Add-on multiple glazing with hygroscopic material

We claim:

1. An architectural glazing unit for converting installed glazing to multiple glazing, comprising:

no more than one transparent pane;

an elongated spacer element adjoining marginal portions of a first major surface of said pane around the perimeter of said pane, each longitudinal portion of said spacer element having a first surface and a second surface on opposite sides thereof, wherein said first surface faces said marginal portions of said pane in adjoining relationship thereto, and said second surface faces outwardly, away from said marginal portions of said pane;

a ribbon of essentially moisture vapor impervious material extending around the perimeter of the unit adhered to said second surface of said spacer element and overlying peripheral edge surface portions of said pane; and

moisture-resistant sealant interposed between said ribbon and edge surface portions of said pane so as to provide adhesion and a hermetic seal therebetween.

2. The glazing unit of claim 1 wherein said spacer element is comprised of a flexible, moisture vapor transmittable, polymeric material.

3. The glazing unit of claim 2 wherein a quantity of desiccant is included within said spacer element.

4. The glazing unit of claim 2 wherein said ribbon is comprised of flexible metallic material.

5. The glazing unit of claim 2 wherein said ribbon is adhered to and sealed to peripheral edge surface portions of said pane and to marginal portions of a second major surface to said pane.

6. The glazing unit of claim 2 wherein said sealant is comprised of a polymeric composition having a moisture vapor transmittance of less than about 15 grams of water per 24 hours per square meter for 1 mil thickness.

7. The glazing unit of claim 2 wherein said first surface of said spacer element is in direct, non-adhering contact with said marginal portions of said first major surface of said pane.

8. The glazing unit of claim 1 wherein said spacer element includes a rigid structure formed from essentially moisture vapor impervious material.

9. The glazing unit of claim 8 wherein said spacer element contains a quantity of desiccant.

10. The glazing unit of claim 8 wherein said ribbon is comprised of flexible material and is essentially moisture vapor impervious.

11. The glazing unit of claim 8 wherein said moisture resistant ribbon is adhered to and sealed to peripheral edge surface portions of said pane and to marginal portions of a second major surface of said pane.

12. The glazing unit of claim 8 wherein said sealant is comprised of a polymeric composition having a moisture vapor transmittance of less than about 15 grams of water per 24 hours per square meter for one mil thickness.

13. The glazing unit of claim 8 wherein said first surface of said spacer element is adhered to said marginal portions of said first major surface of said pane by means of a layer of adhesive interposed therebetween.

14. The glazing unit of claim 8 wherein said spacer element is comprised of a plurality of separate segments, each segment being affixed along one margin of said pane.

15. An architectural glazing unit for converting installed glazing to multiple glazing, comprising:

no more than one transparent pane;

an elongated, rigid spacer element formed from essentially moisture vapor impervious material adjoining marginal portions of a first major surface of said pane around the perimeter of said pane, each longitudinal portion of said spacer element having a first surface and a second surface, wherein said first surface faces said marginal portions of said pane in adjoining relationship thereto, and said second surface faces peripherally outward, away from the central region of said first major surface;

a ribbon of essentially moisture vapor impervious material extending around the perimeter of the unit, overlying said second surface of said spacer element and peripheral edge surface portions of said pane; and

moisture-resistant sealant interposed between said ribbon and said second surface of said spacer element and edge surface portions of said pane so as to provide a resilient structural bond and a hermetic seal therebetween.

16. The glazing unit of claim 15 wherein an additionally extended width of said ribbon is adhered to and sealed to marginal portions of a second major surface of said pane.

17. The glazing unit of claim 16 wherein said ribbon is comprised of flexible metallic material, and said sealant is a polymeric composition having a moisture vapor transmittance of less than 15 grams per 24 hours per square meter for one mil thickness.

