Patent Publication Number: US-2003221381-A1

Title: Exterior vision panel system

Description:
CLAIM FOR PRIORITY, INCORPORATED BY REFERENCE  
     [0001] This application incorporates the disclosure in PCT patent application Ser. No. PCT/US00/28042, filed on Oct. 11, 2000, published on Nov. 1, 2001 and entitled Enhanced Window Frame Assembly and Method. The prior filed PCT Patent Application and any other documentation referenced therein and other documentation referenced herein are incorporated herein in their entirety by reference. If the descriptions and drawings in the prior filed PCT Patent Application and the other referenced documentation are inconsistent with the description and drawings herein, the description and drawings herein take precedence. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] This invention relates to an improvement on an isolated exterior panel, such as a vision panel commonly known as a window, window wall, punch-out windows, or ribbon windows or other non-curtain-wall panel systems. More specifically, the invention relates to an improved window frame assembly that seals against exterior water and air leaking into a building interior.  
       BACKGROUND  
       [0003] Windows and other exterior panels generally allow outward vision from inside a building. However, because of glass or other typically brittle materials of construction, the panels are typically framed and the framed panels supported by other portions of the building. The framed panels may also provide other benefits such as improved aesthetic appearance. One type of exterior arrangement for a building is a curtain wall where exterior vision and/or other framed panels are each generally supported by an associated internal mullion or other interior building support structure, forming an essentially non-load bearing exterior surface of a building.  
       [0004] Another type of building exterior arrangement includes a wall or other exterior structure that supports, at least in part, adjacent windows or other panel systems that are separated or isolated by other portions of the wall, e.g., an isolated vision assembly or system comprising a series of fixed framed window panes placed on a spandrel sill in an exterior load bearing wall of a building. The windows or other panels may be fixed or openable and may also be placed in an exterior door or other adjacent exterior structures that generally support the isolated windows or panels. Exterior building structure such as wall typically comprise some type of masonry structure or mixed structure, e.g., precast concrete, bricks, hollow blocks, masonry, mortar, cement and stucco on a wood or steel stud frame, but other exterior building structures can be doors composed of wood, plastic, metal, or other structural material. Walls or other building exterior structures may be directly load bearing or otherwise supported, e.g., at each floor.  
       [0005] A window wall system normally refers to one type of an isolated vision or other panel assembly extending from a floor surface to a ceiling level between two partitioning vertical masonry walls or other exterior structure such as commonly seen on high-rise apartment building with extended exterior patios. A punch-out window system normally refers to a vision assembly formed within a punch-out area of a load-bearing masonry wall or wooden door. A ribbon window system normally refers to the condition of vision panels forming a horizontal band between two horizontal bands of masonry walls.  
       [0006] The three system types mentioned above and other wall/window systems can be classified as isolated exterior windows or other framed panels in a building wall that provides at least a significant portion of the support for the framed panels. An isolated vision or other panel system is differentiated from a curtain wall panel system where the majority of support for each exterior panel is not provided by an exterior wall structure.  
       [0007] The cost of installing, maintaining, and replacing prior-art isolated windows in a large commercial building is not insignificant. Costs can result from the need to install fixed windows from outside the building, time consuming and costly sealing of window panels in the field, and providing cleaning, repair, maintenance, and other access to the fixed windows, especially access to the exterior surface of the window and/or window frame.  
       [0008] And despite the high installation and maintenance costs, prior isolated or framed window panel systems may still allow excessive air and/or rain water to get into the building, e.g., after seal degradation, under extreme wind conditions, or under extreme structural loadings due to single-events such as seismic events. In addition, inter-floor deflection, dynamic cycles of positive and negative wind loads (e.g., winds and/or wind loads directed towards and away from the building interior on one side of the building), daily thermal expansion and contraction, and other daily ventilation and other equipment operation may cause loosening of building attachment means, structural fatigue failures, and hysteresis loss of seal compression, resulting in still further damage and water leakage.  
       [0009] A significant problem of many exterior vision panel systems is water leakage along the panel, frame, and wall interface areas, especially after time and exposure to various environments/structural loads cause deflection and cracks in seals and/or in masonry walls or wood doors. For example, inter-floor deflection, seismic and other loads that are not sufficient to cause direct failure, may still tend to crack or loosen window panes and damage window seals, especially if the windows are improperly installed or the building structure is slightly deformed. Moreover, repairs may require access from outside the building to accomplish field caulking to resist water and exterior air infiltration (requiring exterior access equipment for upper floor windows) and air and water leakage repair is often temporary in nature and may require repeated repairs. Thus, although significant advancements have been made in achieving some objectives for a window frame or other isolated panel systems, an improved system is still needed.  
