Patent Publication Number: US-2009229204-A1

Title: Moisture removing system and method for structural roofs

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/069,434, filed on Mar. 14, 2008. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to an improved system and method for removing moisture from beneath a structural roof made with low permeability membranes or panels. This invention further relates to a system and method for improving the moisture, and hence mold, resistance of roof assemblies made from elongate sheets of membrane, including but not limited to polyvinyl chloride (PVC), ethylene propylene diene monomer (EPDM), modified bitumen, thermoplastic olefin (TPO), and/or other thermoplastic or thermoset materials. 
     BACKGROUND OF THE INVENTION 
     In recent years, roofing systems using elastomeric membranes have become popular for many commercial structures, i.e., those having a predominantly flat rooftop. For many such applications, a suitable roof membrane is laid over the top surface of a roof substrate. 
     The area between the roof deck and the aforementioned roof membrane is referred to herein as the “roof envelope.” Moisture condensation in the roof envelope is common, especially with mechanically attached roof systems. This is due to the presence of moisture laden air in the roof envelope and outside ambient temperatures. In most cases, moisture enters the roof envelope from one or more sources: from the building interior or exterior; water vapor diffusion (caused by partial water pressure differentials); thermal cycling; and from air infiltration at the roof perimeters and/or flashing points. 
     For those structural roofs made from an ethylene propylene diene monomer (or “EPDM”) rubber-like material, the membrane materials, themselves, are sufficiently porous to allow moisture vapor to pass through. Most white-based roof material alternatives, like polyvinyl chloride (PVC) and/or a thermoplastic olefin (TPO), exhibit lower permeability properties. Such properties inhibit the flow of moisture through the membranes instead containing pockets of moist air within the roof envelope. With white membrane systems, this moisture is allowed to condense due to the reflective properties of such materials and the sheet temperatures associated with same. Unfortunately, the typical operating temperatures for white membrane systems do not reach the level of heat for mitigating the growth of mold within the roof envelope. 
     It is known to treat white membrane materials and/or insulation facers to be used with same with one or more biocides formulated into the various products themselves. While they preclude mold growth at the biocide-treated level, such treatments cannot ensure against mold growth at still other levels of the same roof assembly. Further, biocide-formulated materials do not address the potential damage to other roof system components from moisture exposure. 
     The present invention takes an alternative approach to biocide-treated roof systems, especially those made from white membrane materials. In some cases the invention may be combined with the biocide-treated materials. It minimizes the amount of moisture laden air within the roof envelope by strategically placing a plurality of one-way, moisture relief (“roof”) vents in preferred locations about and through the rooftop. As moisture vapor increases in the roof system, it is promptly exhausted to the outside, minimizing the possibility of moisture capture, condensation, and the likelihood of damaging roof components due to moisture condensation/build up. 
     The system and method of the present invention represent an improvement over existing roof systems, particularly with respect to removing moisture-laden air from beneath roofing membranes exhibiting little to no vapor permeability. The features of the present invention, including custom-designed roof membrane layouts, strategically situated one-way vents within individual roof “channels” and the accommodation of multiple penetrations or occlusions through the roof proper, help eliminate the disadvantages experienced with existing roof systems, especially those made with white-based membrane materials. The referenced roof channels include central region and perimeter channels, each of which is formed by aligning elongate membrane sheets in a row to form a channel; where the sheets align within the channel, the sheets are overlapped and adhered or welded together by means known to those skilled in the art. 
     SUMMARY OF THE INVENTION 
     The invention provides an improved, moisture-resistant system that can be quickly, yet efficiently custom designed for each roof application. 
     Roofing systems of the present invention accommodate various penetrations (or occlusions) into the roof, while providing significant moisture resistance for that rooftop configuration. 
     The roof system can be easily installed, maintained and/or repaired (i.e., periodically serviced). The roof system also can address the addition of subsequent penetrations/occlusions through a roof long after the initial installation of said roof. The system and method of the present invention may apply to numerous mechanically attached varieties of low permeability roofing materials for numerous structural roof layouts. 
