Abstract:
A manufacture and method for reducing thermal transfer through window systems has a composite window cap retainer. The retainer has a metal extrusion at least partially covered by a thermal spacer having reduced relative thermal conductivity. The thermal spacer is mechanically supported by the metal extrusion and mechanically intermediates and thermally insulates between the cap and the metal window structures to which the cap is secured, reducing thermal transfer between the inside and outside environments of a building.

Description:
FIELD 
       [0001]    The present invention relates to building products and more particularly, to window structures, window frames, curtain walls and curtain wall assemblies. 
       BACKGROUND 
       [0002]    Some windows utilize frames made from metal, e.g., aluminum alloy. Metal windows are in use in residential and commercial buildings, e.g., in storefronts and in curtain walls used on the façade of high-rise buildings. The energy transfer characteristics of windows are an important factor in the overall energy efficiency of a building and there is a continued demand for building features and methods of construction that improve energy efficiency. Aesthetic considerations also play an important part in architectural design, including the design of window systems and curtain walls. Improved and/or alternative structures and methods for controlling the heat transfer characteristics of windows, window structures, curtain walls and curtain wall assemblies and for achieving aesthetic design objectives remain desirable. 
       SUMMARY 
       [0003]    The disclosed subject matter relates to a window system for a building including a chassis secured to the building. The chassis has a structural element supporting a glazing unit and the structural element has a niche therein along at least a portion of a length thereof. At least one glazing unit is secured to the structural element adjacent the niche. A cap covers an edge of the at least one glazing unit and a cap retainer is inserted into and retained in the niche at one end and attaching to the cap at the other end. The cap retainer has a first portion made from a material having a first thermal conductivity and a second portion made from a material having a thermal conductivity less than the thermal conductivity of the first material, the second portion interposed between the cap and the niche. 
         [0004]    In another embodiment, the cap retainer is capable of supporting the at least one glazing unit under the influence of gravity. 
         [0005]    In another embodiment, the first portion is a metal extrusion and the second portion is non-metallic and at least partially covers the first portion. 
         [0006]    In another embodiment, the second material is a polymer material. 
         [0007]    In another embodiment, the first material is an aluminum alloy. 
         [0008]    In another embodiment, the second portion is positioned below the first portion and rests on a surface of the niche at a contact area, the cap retainer pivoting on the contact area when subjected to a down-force. 
         [0009]    In another embodiment, the cap retainer has a hook at an end thereof that is received in the niche and the niche has a hook recess therein that matingly receives the hook when the cap retainer is inserted in the niche. 
         [0010]    In another embodiment, the niche has two hook recesses, a first for accommodating the hook when the cap retainer is inserted to a first extent into the niche a second for accommodating the hook when the cap retainer is inserted into the niche to a second extent. 
         [0011]    In another embodiment, the second portion has end grips wrapping around a plurality of edges of the first portion. 
         [0012]    In another embodiment, the first portion is made from a material having a greater mechanical strength than the second portion and stiffens the second portion when conjoined therewith. 
         [0013]    In another embodiment, the second portion is polyamide. 
         [0014]    In another embodiment, the cap has a hollow gripper and the cap retainer has an insertion tip that is slideably insertable into the hollow gripper to a gripping position where the hollow gripper and insertion tip interlock to retain the cap on the window system. 
         [0015]    In another embodiment, the hollow gripper has a disengagement tab that permits disengagement of the hollow gripper from the insertion tip. 
         [0016]    In another embodiment, the second portion may be telescoped into the first portion. 
         [0017]    In another embodiment, further comprising an adapter inserted into the niche, the adapter having a Y-portion from which a niche hook, a niche engagement leg and a retainer support leg extends, the niche hook of the adapter received in a first hook recess in the niche, the niche engagement leg received in a recess in the niche and the support leg providing a support surface upon which the cap retainer rests and pivots when inserted into the niche after the adapter, the cap retainer niche hook received in the second hook recess in the niche. 
         [0018]    In another embodiment, the cap is vertically oriented when in place on the window system and wherein the cap retainer is secured to the chassis by a fastener. 
         [0019]    In another embodiment, the cap is connected to the second portion. 
         [0020]    In another embodiment, the structural element and the cap are horizontally oriented. 
         [0021]    In another embodiment, the cap covers edges and a gap between a pair of adjacent glazing panels. 
