Patent Publication Number: US-8991121-B1

Title: Thermally improved curtain wall connection system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. provisional patent application Ser. No. 61/826,876, filed on May 23, 2013, the disclosure of which is incorporated herein by reference for all purposes. This application also claims the benefit of the filing date of U.S. provisional patent application Ser. No. 61/872,707, filed on Aug. 31, 2013 and U.S. provisional patent application Ser. No. 61/872, 731 filed on Sep. 1, 2013. entitled “Thermally Improved Curtain Wall Connection System” of which all of the disclosures are hereby incorporated by reference for all purposes. 
    
    
     TECHNICAL FIELD 
     The invention relates in general to metal fabrication of curtain wall systems, and in particular to thermally improved curtain wall connection systems. 
     BACKGROUND INFORMATION 
     The use of structural steel and reinforced concrete in construction has allowed for large buildings to be supported by a system of columns rather than their exterior walls. Curtain walls are non-structural walls placed on the exterior of multi-story buildings. The primary purpose of a curtain wall is to provide a barrier between building inhabitants and the outside elements. These curtain walls are traditionally aluminum frames filled with sheets of glass, metal, or stone. Glass is a popular choice because of the added benefit of allowing in natural light. 
     Curtain walls can be classified by their method of fabrication and installation into the following general categories: stick systems and unitized (also known as modular) systems. In the stick system, the curtain wall frame (mullions) and glass or opaque panels are installed and connected together piece by piece. In unitized systems, the curtain wall is composed of large units that are assembled and glazed in the factory, shipped to the site and erected on the building. Vertical and horizontal mullions of the modules mate together with the adjoining modules. Modules are generally constructed one story tall and one module wide but may incorporate multiple modules. Typical units are five to six feet wide. 
     Water penetration resistance is a function of glazing details, drainage details, sealants, and frame construction. Water can enter the exterior wall system by means of five different forces: gravity, kinetic energy, air pressure difference, surface tension, and capillary action. To mitigate water infiltration, all of these forces are usually accounted for in the curtain wall system design. 
     Unlike discontinuous windows, which are smaller units and can rely to a high degree on sill flashings to capture frame corner leakage, curtain walls cover large expanses of wall without sill flashings at each glazed opening. Water penetration of curtain wall frame corners is likely to leak to the interior and/or onto insulating glass below. Watertight frame corner construction and good glazing pocket drainage are critical for reliable water penetration resistance. Additionally, due to the reduction or lack insulation in curtain wall systems, the construction materials may conduct the heat or cold from the exterior of the building, and condensation can form as a result and may create internal weepage within the system. 
     Typically, curtain wall systems transfer their own dead load plus any live loads (which consist primarily of positive and negative wind loads) back to building structure or intermediate framing. In certain situations, the curtain wall system may demonstrate movement caused by thermal changes and wind significantly different than movement of the building structure. Therefore the connections to anchor the curtain wall must be designed to allow differential movement while resisting the loads applied while at the same time allow for weepage and the control of thermal transfers between the outside and inside of the building. 
     What is needed, therefore, is a device to act as an insulating frame and provide an effective gutter system for exterior condensation or rainwater while minimizing any weepage from reaching the interior and offering protection at the weak point of the seal. 
     SUMMARY 
     In response to these and other problems, in one embodiment, there are various disclosures of a horizontal stack joint system for a curtain wall disclosed. In certain embodiments, the joint system comprises a lower subsystem having a dual member projection and an upper subsystem having a channel sized to receive the dual member projection. In certain embodiments, the joint system includes male and female front legs, a gutter, male and female split mullions, a mullion splice, a female joint, sill trim members, mullion fins, horizontal fins, a gasket, a thermal isolator, silicone boot, a shop applied silicone seal and a field applied silicone seal. 
     These and other features, and advantages, will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. It is important to note the drawings are not intended to represent the only aspect of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . is an isometric view of a portion of a typical curtain wall system comprising a plurality of stack joint systems. 
         FIG. 2  is a section view illustrating one embodiment of a horizontal stack joint system which incorporates one or more aspects of the present invention. 
         FIG. 3A  is a section view illustrating the primary elements of one embodiment of a lower subsystem of the system of  FIG. 2  which incorporates one or more aspects of the present invention. 
         FIG. 3B  is a more detailed section view illustrating one embodiment of a lower subsystem of the system of  FIG. 2  which incorporates one or more aspects of the present invention. 
         FIG. 3C  is a top isometric view illustrating two adjacent lower subsystems coupled together. 
         FIG. 3D  is a traditional isometric view illustrating two adjacent lower subsystems coupled together. 
         FIG. 4A  is a section view illustrating one embodiment of an upper subsystem of the system of  FIG. 2 . 
         FIG. 4B  is a traditional isometric view illustrating one embodiment of two adjacent upper subsystems coupled with a vertical mullion subsystem. 
         FIG. 5A  is a section view of a vertical mullion subsystem which may be used with various embodiments of the present invention. 
         FIG. 5B  is a detailed section view of a portion of the vertical mullion subsystem of  FIG. 7A . 
         FIG. 6  is a section view illustrating an embodiment of a horizontal stack joint system which incorporates one or more aspects of the present invention. 
         FIG. 7A  is a section view illustrating the primary elements of one embodiment of a lower subsystem of the system of  FIG. 6 . 
         FIG. 7B  is a more detailed section view illustrating one embodiment of a lower subsystem of the system of  FIG. 6 . 
         FIG. 7C  is a top isometric view illustrating two adjacent lower subsystems coupled together. 
         FIG. 7D  is a traditional isometric view illustrating two adjacent lower subsystems coupled together. 
         FIG. 8A  is a section view illustrating one embodiment of an upper subsystem of the system of  FIG. 6 . 
         FIG. 8B  is a traditional isometric view illustrating one embodiment of two adjacent upper subsystems coupled to a vertical mullion subsystem. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present inventions, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the inventions as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
     When directions, such as outer, inner, exterior, interior, upper, lower, top, bottom, clockwise, counter-clockwise, are discussed in this disclosure, such directions are meant to only supply reference directions for the illustrated figures and for orientated of components in the figures. The directions should not be read to imply actual directions used in any resulting invention or actual use. Under no circumstances, should such directions be read to limit or impart any meaning into the claims. 