       SUMMARY OF THE INVENTION  
       [0010] A preferred embodiment of a panel frame assembly for supporting an exterior panel assembly is attached to at least two exterior building surfaces, the panel frame assembly comprising at least one window frame element sealably connected to a panel forming a framed window subassembly and at least two perimeter frame elements each secured to a building surfaces and each sealably connected to the framed window subassembly with an air seal and a water restrictor. The frames, building surfaces and panel forms at least two airloops and an air space, each having an air seal, a water restrictor and an air passageway for substantially equalizing air pressure within the airloop or air space and the air pressure in the exterior environment. In the preferred embodiment, the cross-sectional area of the air passageways is at least about 0.1 square inches. The embodiment is similar to the airloop system described for a curtain wall assembly in U.S. Pat. No. 5,452,552, but the window perimeter frame, building surfaces, a perimeter air seal, and a perimeter water restrictor form an air space that is pressure equalized through an air passageway. The airloops and air space act to further limit any water transmission from the water restrictor so that the air seals do not have to contend with significant amounts of water. The airloops and air space also include means for draining any water that may be leaked or condensed therein before most of the water can contact the air seals. The airloops, air space, water restrictors, and spaced-apart air seals provide a long term reduction in water leakage problems even after seals become imperfect. Still further, the adverse impacts of relative vertical deflection/displacement between perimeter and panel frames are minimized by a splined male member slidably placed in a female joint area that allows relative displacement between the perimeter frame and panel frame member without the loss of the water restrictor or air seal functions still further reducing long term water leakage problems. Moreover, the preferred embodiment uses slidable clips and splines, allowing installation of the window frame without access from a location exterior to the building. The design also uses compatible panels for adjoining curtain wall or similar windows to minimize interface problems.  
       [0011] Embodiments of the isolated or framed panel assembly may also include some or all of the following features: an air passageway sufficient in size to equalize the pressure in an air loop with the exterior environment and drain the airloop and incorporate baffles or protrusion to create a circuitous path water restrictor to limit water entry, structural retention of a framed window subassembly within a secured frame element for sealing and resisting positive (inward directed) and negative (outward directed) wind loads, thermal breaks in one or more frame elements to increase the resistance to heat transfer between the building interior and the exterior environment, and cover frame elements to allow easier window assembly installation and removal but limit unintentional removal. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a fragmented partial exterior elevation view of a typical airloop exterior-vision panel system of the invention having a single punch-out window panel.  
     [0013]FIG. 2 is a fragmented partial exterior elevation view of a typical airloop exterior vision panel system of the invention having multiple punch-out window panels or having a window wall system.  
     [0014]FIG. 3 is a fragmented partial exterior elevation view of a typical airloop exterior-vision panel system of the invention having a ribbon window system.  
     [0015]FIG. 4 is a partial cross-sectional view taken along line  4 - 4  of FIG. 1 or FIG. 2 or FIG. 3.  
     [0016]FIG. 4 a  is a partial cross-sectional view similar to FIG. 4, but of an alternative spandrel veneer system embodiment.  
     [0017]FIG. 5 is a partial cross-sectional view taken along line  5 - 5  of FIG. 1 or FIG. 2 or FIG. 3.  
     [0018]FIG. 6 is a partial cross-sectional view taken along line  6 - 6  of FIG. 1.  
     [0019]FIG. 7 is a partial cross-sectional view taken along line  7 - 7  of FIG. 2 or FIG. 3.  
     [0020]FIG. 8 is a partial cross-sectional view taken along line  8 - 8  of FIG. 2.  
     [0021]FIG. 9 is an isometric view of the perimeter frames before assembling.  
     [0022]FIG. 10 is an isometric view of the positioning clip for assembling the perimeter frames.  
     [0023]FIGS. 11 a - d  shows air seal corner connections. 
    
    
     [0024] In these Figures, it is to be understood that like reference numerals and/or letters refer to like elements or features with similar functions.  
     [0025] Description  
     [0026] In order to better explain the working principles of the invention, the following terminology will be used herein:  
     [0027] a window or other panel: a glass or other essentially non-load supporting wall element secured and nominally sealed to a window or panel frame;  
     [0028] an inner airloop: an air space substantially forming a loop around and near the perimeter edges of the glass or other panel element and generally within the window frame or panel frame;  
     [0029] an outer airloop: an air space substantially forming a loop around the window pane or panel proximate to the inner air loop;  
     [0030] a perimeter air space—an air space between a field installed perimeter frame and an adjacent building surface, e.g., cut-out surfaces for an isolated window in a masonry wall;  
     [0031] a water seal: a sealant line in an exterior water path towards an interior space within the building, the water seal restricting water infiltration when little or no differential air pressure is present across the sealant line;  
     [0032] a water restrictor: a water seal or other means to minimize water transmission in an exterior water path towards an interior space such as a tortuous path tending to remove water droplets from air passing through; and  
     [0033] an air seal: a sealant line for restricting exterior air infiltration into the building located inboard and spaced-apart from a water seal or other water restrictor.  
     [0034]FIG. 1 illustrates an embodiment of an airloop exterior vision panel system  10  of the punch-out window type comprising a single glass panel  11  with shop installed sill panel frame  12 , head panel frame  13 , and two jamb panel frames  14  and four field installed perimeter frames: sill frame  15 , head frame  16 , and two jamb frames  17 . Although the frames are composed of an extruded aluminum alloy in the preferred embodiment, other materials of construction may be used in alternative embodiments such as extruded steel, PVC or other relatively rigid plastics.  
     [0035] The punch-out window system shown supports a double-pane window panel  11 , which in turn is supported by the masonry wall or stud wall W. In alternative embodiments, the panel  11  may also have metal, plastic, or other connected decorative jamb elements (e.g., forming what appears to be a two or four glass panel system), be composed of a plastic material, a photovoltaic material, or other panel materials instead of glass. In still other alternative embodiments, the window panel  11  may be composed of a single glass panel, a composite material panel, or other types of window-like panels. In still other alternative embodiments, the exterior vision panel system is located in exterior building surfaces other than exterior masonry walls such as a skylight in a roof structure or a window in an exterior door.  