         [0022]    In another embodiment, a cap retainer for holding an extruded aluminum cap on an extruded aluminum chassis of a window system has a first portion made from a polymer extrusion and a second portion made from an aluminum alloy extrusion, the first portion at least partially covering the surface of the second portion and mechanically coupling to the second portion, the first portion being interposed between the aluminum chassis and the cap, the cap attaching to an end of the first portion. 
         [0023]    In another embodiment, a window system for a building includes a chassis secured to the building, the chassis having a structural element supporting a glazing unit, the structural element having a hollow therein along at least a portion of a length thereof; at least one glazing unit secured to the structural element adjacent the hollow; a cap covering an edge of the at least one glazing unit; a cap retainer inserted into the hollow and attached to the structural element within the hollow and attaching to the cap at one end, the cap retainer being a monolithic polymer having a thermal conductivity less than the thermal conductivity of the structural element, the cap retainer interposed between the cap and the niche. 
         [0024]    In another embodiment, the structural element and the cap are aluminum alloy, the cap has a gripper with a hollow and at least one flexible wall and the cap retainer has a tapered insertion head that inserts into the the hollow of the gripper. 
         [0025]    In another embodiment, the gripper has a release lever extending from the flexible wall that selectively opens the gripper when pressed to allow withdrawal of the insertion head. 
         [0026]    In another embodiment, the separation distance between the cap and the structural element is greater than ¼ inch. 
         [0000]    In another embodiment, the separation distance between the cap and the structural element is greater than 1 inch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    For a more complete understanding of the present disclosure, reference is made to the following detailed description of exemplary embodiments considered in conjunction with the accompanying drawings. 
           [0028]      FIG. 1  is an exploded, perspective view of a prior art curtain wall chassis subassembly. 
           [0029]      FIG. 2  is an exploded, perspective view of a plurality of glazed curtain wall subassemblies assembled to form a portion of a curtain wall on a building structure. 
           [0030]      FIG. 3  is an elevational view of a curtain wall. 
           [0031]      FIG. 4  is a cross-sectional view of the curtain wall of  FIG. 3  taken along line  4 - 4  and looking in the direction of the arrows. 
           [0032]      FIG. 5  is a cross-sectional view of a prior art horizontal beam, glazing and cap of a curtain wall, e.g., taken at section line  5 - 5  on  FIG. 3  and looking in the direction of the arrows. 
           [0033]      FIG. 6  is a cross-sectional view of a prior art vertical mullion, glazing and cap of a curtain wall, e.g., taken at section line  6 - 6  on  FIG. 3  and looking in the direction of the arrows. 
           [0034]      FIG. 7  is a cross-sectional view of a horizontal beam, glazing and cap of a curtain wall, in accordance with an embodiment of the present disclosure, taken at section line  7 - 7  on  FIG. 3  and looking in the direction of the arrows. 
           [0035]      FIG. 8  is a cross-sectional view of a horizontal beam, glazing and cap of a curtain wall, in accordance with an embodiment of the present disclosure, taken at section line  8 - 8  on  FIG. 3  and looking in the direction of the arrows. 
           [0036]      FIG. 9  is a cross-sectional view of a vertical mullion, glazing and cap of a curtain wall in accordance with an embodiment of the present disclosure, taken at section line  9 - 9  on  FIG. 3  and looking in the direction of the arrows. 
           [0037]      FIG. 10  is a cross-sectional view of a vertical mullion, glazing and cap of a curtain wall like  FIG. 9  in accordance with another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0038]      FIG. 1  shows a prior art curtain wall chassis subassembly  10  having vertical elements  12 A,  12 B and horizontal elements  14 A,  14 B,  14 C that may be used to frame and hold glazing panels, e.g.  24 A- 24 J ( FIG. 2 ), one or more panes of window glass, polycarbonate or other clear, translucent, tinted or opaque panels. In modern construction, the glazing panels  24 A-J are typically double or triple glazed with air, inert gas and/or plastic film(s) between adjacent panels to control transmission of thermal energy by radiation and convection between an interior of a building and the exterior environment. The curtain wall chassis subassembly  10  shown would typically be made for a large commercial building, such as a skyscraper, and have vertical elements  12 A,  12 B and horizontal elements  14 A,  14 B,  14 C extruded from an aluminum alloy, which is strong, light-weight and corrosion-resistant. The technology of the present disclosure may also be applied to smaller buildings. The vertical elements  12 A,  12 B and horizontal elements  14 A,  14 B,  14 C may be joined by screws  16  or other fastening means, such as rivets, or welding to form the chassis subassembly  10 . 