     Curtain Wall System: 
     Prefabricated or unitized curtain wall systems are usually designed to accommodate the differential movement between the structure and the thermal movement of the frame at the joints between each curtain wall unit. Because these units are frequently custom designed, the amount of movement to be accommodated can be carefully engineered into the system. Anchoring of unitized curtain wall typically consists of a proprietary assembly with three-way dimensional adjustability. For instance,  FIG. 1  illustrates a portion  102  of a unitized curtain wall system  100 . 
     Typically, a plurality of anchors spaced at a predetermined distance, such as anchors  104   a  and  104   b , attach the portion  102  of the curtain wall system  100  to a building structure such as a spandrel beam or floor slabs  106   a  and  106   b . As illustrated in  FIG. 1 , there is typically a plurality of curtain wall units, such as unit  108  (only a portion of unit  108  is illustrated in  FIG. 1 ) and unit  110  hung from the edge of the floor slab  106   a . A unit  112  is about to be hung, and is thus shown positioned away from the floor slab  106   a . Typically, differential movement between the curtain wall units is accommodated at the vertical and horizontal unit joints. 
     Each unit, such as unit  112 , comprises framing members. In the illustrated situation, the unit  112  comprises a pair of vertical mullions  114  and  116  and two or more horizontal framing members, such as a top framing member  118 , an intermediate framing member  120 , and a bottom framing member  122 . The vertical mullions  114  and  116  attach to the anchors  104   a  and  104   b , respectively. When assembled, the bottom framing member  122  is positioned upon the top framing member  124  of the lower adjacent unit  126 . Thus, when in place, the unit  112  spans horizontally from the anchor  104   a  to the anchor  104   b  which as explained above are positioned horizontally along the slab  106   a . The unit  112  spans vertically from the top framing member  124  of the lower adjacent unit  126  to the anchors  104   a  and  104   b , the unit  112  cantilevers above the slab  106   a  to a predetermined distance (for instance, desk height above the floor). Another unit (not shown) may then be placed adjacent to the vertical mullion  116  of the unit  112 . Yet, another unit (not shown) may then be placed on the top framing member  118  of unit  112 . 
     A horizontal stack joint  128  connects the units together to form the curtain wall system  100 . The horizontal stack joints are designed to resist lateral loads while the two floor anchors resist gravity and lateral loads. Usually, at least one of the floor anchors  104   a  or  104   b  will allow movement in plane with the unitized system. 
       FIG. 1  illustrates the horizontal stack joint  128  completed where all adjacent units are in place and an open or incomplete stack joint  130  which will be formed once unit  112  is stacked on top of unit  126 . 
     In the illustrated situation of  FIG. 1 , the units  108 ,  110 , and  112  are composed of a lower panel  132  of “vision glass” and an upper panel  134  of an opaque glass or a glazed spandrel shadow box. In certain embodiments, the upper panel  134  may have an insulated back pan. Surrounding the lower panel  132  and the upper panel  134  are framing members as discussed above. Of course, the vision glass may be in the upper panel in other situations. Additionally, in yet other situations, the units may contain more than two panels. 
     Stack Joint System: 
     Turning now to  FIG. 2 , there is illustrated an exemplary stack joint system  200  generally comprising a lower subsystem  202  (which may be an upper framing member of a curtain wall unit, e.g. top framing member  118  of unit  112  or top framing member  124  or unit  126 ) and an upper subsystem  204  (which may be a lower or bottom framing member of a curtain wall unit, e.g. lower or bottom framing member  122  of unit  112 ). 
       FIG. 2  is a section view of a stack joint system  200  where the lower subsystem  202  is coupled to the upper subsystem  204  to form a completed stack joint system such as illustrated when in  FIG. 1  unit  112  is positioned above unit  126 . For instance, the lower panel  132  of vision glass may be coupled and supported by the upper subsystem  204  which is essentially the bottom framing member  122  of an upper unit, such as unit  112  ( FIG. 1 ). In certain embodiments, the upper portion of opaque glass, such as panel  134  of the unit  112  or a panel  136  of the unit  126  ( FIG. 1 ) may be coupled to and laterally supported by the lower subsystem  202  (which is essentially the top framing member of the respective curtain wall unit). 
     As will be apparent when the details of the stack joint system  200  are discussed below, in certain embodiments, the stack joint system  200  creates an airtight or pressurized chamber  209 . The pressurized chamber  209  may act as an air barrier of the curtain wall. To prevent rain infiltration through the curtain wall, it may be desirable to have an air tight or pressurized chamber, such as pressurized chamber  209 . If the air that leaks in and through cracks and crevices of a curtain wall during a rain storm were limited or stopped, most of the water impinging on the curtain wall would migrate straight down the surface and little would penetrate the wall. Thus, if an airtight or pressurized element is positioned behind the exterior surface of a curtain wall, the chamber formed between the exterior cladding and the airtight element may reach the same air pressure level as is exerted on the cladding surface, thus removing the force which causes air to flow through any curtain wall opening. The “Rain Screen Wall,” therefore is characterized by a chamber behind the exterior surface of the wall that is connected to the exterior but sealed tightly, or as tightly as reasonably possible to the interior. 
     the Lower Subsystem: 
       FIGS. 3A through 3D  are various views of the lower subsystem  202  of the horizontal stack joint system  200 .  FIG. 3A  is a section view illustrating the “structural” primary elements of one embodiment of the lower subsystem  202 . The lower subsystem  202  comprises a male front leg  206 , a male back leg  208 , and a joint gutter  210 . The male front leg  206  comprises an extruded metal member generally formed in the shape of an “L” with a horizontal leg  212  and a vertical leg  214 . A curved protrusion  216  extends away from a lower surface or face  218  of the horizontal leg  212 . As will be explained below, in certain embodiments, the curved protrusion  216  forms a male portion of a connection  220  between the horizontal leg  212  and the joint gutter  210 . 
