CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of the earlier filing dates of United States Provisional Patent Application No. 62/502,916, filed May 8, 2017, United States Provisional Patent Application No. 62/503,986, filed May 10, 2017, United States

Provisional Patent Application No. 62/516,364, filed June 7, 2017, and United States Provisional Patent Application No. 62/524,040, filed June 23, 2017.

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0002] This invention is related to insulated glass design for use in building exterior wall systems such as curtain wall, window wall, and punch-out window.

2. Description of the Background

[0003] An insulated glass unit, commonly known in the industry as an IG unit, comprises a perimeter spacer bar sandwiched between an exterior single glass pane and an interior single glass pane. The two glass panes are bonded and air sealed to the spacer bar normally with shop-applied silicone caulking. The spacer bar is located inwardly away from the edges of the glass at a small distance, normally about 2 to 4 mm, to create a complete loop-around perimeter channel for additional shop-applied air seal caulking around the entire perimeter of the IG unit. The above shop sealing method is intended to form a long-lasting perfect seal around the IG unit.

[0004] The air trapped inside the IG unit provides two important performance functions, namely, thermal insulation and wind load transfer between the exterior glass pane and the interior glass pane. For a positive wind load acting on the exterior glass pane of the IG unit, the dead air space within the IG unit will be in compression, creating a positive differential air pressure relative to the interior air. The differential air pressure will push the interior glass pane inwardly, allowing the sharing of the positive wind load. For a negative wind load acting on the exterior glass pane of the IG unit, the dead air space within the IG unit will be in expansion, creating a negative differential air pressure relative to the interior air. This differential air pressure will push the interior glass pane outwardly, allowing the sharing of the negative wind load.

[0005] It is well known in the industry that the shop-applied perfect perimeter seal around the IG unit will inevitably fail in the form of hair line cracks due to stresses caused by relative structural movements and/or aging of the sealant material. For example, perimeter seal failures are often experienced when IG units are shipped over mountainous areas due to air pressure changes in combination with the effect of structurally unrestrained perimeter edges of the IG units. For the in-service condition of the IG unit (i.e., being glazed in a wall system), perimeter seal failure is normally identified from observation of a change in certain performance functions. The noticed change in the performance functions is unacceptable to building owners and the only repair is to replace the failed IG unit.

[0006] The following terminology regarding an IG unit will be used: (1) Face 1 : the outside-facing surface of the exterior glass pane; (2) Face 2: the inside-facing surface of the exterior glass pane; (3) Face 3 : the outside-facing surface of the interior glass pane; (4) Face 4: the inside-facing surface of the interior glass pane. The terms "outside-facing" and "inside-facing" refer to the direction the glass pane faces, when the IG unit is installed, relative to the building exterior and interior. Thus, "outside-facing" refers to the surface facing the building exterior and "inside-facing" refers to the surface facing the building interior. [0007] It can be readily understood that similar to a flat tire condition, if the perfect seal around the IG unit becomes imperfect allowing air leakage, the structural function of the IG unit will be impaired. This change of performance function is not noticeable in the early stages of seal failure.

[0008] The effect of a hair line crack in the perimeter seal of an IG unit in a conventional exterior wall system is explained as follows. The IG unit is normally glazed into the wall system frame by using a double air-seal system (i.e., air seal around both the exterior and the interior perimeters of the IG unit). The glazing air seal can never be considered a perfect seal, and moisture migration through the glazing air seal is inevitable. Due to vapor pressure, the moisture migration will be in the direction from a high absolute humidity zone to a low absolute humidity zone. For example, in a heated and humidified building during the winter time, interior moisture will migrate through the interior glazed seal line into the joint cavities around the perimeter edges of the IG unit, then through hair line cracks in the perimeter seal into the dead air space of the IG unit, causing water condensation on Face 2 of the IG unit. Similarly, in an air-conditioned building during a humid summer day, exterior moisture will migrate through the exterior glazed seal line into the joint cavities around the perimeter edges of the IG unit, then through hair line cracks in the perimeter seal into the dead air space of the IG unit, causing water condensation on Face 3 of the IG unit. This kind of change in performance function is immediately noticeable (commonly known as a fogged IG unit) and unacceptable to the building occupant. The only solution is to replace the impaired IG unit.

