Vent Pipe Cap for Metal Roof

The present invention pertains to the field of construction. More specifically, the invention comprises a cap for shielding a plumbing vent pipe that penetrates a metal roof.

depicts an exemplary type of prior art metal roof. Metal roof panelincludes flats,and a series of evenly spaced ribs,,. Such panels are usually much longer—10 to 20 feet long—but the cross section is uniform for the entire length.shows only a portion of such a panel, but it serves to illustrate the challenges present in the prior art and the advantages offered by the present invention.

Plumbing drain pipes are generally equipped with a vertically-extending vent pipe. Such vent pipes equalize pressure in the drain system and carry sewage odors outside the structure. Most such vent pipes extend vertically through the roof structure.shows such an installation. Once the location of the vent pipe is determined, openingis cut through the metal roof panel. A tool such as a reciprocating saw is often used—with the result that the opening is somewhat irregular. Vent pipeis then installed, with a portion of the vent pipe sticking up through the roof panel.

It is necessary to create a seal between the vent pipe and the roof structure. For a shingle roof, a metal or plastic flashing piece is usually tucked under the shingles on the slope above the vent pipe and sealed over the top of the shingles in the area below the vent pipe. This is a fairly simple and effective process. The example of, however, illustrates a problem that is often encountered for metal roofs. The roof panels are typically installed before the vent pipes are added. Thus, the location needed for a vent pipe may well intersect one of the ribs. As shown in, openingpasses through portions of flat, rib, and flat. The complex nature of the gap creates a sealing challenge.

shows a known prior art solution for this problem. Tapered boothas a pliable rubber side wall that can be cut to stretch and slip over vent pipe. The lower edge of the boot is bonded to metal flange. The metal flange is thin and bendable. It can usually be bent by hand to conform to the complex shape of the flats,and rib. A large number of fasteners (usually sheet metal screws) are then passed through flangeand into the metal roof panel to hold it secure. Caulk or other sealant is then liberally applied to the joint between the flange and the roof panel and the joint between the tapered boot and the vent pipe.

The system depicted does work, but it is cumbersome and labor intensive. It is also somewhat unsightly when finished. The present invention provides a solution for this problem that is easier to install and more pleasing in its finished appearance.

The present invention comprises a roofing vent cap that is configured for use on a metal roof. The inventive vent cap includes a rib receiver designed to fit closely over a metal roof panel rib. Two lateral shoulders are preferably provided to increase the footprint and internal volume of the hollow vent cap. These lateral shoulders allow the vent pipe to be laterally displaced from the roofing panel rib while the vent cap remains centered on the rib.

depicts the problem to be addressed-a vent pipeprotruding through an openingin a metal roof panel.depicts an embodiment of the present invention installed over the vent pipe and opening. Vent capis a hollow structure configured to secure to the metal roof panel-including lying over one of the upstanding ribs.

The roof panel has a slope, though the slope is not great for the example shown. “Downslope” is the direction water travels under the influence of gravity as it travels off the roof panel. “Upslope” is the opposite direction. First and second lateral direction are orthogonal to the upslope/downslope directions.

Central portionin this example is a hollow “box” structure with an open bottom that fits over the roof panel. Openingis provided—in this case on the downslope side of the vent. Overhangis preferably provided to shield the opening and prevent the ingress of rain. Shoulderextends laterally from a first side of central portionand shoulderextends from the opposite side. The two shoulders expand the interior volume of the hollow structure and provide additional room for possible misalignment of the vent pipe—as will be explained.