     A generally horizontal protrusion  222  extends from a back or interior face  224  of the vertical leg  214 . In certain embodiments, the horizontal protrusion  222  may have one or more screw holes  226  for an assembly screw  228  (see  FIG. 3B ). In certain embodiments, a groove protrusion  230  extends from the top portion of a front face  231  of the vertical leg  214 . The groove protrusion  230  is sized to allow a gasket  318  (see  FIG. 3B ) to fit within a groove  234  formed by the groove protrusion  230 . 
     The male back leg  208  comprises a vertical leg  236 , a front protrusion  238 , an intermediate section  240 , and a back portion  242 . In certain embodiments, the back portion  242  comprises a horizontal portion  244  which connects to a vertical portion  246 . 
     In certain embodiments, the vertical leg  236  may also include a groove protrusion  248  containing a groove  250 . In certain embodiments, the groove protrusion  248  is essentially a mirrored protrusion of the groove protrusion  230 . Thus, the groove protrusion  230  faces towards the exterior of the system and the groove protrusion  248  faces towards the interior of the system and/or building. The front protrusion  238  also has a screw hole  252  such that when the primarily components are assembled into a stack joint, the screw hole  252  aligns with the screw hole  226  of the male front leg  206 , such that the assembly screw  228  can couple the male front leg  206  to the male back leg  208 . 
     In certain embodiments, the intermediate section  240  may also have a screw hole  254 . In certain embodiments, the intermediate section  240  may have a downward vertical portion  256  which joins the intermediate section to the back or interior portion  242 . In certain embodiments, the various legs  206 ,  208 , or joint gutter  210  may have screw splines for connecting screws (not shown) to out of plane members (not shown), such as screw spline  258 . 
     In certain embodiments, the joint gutter  210  may be extruded into a shape which generally comprises a vertical leg  260  joined to an inclined leg or member  262 . In certain embodiments, at a top end of the vertical leg  260 , there may be a groove portion  264  forming a longitudinal groove  266 . At the bottom of the vertical leg  260 , there may be a groove portion  268 , containing a longitudinal groove  270  designed to couple with a gasket (not shown). As discussed above, various screw splines, such as screw spline  272  and screw spline  274  may be formed along the inclined member  262  to couple out-of-plane members (not shown). In certain embodiments, extension members, such as extension member  276 , may be formed to position the screw spline  274  in the correct horizontal and vertical position. The inclined leg  262  may end with a connecting portion  278 . A screw hole  280  may be defined within the connecting portion  278 . When the subsystem  202  is assembled, the screw hole  280  may be aligned with the screw hole  254  of the back leg  208  such that a assembly screw  282  ( FIG. 3B ) can couple the back leg  208  to the joint gutter  210 . 
     Now that exemplary features and geometry of the front leg  206 , the back leg  208 , and the joint gutter  210  have been described, attention will be directed to  FIGS. 3B ,  3 C, and  3 D.  FIG. 3B  is a section view of the stack joint lower subsystem  202  cut at a where the subsystem  202  from one of units meets a similar subsystem from an adjacent unit at a stack joint.  FIG. 3C  is a top isometric view of a lower subsystem  202  for the entire stack joint which is formed by two adjacent subsystems  202 . Similarly,  FIG. 3D  is a side isometric view of the lower subsystem  202  for the entire stack joint. 
     Turning now to  FIGS. 3B ,  3 C, and  3 D, as discussed above, the lower subsystem  202  comprises the male front leg  206 , the male back leg  208 , and the joint gutter  210 . As illustrated in  FIGS. 3C and 3D , when the units are assembled, the male front leg  206  is positioned adjacent to a female front leg  306  of an adjacent subsystem of an adjacent unit. Similarly, the male back leg  208  couples with a female back leg  308  of an adjacent subsystem of the adjacent unit. 
     As illustrated in  FIGS. 3B ,  3 C and  3 D in certain embodiments, the top surfaces of the male front leg  206  and the female front leg  306  may be coupled to a silicone boot  312  at the joint. Once the male front leg  206  and male back leg  208  are assembled, the vertical leg  214  and the vertical leg  236  form a channel  314 . At the joint, the interior of the channel  314  may be lined with a second silicone boot  316 . The silicone boot  312  prevents water from running down the joint created by the male front leg  206  and the female front leg  306 . Similarly, the silicone boot  316  prevents water from running down the joint created by the male back leg  208  and the female back leg  308 . 
     A weather seal, such as a gasket  318  may be inserted into the groove  234  defined within the vertical leg  214 . Similarly, a second weather seal, such as a gasket  320  may be inserted into the groove  250  defined within the vertical leg  236  of the male back leg  208 . In certain embodiments, another thermal isolator, such as a rigid PVC spacer strip  322  may be inserted horizontally into grooves defined within the bottom face of the horizontal protrusion  222  of the male front leg  206  and defined within the top face of the front protrusion  238  of the male back leg  208 . In certain embodiments, the PVC spacer strip  322  may have openings (not shown in  FIG. 3B ) sized to allow one or more assembly screw  228  to pass through the openings. In certain embodiments, the PVC spacer strip  322  is positioned such that the openings of the PVC spacer strip align with the screw holes  226  and  252 . Thus, the assembly screw  228  may extend into the screw hole  226  of the horizontal protrusion  222  through the PVC spacer strip  322  and through the screw hole  252  of the front protrusion  238  of the back leg  208 . In other words, the front leg  206  and the back leg  208  may be connected, but remain relatively thermally isolated. 
     In certain embodiments, another thermal isolator, such as a rigid PVC spacer strip  330  may be inserted horizontally into grooves defined within the bottom face of the intermediate section  240  of the male back leg  208  and defined within the top face of the connecting portion  278  of the joint gutter  210 . In certain embodiments, the PVC spacer strip  330  has one or more openings sized to allow one or more assembly screws  282  to pass through the opening. In certain embodiments, the PVC spacer strip  330  is positioned such that the PVC spacer strip openings align with the screw holes  254  and  280 . Thus, the assembly screw  282  may extend into the screw hole  254  of the intermediate section  240  through the PVC spacer  330  and through the screw hole  280  of the connecting portion  278  of the joint gutter  210 . In other words, the back leg  208  and the joint gutter  210  may be connected, but remain relatively thermally isolated. 