[0009] Another example of change in performance function caused by water infiltration is explained as follows. When exterior rain water infiltrates through the exterior glazed seal line, due to the surface tension of a water drop, the infiltrated water can run slowly along the perimeter seal surface and in contact with hair line cracks in the perimeter seal. During positive dynamic wind load cycles, water may infiltrate through the hair line cracks into the dead air space of the IG unit as explained below. The deformation of the exterior glass pane under a positive wind load will cause an air exhalation from the dead air space of the IG unit through hair line cracks in the perimeter seal. Once the positive wind load starts to recede, a negative pressure is created inside the dead air space causing the water running over a portion of a hair line crack to be sucked into the dead air space of the IG unit. Once the water has infiltrated into the dead air space, it will flow downwardly and accumulate on top of the bottom segment of the spacer bar. Even if some hair line cracks exist in the bottom perimeter seal, the surface tension of a water drop prevents water drainage through the hair line cracks. Therefore, dynamic positive wind load cycles create a one-way pumping action that sucks water into the dead air space of the IG unit. This problem has been observed in curtain wall projects with large IG units due to the fact that the larger the size of the IG unit, the bigger the pumping force. This kind of change in performance function is immediately noticeable and unacceptable to the building occupant, and the only solution is to replace the impaired IG unit.

[0010] A major cause of the above-discussed problems is the requirement of a perfect seal design using caulking along the perimeter of the IG unit. It is desirable to eliminate the discussed functional performance problems by having an IG unit design that does not require a perimeter caulking seal.

SUMMARY OF THE INVENTION

[0011] Preferred aspects of the invention provide a method of shop-assembling a vented

IG unit without caulking along the glass perimeter for use in a pressure-equalized exterior wall or window unit. Preferred embodiments of the disclosed vented IG units provide options for improving thermal and sound insulation values and permit easy replacement of the interior glass pane from the building interior without causing weather exposure during replacement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 shows the horizontal panel joint of a typical airloop curtain wall system with glazed-in vented IG units of the present invention.

[0013] FIG. 2 shows an isometric view of a vented IG unit of the present invention with partially cut away exterior glass pane to illustrate the preferred venting air hole locations.

[0014] FIG. 3 shows a construction detail of the IG perimeter of a preferred embodiment of the present invention.

[0015] FIG. 4 shows a construction detail of the IG perimeter of another preferred embodiment with an alternate arrangement for venting the IG unit.

[0016] FIG. 5 shows a horizontal panel joint between a top panel and a bottom panel of a typical airloop hidden frame curtain wall system with glazed-in vented IG units of the present invention.

[0017] FIG. 6 shows a horizontal panel joint between a top panel and a bottom panel of a typical airloop hidden frame curtain wall system with glazed-in vented IG units of the present invention, including an operable solar shading system.

DETAILED DESCRIPTION OF THE INVENTION

[0018] FIG. 1 shows the horizontal panel joint 12 between a top panel 11a and a bottom panel l ib of a typical airloop curtain wall system (see U.S. Patent No. 7, 134,247, which is incorporated by reference herein). Each panel has a perimeter frame with a glazed-in vented IG unit (i.e., vented IG unit in top panel 11a and vented IG unit in bottom panel 1 lb). The air space

14 formed between the sill frame member of top panel 11a and the head frame member of bottom panel 1 lb is the horizontal segment of the pressure equalized outer airloop. As explained in U.S. Patent No. 7, 134,247, this outer airloop is formed around each airloop curtain wall panel when airloop curtain wall panels are assembled together. The open panel joint 12 permits pressure equalization of air space 14 with exterior air.

[0019] An inner airloop is formed about the perimeter of the IG unit in the perimeter frame of each airloop curtain wall panel. The air space 13b, formed between the head frame member and the IG unit, is the top segment of the pressure equalized inner airloop of the bottom panel 1 lb. The inner airloop is formed around the IG unit in corresponding, connected air spaces formed between the IG unit and jamb frame members, and between the IG unit and the sill frame member of the bottom panel 1 lb.

[0020] The sill frame member of the bottom panel 1 lb has the same configuration as the sill frame member of the top panel 11a, as shown in FIG. 1. The blank portion shown in the thermal break 15 of the sill frame member 16 of the top panel 11a represents air holes connecting the air space 14 and the air space 13a. The air space 13a is the bottom segment of the pressure equalized inner airloop of the top panel 11a. Therefore, the inner airloop of the top panel 11a is pressure equalized through the air holes in the thermal break 15 between air spaces 14 and 13a, and the inner airloop of the bottom panel 1 lb is pressure equalized through corresponding air holes in the thermal break of the sill frame member of the bottom panel 1 lb.