     The present invention addresses an improved system for removing moisture from within a roof envelope made from mechanically fastened, low permeability panels. The system comprises: a plurality of elongate membrane sheets positioned, in adjacent rows, and secured to the roof deck or structure over a central region of the roof. These sheets are overlapped and joined, by means known to those skilled in the art such as welding or other adhesion methods, to form elongate adjacent channels in the roof envelope. Each central region channel has at least one one-way roof vent strategically positioned near one end of each channel, with adjoining channels having these vents at alternating ends of the channels. Location of these vents at the ends of the central region channels maximizes the moisture removal properties of the present invention by placing the vents close to the perimeter of roof. Vents are alternated at the ends of adjoining channels to maximize the beneficial air flow that is caused by wind at either side of the roof system. 
     The system and method of the present invention further includes a perimeter attachment means that provides increased securement of the roof system in the perimeters and corners. This perimeter attachment means is selected from: (a) a plurality of elongate membrane sheets that are joined in the same manner as central region channel sheets to form at least one perimeter channel in the roof envelope at each perimeter side of the roof around the central region channels and that are attached at the roof perimeter; (b) a plurality of elongate membrane sheets that are joined to form at least one perimeter channel positioned and similarly attached at the roof perimeter sides parallel to the central region channels and the use of fasteners bisecting the central field channels along the remaining perimeter sides, e.g., those that run perpendicular to the central channels; (c) fasteners or other attachment means bisecting the central region channels parallel to perimeter sides parallel to said central region channels and fasteners or other attachment means bisecting the central region channels perpendicular to the remaining perimeter sides of the roof; and (d) a fully adhered perimeter. 
     Perimeter channels are formed in the same manner as central region channels, that is, by aligning, overlapping and joining or welding membrane sheets to form channels. Where perimeter channels are use (which does not apply to the fully adhered perimeter), each perimeter channel has at least one one-way vent and may have more based upon the length of the perimeter channel (that is “preset” locations for perimeter channels are dependent upon the length of these channels). A related method is also disclosed. 
     These and other objects and advantages will become more apparent from the following detailed description taken in conjunction with the illustrative  FIGS. 1-4 , and the novel features thereof will be defined in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top schematic view of one embodiment of the present invention showing the relative positioning of central region channels and parallel and perpendicular perimeter channels on a representative roof, along with the relative positioning of one-way roof vents. 
         FIG. 2  is a top schematic view of another embodiment of the present invention showing the relative positioning of central region channels and parallel perimeter channels on a representative roof, along with the relative positioning of one-way roof vents. Perimeter channels are positioned at the perimeter sides parallel to the central regions channels, and fasteners bisect the central region channels at the remaining perimeter sides. 
         FIG. 3  is a top schematic view of a further embodiment of the present invention showing the relative positioning of central region channels on a representative roof, along with the relative positioning of one-way roof vents. Fasteners bisect the central region channels at all perimeters sides of the central region channels. 
         FIG. 4  is a top schematic view of one embodiment of the present invention showing the relative positioning of central region channels secured to the roof deck or structure and a fully adhered perimeter on a representative roof, along with the relative positioning of one-way roof vents. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will now be described in relation to multiple preferred embodiments and implementations thereof which are exemplary in nature and descriptively specific as disclosed. As is customary, it will be understood that no limitation of the scope of the invention is thereby intended. The invention encompasses such alterations and further modifications in the illustrated apparatus and method, and such further applications of the principles of the invention illustrated herein, as would normally occur to persons skilled in the art to which the invention relates. As used herein, the term “substantially parallel” means of two or more lines, or three-dimensional planes, which do not intersect, or contact one another. In a broader sense, components which are substantially parallel shall be substantially equidistant, or spaced about the same distance apart in multiple lines and/or planes. The “roof envelope”, as used herein, refers to the area between the roof deck and a roof membrane. “Fully adhered”, as that terms is used by those skilled in the art and herein, means the use of an adhesive material, such as contact, low rise form, water based adhesives and other glues/adhesives to join a roof membrane to a substrate. 
     As shown in  FIG. 1 , the system and method of one embodiment of the present invention  10  includes: (a) a plurality of elongate perimeter channels  11  positioned about a perimeter of a structural roof; and (b) a plurality of elongate field channels  12  positioned, in adjacent rows, over a central region of a structural roof. Each row of perimeter channels  11  and each row of central region channels  12  is formed by membrane sheets that are aligned in a row, overlapped at points of connection and joined together by welding or other adhesive means. Each such individual roof perimeter or central region channel has at least one strategically positioned one-way roof vent. 