     A third thermal isolator, such as a rigid PVC tubular member  336  may be inserted into the groove  266  defined within the vertical leg  260  of the joint gutter  210  to form a third thermal isolating connection. A circular end portion  338  of the curved protrusion  216  may be inserted into the tubular member  336  as illustrated in  FIG. 3D . Thus, the front leg  206  and the joint gutter  210  may be connected, but remain relatively thermally isolated. 
     Thus, the lower joint subsystem  202  includes the male front leg  206  (having a first vertical leg  214 ) which is coupled to the male back leg  208  (having a second upper or vertical leg  236 ) via a thermal isolation joint (e.g., the assembly screw  228  and the PVC spacer  322 ). The subsystem  202  also includes a joint gutter  210  which couples to the front leg  206  via a second thermal isolation joint (e.g., the curved protrusion  216  and the PVC tubular member  336  which allows some rotation) and couples to the back leg  208  via a third isolation joint (e.g., the assembly screw  282  and the PVC spacer  330 ). 
     As illustrated in  FIGS. 3C and 3D , the male front leg  206  is positioned longitudinally adjacent to the female front leg  306 . A field applied silicone seal  340  may be applied between the male front leg  206  and the female front leg  306 . Similarly, the male back leg  208  is positioned longitudinally adjacent to the female back leg  308 . A field applied silicone seal  342  may be applied between the male back leg  206  and the female back leg  306 . 
     In certain embodiments, there may be one or more weep holes defined with a lower surface of the joint gutter, a baffle  344  may be positioned at the weep hole in order to minimize air from infiltrating the joint (See  FIG. 3B ). In certain embodiments, a baffle, such as baffle  346  may be positioned within the channel  314  (see  FIG. 3C  or  3 D). 
     In certain embodiments, there may also be vertical mullion splice members  348  and  350  which may also function as lifting lugs. The vertical mullion splice member  348  may be coupled to a vertical split mullion male member  352  (see  FIG. 3D ). Similarly, the vertical mullion splice member  350  may be coupled to a vertical split mullion female member  354  (see  FIG. 3D ). In certain embodiments, a shop applied silicone seal  356  may be applied between the male back leg  208  and the vertical splice member  348 . Similarly, a shop applied silicone seal (not shown) may be applied between the female back leg  308  and the vertical mullion splice member  350  to prevent water from seeping through the joint. In various locations, other gaskets and seals may be used to prevent water infiltration such as glazing seal  358  or gasket  360  as is known in the art. Additionally, field applied caulking or sealing may also be employed, such as  390   a ,  390   b , and  390   c.    
     Turning back to  FIG. 3D , three thermal isolation members (e.g., PVC spacer  322 , PVC spacer  330 , and PVC tubular member  336 ) isolate the interior male back leg  208  from the exterior elements: front leg  206  and joint gutter  210 . Additionally, the vertical leg  214  of the front leg  206  and the vertical leg  236  of the back leg  208  along with the gaskets  318  and  320  proved a dual line of defense for the stack joint. The subsystem  202  also provides for internal weepage through weep holes and baffles, such as baffle  344  (not shown). Additionally, the vertical mullion splice members  348  and  350  are positioned behind the vertical legs  236 . 
     the Upper Subsystem: 
       FIG. 4A  is a section view through certain horizontal members of the upper subsection  204  of  FIG. 2  (or lower framing member of a curtain wall unit). As illustrated, in certain embodiments, a stack joint female member  402  may have a plurality of downward pointing vertical members or legs, such as vertical leg  416 , vertical leg  418 , vertical leg  420  and vertical leg  422 . Vertical leg  418  and vertical  420  form the channel  404  and are spaced such that they can accept the vertical legs  214  and  236  of the lower subsystem  202  (See  FIG. 2  and  FIG. 3B ) to create an air tight or pressurized chamber (chamber  209  of  FIG. 2 ). In certain embodiments, the stack joint female member  402  may also have screw splines  424  and  426  for coupling with out of plane screws (not shown). 
     In certain embodiments, a groove portion  428  forming a longitudinal groove  430  may be defined at the lower end of the vertical leg  418 . The vertical leg  416  may have a connecting portion  432 . In certain embodiments, one or more screw hole(s)  434  is defined within the connecting portion  432 . 
     A horizontal fin  440  may be used to support a lower panel of glass, such as lower panel  132  of vision glass which may be part of an upper unit, such as top framing member  118  ( FIG. 1 ). In certain embodiments, a gasket  442  may be coupled to the upper stack joint female member  402  and positioned such that the gasket  442  is between the upper stack joint member  402  and the lower panel  132  of vision glass. A backer rod  444  and seal  446  may be positioned between the lower panel  132  and the horizontal fin  440  as illustrated in  FIG. 4A . In certain embodiments, there may be a longitudinal groove  448  for accepting and coupling with a gasket  450  that is positioned between the horizontal fin  440  and the male front leg  206  of the lower subsystem  202 . 
     In section, an interior end  452  of the horizontal fin  440  is circular and is designed to fit within a thermal isolator, such as a rigid partially tubular PVC member  454 . In turn, the rigid PVC tubular member  454  may be sized to be inserted into the groove  430  defined within the vertical leg  418  of upper stack joint member  402  to form a thermal isolating connection. Thus, the vertical leg  418  and the horizontal fin  440  may be connected, but remain relatively thermally isolated. 
     In certain embodiments, the horizontal fin  440  may have one or more screw holes  456  such that when the horizontal fin is coupled to the stack joint member  402 , the screw hole  456  and screw hole  434  align so that an assembly screw  458  may be placed in the screw holes to couple the connecting portion  432  of the vertical leg  416  to the horizontal fin  440 . The assembly screw  458  may go through a thermal isolating member, such as a PVC spacer strip  460  which may be positioned between the horizontal fin  440  and the connecting portion  432  of the vertical leg  416 . 