Flangeextends outward from the lower portion of the hollow structure. Most of the flange is flat so that it can lay against the flats of the roof panel. However, rib receiveris provided in the flange and adjacent structures in order to accommodate ribof the roofing panel. The ribs on the roofing panel have standard dimensions. Rib receiveris sized to fit snugly over the ribs of the roofing panel. The rib receiver runs all the way from the downslope to the upslope side of the vent cap-though not of course in the hollow central portion where no relief for the upstanding rib is needed. Only the downslope portion of the rib receiver is visible in.

shows the same assembly with half of the vent cap cut away to reveal internal features. The reader will note how the rib receiver fits snugly over the upstanding rib. The reader will also note how central portioneasily accommodates the protruding vent pipe. The vent cap is preferably a thin-walled hollow structure so that the internal volume is maximized. Its internal dimensions are made large enough in the upslope/downslope directions to provide good clearance for the pipe and accommodate any installation errors. The internal dimensions are made even larger in the lateral directions.

illustrates the advantage of providing more lateral internal volume.is looking along the plane of the roof panel in the upslope direction. Vent pipeis installed vertically, which causes it to appear tilted away from the viewer when looking along the plane of the sloping roof panel. The portion of the vent pipe protruding into the inventive vent cap is shown as a hidden line. Shoulderextends away from central portionin a first lateral direction and shoulderextends away in a second lateral direction.

The vent cap functions well with the vent pipe located anywhere within the interior volume. No matter the location of the vent pipe, gasses escaping from the vent pipe will exit opening. However, extending the coverage of shoulders,allows a vent pipe that is farther and farther from the rib on which the inventive vent cap is mounted to be accommodated. In the example shown, rib receiveris provided on the centerline of the inventive vent cap. The reader will appreciate that the vent cap can slide easily along the rib in the upslope/downslope direction, but it cannot move laterally because of the interface between rib receiverand the rib on which the vent cap is mounted.

shows a vent pipethat is offset a greater distance from ribthan was the case in the example of. The presence of shoulderaccommodates this greater offset.shows a lateral view of the same assembly—with the plane of the roof vent panel again being oriented horizontally (though it is of course sloped in the actual installation). Vent pipeis again installed vertically—but appears at an angle because of the view being referenced to the roof panel. The portion of the vent pipe extending into vent capis again shown in hidden lines. The reader will note how adequate clearance is provided in the upslope/downslope directions. This clearance allows for installation errors.

shows a plan view of the same installation-looking down on the plane of the roof panel. The reader will note how flangeruns entirely around the lower portion of the hollow structure. Centerlineis an axis running through the middle of this example. Rib receiverin this example is provided along centerline.

Looking back at, the reader will note that-even with the presence of shoulders,—there is a limit to how much lateral displacement of vent pipefrom ribcan be accommodated. The inventive vent cap can only be placed upon a rib for lateral positioning. Thus, while one can lift it and move it over to the next rib—this will not always accommodate a large vent pipe such as shown inthat is laterally displaced too far from the rib on which the vent cap is mounted. Thus, it is desirable to provide an embodiment with additional lateral capacity.

depicts such an embodiment. Shoulders,include a vertical portion extending up from flangeand a sloping portion that joins central portion. This version increases the lateral displacement of the vent pipe that can be accommodated within the interior volume.illustrates this principle.

In the example of, vent pipehas a diameter w. It is offset from riba distance x. The ribs on the roofing panel have a standard fixed pitch y (the distance from the center of one rib to the center of the next rib). The maximum displacement of the center of the vent pipe from any rib is therefore given by the expression:

2

Shoulders,are offset from the centerline of the vent cap a distance z. In order to accommodate every possible lateral offset of the vent pipe, it is preferable to make z according to the following equation:

where t is the thickness of the wall of the vent cap in the vicinity of the vent pipe. Using this expression as a guide for the vent cap dimensions ensures that you can fit the vent pipe within the vent cap at the current rib installation location (or move the vent cap over to the next rib and install it there).

Some additional explanation as to the installation of the vent cap is helpful. In the view of, the reader will note how flangeconforms to the shape of the flats and ribs of the roof panel. Fastenersare installed through flangeand the roof panel. Holes can be provided in the flange to receive the fasteners. Alternatively, the flange can be made of a material that allows self-tapping or other fasteners to be driven through without the provision of pre-existing holes through the flange.