18. The glazing unit of claim 17 wherein said spacer element is formed from metal and contains a quantity of desiccant.

19. The glazing unit of claim 17 wherein said first surface of said spacer element is adhered to said marginal portions of said first major surface of said pane by means of a layer of adhesive interposed therebetween.

20. An architectural glazing unit for converting installed glazing to multiple glazing, comprising:

no more than one transparent pane;

a spacer element adjoining marginal portions of a major surface of said pane around the perimeter of said pane and spaced from the peripheral edges of said pane; and

a body of at least partially uncured polymeric sealant adhered to said major surface between said spacer element and the peripheral edges of said pane around the perimeter of said pane, said sealant having a dimension normal to said major surface greater than that of said spacer element, said sealant having a moisture vapor transmittance of less than about 15 grams of water per 24 hours per square meter for one mil thickness and which, at room temperature, is coherent and tacky but flowable under pressure.

21. The glazing unit of claim 20 wherein said spacer element is comprised of a flexible moisture vapor transmittable, polymeric material.

22. The glazing unit of claim 20 wherein said spacer element is rigid and is formed from metal.

23. An architectural glazing unit for converting installed glazing to multiple glazing, comprising:

a multiple glazed unit having a plurality of transparent panes with an enclosed airspace therebetween;

an elongated spacer element adjoining marginal portions of a major surface of said glazing unit outside said airspace around the perimeter of said multiple glazed unit, each longitudinal portion of said spacer element having a first surface and a second surface on opposite sides thereof, wherein said first surface faces said marginal portions of said major surface in adjoining relationship thereto, and said second surface faces outwardly, away from said marginal portions of said major surface;

a ribbon of essentially moisture vapor impervious material extending around the perimeter of said glazing unit adhered to said second surface of said spacer element and overlying peripheral edge surface portions of said glazing unit; and

moisture-resistant sealant interposed between said ribbon and edge surface portions of said glazing unit so as to provide adhesion and a hermetic seal therebetween.

24. An architectural glazing unit for converting installed glazing to multiple glazing, comprising:

a multiple glazed unit having a plurality of transparent panes with an enclosed airspace therebetween;

an elongated, rigid spacer element formed from essentially moisture vapor impervious material adjoining marginal portions of a first major surface of said glazing unit outside said airspace around the perimeter of said multiple glazed unit, each longitudinal portion of said spacer element having a first surface and a second surface, wherein said first surface faces said marginal portions of said multiple glazed unit in adjoining relationship thereto, and said second surface faces peripherally outward away from the central region of said major surface;

a ribbon of essentially moisture vapor impervious material extending around the perimeter of the multiple glazed unit, overlying said second surface of said spacer element and peripheral edge surface portions of said multiple glazed unit; and

moisture-resistant sealant interposed between said ribbon and said second surface of said spacer element and edge surface portions of said multiple glazed unit so as to provide adhesion and a hermetic seal therebetween.

25. An architectural glazing unit for converting installed glazing to multiple glazing comprising:

a multiple glazed unit having a plurality of transparent panes with an enclosed airspace therebetween;

a spacer element adjoining marginal portions of a major surface of said multiple glazed unit outside said airspace around the perimeter of said multiple glazed unit and spaced from the peripheral edges of said multiple glazed unit; and

a body of at least partially uncured polymeric sealant adhered to said major surface between said spacer element and the peripheral edges of said multiple glazed unit around the perimeter of said multiple glazed unit, said sealant having a dimension normal to said major surface greater than that of said spacer element, said sealant having a dimension normal to said major surface greater than than of said spacer element, said sealant having a moisture vapor transmittance of less than about 15 grams of water per 24 hours per square meter for one mil thickness and which, at room temperature, is coherent and tacky but flowable under pressure.

