Abstract:
A venting arrangement for a roof includes a plurality of venting stacks each having a first open base end open to an area on top of the roof insulation layer and below the roof outer membrane, the venting stacks arranged spaced apart around a perimeter of the roof. A venting path grid of air permeable material is arranged between the roof membrane and the insulation layer. The grid is in air flow communication with the first open base ends. Centrally located wind-driven turbine ventilators can also be in air flow communication to the grid.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to roof ventilating systems, and particularly to roof ventilating systems for commercial and industrial buildings, that typically have substantially flat roofs. 
     A typical commercial roof includes a structural roof deck, covered by a vapor barrier. A layer of insulation is placed over the vapor barrier. An impermeable synthetic plastic roofing membrane is placed over the insulation. Water leaks from above the membrane may wet the insulation or water from inside the building may condense between the vapor barrier and the plastic roofing membrane and wet the insulation. Wet insulation has a reduced heat transfer resistance and can degrade. 
     Vents are used above the budding roof membrane to vent the space between the membrane and the vapor barrier. With effective roof venting, wet roofs can be dried over a period of time. 
     Another problem with membrane covered flat roofs is that a strong wind flowing across the membrane creates a suction that tends to lift the membrane up off of the roof structure. The present inventor has recognized that roof vents, if in air flow communication with the space beneath the membrane, transfer the suction force caused by the wind to an underside of the membrane and tends to pull the membrane down onto the roof structure in the vicinity of the vent. 
     SUMMARY OF THE INVENTION 
     The present invention provides a roof venting grid applied to a substantially flat roof that not only effectively dries wet insulation between a roof membrane and the vapor barrier, but also effectively holds down the roof membrane to the roof against high winds. 
     The present invention provides at least one lengthwise vapor path that extends substantially along a length of the roof and having a roof vent flow connected to the vapor path at each end of the vapor path. Furthermore the invention can have at least one widthwise vapor path that intersects the lengthwise vapor path and spans substantially the width of the roof and having a roof vent at either end of the widthwise vapor path. 
     Preferably, the invention provides a plurality of spaced apart lengthwise vapor paths and a plurality of spaced apart widthwise vapor paths, the widthwise vapor paths intersecting the lengthwise vapor paths and each of the lengthwise and widthwise vapor paths having a vent at opposite ends thereof, Also preferably, vents can also be located at the intersections of the lengthwise and widthwise vapor paths. Preferably, the vents at the intersections are turbine style vents. 
     According to another aspect, the vents are arranged around a perimeter of the building roof. Additional vents can be applied in corners of the building roof. The vents are all connected to a grid of vapor paths. 
     The vapor paths constitute open mesh fabric or mesh filter material. The open mesh fabric is fit on top of the insulation and below the upper membrane. 
     Numerous other advantages and features of the invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims, and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a flat building roof; 
         FIG. 2  is a sectional view taken generally along line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a sectional view taken generally along line  3 - 3  of  FIG. 1 ; 
     
    
    
     DETAILED DESCRIPTION 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawing and will be described herein in detail specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
       FIG. 1  schematically illustrates a building  18  having venting system  20  arranged on a flat building roof  26 . The roof  26  has a lengthwise dimension Y 1  of about 150 feet and a widthwise dimension X 1  of about 100 feet. The flat roof is substantially covered on a top side by a membrane  30 , typically EPDM material (ethylene propylene diene monomer), The venting system  20  illustrated includes twenty perimeter roof vents  32  and eight central turbine vents  38 . Each vent,  32 ,  38  can be supported on a base mesh fabric  129  described below, although only two are shown tin  FIG. 1  for simplicity. 
     Four transverse pathways  42 ,  44 ,  46 ,  48  extend across the roof  20 . Each pathway includes a perimeter roof vent on each end and a pair of turbine vents  38  between the two roof vents. The remaining roof vents each are in communication with one of twelve tributary pathways  56  that communicate with either the first transverse pathway  42  or the fourth transverse pathway  48 . Interior connecting pathways  66 ,  68  each connect to four turbine vents  38  that are substantially aligned. The pathways  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68  form a grid of pathways that substantially cover the roof top in both the X and Y directions. 
     The vapor paths  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68  are formed by open mesh fabric or filter material such as mesh material designated C06.03, at ⅞ inch thickness; 1 SB10, at 11/8 inch thickness; or 1 ECO, at 1 inch thickness, all available from Superior Fibers Inc. of Bremen, Ohio, US. The open mesh fabric is fit on top of the insulation and below the upper membrane  30  or below the vents  32 ,  38 . The open mesh fabric allows air or vapor to pass horizontally through the fabric and vertically through the fabric. The vapor paths  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68  preferably have a width between 9 and 12 inches wide, and more preferably 10 inches wide. The mesh fabric of the vapor paths can be secured to the insulation by insulation block fasteners and/or by adhesive or sealant. 
     Referring to  FIG. 2 , the roof  26  may typically consist of an interior metal or wood building deck  100 , supported on roof purlins  102  which are part of a typical commercial building&#39;s frame structure. A near impermeable vapor barrier sheet  106 , covers the building deck  100 . Rigid fibrous or foam insulation boards or blocks  112  are provided between the barrier sheet  106  and the outer roof covering membrane  30 . Membrane  30  has an opening  114  in air flow communication with the vent  32 . 
