, whereby said shingle is parallel to the roof.

15. The method of claim 14 wherein said shim and said barrier of reduced permeability are one and the same.

16. The method of claim 10 wherein said step of attaching said vent body to the ridge further comprises: providing a shingle support, said shingle support being supported by said vent body, said shingle support receiving a nail to secure the shingle, said shingle support, and said vent body to the roof, said shingle support in combination with the roof defines said first opening height, said second opening height and said throat height.