     In certain embodiments, the PVC spacer strip  460  may be inserted horizontally into grooves defined within the bottom face of the connecting portion  432  of the vertical leg  416  and defined within the top face of the horizontal fin  440 . In certain embodiments, the PVC spacer strip  460  may have openings (not shown in  FIG. 4B ) sized to allow one or more assembly screw(s)  458  to pass through the openings. In certain embodiments, the PVC spacer strip  460  is positioned such that the openings of the PVC spacer strip align with the screw holes  434  and  456 . Thus, the stack joint member  402  may be coupled and supports the horizontal fin  440 , but is thermally isolated from the horizontal fin via the PVC spacer strip  460  and the rigid tubular PVC tubular member  454 . 
     The female or upper stack joint female member  402  may be made of extruded aluminum. In certain embodiments, the stack joint female member  402  may be coupled to a split male mullion  406  as illustrated in  FIG. 4B . A split female mullion  408  may be coupled to a stack joint female member  410  of an adjacent unit. If required, the stack joint female members  402  and  410  may be coupled to snap on sill trim members  412  and  414 , respectively. 
     The Vertical Mullion System: 
       FIG. 5A  is a detailed section view showing a mullion joint system  500  formed from certain vertical members or mullions. For instance, in  FIG. 4B , mullions  406  and  408  are coupled to the upper subsystems  204 , respectively of adjacent units.  FIG. 5B  is an enlarged detailed portion of the section view illustrated in  FIG. 5A . 
     Turning now to  FIGS. 5A and 5B , there is illustrated in section the interconnection between the split male mullion  406  and the split female mullion  408 . As illustrated, the split male mullion  406  may include a lateral member  502 , a lateral member  504 , a lateral member  506 , and a lateral member  508 . 
     In certain embodiments, the lateral member  502  may have a connecting end portion  510  with a vertical groove  512 . The lateral member  504  may have a side groove portion  514  and a connecting end portion  516  with a circular groove  513  defined on one face and a snap or hook element  515  extending laterally outward. A portion of a flexible member or gasket  537  may be inserted vertically into the circular groove  513  such that the gasket  537  is coupled to the end portion  516  of the lateral member  504 . 
     The lateral member  506  has a connecting end portion  517  with a circular groove  519  defined on one face and a small engagement extension  521  extending laterally outward. A portion of a flexible member or gasket  539  may be inserted vertically into the circular groove  519  such that the gasket  539  is coupled to the end portion  517  of the lateral member  506 . The lateral member  508  has a connecting end portion  518  with a snap or hook element  523  extending laterally outward. 
     Similarly, the split female mullion  408  may include a lateral member  522 , a lateral member  524 , a lateral member  526 , and a lateral member  528 . The lateral member  522  may have a connecting end portion  530  with a vertical groove  532 . The lateral member  524  may have a side groove portion  534  and a connecting end portion  536 . In some embodiments, in section the end portion  536  is shaped to engage a portion of the snap or hook portion  515  of the lateral member  504 . The end portion  536  is also shaped to engage the gasket  537  which is coupled to the end portion  516  of the lateral member  504  so that the connection between the end portion  536  and the end portion  516  is hermetically sealed. 
     In certain embodiments, the lateral member  526  may have a connecting end portion  527  which may be shaped to engage the gasket  539  (which is coupled to the connecting end portion  516  of the member  506 ) so that the connection between the end portion  527  of the lateral member  526  and the end portion  517  of the lateral member  506  is hermetically sealed. Thus, a vertical pressurized or airtight chamber  436  is formed because the connection between lateral members  504  and  524  and the connection between lateral members  506  and  526  are sealed. The airtight chamber  436  is open to and in hermetic communication with airtight chamber  209  (discussed in reference to  FIG. 2 ). A rectangular airtight chamber, therefore, is created for the unit as the units are positioned to create the curtain wall system. 
     In certain embodiments, a mullion fin  540  and a mullion fin  560  may be positioned within the space between the connecting portions  510  and  530  of the lateral members  502  and  522 , respectively. Generally, the mullion fins  540  and  560  extend from the vertical grooves  514  and  534 , to approximately the exterior face of the glass panels (e.g., the glass panels  134  and  136  of  FIG. 1 ). The mullion fins  540  and  560  may comprise a series of “step sections” in cross-section to allow their interior ends to clear the connection between the lateral members  504  and  524 . 
     The mullion fin  540  may have a vertical groove  542  for securing a gasket  543 . The opposing face of the mullion fin  540  may have vertical groove  544  defined therein. The interior end of the mullion fin  540  may also be circular in shape to couple with a thermal isolator, such as a rigid PVC vertical tubular member  546  which may be inserted into the side groove portion  514  of the lateral member  504 . Similarly, the mullion fin  560  may have a vertical groove  562  for securing a gasket  563 . Thus, as illustrated, gasket  543  and gasket  563  are aligned and are pressed against each other. 
     The opposing face of the mullion fin  560  may have a vertical groove  564  defined therein. The interior end of the mullion fin  560  may also be circular in shape to couple with a thermal isolator, such as a rigid PVC vertical tubular member  566  which may be inserted into the groove portion  534  of the lateral member  524 . 
     A thermal isolator, such as a rigid PVC vertical member  548  may be formed to be coupled with a vertical groove  544  defined within the mullion fin  540  and the vertical groove  512  defined within the connecting end portion  510  of the lateral member  502 . In certain embodiments, one or more assembly screws  501  may secure the mullion fin  540  to the connecting end portion  510  of the lateral member  502 . Thus, although the lateral member  502  is mechanically coupled to the mullion fin  540 , the lateral member  502  is thermally isolated from the mullion fin via the PVC vertical member  548 . 