[0021] The vented IG unit has an exterior glass pane 19a and an interior glass pane 19b separated by a spacer bar 20 without glass perimeter caulking, creating the air space 18 between the exterior glass pane 19a and the interior glass pane 19b within the bottom panel IG unit 10b.

The spacer bar 20 has air holes 17a and 17b to pressure equalize the air space 18 with inner airloop air space 13b. The air hole 17a is the inner air hole on the inner flange of the spacer bar 20 represented by the dotted lines and the air hole 17b is the outer air hole through the outer flange of the spacer bar 20. In alternative embodiments, the spacer bar is a solid member with at least one air hole to pressure equalize the air space in the IG unit with the inner airloop air space.

[0022] Due to the pressure equalization of the air space 18, no differential air pressure between the air space 18 and the surrounding air will be created during transportation of the IG unit. The IG unit typically would be structurally secured in the wall panel 1 lb prior to shipping. Thus, the potential problem of perimeter seal damage of a conventional IG unit caused by air pressure changes during transit is eliminated.

[0023] To explain the functional performance of the present invention, the following notations will be used.

[0024] Di = dew point of the building interior air

[0025] D _e = dew point of the building exterior air

[0026] Ti= building interior air temperature

[0027] T _e = building exterior air temperature

[0028] T _a = air temperature inside the air space 18

[0029] Ti = surface temperature on Face 1 (i.e. outside surface of exterior glass pane 19a)

[0030] T ₂ = surface temperature on Face 2 (i.e. inside surface of exterior glass pane 19a)

[0031] T ₃ = surface temperature on Face 3 (i.e. outside surface of interior glass pane 19b)

[0032] T ₄ = surface temperature on Face 4 (i.e. inside surface of interior glass pane 19b)

[0033] During the heating season of the winter time, the following temperature relationship is always true.

[0034] De < Te < Ti < T ₂ < T ₃ < T ₄ < Ti > Di [0035] Due to pressure equalization of air space 18, air space 18 is within the exterior air zone (i.e., cold and low absolute humidity zone). From the above temperature relationship, it is impossible for the surface temperature of Face 2 or Face 3 to become less than the exterior air dew point, D _e . Therefore, potential water condensation on Face 2 or Face 3 (i.e., fogged IG problem) is eliminated.

[0036] During the air conditioning season of the summer time, the following temperature relationship is always true.

[0037] D _e < T _e > Ti > T2 > T ₃ > T4 > Ti > Di

[0038] Due to the pressure equalization of air space 18, air space 18 is within the exterior air zone (i.e., hot and high absolute humidity zone). From the above temperature relationship, it is possible for the surface temperature of Face 3 to become less than the exterior dew point, D _e . Therefore, water condensation on Face 3 (i.e. Fogged IG problem) is possible. However, the probability of water condensation on Face 3 is low and can be ignored in design considerations for the following reasons:

[0039] 1. As compared to the heating season in cold regions, the differential temperature between the exterior air and the interior air is much less in hot regions during the air conditioning season.

[0040] 2. For the most commonly used panel frame material, aluminum, during the air conditioning season, the interior surface temperature of the aluminum extrusion frame will be lower than temperature of Face 3 on the glass surface. Therefore, water condensation on the aluminum frame surface inside the hidden air spaces 13a and 13b will happen first, resulting in reduced moisture content in the air before the air can go through air holes 17a and 17b to reach Face 3 on the glass surface. The condensed water on the hidden surface of the aluminum frame will be drained out from the airloop drainage system.

[0041] If exterior water infiltrates into the inner airloop and makes contact with the contact seam between the spacer bar 20 and the glass pane 19a or 19b, it will not cause water infiltration into air space 18 because air space 18 is pressure equalized with the inner airloop. Thus, the problem of water infiltration through hair line cracks into air space 18 as well as water accumulation at the bottom of air space 18 is eliminated.

