An aerodynamic system attached to the outer side of the roof perimeter edge to mitigate wind generated vortices and uplift loads on the roof perimeter area of a building, applicable for both new constructions and retrofits of existing buildings. A roof edge guard is generally installed alongside a roof edge, and mounted onto an existing fascia or bargeboard. As an option most appropriate for new constructions, it can also be mounted directly onto a roof frame member in place of fascias or bargeboard. The configuration modifies the cross-sectional shape of otherwise abrupt roof edges that tend to generate strong vortex during high winds.

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is entitled to the benefit of Provisional Patent Application Ser. No. 60/559,285, filed 2004 Apr. 5. 


   SEQUENCE LISTING 
   Non-Applicable. 
   BACKGROUND 
   1. Field of Invention 
   This invention relates to an aerodynamic means that mitigate wind generated vortices and uplift loads on the roof perimeter area of a building, in a simple, effective, and economical way, applicable for both new constructions and retrofits of existing buildings. 
   2. Discussion of Prior Art 
   The previous and present roof construction practices normally lead to a roof perimeter configuration that tends to generate edge vortex and subjects the roof perimeter area to severe uplift and high risk of wind damage. Structural methods have been used to mitigate the risk of wind damage. For example, builders may use stronger fasteners or smaller fastener spacing for roof cover and deck in the roof edge and corner area, and use “hurricane straps” in lieu of toenails to tie down the roof framing to the wall structure. Some aerodynamic methods have been recommended, such as those disclosed in U.S. Pat. No. 6,601,348 of Banks et al. (2003), U.S. Pat. No. 4,005,557 of Kramer et al. (1977), and U.S. Pat. No. 5,918,423 of Ponder (1999). Banks et al. described various types of wind spoilers raised above the roof plane that function to mitigate edge vortex formation; however, the exposed structure is rather complicated, and is susceptible to wind damage itself because the raised structure subjects itself to accelerated airflow across the roof edge. Kramer et al.'s conceptions are essentially an earlier version of roof wind spoiler system that bears similar features to Banks et al. but its limited breadth impedes its effectiveness. Ponder disclosed a wind spoiler ridge cap that is specifically designed for protecting pitched gable roof ridges, while this present invention primarily deals with roof perimeter edges. 
   In U.S. Pat. No. 6,606,828 of this applicant et al., a series of roof edge configurations are recommended for use to mitigate vortex and high uplift in the roof perimeter areas, which are more suitable for flat and low-slope roofs that are often constructed with single ply membrane or built-up roofing. The present invention discloses roof edge configurations that are chiefly designed for deeper slope roofs that are often constructed with asphalt shingles, roof tiles and metal panels etc, and normally presented with different details at the roof perimeter. 
   SUMMARY OF THE INVENTION 
   This invention discloses an aerodynamic means that mitigate wind generated vortices and uplift loads on the roof perimeter area of a building, in a simple, effective, and economical way, applicable for both new constructions and retrofits of existing buildings. This is achieved by using a roof edge guard of an aerodynamic cross-sectional shape, attached to the outer side of the roof perimeter edge, as exemplified hereafter in the description section. The roof edge guard is generally installed alongside a roof edge, and mounted onto an existing fascia or bargeboard. As an option most appropriate for new constructions, it can also be mounted directly onto a roof frame member in place of fascias or bargeboard. The configuration modifies the cross-sectional shape of otherwise abrupt roof edges that tend to generate strong vortex during high winds. This invention is primarily applicable for gable, gambrel, mono-slope and overhung flat roof edges where there is no significant rainwater runoff. It is also applicable for roof edges where there is rainwater runoff but no draining devices such as a gutter system being installed, for example, the eaves of gable and hip roofs without gutters being attached thereon. 