     [0036]FIG. 1 shows mitered corners on the various frame members. As discussed below and shown in FIGS. 11 a  through  11   d , the corners of the frames may also connect air seal such that air spaces or airloops may allow air and/or water to flow around the perimeter of the window panel  11  without penetrating the building interior I. (See FIG. 4 for building interior, air loops, and air spaces. See FIGS. 11 a - 11   d  for a preferred seal embodiment at the corners.) If corner-connected, the airloops and air spaces may allow water to drain from upper airloop portions to one or more drain holes in lower airloop portions, e.g., as shown on FIG. 4. If the airloops or air spaces are not corner connected, each segment or portion may include an air passageway to equalize air pressure and/or drain water.  
     [0037]FIG. 2 illustrates an embodiment of the airloop exterior vision panel system  20  of the window wall type comprising multiple vision glass panels  11 , each with shop installed sill panel frame  12 , head panel frame  13 , and two jamb panel frames  14 , all sealably connected to the perimeter frames. Four perimeter frames are typically field installed to form a perimeter frame assembly: a sill frame  15 , a head frame  16 , and two jamb frames  18 . The window wall system  20  is supported by the masonry wall W. Similar to the punch out window system described above, alternative materials and designs may be used for the glass panels  11  in alternative embodiments. In addition to the fixed window panel shown in FIG. 2, double-hung windows, casement or other types of panels or windows may be incorporated in alternative embodiments.  
     [0038]FIG. 2 also shows mitered frame corners. Similar to the above discussion and as discussed below and shown in FIGS. 11 a ,  11   b ,  11   c , and  11   d , the mitered corners may also provide additional corner seals and fluid pathways for various airloops and air spaces that extend around the perimeter of the window wall system.  
     [0039]FIG. 3 illustrates an embodiment of the airloop exterior vision panel system  30  of the ribbon window type comprising multiple vision glass panels  11 , each with a shop installed sill panel frame  12 , head panel frame  13 , two jamb panel frames  14  and connected to two perimeter frames that are typically field installed: sill frame  15  and head frame  16 . The ribbon window is supported by a masonry or stud wall W. In alternative embodiments, the ribbon window may include patio or other doors, casement or other openable windows, and have other variations similar to that described above.  
     [0040]FIG. 3 also shows mitered corners. Similar to the above discussion and as discussed below, the mitered corners may provide air and/or water drainage pathways for various airloops that extend around the perimeter of the ribbon wall system.  
     [0041]FIG. 4 shows a typical fragmentary cross-section of one embodiment of the perimeter sill condition taken along line  4 - 4  of FIG. 1 or FIG. 2 or FIG. 3. The perimeter sill frame  15  is typically field installed and comprises an open and/or cantilevered structural perimeter sill member  15   a  and an interior sill cover  15   b . The perimeter sill member  15   a  is supported by a masonry wall W. In alternative embodiments, the structural perimeter sill member  15   a  may be supported by a window spandrel beam or other structural member which is in turn supported by an alternative wall, door, or other support structure. In addition, flashing, insulation, sealing, or other interface materials may be placed in between the cantilevered sill member  15   a  and wall W.  
     [0042] Wall W preferably includes a recessed edge  24 . Although the depth of the recessed edge  24  (from the wall surface where a first fastener  25  attaches the perimeter sill member  15   a  to the wall W) can vary, the depth is preferably at least about ⅛ inch (0.32 cm), more preferably at least about ¼× inch (0.63 cm), and most preferably at least about ½ inch (1.27 cm). If the outboard edge of wall W is also downwardly sloped outward as shown, the depth of the sloped portion at the exterior edge of the wall W (also from the wall surface where the first fastener  25  attaches the perimeter sill member  15   a  to the wall W) is at least about ¼ inch (0.63 cm), more preferably at least about ½ inch (1.27 cm), and most preferably at least about 1 inch (2.54 cm)  
     [0043] Cover projections  15   bp  of the interior sill cover  15   b  are preferably snap fit with sill member projections  15   ap . However, in alternative embodiments, other means for attaching the interior sill cover  15   b  to the sill member  15   a  may be used, e.g., screws, clamps, adhesives, latches, openable hinges, or other fasteners.  
     [0044] The design of the sill frame member  15   a  and a lower panel-to-perimeter interface frame or sill frame  12  produces two unsealed openings to a perimeter air space  23  and an outer airloop  22 . The unsealed openings allow air from the exterior environment E to enter and equalize pressure on both sides of one or more drainage holes  57 . However, the path of any air flow into the interior portion of the perimeter air space  23  or outer airloop  22  is tortuous to act as a water restrictor and/or water removal device from the air moving towards the interior environment I. Although the dimensional size of the perimeter air space  23  can vary widely, an excessively small size can result in interference and tolerance problems between the perimeter sill frame  15   a  and wall W, especially if deflections of the wall are encountered. However, an excessively large opening and cross-sectional dimensions of the perimeter air space  23  (and outer airloop  22 ) can result in a less tortuous path and water penetration deep inside the perimeter air space. In the preferred embodiment, a nominal distance between any surface of the perimeter sill member  15   a  and the masonry sill edge  24  (outward of the drainage hole  57  and outward of the first attachment means and attachment shim  60 ) ranges from at least about 0.01 inch (0.025 cm) to no more than about 1 inch (2.5 cm) or more, more preferably from at least about 0.1 inch (0.25 cm) to no more than about 0.5 inch (1.25 cm), and still more preferably from at least about 0.125 inch (0.32 cm) to no more than about 0.375 inch (0.96 cm).  