26. A multiple glazed installation comprising:

a building wall having an opening defined by a frame member;

an installed transparent pane having its peripheral edges retained in said frame member;

an added transparent pane overlying said installed pane within the outline of said frame member, in generally parallel, spaced relation to said installed pane;

an elongated spacer element disposed between opposing major surfaces of said panes, adjoining marginal portions of the opposed major surface of said added pane around the perimeter of said added pane so as to define an enclosed space between said panes, each longitudinal portion of said spacer element having a first surface facing sad added pane and a second surface facing said installed pane;

a ribbon of essentially moisture vapor impervious material having a portion of its width adhered to said second surface of said spacer element and another portion of its width sealed to edge surface portions of said added pane around the perimeter of said added pane; and

a layer of sealant interposed between said installed pane and the portion of said ribbon which is adhered to said second surface of said spacer element, forming a resilient structural bond and a hermetic seal therebetween.

27. A multiple glazed installation comprising:

a building wall having an opening defined by a frame member;

an installed transparent pane having its peripheral edges retained in said frame member;

an added transparent pane overlying said installed pane within the outline of said frame member, in generally parallel, spaced relation to said installed pane;

an elongated, rigid spacer element, formed from essentially moisture vapor impervious material, disposed between opposing major surfaces of said panes, adjoining marginal portions of the opposed major surface of said added pane around the perimeter of said added pane so as to define an enclosed space between said panes, each longitudinal portion of said spacer having a first surface facing said added pane, a second surface facing said installed pane, and a third surface substantially perpendicular to said first and second surfaces on the exterior of said enclosed space;

a ribbon of essentially moisture vapor impervious material extending around the perimeter of the added pane, sealed to said third surface of said spacer assembly and to edge surface portions of said added pane; and

a layer of sealant interposed between said installed pane and said second surface of said spacer element, forming a resilient structural bond and a hermetic seal therebetween.

28. A method of increasing the insulating value of a vision opening in a building wall structure glazed with an installed transparent pane, comprising the steps of:

providing at an installation site a subassembly which includes an additional transparent pane and a spacer element affixed to marginal portions of one major surface of said additional pane, having a hermetically sealed barrier against moisture penetration through said spacer element and between said spacer and said pane;

aligning said subassembly in a generally parallel relationship to a major surface of the installed pane, with said spacer element disposed between said panes, and with a band of an at least partially uncured sealant disposed between said spacer element and said installed pane, said sealant being comprised of a polymeric composition having a moisture vapor transmittance of less than about 15 grams of water per 24 hours per square meter for 1 mil thickness and being coherent and tacky but flowable under pressure at room temperature; and

biasing said subassembly onto said major surface of the installed pane and applying a compressive force on said sealant band therebetween until the sealant flows and forms a resilient structural bond and a hermetic seal between said spacer element and said major surface of said installed pane.

29. The method of claim 28 wherein said spacer element is sealed onto said additional pane at said installation site.

30. The method of claim 29 wherein the sealing of said spacer element onto said additional pane includes the step of adhering a ribbon of essentially moisture vapor impervious material onto said spacer element and peripheral edge surface portions of said additional pane around the perimeter of said additional pane.

31. The method of claim 28 wherein said subassembly is provided at said installation site in prefabricated form.

32. A method of increasing the insulating value of a vision opening in a building wall structure glazed with an installed transparent pane, comprising the steps of:

applying a spacer element onto marginal portions of a major surface of an additional transparent pane around the perimeter of said additional pane, and spacing said spacer element from peripheral edges of said addition pane;

adhering a body of sealant to said major surface of said additional pane between said spacer element and the peripheral edges of said additional pane, said body of sealant being applied with a thickness in the direction normal to said major surface greater than that of said spacer element, said sealant being comprised of an at least partially uncured polymeric composition having a moisture vapor transmittance of at least 15 grams of water per 24 hours per square meter for 1 mil thickness and which, at room temperaure, is coherent and tacky but flowable under pressure;

aligning said subassembly in a generally parallel relationship to a major surface of the installed pane, with said spacer element and said sealant disposed between said panes; and

biasing the additional pane toward the installed pane to contact said major surface of the installed pane with said body of sealant and applying a compressive force on said body of sealant until the sealant flows and forms a resilient structural bond and a hermetic seal between said panes.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

This invention relates to the conversion of installed single glazed windows into multiple glazed windows, more particularly to an improved structure and method for affixing an additional pane of glass and a spacer element to an existing window installation so as to create a double glazed unit having a hermetically sealed, insulating airspace between the panes.