   OBJECTS AND ADVANTAGES 
   Accordingly, several objects and advantages of the present invention are: 
   to provide roof edge configurations which reduce wind loads on the roof edge details; 
   to provide roof edge configurations which reduce wind loads on roofing materials, roof decks and framing in the roof perimeter areas; 
   to provide roof edge configurations which reduce wind uplift loads generally on a building structure that are transferred from the roof; 
   to provide roof edge configurations which reduce vortex scouring of roofing materials, such as asphalt shingles, roofing tiles, paver etc, and prevent them from becoming wind-borne missiles injuring people and damaging adjacent building envelopes during severe wind events; 
   to provide roof edge configurations which stabilize wind flow over the roof and minimize cyclic loads on roof components resulting from recurring winds, reducing the chances of damage due to material fatigues; 
   to provide roof edge configurations which prevent rainwater from being driven sideward and upward by wind turbulence and pressed through the gaps between roofing material and roof deck, and into the inner space of the roof assembly, during wind/rain events; 
   to provide roof edge configurations which possess the desired aerodynamic performance while maintaining an aesthetic and waterproofing functionality under both extreme and recurring weather conditions. 
   Further objects or advantages are to provide roof edge configurations which add an important function to a roof edge system, and which are still among the simplest, inexpensive to manufacture and convenient to install. These and still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  schematically illustrates the cross-sectional view of one of the preferred basic configurations formed with sheet material, as being installed on an overhung gable roof edge as an example. 
       FIG. 1B  shows a similar exterior configuration as being installed on a non-overhung gable roof edge as an example. 
       FIG. 2  illustrates a similar exterior configuration formed with solid material as an option. 
       FIGS. 3 ,  4  and  5  exemplify exterior shapes that have little compromises in functionality while providing alternative appearances for aesthetic purposes. 
       FIG. 6  illustrates an example to showcase the recommended installation option for situations where roof covering is wrapped downward around the roof deck edge, as often seen for metal roofing. 
       FIG. 7  demonstrates the usage of an example roof edge guard according to this invention for eave edges where no gutter system is used. 
       FIG. 8  schematically illustrates corrugated segments that can be formed on the outer face of the fascia member. 
   


   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A through 1C  illustrate one of the preferred basic configurations of the present A roof edge guard is generally an elongated assembly and is disposed longitudinally in parallel with a roof edge.  FIG. 1A  shows a cross-section view for one of the preferred configurations of the present invention, a roof edge guard  110  being installed on a gable-end overhang  10  of a roof structure. A typical roof overhang is a portion of a roof structure that is supported by and hangs over a wall  20  of a building, and extends substantially outwards beyond the outer wall surface  21 . The gable-end overhang  10  and associated components  11 ,  12 ,  13 ,  14 ,  15 , and  16 , as well as trim members  31  and  32 , are not part of this invention themselves, but are included here to illustrate their relationship with the edge guard  110  that is the subject matter of this invention. Some gable roofs do not have a gable-end overhang, as exemplified in  FIG. 1B , or do not have one as shown, nevertheless the spirit of the present invention holds wherever the herein-described aerodynamic roof edge guard may be installed properly on the gable edge of a roof. Moreover, although many of the examples in this application are illustrated for gable edges, the present invention is applicable on other types of roof edges, particularly for roof edges where there is no significant rainwater runoff. Examples of such roof edges include gable, gambrel, mono-slope (so-called lean-to), and overhung flat roof edges. For roof edges where there will be certain rainwater runoff, such as the eaves of various roof types including gable and hip roofs, this invention is also applicable if no water draining devices such as gutters are being used therein, as described later in this application. 
   The roof edge guard  110 , exemplified here as made of sheet material, consists of an upper face portion  111 , an intermediate face portion  112 , and a lower face portion  113 . The upper face portion  111 , disposed in close proximity to the outer edge  17  of the roof covering  11  and positioned flush, or at a reasonable angle within ±55°, with the plane of the roof covering  11 , facilitates a smooth wind flow across the roof edge, minimizing flow separation therein. Minor upward deviation or tolerance at installation is permissible for such roof edges where there is no significant rainwater runoff, to the extent that the upward deviation is not expected to cause debris clogging and accumulation along the roof edge. The lower face portion  113  is disposed with its edge above or in vicinity to the lower end of the bargeboard  14 , or onto the wall surface below the bargeboard as shown in  FIG. 1B  for non-overhung roof edges, and extends generally outwardly while also upwardly in this example. The intermediate face portion  112 , having one or more straight or curved segments, connects the lower and upper face portions in such a way that slope change across a junction between any adjacent two of the face portions, or of segments therein, is generally within ±55°. A gradual slope change minimizes the chances of wind flow separation and vortex formation. Notwithstanding with this general or global slope change limit, corrugated segment or segments, or small step or steps on the outer face of a roof edge guard, can be used within, or in lieu of, the face portions without compromising its functionality. Local slope change exceeding ±55° within the segment of corrugation or steps is permissible as long as the depth of the corrugation or the riser size of the step is sufficiently small and does not increase the chances of major flow separation. 