     [0045] The bottom segment of an outer open airloop  22  is formed between the perimeter sill member  15   a  and the interface or panel sill frame  12  forming a water restrictor, in this case a tortuous air path from the external environment E to air hole  55  as shown by arrow path TP. The tortuous path TP is similar in function to the recessed water path in the perimeter air space  23 . The tortuous path TP within a portion of the outer airloop  22  tends to remove water droplets for air moving towards the building interior I prior to any air entering the air hole  55  or contact with air seal  21 . Water removed from the outer airloop  22  is drained through drain hole  57  into the lower air space portion  23  to be drain to the exterior of the wall W.  
     [0046] The lower air space portion  23  shown is also pressure equalized to the exterior E through the passageway between the wall W and the outer portion of the perimeter sill frame  15   a . The perimeter sill member  15   a  is structurally secured to the masonry edge preferably using at least two first-fasteners  25 . The male spline  19  (when combined with an air seal  21 ) is designed to cause the structural engagement of the perimeter sill member  15   a  with the interface frame (or panel sill frame)  12 . The interface or panel sill frame  12  has one or more air holes  55  allowing pressure equalization of the inner airloop  56  from the pressure equalized, lower air space portion  23 .  
     [0047] The interior cover  15   b  is designed to provide an interior sill finish. In the embodiment shown in FIG. 4, the interior cover  15   b  also covers the top edge of an interior wall  26 , but other embodiments may not include an interior wall.  
     [0048] The perimeter air seal  43   a  is formed between the structural sill member  15   a  and the masonry sill edge  24  preferably using curable caulking, however other sealing materials may be used in alternative embodiments. One or more drainage holes  57  are provided in the perimeter sill member  15   a , e.g., below the center of the punch out window panel  11  shown in FIG. 1.  
     [0049] Besides the snap fit connection embodiment shown, various shapes and means for connecting the perimeter sill member  15   a  and the interior sill cover  15   b  can be contemplated, for example, a sill cover and perimeter sill member screw connection, hinged connection, and a slotted connection. However, essentially all of the alternative shapes of a perimeter sill member  15   a  provide a water restrictor between the wall and perimeter sill member, such as an elastomeric water seal or the tortuous path for entering air shown. In other embodiments, a screen or other water contacting device can replace or supplement the tortuous path or be placed over the drain hole  57 .  
     [0050] The dimensioning of the drainage hole  57  may vary widely, e.g., depending upon the wind and rain loads expected to enter the outer airloop  22 , along with channel members CM to provide a channel CH between drainage holes to direct collected water between drainage holes  57  to a proximate drainage hole. However, the drainage holes  57  should not be too large so as to allow substantial amounts of water-laden air to flow from the outer portions of the perimeter air space  23  to the outer airloop  22 . For a nominal punch out window, at least one drainage hole  57  preferably has a cross sectional area of at least about 0.01 square inches (0.064 sq. cm), e.g., at least a nominal ⅛ inch (0.32 cm) diameter hole is preferred. However, other applications may require multiple drainage holes with larger or smaller dimensions, more preferably at least about two drainage holes located at or near the center and each having an opening of at least about 0.196 square inches (1.267 square centimeters), e.g., a nominal ½ inch (1.27 cm) diameter drainage hole.  
     [0051] The one or more air holes  55  are also sized to drain leaked or condensed water (e.g., leaking water from one or more water seals WS) as well as to simultaneously pressure equalize the inner airloop  56 , e.g., allowing water to drain down while also allowing exterior air to flow up. This can be accomplished by having more than one air hole  55  at different locations (for example, near one or more corners) and sizes, e.g., larger to allow water and air flows. However, the size of each air holes  55  is preferably similar to the preferred drainage hole  57  discussed above.  
     [0052] The dimensions of the tortuous path TP of the outer airloop  22  are also limited in order to minimize water droplet carryover. The tortuous path TP does not allow a straight path flow of air from the exterior environment E to enter the air hole  55 . Preferably, the tortuous path consists of at least two baffles with one located on the sill member  15   a  and one located on the panel sill frame  12 . The air flow cross-sectional area through the tortuous path is typically sized to be at least double the cross-sectional area of the air hole  55 , but also requiring the air flow from the exterior environment E to turn and change direction at least once. Similar to the above discussed spacing between the perimeter sill member  15   a  and sill surface  24  of wall W, the closest any portion of the perimeter sill member  15   a  approaches the lower interface frame (or panel sill frame)  12  outboard of the air hole  56  is preferably at least about from at least about 0.01 inch (0.025 cm) to no more than about 1 inch (2.5 cm) or more, more preferably from at least about 0.1 inch (0.25 cm) to no more than about 0.5 inch (1.25 cm), and still more preferably from at least about 0.125 inch (0.32 cm) to no more than about 0.375 inch (0.96 cm). In alternative embodiments, a water seal may take the place of the tortuous path TP.  
     [0053] The dual glass panel  11  is supported by one or more setting blocks B that, in turn, are supported by the panel sill frame  12 . If a single block B is used, it is preferably discontinuous to allow a path for any water leaking past the window water seal WS to drain at one or more air holes  55 . The pressure equalization of the inner airloop  56  with the external environment E minimizes water leakage past the window water seal WS even when the window water seal in imperfect, e.g., the window water seal is cracked due to aging and/or stress and acts as a tortuous path water restrictor.  
