CA3004733A1 - Multi-pane interior storm window system and installation method for same - Google Patents

Abstract

A multi-pane interior storm window system features a first storm window unit with a primary mounting frame spanning around a first auxiliary pane, and a second first storm window unit with a secondary mounting frame spanning around a second auxiliary pane. The primary mounting frame is fastened within a window space bound by the frame extension of an existing window to create a first air gap between the first auxiliary pane and the existing window. The secondary mounting frame is magnetically attached to the primary mounting frame to hold the second auxiliary pane in overlying relation to the first auxiliary pane, thereby creating a second air gap. In the event of a pressure buildup in the second air gap that exceeds the magnetic attraction force, an exhaust space is momentarily opened between the mounting frames to relieve said pressure buildup.

Description

MULTI-PANE INTERIOR STORM WINDOW SYSTEM AND INSTALLATION
METHOD FOR SAME
FIELD OF THE INVENTION
The present invention relates generally to interior storm windows, and more particularly to an improved interior storm window system employing a unique multi-pane configuration to improve thermal performance.
BACKGROUND
In cold weather climates, it is known to install additional auxiliary panes on the interior side of an existing window in order to serve as a temporary storm window over the winter to impart improved thermal insulation properties to the existing window.
This reduces thermal losses from the building during the cold weather season, where the temperature differential between the building interior and the exterior environment can be dramatic.
One solution for removable mounting of interior storm windows is the use of a single magnet-equipped auxiliary pane to enable simple and convenient installation and removal of the auxiliary pane before and after the cold weather season.
U.S. Patent 4,194,331 discloses one example where magnetically mateable strips are adhesively attached to the existing and auxiliary window panes to enable magnetic coupling therebetween. Another example is found in U.S. Patent 9,493,978, where a metal-based primary mounting frame is permanently installed on the window frame extensions to form a base to which a magnet-equipped auxiliary pane unit is selectively attachable and detachable.
However, such single-pane solutions are limited in the incremental amount of thermal efficiency they can provide. Accordingly, there remains room for improvement in the field of interior storm windows.

2 SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a multi-pane interior storm window system for interior installation over on an existing window of a building that has one or more existing panes surrounded by a perimeter frame from which frame extensions project on an interior side of said existing window to reach into an interior space of said building, said interior storm window system comprising:
a first storm window unit comprising:
a first auxiliary pane;
a primary mounting frame spanning around a perimeter of the first auxiliary pane, outer dimensions of said primary mounting frame being sized for placement thereof within a window space bound by the frame extensions of the existing window in a manner placing sides of the primary mounting frame respectively adjacent said frame extensions for subsequent securement thereto to hold said first auxiliary pane in overlying relation to the one or more existing panes, thereby creating a first air gap between said first auxiliary pane and said one or more existing panes;
a second storm window unit comprising:
a second auxiliary pane; and a secondary mounting frame spanning around a perimeter of the second auxiliary pane, outer dimensions of said secondary mounting frame being sized for placement thereof in at least partially overlapping relationship with the primary mounting frame on an interior side thereof opposite the perimeter frame of the existing window; and a magnetic mounting mechanism comprising magnetic elements and magnetically attractable elements disposed oppositely of one another on the primary and secondary mounting frames such that placement of the secondary mounting frame

3 into the at least partially overlapping relationship with the primary mounting frame on the interior side thereof magnetically couples said secondary mounting frame to the primary mounting frame to hold said second auxiliary pane in overlying relation to the first auxiliary pane, thereby creating a second air gap between said first and second auxiliary panes.
According to a second aspect of the invention, there is provided a multi-pane interior storm window system for an existing window of a building that has one or more existing panes surrounded by a perimeter frame from which frame extensions project on an interior side of said existing window to reach into an interior space of said building, said interior storm window system comprising:
a first storm window unit comprising:
a first auxiliary pane; and a primary mounting frame spanning around a perimeter of the first auxiliary pane within a window space bound by the frame extensions of the existing window, with sides of the primary mounting frame being respectively attached to the frame extensions and holding said first auxiliary pane in overlying relation to the one or more existing panes at a spaced distance therefrom within said window space, thereby creating a first air gap between said first auxiliary pane and said one or more existing panes; and a second storm window unit comprising:
a second auxiliary pane; and a secondary mounting frame spanning around a perimeter of the second auxiliary pane on an interior side of the primary mounting frame opposite the perimeter frame of the existing window, the secondary mounting frame at least partially overlapping the primary mounting frame and being magnetically coupled thereto, and