         [0039]      FIG. 2  shows a plurality of glazed curtain wall chassis subassemblies  10  assembled to form a portion of a curtain wall  18  on a building structure (beams)  20  via coupling to one another and to brackets  22  tied to the building structure  20 . The subassemblies  10  have glazing units (e.g., glass)  24 A-J installed therein between the vertical and horizontal elements ( 12 B and  14 A shown). While a principle method for holding the glazing units  24 A-J to the chassis subassemblies  10  is by way of a silicone adhesive/sealer, cap elements (caps)  26  may be utilized to provide an architectural finishing detail between adjacent glazing units  24 A-J and/or to provide a device for supporting the glazing units  24 A-J in place on the curtain wall  18 , e.g., as a back-up or supplemental support for a glazing unit, which is adhered to the chassis subassembly  10 . Moreover, in accordance with the present disclosure, the caps  26  may be used to insulate the gap  28  between adjacent glazing units, e.g.,  24 A,  24 B and exclude foreign materials, such as dirt, leaves, paper, insects (bees/wasps, etc.), birds, etc. from the gap  28  and/or to reduce wind noise generated by air flowing through or proximate the gap  28 . 
         [0040]      FIGS. 3 and 4  show a curtain wall  118  having similar attributes to those described above in relation to  FIGS. 1 and 2 , such as a plurality of glazing units  124 A-L and caps  126 . The chassis subassemblies  110  are fastened to the building structure  120  to form curtain wall  118 . Curtain wall  118  is “fully captured” in that the glazing units  124 A-L are surrounded on all sides by cap elements  126  in the vertical and horizontal directions. For purposes of illustration, the curtain wall  118  has features that are in accord with the prior art (for comparison purposes) and also in accordance with embodiments of the present disclosure. More particularly, the structures revealed at the cross-sections taken at lines  5 - 5  and  6 - 6  and shown in  FIGS. 5 and 6 , respectively, represent structures in accord with the prior art. The structures revealed at the cross-sections taken at lines  7 - 7  and  8 - 8  and  9 - 9  and shown in  FIGS. 7, 8   9  and  10 , respectively, represent structures in accord with the present disclosure. While it would be possible to have a single curtain wall with multiple structural approaches, e.g., in the case of a building in which the structural approach is changed when partially completed to take advantage of new designs, the normative approach is to have consistent structural design throughout and the mixed arrangement shown in  FIGS. 3-10  is for illustration. 
         [0041]      FIG. 5  shows a prior art horizontal element  214  in the form of an aluminum extrusion having a box portion  214 A with screw channels  214 AC that allow connection to vertical elements like  12 A,  12 B of  FIG. 1  via a plurality of screws  16  or other fasteners. The horizontal element  214  has a tongue  214 B with a tongue cavity  214 BC for supporting and positioning an upper glazing panel  224 E under the influence of gravity G. In  FIG. 5 , the glazing panel  224 E has a first glass panel  224 E 1  and a second glass panel  224 E 2  with a spacer  224 ES there between, a conventional “double-glazed” arrangement. A lower glazing panel  224 F is similarly constructed. Each glazing panel  224 E,  224 F is adhered to the horizontal member  214  by a bead of silicone seal  230 . A gasket  232  may be used to form a consistent thickness of the silicone seal  230 . A polymer/elastomeric setting block  234  may be used to position the glazing panel  224 E vertically relative to the horizontal element  214  (and the remainder of the curtain wall chassis  10  ( FIG. 1 ) in which it is received, when the glazing panel  224 E is adhered by the silicone seal  230 . A cap assembly  226  with a base plate  226 B (elongated extrusion) is retained in association with the tongue  214 B by one or more bolts  226 D extending through a thermal barrier  226  TB the base plate  226 B and into the tongue cavity  214 BC. A cap cover  226 C is snap-fitted onto the base plate  226 B, covering the bolt(s)  226 D. First and second cap gaskets  226 E,  226 F press against the glazing panels  224 E,  224 F when the base plate  226 B is in place. The distance S 1  between the extruded aluminum cap assembly  226  and the tongue  214 B is on the order of about ⅛ to ¼ inch and the separation gap may be filled with an elastomer, which is capable of thermal conduction, e.g., by convection and radiation. 