[0042] For thermal insulation performance, it is well known in the industry that a dead air space will provide good thermal insulation, which is the basis of conventional IG unit design. In a light or no wind condition, the vented IG unit design of the present invention has no impact on the thermal insulation performance. In a windy condition, there will be a small air exchange between the air space 18 and the air space 13b. However, the effect of the small air exchange on the thermal insulation performance is insignificant, as evidenced by nearly two decades of field performance of erected airloop curtain wall systems. The good field thermal insulation performance of erected airloop curtain wall systems can be explained by a thermal sponge theory where in a windy condition, most of the air inside the inter-connected airloops can simply move from a higher pressure airloop zone to a lower pressure airloop zone without being pushed out of the airloops (i.e., no significant air exchange between the air in the airloops and the exterior air). In a solar gain condition, hot air in air space 18 will be vented out through air holes 17a and 17b. This is beneficial in the air-conditioning season. In summary, the overall effect of the vented IG unit design has little effect on the thermal insulation performance compared to a conventional, sealed IG unit. [0043] FIG. 2 shows an isometric view of the vented IG unit 10b as shown in FIG. 1, with a partially cut away exterior glass pane to illustrate the preferred venting air hole locations. The vent air holes 17a and 17b are preferably pre-drilled in the spacer bar 20 before assembly into the airloop panel frame. To reduce the probability of insects and airborne dirt entering air space 18, the locations of the air holes 17a and 17b are preferably offset as shown in FIG. 2. The air holes may optionally be filled with a filtering material to prevent entry of insects and dirt.

[0044] FIG. 3 shows an alternate construction detail of an IG unit perimeter of a preferred embodiment of the present invention. Eliminating the perimeter caulking provides the following advantages.

[0045] 1. It eliminates shop labor needed to assemble the IG unit.

[0046] 2. It eliminates the wait time for curing of the perimeter caulking in the shop, resulting in a significant shop space saving.

[0047] 3. The air holes 17a and 17b can be pre-drilled and all drill shavings cleaned before assembling the IG unit into the airloop panel frame.

[0048] 4. Quick curing adhesive such as epoxy or double-sided adhesive tape can be used as a sealing agent 21 between the exterior glass pane 19a and the spacer bar 20, and as a sealing agent 22 between the interior glass pane 19b and the spacer bar 20.

[0049] 5. If the interior glass pane 19b is a special functioning glass such as a commercial glass known as "smart-tinting" dynamic glass or a solar energy unit, the ease of replacing a dysfunctional special glass pane in an erected wall is an important design consideration. For this consideration, the sealing agent 22 on the side of the special functioning glass 19b may be a one-sided adhesive sealing foam tape 22 for easy replacement of a dysfunctional special glass 19b and significant cost savings by re-using the exterior glass pane 19a. The airloop system shown in FIG. 1 provides interior access for easy replacement of the interior glass pane of the IG unit. The adhesive side of the one-sided adhesive sealing foam tape 22 is adhered to the spacer bar 20 and the non-adhesive side forms a dirt-repelling seal with the special functioning glass 19b in the shop glazing operation.

[0050] 6. Since the outside flange of the spacer bar 20 is exposed to the pressure equalized air space 13b, a material with a low thermal conductivity such as PVC is preferred to be used for the spacer bar.

[0051] FIG. 4 is an isometric cut-away view of an alternate construction detail of the IG unit perimeter of another preferred embodiment. For clarity, only one glass pane 41 is shown. The glass pane 41 may be either the interior or exterior glass pane of the IG unit. The horizontal spacer bar 42 between the glass panes is butt-ended against the side of the vertical spacer bar 43. Each open end of the vertical spacer bar 43 is approximately flush with the top and bottom glass edges, respectively. When an IG unit having such an open end design is installed in an airloop system, configured as shown in FIG. 1, the open ends of vertical spacer bar 43 will connect and pressure equalize air space 45 inside the vertical spacer bar with airloop air spaces 13a and 13b. To pressure equalize the air space between the glass panes of such an IG unit (equivalent to air space 18 shown in FIG. 1), at least one predrilled air hole 46 (similar to air hole 17a on spacer bar 20 shown in FIGS. 1 and 3) may be provided on the inside face of the spacer bar 43. No air hole is needed on the outside face of the spacer bar 43. To maximize thermal insulation performance, air hole 46 preferably is located as far as possible from exterior air (i.e., near the mid-height of the IG unit), and the inside corner 47 of the butt joint between the horizontal spacer bar 42 and the vertical spacer bar 43 preferably is air sealed. [0052] Summarizing from the above, shop assembling a vented IG unit without glass perimeter caulking into an airloop panel frame eliminates many problems associated with conventional IG units.