Although it has long been recognized that double glazed windows possess much greater insulating ability than single glazed windows, most installations have been provided with single glazing for the sake of economizing on construction costs. But with the rapid rise of the costs of heating and cooling buildings, this economy has proven to be false. Thus, it has become increasingly desirable to convert single glazing to double glazing, not only for improving the insulating properties, but also for the sake of the advantages attained from the addition of a tinted or reflectively coated pane. Unfortunately, removing and discarding existing windows and installing whole double glazed units in their place incurs prohibitive costs for labor and materials.

Accordingly, it is an object of this invention to provide a method and means for quickly and easily converting a single glazed window into a double glazed window by sealing an additional pane of glass to the existing installation. The present invention is specifically adapted to provide easy installation, ready adaptability to any size of window opening or frame construction, superior moisture barrier integrity, and improved structural strength.

Various attempts have been made in the prior art to provide on-site installation of secondary panes of glass, but all suffer from certain shortcomings that have discouraged their use. A typical prior art approach can be seen in U.S. Pat. No. 2,436,037 (Doney) where a rubber gasket serves as both spacer and sealing means. The rubber-to-glass seal utilized therein is a relatively poor moisture barrier, since most natural and synthetic rubbers are somewhat pervious, thus rendering the surfaces of the airspace susceptible to condensation. Rubber is also susceptible to degradation upon exposure to sunlight and weather conditions. Such an arrangement is limited to installation from the outside on relatively deep frames, a distinct disadvantage at many locations, especially on large buildings. Furthermore, sealing difficulties would be encountered at the mitered corner joints called for in Doney. Another prior art approach is shown in U.S. Pat. No. 3,299,591 (Woelk) where a strip of epoxy resin serves as both spacer and sealant. That arrangement provides only a short barrier against moisture penetration, and the epoxy resin, which is apparently required for the sake of high adhesion strength and room temperature curability, is not a reliable sealing material because of its moisture vapor transmissibility and low temperature inflexibility. In order to obtain an attractive appearance, it also appears that specialized extruding or casting equipment for the epoxy would have to be employed at the installation site. A further prior art approach is disclosed in U.S. Pat. No. 3,573,149 (Tibble et al). In that patent, a neoprene composition is melted and cured in situ to effect a seal. Again, the barrier in the path of moisture penetration is short in length, and the curable thermoplastic material required is not noted for its moisture barrier properties. Installation requires the use of specialized electrical equipment at the site and lengthy heating times. The technique is also susceptible to uneven heating which may, in turn, yield uneven sealing.

Add-on glazing devices of a different type can also be seen in the following four U.S. Patents relating to automobile windows:

U.S. Pat. No. 1,777,435 Hogelund " 1,915,098 Kile " 1,945,742 Hilger " 2,098,127 Auger

Each of these references suffers from lack of permanency and integrity of seal, which are required for acceptance in the architectural glazing field. Each employs an unprotected organic spacer which is subject to moisture penetration.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided a method which includes affixing a spacer element to the periphery of a pane of glass to be added to an installed window pane so as to provide a moisture resistant barrier and/or improved structural strength. The additional pane, with the strip and spacer attached is then sealed to the installed pane by interposing a tacky, preferably non-curing sealant material between the spacer and the installed glass and then pressing them together.

The invention also embraces a subassembled article comprising an unmounted pane of glass having a spacer element attached around the periphery which possess superior sealing and structural properties. Such subassemblies may be efficiently mass-produced at a manufacturing or central distribution facility, thus freeing the glazier from almost all assembly tasks at the site and assuring more uniform quality.