         [0042]    An aspect of the present disclosure is the recognition that the cap assembly  226 , bolt  226 D, tongue  214 B and box portion  214 A (which are typically fabricated from metal, e.g., the bolt  226 D is made from steel and the box portion  214 A is made from extruded aluminum alloy, to provide the necessary material strength and architectural appearance for the application) constitute a conductive pathway for thermal energy between the exterior environment of a building and the climate controlled interior of the building. An aspect of the present disclosure is a system for securing caps like  226  to a window system  118  that has reduced conductivity to thermal energy. Another aspect of the present disclosure is the recognition that the process of securing a cap assembly  226  to a window chassis element, e.g.,  214  via bolts/screws is labor intensive and that a system that does not employ a threaded attachment may promote ease and economy of assembly. 
         [0043]      FIG. 6  shows a prior art composite vertical element  312  in the form of a pair of mating aluminum extrusions  312 R and  312 L, which snap together and, when assembled, feature a rear portion  312 A and a front portion  312 F that interacts with glazing panels  324 E,  324 G (in this instance, single-glazed) and a vertical cap assembly  326 . The vertical cap assembly  326  is made from metal, e.g., extruded aluminum alloy and has a pair of legs  326 L 1 ,  326 L 2  with corresponding retainers  326 R 1 ,  326 R 2  at one end thereof. A base plate  326 B serves as a mounting point for gaskets  326 G 1  and  326 G 2 , as well as, snap-fit cover  326 C. The cap assembly  326  is secured in place by inserting the legs  326 L 1  and  326 L 2  and retainers  326 R 1 ,  326 R 2 , into a channel  312 CN within the vertical member  312  front portion  312 F with the retainers  326 R 1 ,  326 R 2  engaging the channel  312 CN and preventing withdrawal past channel members  312 CN 1 ,  312 CN 2 . Thermal barriers  312 TB 1  and  312 TB 2  may be interposed between the retainers  326 R 1 ,  326 R 2  and the channel members  312 CN 1 ,  312 CN 2  to prevent direct contact. A gasket  326 RG may be used to divide the space within the channel  312 CH, providing an additional thermal zone. As with the cap  226 C, a metal vertical cap assembly  326  acts as a conductor of thermal energy between the exterior environment of the building and the climate controlled interior of the building. The distances S 2 A, S 2 B and S 2 C between the retainers  326 R 1 ,  326 R 2  (which are in thermal conductive continuity with the extruded aluminum cap assembly  326 ) and the front portion  312 F at channel  312 CN 1  and  312 CN 2  and the rear portion  312 R of the vertical element  312  is on the order of about ⅛ to ¼ inch and the separation gap is filled with a polymeric material, which is capable of thermal conduction, e.g., by convection and radiation. 
         [0044]      FIG. 7  shows an embodiment of the present disclosure with a horizontal element  414  (extrusion) having a box portion  414 A with screw channels  414 AC and an inwardly directed niche  440 . The niche  440  has first and second canted spacer engagement recesses  440 R 1 ,  440 R 2  for interacting with a glass support and cover retention assembly  441  in two alternative (index) positions, as shall be described below. The glass support and cover retention assembly  441  has a glass support plate (metal extrusion)  442  with a setting block positioning bead  442 L and a front bead  442 F. The glass support plate  442  assembles with a thermal spacer  444 , e.g., made from a polymer, such as polyamide or fiberglass, to form the glass support and cover retention assembly  441 . The glass support and cover retention assembly  441  may be used to support a glazing panel  424 E, e.g., during adherence via a silicone seal  430 . In addition, the glass support and cover retention assembly  441  may be used to secure a cover assembly  426  in place. The cover assembly  426 , which may be an aluminum extrusion, has a receiver  426 R with strengthening ribs  426 RR 1 ,  426 RR 2  and a disengagement tab  426 RD. The disengagement tab  426 RD acts as a lever on engagement lip  426 RL, which interacts with thermal spacer  444 , as described further below. The cover assembly  426  has first and second cap gaskets  426 E,  426 F for forming a seal with the glazing panels  424 E,  424 F. The thermal spacer  444  is assembled to the glass support plate  442  with the front bead  442 F extending into a first plate grip  444 G 1  and a rear tang  442 RT extending into a second plate grip  444 G 2 . Since both the support plate  442  and the thermal spacer  444  may be elongated extrusions having the cross-sectional shape shown, the support plate  442  may be slid (telescoped) into engagement with the thermal spacer  444  to achieve the relative position shown in  FIG. 7  and assemble the glass support and cover retention assembly  441 . Once assembled, the glass support and cover retention assembly  441  may be used to retain the cover assembly  426  by inserting niche engagement hook  444 H into niche recess  440 R 2  and resting the foot  444 F of the thermal spacer  444  on an inside surface  440 S of the niche  440 . Any down force exerted by the glazing panel  424 E (transmitted through setting block  434 ) on the glass support and cover retention assembly  441  forward of the foot  444 F will pivot the assembly  441  on the foot  444 F and rotate the niche engagement hook  444 H into firmer engagement with niche recess  440 R 2 . Any pull exerted by the cap assembly  426  on the glass support and cover assembly  441  also pulls the niche engagement hook  444 H into firmer engagement with niche recess  440 R 2 . 