     Similarly, a thermal isolator, such as a rigid PVC vertical member  568  may be formed to be couple with the groove  564  defined within the mullion fin  560  and a groove  532  defined within the connecting end portion  530  of the lateral member  522 . In certain embodiments, one or more assembly screws  561  may secure the mullion fin  560  to the connecting end portion  530  of the lateral member  522 . Thus, although the lateral member  522  is mechanically coupled to the mullion fin  560 , the lateral member  522  is thermally isolated from the mullion fin via the PVC vertical member  568 . 
     The exterior corner of the split male mullion  406  may be formed to engage and couple with a gasket  570 . Similarly, the exterior corner of the split female mullion  408  may be formed to engage and couple with a gasket  572 . As illustrated, the gaskets  570  and  572  are positioned between the respective mullions and the glass panels (e.g., the glass panels  134  and  136  of  FIG. 1 ). 
     Turning back to  FIG. 1 , it is apparent that most of the units (e.g. unit  112 ) in the curtain wall system  100  comprise a top or upper horizontal system which is similar to the lower subsystem  202  of  FIG. 2 ; a bottom or lower horizontal system which is similar to the upper subsystem  204  of  FIG. 2 , a side mullion system which contains the mullion  406 , and a side mullion system which contains the mullion  408 . As the units are positioned or “stacked” adjacent to and above one another, joint systems are formed between the units. For instance, stack joint systems  200  ( FIG. 2 ) are formed horizontally between the respective units and mullion joint systems  500  ( FIGS. 5A and 5B ) are formed vertically between the respective units. 
     Stack Joint System (Alternative Embodiment): 
     Turning now to  FIG. 6 , there is illustrated an exemplary stack joint system  1200  generally comprising a lower subsystem  1202  (which may be an upper framing member of a curtain wall unit, e.g. top framing member  118  of unit  112  or top framing member  124  or unit  126  ( FIG. 1 )) and an upper subsystem  1204  (which may be a lower or bottom framing member of a curtain wall unit, e.g. lower or bottom framing member  122  of unit  112  ( FIG. 1 )). 
       FIG. 6  is a section view of a stack joint system  1200  where the lower subsystem  1202  is coupled to the upper subsystem  1204  to form a completed stack joint system such as illustrated when in  FIG. 1  unit  112  is positioned above unit  126 . For instance, the lower panel  1132  of vision glass may be coupled and supported by the upper subsystem  1204  which is essentially the bottom framing member  122  of an upper unit, such as unit  112  ( FIG. 1 ). In certain embodiments, the upper portion of opaque glass, such as panel  1134  of the unit  112  or a panel  136  of the unit  126  ( FIG. 1 ) may be coupled to and laterally supported by the lower subsystem  1202  (which is essentially the top framing member of the respective curtain wall unit). 
     As will be apparent when the details of the stack joint system  1200  are discussed below, in certain embodiments, the stack joint system  1200  creates an airtight or pressurized chamber  1209 . The pressurized chamber  1209  may act as an air barrier of the curtain wall. To prevent rain infiltration through the curtain wall, it may be desirable to have an air tight or pressurized chamber, such as pressurized chamber  1209 . If the air that leaks in and through cracks and crevices of a curtain wall during a rain storm were limited or stopped, most of the water impinging on the curtain wall would migrate straight down the surface and little would penetrate the wall. Thus, if an airtight or pressurized element is positioned behind the exterior surface of a curtain wall, the chamber formed between the exterior cladding and the airtight element may reach the same air pressure level as is exerted on the cladding surface, thus removing the force which causes air to flow through any curtain wall opening. The “Rain Screen Wall,” therefore is characterized by a chamber behind the exterior surface of the wall that is connected to the exterior but sealed tightly, or as tightly as reasonably possible to the interior. 
     The Lower Subsystem (Second Embodiment): 
       FIGS. 7A through 7D  are various figures illustrating various aspects of the lower subsystem  1202 .  FIG. 7A  is a section view illustrating the primary “structural” elements of one embodiment of the lower subsystem  1202 . The lower subsystem  1202  comprises a male front leg  1206 , a male back leg  1208 , and a joint gutter  1210 . The male front leg  1206  comprises an extruded metal member generally formed in the shape of an “L” with a horizontal leg  1212  and a vertical leg  1214 . A curved protrusion  1216  extends away from a lower surface or face  1218  of the horizontal leg  1212 . As will be explained below, in certain embodiments, the curved protrusion  1216  forms a male portion of a connection  1220  between the horizontal leg  1212  and the joint gutter  1210 . 
     In certain embodiments, the horizontal leg  1212  may have one or more screw holes  1226  for an assembly screw  1228  (not shown). In certain embodiments, a groove protrusion  1230  extends from the top portion of a front face  1231  of the vertical leg  1214 . The groove protrusion  1230  is sized to allow a gasket  1318  (see  FIG. 7B ) to fit within a groove  1234  formed by the groove protrusion  1230 . 
     The male back leg  1208  comprises a vertical leg  1236 , a front protrusion  1238 , an intermediate section  1240 , and a back portion  1242 . In certain embodiments, the back portion  1242  comprises a horizontal portion  1244  which connects to a vertical portion  1246 . 
     In certain embodiments, the vertical leg  1236  may also include a groove protrusion  1248  containing a groove  1250 . In certain embodiments, the groove protrusion  1248  is essentially a mirrored protrusion of the groove protrusion  1230 . Thus, the groove protrusion  1230  faces towards the exterior of the system and the groove protrusion  1248  faces towards the interior of the system and/or building. 
     In certain embodiments, the intermediate section  1240  may also have a screw hole  1254 . In certain embodiments, the intermediate section  1240  may have a downward vertical portion  1256  which joins the intermediate section to the back or interior portion  1242 . In certain embodiments, the various legs  1206 ,  1208 , or joint gutter  1210  may have screw splines for connecting screws (not shown) to out of plane members (not shown), such as screw spline  1258 . 