The invention further includes a novel multiple glazed window comprising a plurality of substantially parallel spaced panes, produced in accordance with the practice of the disclosed method of on-site installation, and which possesses superior sealing qualities and structural integrity.

DETAILED DESCRIPTION OF THE INVENTION

A complete understanding of the invention will be obtained from the following detailed description taken together with the drawings in which:

FIG. 1 is a perspective interior view, partially cut away, of a typical single glazed window installation upon which the present invention may be practiced;

FIG. 2 is a cross-sectional view of an edge strip assembly having an organic spacer and sealant material applied to a moisture resistant ribbon in accordance with an embodiment of the present invention;

FIG. 3 is a cross-sectional view of an alternate embodiment of the edge strip assembly;

FIG. 4 is a fragmentary cross-sectional view of the edge strip shown in FIG. 2 applied to the periphery of a pane of glass to form a subassembly;

FIG. 5 is a fragmentary cross-sectional view of the subassembly shown in FIG. 4 with sealant material applied thereto;

FIG. 6 is a cross-sectional view of the subassembly shown in FIG. 5 in a packaged form for handling and shipping;

FIG. 7 is a cross-sectional view of the subassembly shown in FIG. 5 in an alternate packaged form.

FIG. 8 is a perspective interior view, partially broken away, of the window structure shown in FIG. 1 after conversion to double glazing in accordance with one embodiment of the present invention;

FIG. 9 is a fragmentary cross-sectional view, taken along lines 9--9 in FIG. 8 of a completed installation of the subassembly shown in FIG. 4 onto a previously single glazed window;

FIG. 10 is a fragmentary elevation of a subassembly mounted onto an existing glazing installation showing one means for vacuuming the airspace;

FIG. 11 is a fragmentary elevation of a subassembly having a vacuuming tube placed in a joint;

FIG. 12 is a schematic, fragmentary, cross-sectional view of an alternate framing treatment for a narrow window frame in conjunction with the present invention;

FIG. 13 is a schematic, fragmentary, cross-sectional view of an alternate framing treatment for a wide window frame in conjunction with the present invention;

FIG. 14 is a schematic, fragmentary, cross-sectional view of an alternate framing treatment using a nail-less, screw-less trim insert in conjunction with the present invention;

FIG. 15 is a fragmentary cross-sectional view of an alternate subassembly embodiment utilizing a rigid spacer;

FIG. 16 is a fragmentary cross-sectional view of a completed installation of the subassembly shown in FIG. 15 onto a previously single glazed window;

FIG. 17 is an exploded, fragmentary, cross-sectional view of another embodiment of the invention showing the relationship of the parts prior to assembly;

FIG. 18 is a fragmentary, cross-sectional view of a completed installation of the embodiment of FIG. 17;

FIG. 19 is a fragmentary cross-sectional view of another subassembly embodiment which has a moisture barrier of sealants only;

FIGS. 20, 21 and 22 are fragmentary cross-sectional views of variations of the subassembly embodiment shown in FIG. 19;

FIG. 23 is a fragmentary cross-sectional view of a simplified subassembly embodiment employing a metal spacer; and

FIG. 24 is a fragmentary cross-sectional view of yet another subassembly embodiment which provides an organic spacer with a moisture resistant wrapper.

FIG. 25 is a fragmentary cross-sectional view of a completed installation of the subassembly shown in FIG. 21 onto a previously single glazed window.

FIGS. 26, 27 and 28 are fragmentary cross-sectional views of subassemblies corresponding to FIGS. 4, 15, and 21, respectively, based on double glazed units.

Depicted in FIG. 1 is an interior view of a single glazed window unit that would typically form part of a building wall structure, the window comprising a pane of glass 15 and a frame 16. The conversion of such a window to double glazing will serve as an illustrative example of this invention.