     FIG. 8  schematically illustrates corrugated segments  819  that can be formed on the outer face of the fascia member. 
   The roof edge guard  110  may be mounted on to the roof edge with any appropriate means that can ensure the configurations of the outer face of the roof edge guard as described in detail herein and defined by the accompanied claims. An exemplary mounting method is described here merely to showcase a relatively simple method that uses anchor bars  120  and fasteners  130 , for an aerodynamic roof edge guard  110  made from resilient sheet material. In  FIG. 1A , and similarly in  FIG. 1B , an anchor bar  120  is secured to the bargeboard  14  with a plurality of fasteners. The roof edge guard  110  is then snapped on to the anchor bar  120 . This is done by hooking the edge guard's top bend  114  on the anchor bar's top bend  124  and pressing the edge guard downwards and inwards until the edge guard's bottom bend  115  clicked into the anchor bar's bottom bend  125 . A spring clip  140  provides additional support for the edge guard  110 . Small amount of rainwater may slip through the gap between the top bend  114  of the edge guard and the protruding portion  17  of the roof covering. A V-shape  128  on the upper part of the anchor bar forms a channel to catch and guide this small amount of water down the slope along the gable edge, prevent it from wetting the normally wooden components  31  and  14 , and drain it off where the anchor bar terminates. Along the length of the gable edge, either multiple discrete anchor bars  120 , or continuous cleats of such similar cross-sectional shapes, can be used for sloped roof edges. 
   In fact, any other suitable mechanisms of similar functions may be used for mounting the roof edge guard  110  onto a roof edge. 
   Very limited amount of rainwater or moisture may also slip into the inside chamber of the edge guard  110 . Practically, since a roof edge guard mounted on a gable edge is sloped down along the gable edge, water inside the edge guard  110  can drain out through its lower end. For roof edges that are horizontal or with a low slope, a plurality of drain holes  116  can be drilled along the bottom edge of the edge guard  110  providing a means for draining and venting of condensation water or residual rainwater inside the edge guard's chamber. Similar optional drain holes (not shown) can also be used on the lower edge of the channel  128  for a continuous mounting cleat. 
   The aerodynamic roof edge guard  110  has at least three functions. The first is to minimize the extent of flow separation and the strength of associated vortices over a roof edge, or to completely eliminate them for some approach wind directions. These effects tend to be more pronounced for higher wind speeds as desired. High uplifts and strong scouring that result from wind-induced edge vortices above the roof, are prime causes for wind damage to roof components. Secondly, it shields the underside of the protruding portion  17  of the roof covering  11 , such as an array of shingles, shakes, or metal panels, from upward flow and pressure that tend to peel the roof covering  11  upwards and away from other parts of the roof edge assembly  10 . The third function is to prevent upward flow-driven rain from being pressured to infiltrate into the roof structure through the unsealed gaps between the roof covering  11  and the trim member  31 . 
   For roof edges without overhang, as illustrated in  FIG. 1B , a roof edge guard  110   b  can be mounted with the bottom bend  115   b  attached directly to the wall surface  21   b  or any vertical or nearly vertical surface therein. For applications on existing buildings, this optional method can be used only if the wall siding or surface material thereof is suitable for mounting; otherwise, mounting the edge guard  110   b  onto a fascia or bargeboard  14   b , similar to the method illustrated in  FIG. 1A , is recommended. 
   An aerodynamic roof edge guard can also be made from solid materials, such as solid wood, or any other suitable materials, and be mounted on a roof edge with any applicable means, so long as the aerodynamic shapes of the outer face portions are maintained.  FIG. 2  exemplifies an aerodynamic roof edge guard  210  made from solid wood material as being mounted on a gable-end overhang  10 , where the outer face portions  211 ,  212  and  213  are equivalent to the face portions  111 ,  112  and  113  in  FIG. 1A . 