     In certain embodiments, the joint gutter  1210  may be extruded into a shape which generally comprises a vertical leg  1260  joined to an inclined leg or member  1262 . In certain embodiments, at a top end of the vertical leg  1260 , there may be a groove portion  1264  forming a longitudinal groove  1266 . At the bottom of the vertical leg  1260 , there may be a groove portion  1268 , defining a longitudinal groove  1270  designed to couple with a gasket (not shown). In certain embodiments, an extension member  1276  may project upwards and contain a horizontal connecting portion  1277 . One or more screw holes  1252  may be defined within the horizontal connecting portion  1277 . As noted above, the horizontal leg  1212  may have one or more screw holes  1226  which may align with the screw holes  1252  when the primary components are assembled into a lower subsystem  1202  of the stack joint  1200 . 
     In certain embodiments, the inclined leg  1262  may end with a connecting portion  1278  and may be formed to position the screw spline  1274 . A screw hole  1280  may be defined within the connecting portion  1278 . When the subsystem  1202  is assembled, the screw hole  1280  may be aligned with the screw hole  1254  of the back leg  1208  such that an assembly screw  1282  ( FIG. 7B ) can couple the back leg  1208  to the joint gutter  1210 . 
     As discussed above, various screw splines, such as screw spline  1272  and screw spline  1274  may be formed along the inclined member  1262  to couple out-of-plane members (not shown). 
     Now that exemplary features and geometry of the front leg  1206 , the back leg  1208 , and the joint gutter  1210  have been described, attention will be directed to  FIGS. 7B ,  7 C and  7 D.  FIG. 7B  is a section view of the stack joint lower subsystem  1202  cut at where the subsystem  1202  from one of units meets a similar subsystem from an adjacent unit.  FIG. 7C  is a top isometric view of a lower subsystem  1202  for the entire stack joint which is formed by two adjacent subsystems  1202 . Similarly,  FIG. 7D  is a side isometric view of the lower subsystem  1202  for the entire stack joint. 
     Turning now to  FIGS. 7B ,  7 C, and  7 D, as discussed above, the lower subsystem  1202  comprises the male front leg  1206 , the male back leg  1208 , and the joint gutter  1210 . As illustrated in  FIGS. 7C and 7D , when the units are assembled, the male front leg  1206  is positioned adjacent to a female front leg  1306  of an adjacent subsystem of an adjacent unit. Similarly, the male back leg  1208  couples with a female back leg  1308  of an adjacent subsystem of the adjacent unit. 
     As illustrated in  FIGS. 7B ,  7 C and  7 D in certain embodiments, the top surfaces of the male front leg  1206  and the female front leg  1306  may be coupled to a silicone boot  1312  at the joint. Once the male front leg  1206  and male back leg  1208  are assembled, the vertical leg  1214  and the vertical leg  1236  form a channel  1314 . At the joint, the interior of the channel  1314  may be lined with a second silicone boot  1316 . The silicone boot  1312  prevents water from running down the joint created by the male front leg  1206  and the female front leg  1306 . Similarly, the silicone boot  1316  prevents water from running down the joint created by the male back leg  1208  and the female back leg  1308 . 
     A weather seal, such as a gasket  1318  may be inserted into the groove  1234  defined within the vertical leg  1214 . Similarly, a second weather seal, such as a gasket  1320  may be inserted into the groove  1250  defined within the vertical leg  1236  of the male back leg  1208 . In certain embodiments, a thermal isolator, such as a rigid PVC spacer strip  1322  may be inserted horizontally into space defined by the lower surface  1218  of the horizontal leg  1212  of the male front leg  1206  and the top face of the connecting portion  1277  of the extension member  1276  of the joint gutter  1210 . In certain embodiments, the PVC spacer strip  1322  may have openings (not shown in  FIG. 7B ) sized to allow one or more assembly screws (not shown) to pass through the openings. In certain embodiments, the PVC spacer strip  1322  is positioned such that the openings of the PVC spacer strip align with the screw holes  1226  and  1252 . Thus, the assembly screw  1228  may extend into the screw hole  1226  of the horizontal leg  1212  through the PVC spacer strip  1322  and through the screw hole  1252  of the connecting portion  1277  of the front leg  1206 . In other words, the front leg  1206  and the joint gutter  1210  may be connected, but remain relatively thermally isolated. 
     In certain embodiments, another thermal isolator, such as a rigid PVC spacer strip  1330  may be inserted horizontally into the space defined by the bottom face of the intermediate section  1240  of the male back leg  1208  and the top face of the connecting portion  1278  of the joint gutter  1210 . In certain embodiments, the PVC spacer strip  1330  has one or more openings sized to allow one or more assembly screws  1282  to pass through the opening. In certain embodiments, the PVC spacer strip  1330  is positioned such that the PVC spacer strip openings align with the screw holes  1254  and  1280 . Thus, the assembly screw  1282  may extend into the screw hole  1254  of the intermediate section  1240  through the PVC spacer  1330  and through the screw hole  1280  of the connecting portion  1278  of the joint gutter  1210 . In other words, the back leg  1208  and the joint gutter  1210  may be connected, but remain relatively thermally isolated. 
     A third thermal isolator, such as a rigid PVC tubular member  1336  may be inserted into the groove  1266  ( FIG. 7A ) defined within the vertical leg  1260  of the joint gutter  1210  to form a third thermal isolating connection. A circular end portion  1338  of the curved protrusion  1216  may be inserted into the tubular member  1336  as illustrated in  FIG. 7D . Thus, the front leg  1206  and the joint gutter  1210  may be connected, but remain relatively thermally isolated. 
     Thus, the lower joint subsystem  1202  includes the male front leg  1206  (having a first vertical leg  1214 ) which is coupled to the male back leg  1208  (having a second upper or vertical leg  1236 ) via a thermal isolation joint (e.g., the assembly screw  1228  and the PVC spacer  1322 ). The subsystem  1202  also includes the joint gutter  1210  which couples to the front leg  1206  via a second thermal isolation joint (e.g., the curved protrusion  1216  and the PVC tubular member  1336  which allows some rotation) and couples to the back leg  1208  via a third isolation joint (e.g., the assembly screw  1282  and the PVC spacer  1330 ). 