In FIG. 2, there can be seen a cross-sectional view of a preferred embodiment of an edge strip arrangement which forms the basis for the present invention. The edge strip includes as a base element a continuous ribbon of moisture resistant (essentially moisture impermeable) material 20, preferably an aluminum foil or strip having a thickness of about 8 mils. Although somewhat more susceptible to moisture penetration, various films of plastic, such as the dense polyethylenes, may be used for the ribbon 20. A continuous length of organic spacer element 21 is affixed along the length of the ribbon by means of an adhesive layer 22. Adhesive 22 may be a sealant material, but is selected with strong adhesion as the primary desideratum so as to prevent dislocation of the flexible organic spacer in the completed installation. The adhesive 22 should be rigid in the temperature range encountered in window installations, and for ease of manufacturing, it should be capable of forming an instant bond between the foil and the spacer. An adhesive that has been found suitable is USM 1311, a polyethylene copolymer sold by United States Machinery Corporation, which is applied in a hot melt form to the foil which is also heated. Such an adhesive forms an exceptionally strong bond after the adhesive has cooled and set, the 180.degree. peel strength between the spacer and the ribbon exceeding 25 pounds per lineal inch as determined by A. S. T. M. D-903-49T.

The expressions "moisture resistant", "barrier against moisture penetration", and "hermetic seal", as used herein, refer to an ability to prevent passage of water vapor to such an extent that the subject material or structure is capable of being utilized in a multiple glazed architectural installation. To qualify for such architectural use, a material or structure should present enough of an obstacle to water vapor transmission to preclude condensation of water vapor in the interior of a multiple glazed unit at temperatures down to about 0.degree.F. (i.e., about 1.77 .times. 10.sup.-.sup.5 grams of water per cubic inch of air in the unit) and preferably lower, over a period of several years. The time period required is at least about 3 to about 5 years, but preferably is at least about 10 years, and in optimum cases is at least about 20 years. The amount of water vapor penetration depends not only on the inherent moisture vapor transmission of the material employed as the obstacle, but also on the dimensions (e.g., thickness) of the obstacle in the path of water vapor penetration. Because visual aesthetics must be considered in regard to architectural glazing, it is desirable to minimize the dimensions of the water vapor barriers, thus materials having a relatively low moisture vapor transmission are preferred. For this reason, it is generally preferred that the materials used for moisture barriers in multiple glazing have a moisture vapor transmission of less than about 15 grams (preferably less than about 6 grams) per 24 hours per square meter per mil thickness at 100.degree.F. and 90% relative humidity as determined by A. S. T. M. E-96-66E. Desiccants are often included in multiple glazed units to adsorb moisture vapor in the airspace, and when a desiccant is employed, the requirements for moisture barriers may be relaxed by an amount corresponding to the water adsorbing capacity of the desiccant.

Referring again to FIG. 2, spacer 21 may be any solid or semisolid rubber or synthetic polymeric material which maintains sufficient rigidity under ambient temperature conditions to retain two panes of glass in substantially parallel, spaced relationship. A preferred spacer is the spacer-dehydrator disclosed in U.S. Pat. No. 3,758,996, which may be described generally as a moisture vapor transmittable matrix of a block copolymer of styrene and butadiene having interspersed therein a desiccating material. If such a spacer-dehydrator is not used, separate desiccating material is preferably affixed to or embedded in at least a portion of the spacer along its length or placed in the airspace at the time of installation at the site.