[0053] Even though the vented IG unit design is shown in FIG. 1 in a typical airloop curtain wall system, it can be used on any pressure equalized curtain wall, window wall, or punch-out window system. Similarly, the embodiment of FIG. 4 may be used on any pressure equalized curtain wall, window wall, or punch-out window system. However, the pressure equalized air space in a conventional system normally is a segmented air space with end blocks resulting in a very short path for the exterior air to reach the pressure equalized air space where the air hole 17b or the open end of the vertical spacer bar 43 is located. Due to the short path for the exterior air to reach the location of the air hole 17b of the open end of the vertical spacer bar 43, the efficiency in thermal insulation performance is reduced as compared to an airloop system.

[0054] FIG. 5 shows a horizontal panel joint 52 between a top panel 51a and a bottom panel 51b of a typical airloop hidden frame curtain wall system with a glazed-in vented IG unit in each of the panels. Because the curtain wall panels with a vented IG unit do not require a prefabricated, sealed IG unit, the curtain wall panels may be configured such that the interior glass of the vented IG unit is accessible from the building interior for easy replacement. The exterior glass for each wall panel is mounted on the exterior side of the panel perimeter frame. As shown in FIG. 5, the exterior glass 70a of the top panel 51a is bonded to the exterior side of the mounting flange 72a of the perimeter frame sill member 74a with structural adhesive agent 71a. Similarly, the exterior glass 70b of the bottom panel 51b is bonded to exterior side of the mounting flange 72b of the perimeter frame head member 74b with structural adhesive agent 71b. The functions of the exterior glass 70a, 70b include exterior frameless aesthetic performance and weather barrier performance.

[0055] Unlike use of a conventional, prefabricated, sealed IG unit, which would be completely mounted on the exterior side of the frame mounting flange in a hidden frame system, the interior glass of a vented IG unit may be mounted on the interior side of the mounting flange, such that an inner airloop is formed in the perimeter frame about the perimeter of the interior glass. The interior glass 50a is glazed into the sill member 74a of the top panel 51a using the removable glazing bead 73a with the sealing gasket 76a. The interior glass 50a is structurally secured between the interior side of the mounting flange 72a of the hidden frame sill member 74a and the glazing bead 73a using a spacer bar 60a with interface sealing agent 61a between the spacer bar 60a and the interior side of the mounting flange 72a, and interface sealing agent 62a between the spacer bar 60a and the interior glass 50a. Similarly, the interior glass 50b is glazed into the head member 74b of the bottom panel 51b using the removable glazing bead 73b with a sealing gasket 76b. The interior glass 50b is structurally secured between the mounting flange 72b of the hidden frame head member 74b and the glazing bead 73b using a spacer bar 60b with interface sealing agents 61b and 62b.

[0056] The sealing agents 61a and 62a are provided to prevent insects and dirt from entering the air space 75a between the exterior glass 70a and interior glass 50a. For the same reason, the air holes 57b exposed to the inner airloop space 53a preferably are filled with air filtering material. The sealing agents 61b and 62b shown in the lower panel are similarly provided to prevent insects and dirt from entering the air space 75b, and the air holes 57b preferably are filled with air filtering material. The sealing agents 61a, 62a, 61b, and 62b may be an adhesive such as epoxy or an adhesive tape. The sealing agents 61a, 61b between the mounting flanges 72a, 72b and the spacer bars 60a, 60b, preferably are a two-sided adhesive tape. The sealing agents 62a, 62b between the spacer bars 60a, 60b and the interior glass 50a, 50b preferably are a one-sided adhesive tape with the adhesive side adhered to the spacer bars 60a, 60b to permit easy replacement of the interior glass 50a, 50b.

[0057] The following pressure equalization process is explained with the understanding that the head member of top panel 51a will have the same configuration as the head member 74b shown for the bottom panel 51b in FIG. 5. Exterior air enters through the open panel joint 52 into the outer airloop space 54, and then through the air holes 55 into the inner airloop space 53a in sill member 74a. The inner airloop formed by corresponding airspaces in the sill, jamb, and head members of the panel frame connects inner airloop space 53a in the sill member of top panel 51a with the inner airloop space in the head member of top panel 51a (analogous to inner airloop space 53b shown in bottom panel 51b). Air holes 57a, 57b connect air in the inner airloop spaces to the air space 75a between the exterior glass 70a and interior glass 50a, pressure equalizing air space 75a with the inner airloop spaces 53a, 53b.