     [0054] The removal of leaking water through the air hole  55  and drainage hole  57  allows the interior window seal IS to restrict exterior air infiltration (or loss of interior air to the exterior environment) without the need to also seal against water leakage at this point. Any pressure difference between the interior I and exterior E environments will tend to leak air across the interior window seal IS, but not water since water contact with the air seal has been substantially precluded by the air holes, drains, water seals, and/or water restrictors. This exclusion of water tends to prevent corrosion, erosion, and further deterioration of interior portions of the panel or window system and interior window seal IS, improving long term performance. Because water is effectively excluded from contacting the window air seal IS, many types of air seals can be used that might otherwise be degraded by contact with water.  
     [0055] The mitered corners of the frame members shown in FIGS.  1 - 3  produce inner and outer airloop segments (e.g., having lower airloop segment  22  and  56  shown in FIG. 4) and a perimeter air space segments (e.g., the lower airspace segment  23  shown in FIG. 4) that together with other segments may extend around the perimeter of the window assembly. (See also FIGS. 11 a - 11   d .) However, the inner and outer airloops e.g., see lower airloops  56  and  22  in FIG. 4) and the perimeter airspace segments  23  may not extend around the perimeter in some alternative embodiments. For example, flashing may be used to cover other portions of the frame to wall interfaces and avoid the need for a substantial perimeter airspace and restrict water transmission around the entire perimeter of the window system without a water restrictor. Other reasons for airloops or an airspace that does not extend around the entire perimeter of the window system include separate airloops and drainage paths around each side, support interfaces preventing airloop continuation, and an open interior space I not requiring air or water sealing.  
     [0056] The first fastener  25  is preferably a removable masonry screw securing perimeter sill member  15  to spacer  60   a  and wall W. In alternative embodiments, other means for spacing and fastening a frame element to a building wall W may be used, e.g., anchor bolts.  
     [0057] Protrusions CM in the perimeter sill frame  15  form a portion of a channel CH for slidably retaining the clip  48  (see FIGS. 9 &amp; 10). The channel CH preferably slidably mates with clip  48  (as shown in FIGS. 9 and 10) across the entire length of the frame element  15   a , but sliding may also be limited to an area near the ends of the frame element. The protrusions CM may also serve as baffles or additional tortuous path surface area acting as a water restrictor. In an alternative embodiment, the protrusions CM may be extended upwardly into the tortuous path to replace one of the baffles shown.  
     [0058]FIG. 4 a  is a cross-sectional view similar to FIG. 4, but of an alternative embodiment that uses a spandrel veneer system instead of a masonry wall. This type of spandrel veneer system typically includes spaced apart vertical stud members  61   a  (generally composed of steel), stud track member  61   b  structural face  64 , insulating foam board  62 , and a water-resistant protective skin  63 . A flushing plate  66  (generally composed of aluminum) is attached (generally with glue or other adhesive) to the top surface of the spandrel veneer system to form a drainage surface. In comparison to FIG. 4, the structural perimeter sill member  15   a  is replaced with an alternative perimeter sill member  15   c  in FIG. 4 a  and the water restrictor path shown in FIG. 4 is replaced with a water seal  65 , generally a shop installed foam tape. The water seal  65  is preferably not continuous, but leaves a small gap of at least about 0.1 inch (0.25 cm) near the center for water drainage, more preferably the gap is about 1 inch or 2.5 cm. The discontinuous water seal  65  plus the overhang OV of the alternative sill member  15   c  acts as a tortuous path and water restrictor in the air space between the sell member  15   c  and spandrel veneer system wall, substantially allowing air to equalize in pressure to the exterior environment but preventing water droplets from being transmitted past the discontinuous water seal  65 . The overhang OV is preferably at least about 1 inch (2.5 cm), more preferably at least about 2 inches (5.1 cm) in order to limit water entry past the discontinuous water seal  65 . Other portions of the alternative embodiment for a spandrel veneer sill, including the lower interface frame  12 , are similar to that shown for a masonry wall in FIG. 4.  
     [0059]FIG. 5 shows a typical fragmentary cross-section of one embodiment of the perimeter head portion taken along line  5 - 5  of FIG. 1 or FIG. 2 or FIG. 3. The top segment of an upper outer airloop  27  is formed between the perimeter head member  16  and the window panel head frame  13 . As discussed elsewhere herein and shown in FIGS. 11 a - 11   d , the mitered corner joints may fluidly connect the upper outer airloop  27  to the lower outer airloop  22 . Preferably, the upper perimeter air space  28 , the lower perimeter air space  23  (shown on FIG. 4), and the side perimeter air space  36  (shown on FIGS. 6 and 8) are each independently pressure equalized with air holes or openings. The upper perimeter air space  28  is formed between the perimeter head member  16  and a masonry head edge  31  of the building wall W. The perimeter head member  16  is structurally secured to the masonry edge  31  preferably using at least two second fasteners  32 . The first and second fasteners are preferably similar, but other means for fastening as discussed above may also be used.  
     [0060] The perimeter head member  16  has a female joint and seal space  33  to engage the panel head frame  13 , spline  52  and air seal  34 . The panel head frame  13  is held in the engaged position by male joint spline  52  and third fastener  53  that is attached to the ceiling edge supporting angle  54  using a third fastener  53  and ceiling angle shim or spacer  60   a . (Attachment of ceiling edge supporting angle  54  to ceiling or other building support is not shown for clarity.) The spline  52  and third fastener  53  allow the installation and removal of the panel assembly from the building interior without requiring exterior access. In alternative embodiments, other means for connecting and attaching (as discussed above) and other sealing engagements may be used, e.g., retained 0-rings and slidable gasketed joints.  