As shown in FIG. 2, a continuous band of mastic 23 is applied to ribbon 20 parallel to spacer 21. The composition and width of mastic 23 are selected so as to form a moisture resistant barrier when bonded to the glass surface, as will be set forth with more particularity hereinbelow. Mastic 23 is desirably a room temperature curable or vulcanizable material that will cold flow to form a moisture resistant seal and a resilient structural bond. Butyl-based mastics are preferred, such as the two component, room temperature curable, butyl-based mastic disclosed in U.S. Pat. No. 3,791,910 to George H. Bowser. On-site assembly is substantially expedited by providing a tacky, non-curing composition for mastic 23. A preferred non-curing mastic is disclosed in U.S. patent application Ser. No. 454,336 filed under the name of George H. Bowser on even date herewith and assigned to the assignee of the present invention. The mastic disclosed in that application has the following composition:

(Component) (Weight %) ______________________________________ polyisobutylene (viscosity average molecular weight 75,000 - 100,000) 15-50 polyisobutylene (viscosity average molecular weight 8,000 - 10,000) 10-45 carbon black 10-45 silica pigment 5-15 zirconium orthosilicate 5-15 polybutene 20-50 zinc oxide 0-5 gamma-glycidoxy-propyltrimethoxysilane 0-5 ______________________________________

On an extending portion of ribbon 20, on the opposite side of spacer 21 from mastic 23, there is provided a band of adhesive 24. The primary function of adhesive 24 is to hold the extending portion of ribbon 20 against the side of spacer 21 when the ribbon is folded in accordance with assembly procedures to be set forth below. Thus, adhesive 24 may be merely a narrow bead or discontinuous spots of adhesive material. In most cases, however, band 24 may be the same compound as mastic 23. As an alternate embodiment for the edge strip, there may be a single mastic-adhesive layer 25 applied to substantially the entire surface of one side of ribbon 20 as shown in FIG. 3. Although the FIG. 3 embodiment lacks the advantages of using the hot-melt adhesive 22 of the FIG. 2 embodiment, it possesses sealing advantages in that the organic spacer 21 may be protected by a continuous layer of moisture resistant mastic. Mastic 25 may consist of the compositions disclosed in U.S. Pat. No. 3,791,910 or the aforementioned copending application of George H. Bowser.

Turning now to FIG. 4, there is shown the edge strip of FIG. 2 applied to a rigid transparent pane 30, which is the additional pane to be added to the existing installation. Pane 30 may be glass or plastic, and may be tinted or reflectively coated in accordance with known methods in the art. When the pane 30 is coated, especially when the coatings are subject to deterioration, the coating should be on inner surface 31, which will ultimately be exposed to only a sealed airspace. Care must be taken to clean all oil, dirt, and other contaminants from the pane using appropriate solvents. Glass panes may also have their edges lightly seamed to reduce lacerative risk to personnel and to prevent tearing of ribbon 20.

As shown in FIG 4, the spacer 21 is placed with one side in close contact with surface 31 of the pane. Sealant or adhesive may optionally be included between the spacer and the pane for extra sealing or extra strength but is usually not needed. The extending portion of ribbon 20, which carries mastic 23, is folded around the edge of pane 30 and is pressed against the pane so as to flow the mastic and create a seal between the ribbon and the peripheral edge 32 of the pane as well as to the margin of major surface 33. The other extending portion of the ribbon, carrying adhesive or mastic 24, is folded against and adhered to the side of spacer 21 which is adjacent to the side already adhered to the ribbon. Generally, the attachment of the edge strip assembly is started at one corner of the pane and is continued about the entire periphery of the pane with a single length of the edge strip. At corners, the spacer may be notched to produce mitered joints. Where the ends meet, the edge strip may be trimmed to butt the ends together and sealant added to the joint, or the spacer may be cut from an overlapping length of the edge strip and the extra length of ribbon 20 sealed across and beyond the joint.

Several important advantages for the presence of ribbon 20 can be seen at this point. First, a flexible organic spacer is given structural rigidity by reason of its attachment to the ribbon. Also, a spacer, flexible or rigid, is thereby provided with a stronger structural attachment to pane 30. Another important advantage is that the presence of ribbon 20 permits the use of a greater width of moisture resistant material (sealant 23) for sealing the interface between the spacer and pane 30, and because the moisture resistant material is deployed between the ribbon and surfaces of pane 30 rather than between the spacer and the pane, it enables one to exert greater and more uniform pressure on the material to form a good seal than could be done by attempting to press a flexible organic spacer itself onto the pane. Furthermore, the ribbon provides a laterally and longitudinally continuous, moisture resistant barrier in the path of moisture penetration into a pervious organic spacer.