A seal between the flange and the roof panel is important, particularly on the upslope side. An adhesive or sealant can be applied to the underside of the flange before the vent cap it pressed down into position. The adhesive/sealant can even be applied as part of the manufacturing process and covered by a removable strip. The strip would be removed just prior to installation.

Compressible butyl tape is a particularly effective sealant. This substance has been used in the roofing industry for many years and its performance and endurance is well established. Double-sided butyl tape is preferably adhered to the downward-facing surfaces of the flange. The downward-facing surface of the butyl tape is then covered by a removable strip. The strip is left in place while the vent pipe cap is test fitted. When it is time to permanently install the cap, the strip is removed and the tape is pressed against the roofing panel. Securing screws can then be driven through the flange, the butyl tape, and the roofing panel. The screws are tightened to compress the tape and secure a good seal.

Alternatively, the vent cap can be screwed in place and the adhesive/sealant can be added after the mechanical installation is complete. The invention is not limited to any particular method of installation. Many other methods will occur to those skilled in the art.

The invention can assume many other forms incorporating desirable features in different combinations.provides an alternate embodiment of the inventive vent cap. The vantage point is from the up slope side of the installation. In this embodiment, a flow-directing feature is provided to the up slope side of the vent cap. Cricketdivides the water flow coming down the roof and helps it split and flow around the vent cap without pooling against the uphill side of the vent cap. The “vee” shape is commonly called a cricket in the field of roofing. Many other shapes can be employed for the cricket, so long as they direct the water around the vent cap. The reader will note how flangeand rib receiverconform to the shape of the cricket used.

The rib receiver provided in a particular embodiment is preferably shaped to fit closely over a particular type of rib. As those skilled in the art will know, many different rib types are used in roofing panels.provide sectional elevation views through two very different types of ribs.shows convoluted rib. A corresponding rib receiveris provided to approximate the shape of the convoluted rib. Butyl tapeis compressed between the rib receiver and the convoluted rib. The butyl tape is quite compressible-allowing it to accommodate some mismatch between the shape of the rib receiver and the shape of the convoluted rib.

shows a rib created by a junction in a standing seam metal roof-designated as standing seam rib. Rib receiveris provided to conform to the shape of the standing seam rib. Butyl tape is again provided. The reader will note how a very different shape of the rib receiver is provided inas compared to the example of. Many different shapes for the rib receiver can be provided and the invention is not limited to any particular shape.

shows a section view through another embodiment of the inventive vent cap. This embodiment features a more horizontally-oriented opening(covered by screen or mesh), contained within setback. Drip railis provided so that even a hard rain will not tend to drip into the opening. Many other shapes and locations for these features are possible.

Most embodiments of the inventive vent cap will include thin walls surrounding a hollow interior. This results in the vent cap having a low overall density. Such bulky but light items are inefficient for shipping and storage. It is beneficial to provide an alternate design that can be nested and stacked-thereby increasing storage and shipping efficiency.shows such an embodiment. The inventive vent capsshown include thin walls surrounding a hollow interior. All of the side walls are given a suitable draft angle so that they tilt inward when proceeding from bottom to top. Suitable fillet radii are preferably also provided on the corners. These features allow multiple instances of the vent capto be stacked as shown. The instances can be urged together until central portionof the lower instance bears against setbackof the upper instance. Even deeper nesting can be provided by eliminating the use of setback.

Many other variations are possible for the inventive embodiments. As an example, the inventive vent pipe cap can be made with tapering sidewalls so that multiple instances of the invention can be stacked for storage and shipping. Metal versions can be provided using galvanized steel. Injection-molded plastic versions can be provided. Still other versions can be pressed from sheet molding compound.

The preceding description contains significant detail regarding the novel aspects of the present invention. It should not be construed, however, as limiting the scope of the invention but rather as providing illustrations of the preferred embodiments of the invention. Thus, the scope of the invention should be fixed by the claims ultimately drafted, rather than by the examples given.