     More specifically, for central region channels, one way vents are located at alternating ends of adjacent channels as shown in  FIG. 1  (this is also shown for central region channels in  FIGS. 2-4 ). Installation of the vents at or very near the perimeters of the respective membrane channels, where the pressure differentials between the roof envelope and the roof exterior will assist with the movement (i.e. non-mechanical) of moisture-laden air to the outside, best maximizes the “moisture pumping” action of the one-way vents of the system. Alternating the end location of vents in the central region channels allows the roof system to pick up wind, which aids the pumping action of the vents, from alternating directions. The pattern of placement of vents at the ends of central region channels can vary, though, and need not alternate between adjacent channels. 
     Central region and perimeter channels of membrane sheets or materials typically include a linear lap seam attachment at the point of intersection of parallel channels. This linear lap seam separates and creates individual channels allows air to move more easily from the central/interior sections of each channel to the corresponding vent or vents placed at the ends of the channels toward the roof outer perimeter. 
     In the event a particular “channel” of this invention is occluded by a roof penetration of any sort, i.e. gas vent, round or rectangular skylight, etc. (see opening  15  in  FIG. 1 ; also shown by corresponding openings  28   a    37   a  and  44 , respectively in  FIGS. 2-4 ), at least one additional one-way vent should be situated on either side of the penetration/occlusion in that given roof channel for enhancing air movement around and about the interrupting channel penetration/occlusion. 
     Each perimeter channel also, preferably, has at least one one-way vent. As further shown in  FIGS. 1-3 , two one-way roof vents are preferably located at each perimeter corner (vents  13   b  are shown at the corners of roof system  10  in  FIG. 1 ). Such vent locations are applicable to both inside and outside corners for roofing systems. Similar to the central region channels, positioning one way vents at the ends of the perimeter channels helps maximize the pumping action of the vents. In roof system  10  shown in  FIG. 1 , the perimeter channels overlap at the corners so that vents  13   b  help provide pumping action to two perimeter channels, i.e., one running parallel to the central region channels and one running perpendicular to the central region channels. 
     Also similar to the central region channels, parallel perimeter channels have a linear lap seam attachment. Accordingly for roof system  10  shown in  FIG. 1 , the perimeter channels are assembled in a picture frame-like pattern and attached along their respective seams. Such an arrangement creates individual air pockets, or channels, between adjacent rows of lap seam attachments or fasteners. 
     One way vents are also located near the middle of long perimeter channels. Specifically, the addition of such additional one-way vents is dependant on the length of such channels and other factors, including the distance between vents, building geometry (size, roof level heights, and height of parapets if present), and design wind speed (as is known to those skilled in the art and outlined in various wind design guides such as ASCE 7-05). In the present invention, it has been determined that the maximum desired spacing between perimeter channel vents, in order to allow for adequate ventilation and removal of moisture-laden air, is about fifty (50) feet. However, the desired placement of vent in the middle of perimeter channels result in separation distances that are less than fifty (50) feet, such as when the perimeter channel lengths are small, e.g., where the perimeter is less than one hundred (100) feet. The maximum desired spacing between perimeter channel vents can vary, and, where adjacent perimeter channels are used, inner channels may not necessarily require vents in the middle of such channels. 
     By way of example (see  FIG. 1 ), but not limitation, in a small box roof, perimeter vents  13   a  can be installed at about every fifty (50) foot interval along the perimeter channels nearest the edge, as well as two (2) vents  13   b  in each outside corner. If more than one perimeter channel exists, each channel should preferably have a minimum of one vent, although inner channels may not have vents at other than the outside corners. Where an outer perimeter channel is less than about fifty (50) feet in length, at least one vent  13   c  should be installed in the middle of the channel. Where a perimeter channel is longer than fifty (50) feet, more than one internal vent may be required in order to address the desired minimum distance between vents. 
     In this same example, vents  14  are installed at alternating opposite ends of each adjacent field channel in the central region of the roof. Finally, where the roof system is penetrated by, e.g. an opening  15 , an additional vent  14   a  is placed in the channel where the penetration occurs. This system is custom designed for each individual roof such that the location of the vents, the number of perimeter channels and other factors may change. In general, though, each perimeter and field channel has at least one vent. 