Optionally, a band of mastic 34 may be applied along the exposed surface of the portion or ribbon 20 which extends around the spacer and is parallel to the major surfaces of pane 30 as shown in FIG. 5. Mastic 34 should be tacky and non-curing, preferably the butyl-based composition described above in connection with mastic 23, and may be conveniently supplied in strips on release paper. The release paper may be pressed in place to flow the mastic and to effect a seal and then peeled from the mastic. Mastic layer 34 should cover substantially all of the surface of the aforesaid portion of the ribbon. The addition of mastic 34 may be omitted without seriously affecting performance of the unit, but its presence has been found to result in the formation of a superior seal with a minimum amount of applied pressure.

The subassembly shown in FIG. 5 is ready for mounting onto the existing glazing. The preceding fabrication of the subassembly may take place at a central location and the subassemblies shipped to the job site, or the fabrication may be performed at the site. When the subassemblies are shipped in prefabricated form it is desirable to protect mastic 34 such as by retaining release paper 35 thereon as shown in FIG. 6, or by providing a strippable overlay of sheet material 36 (FIG. 7) over the entire open face of the subassembly. Overlay 36 not only protects mastic 34 but also maintains the cleanliness of the inner surface 31 of pane 30 and, if the overlay is a relatively impervious material, preserves the desiccant that may be carried by the spacer and protects the inner surface from moisture.

In FIG. 8, the subassembly of FIG. 5 is shown installed onto the interior of the existing single glazed window depicted in FIG. 1. Interior installation is advantageous for the sake of easy accessibility, but the present invention can also be used for adding glazing on the exterior side. Exterior installation may even be preferred in some cases because of particular sash configurations or for better reflectivity when reflectively coated glass is being added. Optional decorative trim 40 is also shown in FIG. 8 applied around the periphery of the window. Details of the installation may be seen in FIG. 9, which is a cross-sectional view of the edge portion of the window, taken along lines 9--9 in FIG. 8.

When installing the subassembly to surface 41 of existing pane 15, that surface and the adjacent areas of frame 16 must be thoroughly cleaned. A layer of moisture resistant mastic 42 is then applied around the periphery of pane 15 along a path corresponding generally to the outline of spacer 21 on the subassembly as shown in FIG. 9. The width of the layer 42 may be wide enough to extend at least slightly above and below the outline of the area that spacer 21 will contact on surface 41 so as to provide a maximum area of contact and some margin for error. Extending mastic 42 all the way to frame 16 will provide an even greater margin for error and expedite alignment of mastic 42 on surface 41. Mastic 42 is tacky, preferably the non-curing, butyl-based sealant described above in reference to mastic 23, and may be carried on release paper which is pressed against the pane 15 and then peeled off. The combined thicknesses of mastic 34 and mastic 42 should be sufficient to assure a flowing of the mastic material when they are pressed together, thus eliminating voids and effecting a continous hermetic seal. It has been found satisfactory to provide mastics 34 and 42 each with thickness of about one-sixteenth of an inch, or, when mastic 34 is not employed, to provide mastic 42 alone with a thickness of about one-eighth of an inch.

The subassembly is next moved into position and aligned with mastic 42. Setting blocks of a resilient material such as neoprene are inserted at spaced intervals across the bottom edge of the subassemby in the space between the subassembly and frame 16 in accordance with conventional glazing techniques. The subassembly is then pressed against pane 15 to effect a seal with mastic 42. Pressure may be applied by clamp means carried by the glass holding equipment, or by special leverage means coacting with the frame or wall structure. An