     The vent  32  is more particularly described in U.S. Pat. No. 4,909,135, herein incorporated by reference. The vent  32  is fabricated in two component parts and, as shown, these parts include an upwardly extending open-ended tube  126  formed at its lower end with a radially outwardly extending annular flange  128 . The flange  128  is supported on one or more layers of a base mesh fabric  129 , which can be approximately 2 feet by 2 feet, and overlies the path  46  of mesh fabric. The flange  128  can be adhesively secured to the base mesh fabric  129 . The base mesh fabric  129  can be composed of one or more layers of mesh material K02.03, at 1½ inch thickness per layer and available from Superior Fibers Inc. of Bremen, Ohio, USA. The base mesh fabric is air permeable vertically and can be air permeable horizontally as well. The base mesh fabric must support the vent while at the same time not becoming too compressed by the weight of the vent to adversely affect its air permeability. The base mesh fabric can be secured to the insulation by block insulation fasters and/or by adhesive or sealant. The skirt  130  typically composed of cured EPDM wide cover tape adhered onto the membrane  30  around the vent and sealed by calk or sealant around its inside and outside perimeter to the tube  126  and to the membrane  30 . The tape of the skirt  130  can be applied in two strips and sealed along its seam, to form approximately a 2 foot by 2 foot skirt. 
     As shown in  FIG. 2 , the tube structure  126  has an upwardly tapered peripheral wall portion  140 , terminating to leave a top opening (not shown) in the upper end of tube  126 . The lower end of tube  126  is open to a space  142 , provided above the insulation blocks  112  and occupied by the pathway  46  of mesh fabric and the base mesh fabric  129 . 
     A cap or hood, generally designated  152 , is provided for the upper end of the tube or stack  126  to prevent the entry of rain, snow and the like, and comprises a top wall  154  spaced above the top opening of the tube  126 , and has a downwardly divergent peripheral wall  156  extending generally parallel to wall portion  140  but overhanging the wall  140 . 
     When wind is present, an air stream traveling up between the walls  140  and  156  is converged by the fins within the hood  152 , such that its velocity is increased, and a venturi suction is created tending to pull an air current upwardly out of the tube  126 . The air pulled upwardly out of tube  126  is then moved outwardly, along the path “x”. 
     The vent  32  can alternately be constructed according to U.S. Pat. Nos. 6,234,198; 5,749,780; 4,593,504; or 3,984,947 which are all herein incorporated by reference. The roof vents in these patents incorporate a one way valve to allow air or vapor to exit the vent to ambient, but closes to prevent outside air from entering the vent  32  and flowing into the space between the membrane  30  and the barrier  106 . 
       FIG. 3  illustrates a typical turbine style vent  38 . The vent depicted can be constructed in accordance with U.S. Pat. Nos. 3,893,383 or 3,797,374, herein incorporated by reference. The vent  38  can also be constructed according to U.S. Pat. Nos. 3,066,596; 6,352,473 or 6,302,778 all herein incorporated by reference. 
     The vent  38  includes a turbine ventilator  164  mounted on an open-ended tube or stack  165 . The turbine ventilator  164  comprises a rotatable turbine  166  mounted on a shaft  174 . The shaft is stationary and supports the turbine  166  on a bearing assembly  176 . The bearing assembly is received in a socket or recessed opening on the lower side of a bonnet  178 . The bonnet  178  covers the top portions of the turbine  166 . The bonnet  178  is curved and approximates a segment of a sphere although it need not be precisely spherical in shape. It extends outwardly to a flat portion or encircling lip  180 . The lip  180  is preferably in a single plane which is perpendicular to the shaft  174  which supports the turbine  166 . 
     The bonnet  178  supports a number of ribs  184 . There are many ribs, and they are preferably arranged evenly around the bonnet  178 . They all extend downwardly to a ring  190 . Rotation of the turbine  166 , particularly the ribs, causes air or vapor to be drawn up the open ended tube  165  along the path x. 
     The stack  165  is installed onto the roof in identical fashion as the stack  126  shown in  FIG. 2  and supported on one or more layers of base mesh fabric  129  that overlies the path  68  of mesh fabric. 
     Each of the vents  32  is installed in similar fashion to that shown in  FIG. 2  and each of the vents  38  is installed in similar fashion to that shown in  FIG. 3 . Each of the vents  32 ,  38  is supported on, and in air flow communication with, one or more layers of a base mesh fabric  129  which is in air flow communication with a path of mesh fabric such as to exert an upward suction through the base mesh fabric  129  and the particular path depending on the wind condition on the roof. 
     The vapor paths  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68 , allow air to be drawn though one or more of the turbine ventilators  38  and/or one or more of the vents  32  to dry out wet insulation and also to hold down the membrane  30  tightly to the insulation  112 . Because each path has two or more vents  32 ,  38  in air flow communication with the pathways, any wind direction across the roof assists in drying large portions of the roof and assists in holding down the roof membrane. 
     Because of the interconnection of the paths  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68  an overall drying of the insulation  112  can be achieved no matter the wind direction. Because of the interconnection of the paths  56 ,  42 ,  44 ,  46 ,  48 ,  66  and  68  an overall hold down of the membrane  30  to the insulation  112  can be achieved no matter the wind direction. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.