     [0061] The slidable seal  34  and female joint/seal space  33  configuration allows relative motion between the perimeter frame  16  and the panel head frame  13 . Relative motion may be caused by deflections of portions of some wall structures, e.g., under variations in live loads in adjacent floor, the distance between opposing window cutout surfaces supporting a perimeter frame segment may vary. However, this type of supporting wall surface deflection motion is typically limited by the structural stiffness of the building structure. Under a maximum design live load on a floor, the deflections are typically about ⅜ inch (0.95 cm), at least about ¼ inch (0.64 cm) and no more than about 0.5 inches (1.27 cm). For preferred spline  52  and spline penetration into the depth D of the female joint and seal space  33 , the depth is typically at least about at least about ⅜ inch (0.95 cm) and still more typically at least about ½ inch (1.27 cm). In alternative configurations, the slidable seal  34  may be configured as a lubricated gasket, O-ring, or other type of seal that will accommodate these relative motions between sealing surfaces of the panel head frame  13  and spline  52 .  
     [0062] The upper outer airloop portion  27  includes snap-on impinging baffle SB within the airloop to form another tortuous path as shown by arrow TP and similar in function and design to the prior described tortuous paths TP (see, e.g., FIG. 4). The water impinging upon the exterior surface of snap-on baffle SB drains back towards the exterior environment. Water otherwise removed in the upper outer airloop  27  may also drain to one or more mitered corners and from there to other portions of the outer airloop until the water is drained to the exterior building wall surface, e.g., from drainage hole  57  as shown in FIG. 4. Since the fastener  53  is applied from the inside, the baffle SB can be made as an integral part of the head panel frame  13  in an alternative embodiment. The shape of the upper outer airloop portion  27  can vary widely, but the TP air passageway has functions similar to the pressure equalization and water restrictor functions of the lower outer portion  22  described above.  
     [0063] The upper perimeter air seal  43   b , upper perimeter water seal  44   a , portions of perimeter head frame  16  and portions of the masonry edge  31  form the other boundaries of the upper perimeter air space  28 . The upper perimeter air seal  43   b  preferably uses field installed curable caulking and the perimeter water seal  44   a  preferably uses a foam tape shop installed on the perimeter head frame  16 , however, other sealing methods and/or materials can be used in alternative embodiments, e.g., o-rings, C-type seals, and gaskets. To drain condensed or leaked water and/or to pressure equalize the upper perimeter air space  28 , one or more air holes  29  are provided at locations preferably spaced apart from the fasteners  32 . Various shapes for the perimeter head member  16  and various connection methods can be contemplated, e.g., protrusions and/or alternative shapes that form an alternative tortuous path TP replacing the upper perimeter water seal  44   a.    
     [0064]FIG. 6 shows a typical fragmentary cross-section of one embodiment of the perimeter jamb frame  17  taken along line  6 - 6  of FIG. 1. The perimeter jamb frame  17  is preferably field installed and comprises a structural perimeter jamb member  17   a , a jamb air cover member  17   b , and an interior jamb cover  17   c . The perimeter jamb frame  17  is attached to the perimeter head member  16  and the perimeter sill member  15  to form a continuous or discontinuous panel outer airloop and/or perimeter air space segments.  
     [0065] The side portion or segment of the outer airloop  35  is formed between the perimeter jamb member  17   a  and the panel jamb frame  14 . Baffles or other protrusions into the outer airloop side portion  35  again provide a tortuous air path similar to the tortuous air paths described for other portions of the outer airloop. A side perimeter air space portion  36  is formed between the jamb members  17   a  &amp;  17   b  and the masonry jamb edge  38  of the wall W. The side perimeter air space portion  36  is pressure equalized to the exterior environment E preferably through one or more air holes  37  typically spaced apart from the locations of the side fasteners  39 . In other embodiments, the air holes  37  are not needed if protrusions or wipers form a water restrictor replace the water seal  44   b  and/or access to exterior air from a different perimeter segment is available at the frame corners.  
     [0066] The perimeter jamb member  17   a  is structurally secured to the masonry edge  38  of wall W using one or more side fasteners  39  spaced apart from the wall W by one or more shims or spacers  60 . Although the preferred side shims or spacers  60  and side fasteners  39  are similar to the top and side fasteners previously discussed, alternative fasteners, shims, and spacers as previously discussed may also be used.  
     [0067] The jamb air cover member  17   b  and air seal  41   a  are structurally secured to the jamb member  17   a  using air cover fastener  42  which is accessible from the building interior I before the installation of the snap-on interior cover  17   c . The side segment of the outer airloop  35  is formed between the perimeter jamb member  17   a  and the panel jamb frame  14  with a tortuous path shape similar to the other portions of the outer airloop. A perimeter air space  36  is formed between the perimeter water seal  44   b , the perimeter air seal  43   b , the side jamb  17  and the side jamb edge  38  of the masonry wall W similar to head portion of the air space  28  (see FIG. 5). The interior cover  17   c  is designed to provide the optional interior jamb finish and can alternatively be connected to the jamb air seal member  17   b  with other means of attachment instead of the snap-on feature as shown.  