[0058] For a typical airloop hidden frame system, it is impossible to replace a dysfunctional IG unit from the building interior because the entire IG unit (i.e., both the exterior and interior glass) is mounted on the exterior side of the mounting flange of the frame. In contrast, the interior glass of the embodiment shown in FIG. 5 can be replaced from the building interior. If interior glass 50a needs to be replaced (e.g., a dysfunctional solar energy glass or smart tinting glass), interior glass 50a can be replaced from the interior side of the building by removing the gasket 76a and the glazing bead 73a to gain access. For easy replacement of the interior glass 50a, it is desirable that the sealing agent 61a is bonded to the flange 72a and the spacer bar 60a while the sealing agent 62a is only bonded to the spacer bar 60a without bonding to the interior glass 50a. In this arrangement, interior glass 50a can be easily replaced from the interior side without disturbing the spacer bar 60a. As shown, the interior glass 50a is a single pane glass, but the interior glass also may be a unit with multiple panes of glass (e.g., a functional glass with multiple glass panes).

[0059] FIG. 6 shows the horizontal panel joint shown in FIG. 5, except that the embodiment shown in FIG. 6 includes an operable solar shading system 80 within the air space between the exterior glass 70 and the interior glass 50 of the panels. The following description of FIG. 6 is made with the understanding that the head member of top panel 51a will have the same configuration as the shown head member 74b for the bottom panel, and the sill member of the bottom panel will have the same configuration as shown for sill member 74a of the top panel. Because the depth of the air space between the two panes of glass can be adjusted to accommodate a specific operable solar shading system, practically all operable solar shading systems available in today's market can be installed in a wall panel of the present invention.

[0060] Because the wall panels with a vented IG unit of the present invention do not require a prefabricated, sealed IG unit, the vented IG unit may be assembled when the wall panel is assembled. For example, in the embodiment shown in FIG. 1, the exterior glass 19a may be attached to the perimeter frame with a two-sided adhesive tape. Next, the spacer bar 20 is positioned around the perimeter of the exterior glass 19a. The spacer bar 20 preferably is attached to the exterior glass 19a using a sealing agent such as a two-sided adhesive tape. The interior glass 19b is then placed against spacer bar 20, preferably with a sealing agent in between the spacer bar 20 and the interior glass 19b, and the assembled vented IG unit is glazed into the perimeter frame with a glazing bead and gasket. [0061] The hidden frame wall embodiment shown in FIG. 5 may be assembled using a similar procedure. First, the spacer bar 60a is positioned against the interior side of the mounting flange 72a. The spacer bar 60a preferably is attached to the mounting flange 72a with a sealing agent 61a, such as a two-sided adhesive tape. Next, the interior glass 50a is positioned against the spacer bar 60a, preferably with a sealing agent 62a in between the spacer bar 60a and the interior glass 50a. The spacer bar 60a and interior glass 50a are then glazed into the perimeter frame with a glazing bead 73a and gasket 76a. Next, the exterior glass 70a can be mounted to the mounting flange 72a using structural adhesive agent 71a to form the vented IG unit.

[0062] The solar shading system can be secured in position by fasteners (not shown) through the spacer bar 60b into the flange 81b in the head frame 74b at the top and/or through the spacer bar 60a into the flange 81a in the sill frame 74a at the bottom. Because the interior glass 50 can be easily removed from the building interior as explained in the description of FIG. 5, the operable solar shading system 80 may be easily accessed for maintenance or replacement, including changing to a different operable solar shading system.

[0063] The present invention may be applied to any commercially available operable window system or punch-out window system or pressure equalized window wall system by providing a means to allow exterior air to enter the perimeter air space around the interior glass without causing water leakage. For example, a shielded air entering gap can be provided below the spacer bar along the bottom edge of the interior glass.

[0064] Nothing in the above description is meant to limit the present invention to any specific materials, geometry, or orientation of elements. Various changes could be made in the construction and methods disclosed above without departing from the scope of the invention are contemplated within the scope of the present invention and will be apparent to those skilled in the art. The embodiments described herein were presented by way of example only and should not be used to limit the scope of the invention.