         [0045]    Once in place within the niche  440 , the glass support and cover retention assembly  441  may be used to retain the cover assembly  426 . More particularly, the cover assembly  426  may be brought into registration with the glass support and cover retention assembly  441  allowing insertion of the insertion tip  4441  into the retainer  426 R up to the stop bead  444 S, whereupon the engagement lip  426 RL snaps into engagement with engagement recess  444 ER. A disengagement relief  444 D in the insertion tip  4441  permits the deflection of the wall of the retainer  426 R between the rib  426 RR 2  and the disengagement tab  426 RD to facilitate disengagement from the curtain wall  418  when desired, e.g., to replace a broken glazing panel  426 E. A tool (not shown), such as an angled lever, may be forced between the gasket  426 E and the glazing panel  424 E to pry against the disengagement tab  426 RD to disengage the engagement lip  426 RL from the engagement recess  444 ER to remove the cover assembly  426 . The extension  444 EX of the thermal spacer  444  between the foot  444 F and the insertion tip  4441  may feature a seal recess  444 ER for receiving a weather seal  444 S (shown in dotted lines). The support plate  442  may feature a recess  442 SR to accommodate the thermal spacer  444  proximate the seal recess  444 ER. The distance S 3  between the retainer  426 R, which is in thermal conductive continuity with the extruded aluminum cap assembly  426 , and the horizontal element  414  is greater than 1 inch. This magnitude of separation gap S 3  reduces the thermal conductivity between the cap assembly  426  and the horizontal element  414  by about 30% over prior art structures, e.g., as described above relative to  FIG. 5 . In one example, a prior art structure having a glazing unit with thermal conductivity of 0.24 in combination with the prior art approach as shown in  FIG. 5  would have a resultant conductivity of 0.46, but with the approach shown in  FIG. 7  would have a conductivity of 0.33. 
         [0046]      FIG. 8  shows an alternative embodiment of the present disclosure similar to that shown in  FIG. 7 , but wherein a glass chair adapter  550  is utilized to shift the glass support and cover retention assembly  541  forward in the niche  540  in order to accommodate a thicker (triple glazed) glazing panel  524 K. The glass chair adapter  550  has a Y-portion  550 Y from which extends a first niche engagement hook  550 H 1  that is received in niche recess  540 R 2 . A niche engagement leg  550 L extends from the Y-portion  550 Y and is received in leg reception recess  540 LR in the niche  540 . The glass chair adapter  550  may be an aluminum alloy extrusion. A support leg  550 SL also extends from the Y-portion  550 Y and rests on surface  540 S on the niche  540 . Once the glass chair adapter  550  is in place in the niche  540 , the glass support and cover retention assembly  541  may be inserted into the niche  540  with the niche engagement hook  544 H engaged with the first spacer engagement recess  540 R 1 . Since the glass support and cover retention assembly  541  does not extend as far into the niche  540 , the foot  544 F of the thermal spacer  544  does not contact the niche support surface  540 S and a portion of the spacer  544  rearward of the foot  544 F rests and pivots upon the support leg  550 SL of the glass chair adapter  550  when subjected to down-force in the direction of the force of gravity G. As in the embodiment of  FIG. 7 , the cover assembly  526  may be brought into registration with the glass support and cover retention assembly  541  allowing insertion of the insertion tip  5441  into the retainer  526 R, whereupon the engagement lip  526 RL snaps into engagement with engagement recess  544 ER to retain the cover assembly  526  in removable association with the curtain wall  518 . The distance S 4  between the retainer  526 R, which is in thermal conductive continuity with the extruded aluminum cap assembly  526 , and the horizontal element  514  is greater than 1 inch. This magnitude of the separation gap S 4  reduces the thermal conductivity between the cap assembly  526  and the horizontal element  514  by 30% over prior art structures, e.g., as described above relative to  FIG. 5 . 