   Some other embodiments of this invention are illustrated in  FIGS. 3 through 7 .  FIG. 3  shows an edge guard  310  shaped primarily with a semi-circle or semi-ellipse, where the outer face portions  311 ,  312  and  313  are equivalent to the face portions  111 ,  112  and  113  in  FIG. 1A . It should be noted that this configuration is not a preferred one for roof edges with no overhang since strong upward flow along the wall surface would exert significant pressure on the underside of the lower face portion  313  given its nearly horizontal layout. Such high pressure would have several undesired effects. The first is to increase the upward load on the edge guard  310 . Secondly, this high pressure would transmit into the inside chamber of the edge guard  310  through the unsealed gap between the edge guard bottom bend  315  and the wall surface, and thus increase the outward load on the edge guard. If discrete anchor bars are used along the roof edge for mounting, the residual of this high pressure could also reach and exert on the underside of the protruding portion  17  of roof covering  11 . The third undesired effect would be the potential pressure-driven infiltration of residual rainwater or moisture from the pressurized inside chamber of the edge guard  310  into the roof edge assembly, to which the edge guard  310  would have been attached. In addition, this configuration will conceivably yield higher outward negative pressures on the outer face of the edge guard  310  for such a direct wall contact application. Hence, for roof edges without overhang, configurations such as one depicted in  FIG. 1B  are recommended. 
   For aesthetic considerations, certain modifications to the profile shape of the outer face of a roof edge guard are allowable. For example, the lower face portion of a roof edge guard can be shaped to match or to approximate the shape of some of the roof edge gutters that may be common in a geographic region or prevailing for a specific roof edge system maker.  FIG. 4  shows an example of such modifications, where the outer face portions  411 ,  412  and  413  are equivalent to the face portions  111 ,  112  and  113  in  FIG. 1A . Other modified profiles are also possible; however, such modified profiles should only contain steps, if any, that have a riser size  417  less than 25% of the total height  418  of the edge guard. Again, for roof edges without overhang or other direct wall contact applications, the slope of the lower face portion  413  should be steeper where it contacts or approaches the wall surface  21 . 
   Configurations primarily comprising of plane surfaces can also be utilized.  FIG. 5  shows an example of such alternative configurations, where the outer face portions  511 ,  512  and  513  are equivalent to the face portions  111 ,  112  and  113  in  FIG. 1A . 
     FIG. 6  provides an example for an edge guard  610  being installed on a roof edge that has the roof covering  18  wrapped downwards, most often seen with metal roof coverings, such as metal tiles, metal shakes and metal panels, as well as clay tiles in some instances. 
     FIG. 7  illustrates a roof edge guard  710  being used on an eave edge of a sloped roof where a draining device such as a gutter system is not being used. For this application, the upper arris  717  of the roof edge guard cover  710  is also disposed in close proximity to, but slightly lower than, the protruding edge  77  of the roof covering  71 . An outwardly and downwardly extending upper face portion  711  is also preferred to allow rainwater shed off from the roof to continue run over, and eventually be shed off from, the roof edge guard  710 . Discrete anchor bars  120 , instead of continuous cleat, mounted along the eave edge, are preferred for this application. This is to prevent runoff rainwater, of which a limited amount can slip through the gap between the edge guard upper arris  717  and the roof covering outer edge  77 , from being built up in the V-shaped channel  128 . 
   INSTALLATION AND OPERATION 
   An embodiment of this invention is a passive flow control device or design for building roof edges. Once installed properly, it stays functioning in such a way that it mitigates vortex formation at a roof edge and reduces uplifts and roof vortex scouring, whenever the wind blows towards a building bearing atop such roof edge devices or designs, and requires no active operational intervention. 
   CONCLUSION, RAMIFICATIONS, AND SCOPE 
   It is apparent that roof edge guards of this invention provide aerodynamically advantageous devices or designs for mitigating roof edge vortex and roof uplift, and are still among the simplest, most inexpensive to manufacture and convenient to install. 
   Although the description above contains many specifications, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Various changes, modifications, variations can be made therein without departing from the spirit of the invention. Roof edge guards can be made of any reasonably durable material with any appropriate means of fabrication as long as a configuration according to the spirit of this invention is accomplished to support the described working mechanism and to provide the associated functionality. Various surface portions of a roof edge guard may also bear such surface details as corrugation or steps of adequate sizes, as opposed to perfectly smooth surfaces. Any appropriate conventional or new mounting method can be used to secure a roof edge guard to a roof perimeter without departing from the spirit of this invention. Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.