     [0068] The side perimeter air seal  43   b  is preferably comprised of a curable caulking placed in the field between the jamb air seal member  17   b  and the masonry jamb edge  38 . The side perimeter water seal  44   a  preferably comprises foam tape shop installed on the perimeter jamb frame  17  and is placed between the structural jamb member  17   a  and the masonry jamb edge  38  is similar to the other perimeter water seals at the other perimeter frame elements. Various shapes for the perimeter jamb member  17   a  and the jamb air seal member  17   b  and various connection methods can be contemplated that form sealing surfaces and/or alternative tortuous paths.  
     [0069]FIG. 7 shows a typical fragmentary cross-section of one embodiment of the intermediate vertical panel joint taken along line  7 - 7  of FIG. 2 or FIG. 3. The vertical or protruding joint member  45  with first and second intermediate air seals  46   a  &amp;  46   b  is preferably shop installed. Intermediate water seals  47  are preferably comprised of a foam tape preferably shop installed on protruding joint member  45 . Intermediate fasteners  53  secure the vertical joint member  45  to the panel assembly  11 . Intermediate outer airloop  35   a  is similar in shape and function to the side segment of the outer airloop  35  shown on FIG. 7.  
     [0070]FIG. 8 shows a typical fragmentary cross-section of another embodiment of a perimeter jamb  18  taken along line  8 - 8  of FIG. 2. The descriptions and functional explanations are similar to FIG. 6 except that the perimeter jamb frame  18  is an alternative single member rather than the three parts of a perimeter jamb member  17  shown in FIG. 6.  
     [0071] In the above explanations, the ends of the vertical members  17   a ,  17   b ,  17   c ,  18  and  45  must be notched to allow passage of the perimeter sill frame  15  and the perimeter head frame  16 . As shown in FIGS.  4 - 8  and FIGS. 11 a - 11   d , to complete the perimeter air seal, the following seal connections must be accomplished:  
     [0072] 1. connecting air seals  43   a  to  43   c  along the end profile of the perimeter sill member  15   a;    
     [0073] 2. connecting air seals  43   c  to  41  along the end profile of the jamb air seal member  17   b;    
     [0074] 3. connecting air seals  43   c  to  43   b  at the corner; and  
     [0075] 4. connecting air seals  46   a  to  46   b  at the ends of the vertical joint member  45 .  
     [0076]FIG. 9 shows an isometric and exploded view of perimeter head and sill members  15   a  &amp;  16 , and two jamb perimeter members  17   a , preferably shop fabricated, in an exploded position prior to field assembling and attachment to the building wall (e.g., see FIGS. 4, 5,  6 , and  7 ). To facilitate the field erection, the perimeter head frame  16  and the perimeter sill member  15   a  are preferably shop attached with end positioning clips  48  using set screws  51  at an assembling position  49 . An assembling position with a representative exploded view shown in FIG. 9 prior to sliding the clips (in engaging pocket  59 ) and set screws  51  to the installed positions  50 . The assembling position is about six inches away from the perimeter head frame  16  end and the sill member  15   a  end. The screw holes  50  may also be provided to secure the clips  48  in the installed positions on the head and perimeter sill members  18  and  15   a.    
     [0077]FIG. 10 shows an isometric view of the positioning clip  48 . The clip has corner notches  58  to allow the clip  48  to slide freely within the engaging pocket  59  (e.g., see FIG. 6) in the frame members  15   a ,  16 ,  17   a , and  18 .  
     [0078]FIG. 11 a  shows the air seal  43   c  connected to air seal  43   a  using corner air seal  43   d  at an end of the frame elements. Air seal  43   d  is preferably field applied caulking, but other sealing means may also be used. Other items shown are similar in function to that shown in FIG. 4.  
     [0079]FIG. 11 b  shows air seal  43   c  connected to air seal  41  by using corner air seals  41   b  and  41   a . Comer air seal  41   a  is typically shop applied foam tape. Comer air seal  41   b  is typically field applied caulking. Other items shown are similar in function to that shown in FIG. 4.  
     [0080]FIG. 11 c  shows air seal  43   c  connected to air seal  43   b  at the corner. Air seals  43   b  and  43   c  are typically field applied caulking. Other items shown are similar to that shown in FIG. 5.  
     [0081]FIG. 11 d  shows air seal  46   a  connected to air seal  46   b  by using air seal  46   c . Air seal  46   c  is preferably a shop applied foam tape. Other items shown are similar in function to that shown in FIG. 4.  
     [0082] Referring to FIGS.  1 - 11   d , representative field erection procedures for the perimeter frames include the following steps.  
     [0083] Step 1: Slide the vertical jamb members  17   a  or  18  into engagement with the positioning clips  48 .  
     [0084] Step 2: Place the perimeter head frame  16  with the positioning clips  48  on top of the jamb members  17   a  or  18  to cause clip engagement with the jamb members. At this stage, the perimeter frames are in an assembling position but not connected to the jamb members  17   a  or  18 . Optionally, additional set screws can be applied at this stage to secure the jamb members  17   a  or  18  to the clips  48  for easier handling.  
     [0085] Step 3: Lift the assembled perimeter frame into the vision hole in the wall and adjust the head and the sill frame to the installed position using spacers or shims  60  (see FIGS. 4, 4 a , and  5 ) as required.  
     [0086] Step 4: Apply the fasteners  25  and  32  to secure the head  16  and the sill  15   a  or  15   c  into the masonry wall.  
     [0087] Step 5: Apply curable caulking along the ends of sill frame  15   a  or  15   c  and head frame  16  to the edge surfaces of the masonry wall. It must be noted that these member ends are accessible at this stage due to the fact that the jambs  17   a  or  18  are away from the corner at the assembling position  49 .  