     As illustrated in  FIGS. 7C and 7D , the male front leg  1206  is positioned longitudinally adjacent to the female front leg  1306 . A field applied silicone seal  1340  may be applied between the male front leg  1206  and the female front leg  1306 . Similarly, the male back leg  1208  is positioned longitudinally adjacent to the female back leg  1308 . A field applied silicone seal  1342  may be applied between the male back leg  1206  and the female back leg  1306 . 
     In certain embodiments, there may be one or more weep holes defined with a lower surface of the joint gutter, a baffle  1344  may be positioned at the weep hole in order to minimize air from infiltrating the joint (See  FIG. 7B ). 
     In certain embodiments, there may also be vertical mullion splice members  1348  and  1350  which may also function as lifting lugs. The vertical mullion splice member  1348  may be coupled to a vertical split mullion male member  1352  (see  FIG. 7D ). Similarly, the vertical mullion splice member  1350  may be coupled to a vertical split mullion female member  1354  (see  FIG. 7D ). In certain embodiments, a shop applied silicone seal  1356  may be applied between the male back leg  1208  and the vertical splice member  1348 . Similarly, a shop applied silicone seal (not shown) may be applied between the female back leg  1308  and the vertical mullion splice member  1350  to prevent water from seeping through the joint. In various locations, other gaskets and seals may be used to prevent water infiltration such as glazing seal  1358  or gasket  1360  as is known in the art ( FIG. 7B ). Field applied seals or caulking may also be used such as  1390   a ,  1390   b , and  1390   c.    
     Turning back to  FIG. 7D , three thermal isolation members (e.g., PVC spacer  1322 , PVC spacer  1330 , and PVC tubular member  1336 ) isolate the interior male back leg  1208  from the exterior elements: front leg  1206  and joint gutter  1210 . Additionally, the vertical leg  1214  of the front leg  1206  and the vertical leg  1236  of the back leg  1208  along with the gaskets  1318  and  1320  proved a dual line of defense for the stack joint. The subsystem  1202  also provides for internal weepage through weep holes and baffles, such as baffle  1344  (not shown). 
     The Upper Subsystem (Second Embodiment): 
       FIG. 8A  is a section view through certain horizontal members of the upper subsection  1204  of  FIG. 6  (or lower framing member of a curtain wall unit). As illustrated, in certain embodiments, a stack joint female member  1402  may have a plurality of downward pointing vertical members or legs, such as vertical leg  1416 , vertical leg  1418 , vertical leg  1420  and vertical leg  1422 . Vertical leg  1418  and vertical  1420  form the channel  1404  and are spaced such that they can accept the vertical legs  1214  and  1236  of the lower subsystem  1202  (See  FIG. 6  and  FIG. 7B ) to create an air tight or pressurized chamber (chamber  2209  of  FIG. 6 ). In certain embodiments, the stack joint female member  1402  may also have screw splines  1424  and  1426  for coupling with out of plane screws (not shown). 
     In certain embodiments, a groove portion  1428  forming a longitudinal groove  1430  may be defined at the lower end of the vertical leg  1418 . The vertical leg  1416  may have a connecting portion  1432 . In certain embodiments, one or more screw hole(s)  1434  is defined within the connecting portion  1432 . 
     A horizontal fin  1440  may be used to support a lower panel of glass, such as lower panel  132  of vision glass which may be part of an upper unit, such as top framing member  118  ( FIG. 1 ). In certain embodiments, a gasket  1442  may be coupled to the upper stack joint female member  1402  and positioned such that the gasket  1442  is between the upper stack joint member  1402  and the lower panel  132  of vision glass. A backer rod  1444  and seal  1446  may be positioned between the lower panel  132  and the horizontal fin  1440  as illustrated in  FIG. 8A . In certain embodiments, there may be a longitudinal groove  1448  for accepting and coupling with a gasket  1451  that is positioned between the horizontal fin  1440  and the male front leg  1206  of the lower subsystem  1202 . 
     In section, an interior end  1452  of the horizontal fin  1440  is circular and is designed to fit within a thermal isolator, such as a rigid partially tubular PVC member  1454 . In turn, the rigid PVC tubular member  1454  may be sized to be inserted into the groove  1430  defined within the vertical leg  1418  of upper stack joint member  1402  to form a thermal isolating connection. Thus, the vertical leg  1418  and the horizontal fin  1440  may be connected, but remain relatively thermally isolated. 
     In certain embodiments, the horizontal fin  1440  may have one or more screw holes  1456  such that when the horizontal fin is coupled to the stack joint member  1402 , the screw hole  1456  and screw hole  1434  align so that an assembly screw  1458  may be placed in the screw holes to couple the connecting portion  1432  of the vertical leg  1416  to the horizontal fin  1440 . The assembly screw  1458  may go through a thermal isolating member, such as a PVC spacer strip  1460  which may be positioned between the horizontal fin  1440  and the connecting portion  1432  of the vertical leg  1416 . 
     In certain embodiments, the PVC spacer strip  1460  may be inserted horizontally into grooves defined within the bottom face of the connecting portion  1432  of the vertical leg  1416  and defined within the top face of the horizontal fin  1440 . In certain embodiments, the PVC spacer strip  1460  may have openings (not shown in  FIG. 8B ) sized to allow one or more assembly screw(s) (not shown) to pass through the openings. In certain embodiments, the PVC spacer strip  1460  is positioned such that the openings of the PVC spacer strip align with the screw holes  1434  and  1456 . Thus, the stack joint member  1402  may be coupled and supports the horizontal fin  1440 , but is thermally isolated from the horizontal fin via the PVC spacer strip  1460  and the rigid tubular PVC tubular member  1454 . 
     The female or upper stack joint female member  1402  may be made of extruded aluminum. In certain embodiments, the stack joint female member  1402  may be coupled to a split male mullion  1406  as illustrated in  FIG. 8B . A split female mullion  1408  may be coupled to a stack joint female member  1410  of an adjacent unit. If required, the stack joint female members  1402  and  1410  may be coupled to snap on sill trim members  1412  and  1414 , respectively. 
     The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many combinations, modifications and variations are possible in light of the above teaching. Undescribed embodiments which have interchanged components are still within the scope of the present invention. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.