       FIG. 2  depicts another embodiment  20  of the present invention, where the perimeter channels  21  are only installed parallel to the field channels  22 . The additional fastening required at the perimeter sides  23  perpendicular to the longitudinal direction of the field channels  21  is accomplished by: (a) bisecting the field channels with fasteners installed through the membrane perpendicular to the perimeter sides and installing a patch over the fastener row; or (b) bisecting the field channel by an attachment system  24  perpendicular to the perimeter side under the membrane which is then attached to the underside of the field channel. Embodiment  20 , like embodiment  10 , also has corner vents  25 , perimeter channel vents  26 , and alternating field channel vents  27 , with an extra vent  27   a  in the field channel having a penetration such as opening  28 . 
     Yet another embodiment  30  of the roofing system of the present invention is shown  FIG. 3 , where there are no perimeter channels utilized and parallel field channels  32  are only used. The additional fastening required in the side perimeters shown in  FIG. 3 , i.e., the sides perpendicular to the length of the field channels  32  (the sides shown at the right and left in  FIG. 3 ) is accomplished by: (a) bisecting the field channels with row of fasteners installed through the membrane perpendicular to these perimeter sides and installing a patch over the fastener row or; (b) bisecting the field channel by attaching an attachment system  31  under the membrane perpendicular to theses perimeter sides which is then attached to the underside of the field channel. The additional fastening required at the perimeter sides that are parallel with the field channels, i.e., the top and bottom in  FIG. 3 , is accomplished by: (a) bisecting the top and bottom field channels  32   a  and  32   b , respectively, with row of fasteners installed through the membrane parallel to the top and bottom perimeter sides and installing a patch over the fastener row; or (b) bisecting the field channel by attaching an attachment system  33  under the membrane parallel to the top and bottom perimeter sides which is then attached to the underside of the field channel. The latter of these attachment options can effectively bisects field channels  32   a  and  32   b  and create two perimeter channels. Embodiment  30 , like embodiment  10 , also has corner vents  34 , perimeter vents  35 , and alternating field channel vents  36 , with an extra vent  36   a  in the field channel having a penetration such as opening  37 . 
     Finally,  FIG. 4  depicts a roof system  40  where the perimeter areas are fully adhered and the field channels  41  are mechanically attached up to the fully adhered border  42 . System  40  again has alternating field channel vents  43 , with extra vent  43   a  in the channel penetrated by opening  44 . The perimeter area is fully adhered by adhering the membrane to a layer of insulation or separator board or the existing substrate of roof system  40 . Where a layer of insulation or separator board is used, mechanical fasteners, also known to those skilled in the art, are utilized to attach the insulation layer/separator board to the substrate of the roof. 
     For all embodiments, the system utilizes standard means to mechanically secure the perimeter and central region/field channels to a roof surface. Any type of fastening means known to those skilled in the art can be used, including, by way of example only, a threaded or rivet type fastener inserted through a metal or plastic disc or batten and attached to the roof substrate. The fasteners and discs or battens are installed along the longitudinal edge and covered by the adjacent layer of material. 
     The perimeter and central region/field sheets are comprised of thermoplastic or thermoset materials, including but not limited to PVC, TPO, chlorinated polyethylene, chlorosulfonated polyethylene, EPDM and combinations thereof. 
     The one-way roof vents of the present systems can have differing structural components so long as, in function, they allow venting of air from the inside to the outside of the roofing system. 
     The present invention also includes a method for rendering a structural roof system more moisture resistant, with this method comprising the steps of: (a) positioning and fastening a plurality of elongate membrane sheets with low permeability over a central region of the structural roof to form individual central region channels; (b) positioning a one-way roof vent into the ends of each individual central region channel for moisture to escape through said roof vent (as described above), and (c) installing a perimeter attachment system that may involve the use of perimeter channels (as described above), mechanical fasteners and/or fully adhering perimeter sides. Where perimeter channels are used, the method can further comprise the step of positioning a one-way roof vent at or near an end of every perimeter channels over a corner of said structural roof. At least one one-way roof vent is located in each perimeter channel, and, as described above, perimeter channels may also have internal vents. 
     The foregoing description of the preferred embodiment of the present invention is to be considered as illustrative only. Furthermore, since numerous modifications and variations will readily occur to those skilled in the relevant art, it is not desired to limit the scope of the present invention to the exact construction and operation shown and described and, accordingly, all suitable modifications and equivalents which fall within the scope of the claims may be resorted to.