     [0088] Step 6: Release the set screws  51  and push the jambs  17   a  or  18  to the corner and re-apply the set screws to the installed positions  50 . At this stage, the correct frame dimensions are ensured.  
     [0089] Step 7: Shim the jambs  17   a  or  18  using shims  60  (see FIGS.  6  or  8 ) as required and apply the fasteners  39  to secure the jambs to the masonry wall.  
     [0090] Step 8: Apply field caulking to complete the water seals and air seals as previously described.  
     [0091] In case of a punch-out window system with a single vision panel, the panel erection procedures after the perimeter frames have been installed are stated below.  
     [0092] Step 1: Lift the panel  11  and tilt the panel bottom to the outside and then, engage the panel male joint spline  52  into the female joint  33  (see FIG. 5) in a tilted angle and slide the panel upwardly until the bottom clears the male lip  19  (see FIG. 4), then, straighten up the panel and drop the panel down to cause the panel bottom engagement with the male lip  19 . Center and adjust the left to right position if required.  
     [0093] Step 2: Slide the jamb air seal members  17   b  into position on both sides, apply the fasteners  42  to secure  17   b  to  17   a , and apply marriage caulking  41   b  along the ends of  17   b  to connect the air seal  43   c  to air seal  41 . Snap on the cover  17   c  if required.  
     [0094] Step 3: Apply the panel screws  53  through  17   b  into the panel male joint spline  52 . Optionally, the ceiling edge support angle  54  (see FIG. 5) can be secured at the same time.  
     [0095] In case of a window wall system or a punch-out window system with multiple vision panels, a representative set of remaining panel erection procedures can be as stated below.  
     [0096] Step 1: Lift the first panel  11  and tilt the panel bottom to the outside and then engage the panel male joint spline  52  into the female joint  33  (see FIG. 5) in a tilted angle and slide the panel upwardly until the bottom clears the male lip  19  (see FIG. 4), then, straighten up the panel and drop the panel down to cause the panel bottom engagement with the male lip  19 . Push the panel all the way to the left to over engage with the left-side perimeter jamb frame  18  (see FIG. 2).  
     [0097] Step 2: Slide the vertical joint member  45  from the side into engagement with the first panel  11  and push the member  45  all the way to the left. At this stage, if there is only two panels in the masonry wall hole, the room on the right side should be enough to prevent the interference with the right-side perimeter jamb frame  18 .  
     [0098] Step 3: Repeat Steps 1 and 2 to get all panels into the engaged positions at the top and the bottom. Then, adjust the left to right positions for all panels  11  (see FIG. 2) and the vertical joint members  45  (see FIG. 7).  
     [0099] Step 4: Apply the panel fasteners  53  through members  18  (see FIG. 8) and members  45  (see FIG. 7) into the panel male joint spline  52  (see FIG. 5). Optionally, the ceiling edge support angle  54  (see FIG. 5) can be secured at about the same time using fastener  53 .  
     [0100] In case of a ribbon window system, a set of representative panel erection procedures is stated below.  
     [0101] Step 1: Lift the first panel and tilt the panel bottom to the outside and the engage the panel male joint spline  52  into the female joint  33  (see FIG. 5) in a tilted angle and slide the panel upwardly until the bottom clears the male lip  19  (see FIG. 4), then, straighten up the panel and drop the panel down to cause the panel bottom engagement with the male lip  19 . Adjust the left to right position as required.  
     [0102] Step 2: Slide the vertical joint member  45  into position and apply the fasteners  53  through the installed member  45  into the panel male joint spline  52  (see FIG. 5). Optionally, the fasteners  53  can be applied after a number of panels have been placed in position and the ceiling edge support angle  54  can be secured at about the same time.  
     [0103] Step 3: Repeat Steps 1 and 2 till all panels are installed. If clearance room is needed for the last panel, follow the steps in the prior procedures with multiple panels.  
     [0104] The performance improvements mostly achieved by the invention are summarized below.  
     [0105] 1. As explained above, perimeter seal design includes the airloop principle with separation of air seals and water restrictors using pressure equalized air spaces. Therefore, improved long-term watertightness is expected.  
     [0106] 2. As explained in the erection procedures above, all field assembling and sealing are performed from the interior on the floor level, therefore, the invention avoids the requirement for exterior access during installation.  
     [0107] 3. As explained above, the vision or other panels can be the same as a compatible airloop curtain-wall panel, therefore, interface problem with a curtain wall is minimized.  
     [0108] 4. As it can be seen on FIG. 5, relative motion of support surfaces, e.g. caused by one or more inter-floor deflections, is designed to be absorbed by the joint formed by the panel male spline  52  and the female joint  33  of the top perimeter frame  16  and slidable seals are not affected by the inter-floor deflection.  
     [0109] Many other variations can be contemplated. For example, in a window frame system, one of the vision glass panels can be replaced with a door panel for access to the exterior patio. In another embodiment, especially for applications in areas with a high wind load and/or a large panel height, the vertical joint member  45  can be designed as a structural support member by extending either inwardly or outwardly, e.g., with a ribbed design. Thermal breaks can be added to the frame members for embodiments requiring improved thermal insulation performance.  
     [0110] Although the preferred embodiment of the invention has been shown and described, and some alternative embodiments also shown and/or described, changes and modifications may be made thereto without departing from the invention. Accordingly, it is intended to embrace within the invention all such changes, modifications, and alternative embodiments as fall within the spirit and scope of the appended claims.