         [0047]      FIG. 9  shows another embodiment of the present disclosure as applied to a composite vertical element  612  formed from a pair of mating aluminum extrusions  612 R,  612 L that are coupled together in a snap-fitting relationship. The composite vertical element  612  has a rear portion  612 A and a front portion  612 F with channel  612 CN. Fastener recesses  612 CN 1 ,  612 CN 2  are formed in the front portion  612 F for receiving fasteners  612 S, such as rivets or screws, for securing a glass support and cover retention assembly  641 . The glass support and cover retention assembly  641  features a support plate  642  and a thermal spacer  644  that are conjoined in a similar manner as in the glass support and cover retention assemblies  441  and  541  of prior embodiments, but also by the action of the fastener(s)  612 S, which extends through each. As in the preceding embodiments of  FIGS. 7 and 8 , the receiver  626 R receives the insertion tip  6441  of the thermal spacer  644  and interlocks there with to secure the cover assembly  626  to the curtain wall  618 . The distance S 5  between the retainer  626 R, which is in thermal conductive continuity with the extruded aluminum cap assembly  626 , and the vertical element  612  is greater than 1 inch. This magnitude of the separation gap S 5  reduces the thermal conductivity between the cap assembly  626  and the vertical element  612  by about 30% over prior art structures, e.g., as described above relative to  FIG. 6 . 
         [0048]      FIG. 10  shows another embodiment of the present disclosure analagous to  FIG. 9 , but applied to triple glazed panels  724 J,  724 L. As before, a composite vertical element  712  formed from a pair of mating aluminum extrusions  712 R,  712 L are coupled together in a snap-fitting relationship. The composite vertical element  712  has a rear portion  712 A and a front portion  712 F with channel  712 CN. Fastener recesses  712 CN 1 ,  712 CN 2  are formed in the front portion  712 F for receiving fasteners  712 S, such as rivets or screws, for securing a glass support and cover retention assembly  741 . In the embodiment shown, the glass support and cover retention assembly  741  features only a thermal spacer  744 . If desired, a support plate like  642  of  FIG. 9  could be conjoined to the thermal spacer  744  in a manner similar to that shown in  FIG. 9 . The receiver  726 R receives the insertion tip  7441  of the thermal spacer  744  and interlocks there with to secure the cover assembly  726  to the curtain wall  718 . The distance S 6  between the retainer  726 R, which is in thermal conductive continuity with the extruded aluminum cap assembly  726 , and the vertical element  712  is greater than 1 inch. This magnitude of the separation gap S 6  reduces the thermal conductivity between the cap assembly  726  and the vertical element  712  by about 30% over prior art structures, e.g., as described above relative to  FIG. 6 . 
         [0049]    In each of the embodiments of  FIGS. 7, 8, 9 and 10 , a metal cover assembly  426 ,  526 ,  626 ,  726  is securely connected to a curtain wall system  418 ,  518 ,  618 ,  718  via a simple snap fit that is accomplished without tools. The thermal transmission from the cover assembly  426 ,  526 ,  626 ,  726  is interrupted by a thermal spacer  444 ,  544 ,  644 ,  744  that exhibits reduced thermal conductivity relative to the cover assembly  426 ,  526 ,  626 ,  726  and the horizontal and vertical members, e.g.,  414 ,  514 ,  612 ,  712  of the curtain wall  418 ,  518 ,  618 ,  718 . For example, in the case of a thermal spacer  444  made from polyamide, the thermal conductivity of polyamide is 0.3 W/m·K compared to that of aluminum alloy, which is in the range of 160 W/m·K. This difference in thermal conductivity, when applied to multiple window units corresponds to a significant amount of energy transfer, especially when the temperature differential between the inside and outside environments is large. 
         [0050]    Another aspect of the apparatus and methods of the present disclosure is the magnitude of the resultant separation distance between the interior and the exterior structures made from aluminum alloy. The separation distance provided by thermal barriers  326  TB,  312 TB 1 ,  312 TB 2  ( FIGS. 5 and 6 ) is only about ⅛ inch to ¼ inch. In the present disclosure, the separation provided by the thermal spacer  444 ,  544 ,  644 ,  744  is greater than 1 inch. This increase in separation between the interior and exterior aluminum improves the thermal transmittance of the frame by about 40-50%. 
         [0051]    While the present disclosure has been expressed in terms of curtain walls, which are commonly associated with large buildings, such as skyscrapers, the technology disclosed herein would also be applicable to window arrays for smaller buildings, such as stores, motels, homes, etc.