4 thereby holding said second auxiliary pane in overlying relation to the first auxiliary pane at a distance therefrom, thereby creating a second air gap between said first and second auxiliary panes.
Preferably, said primary mounting frame is attached to the frame extensions of the existing window in an air-tight manner by a seal spanning fully around said primary mounting frame.
Preferably, there are fasteners driven outwardly through said primary mounting frame into the frame extensions of the existing window to secure said primary mounting frame in place within the window space.
Preferably, the primary mounting frame comprises closed-cell foam.
Preferably, the primary mounting frame comprises a recessed channel running along an inner edge of each side thereof, and perimeter edges of the first auxiliary pane are received within said recessed channels of the primary mounting frame such that said primary mounting frame embraces around each perimeter edge of the first auxiliary pane.
Preferably, sealant is received within said recessed channels of the primary mounting frame and providing an air-tight seal between the primary mounting frame and there first auxiliary pane fully around a substantial entirety thereof.
Preferably, the primary mounting frame comprises a layer of magnetically attractable material affixed to a materially distinct constituent body of the primary mounting frame at a front face thereof that faces into the interior space of the building in an installed state of the primary mounting frame to enable the magnetic coupling of the secondary mounting frame to said layer of magnetically attractable material.
Preferably, said layer of magnetically attractable material has a finished outer surface facing away from the constituent body to leave an aesthetic appearance

5 at said front face of the primary mounting frame when the secondary mounting frame is removed therefrom.
Preferably, the finished outer surface of said magnetically attractable material is powder coated.
Preferably, said layer of magnetically attractable material is adhered to said constituent body.
Preferably, said layer of magnetically attractable material is adhered to said constituent body by double sided tape.
Preferably, there is an air passage in the primary mounting frame that crosses a plane occupied by the first auxiliary pane to fluidly communicate the first and second air gaps with one another to enable airflow therebetween.
According to a third aspect of the invention, there is provided a method of installing a multi-pane interior storm window system, said method comprising:
(a) installing a first storm window unit of said system within an window space bound between frame extensions of the existing window that project to an interior side of one or more existing panes of said existing window into an interior space of a building, including attaching respective sides of a primary mounting frame of said first storm window unit to the frame extensions of the existing window to support a first auxiliary pane of said first storm window unit in an installed position overlying the one or more existing panes at a distance therefrom within said window space to create a first air gap between said first auxiliary pane and said one or more existing panes; and (b) removably installing a second storm window unit of said system by magnetically coupling a secondary mounting frame of said second storm window unit to the primary mounting frame of the first storm window unit, thereby removably securing a second auxiliary pane of said second storm window unit in a mounted

6 position overlying the first auxiliary pane at a distance therefrom to create a second air gap between said first and second auxiliary panes.
Preferably, step (a) comprises applying a bead of sealant spanning fully around the window space to form an air-tight seal between the primary mounting frame and the frame extensions of the existing window.
Preferably, step (a) comprises driving fasteners outwardly through said primary mounting frame into the frame extensions of the existing window.
Preferably, the first storm window unit is a prefabricated unit in which the primary mounting frame is pre-assembled to the first auxiliary pane in a positioning spanning fully around a perimeter thereof.
According to a fourth aspect of the invention, there is provided a method of relieving excess pressure from an air gap in an interior storm window installation with an auxiliary pane whose frame is normally held in a default position by magnetic attraction, said method comprising using a force exerted on said pane by said excess pressure to momentarily overcome said magnetic attraction, thereby momentarily displacing said frame out of the default position and opening up a momentary exhaust space through which air is released from said air gap to relieve said excess pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:
Figure 1 is a cross-sectional view of a multi-pane interior storm window system of the present invention in a fully installed state on an existing window.
Figure 2 is a cross-sectional view showing application of a bead of sealant to frame extension of the existing window in a first step of installing the storm window system of Figure 1.

7 Figure 3 is cross-sectional view showing a first storm window unit of the Figure 1 system in an installed position sealed and fastened to the frame extensions, and illustrating subsequent addition of a second storm window unit that magnetically and removably attaches to the first unit.
Figure 4 is a cross-sectional view similar to Figure 1, but sectioned in a different plane to illustrate a an air passage by which air can pass between two air gaps of the fully installed two-piece storm window system.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Figure 1 is a cross-sectional view of a window installation that features an existing window assembly of conventional construction and a novel multi-pane interior storm window system of the present invention. The cross-sectional views in the drawings are taken in vertical cutting planes parallel to the one or more panes of existing window. For illustrative simplicity, the drawings show the existing window as a single-pane window unit, though it will be appreciated from the following description that the storm window system of the present invention may be similarly installed on existing multi-pane sealed window units that feature air or gas-filled chambers located between adjacent panes.
The existing window 10 features a perimeter frame 12 which is generally formed of four frame members connected in series about the rectangular perimeter of the existing glass pane 14 so that each frame member spans a respective side of the window assembly. Three of the four perimeter frame members 12a, 12b, 12c are visible in the cross-section vantage points of the accompanying figures. Each frame member is a hollow extruded member, for example a PVC or aluminum extrusion, which includes

8 a first channel 16 recessed into an inner side that faces inwardly toward the opposing frame member. This first channel 16 of each perimeter frame members 12a, 12b, 12c receives a respective perimeter edge of the existing glass pane 14 pane in a sealed, air-tight manner preventing air-flow across the pane between the interior space of the building and the surrounding external environment.
The frame members of the existing window's perimeter frame further include a second channel 18 at a front side thereof. The front sides of the frame members are in flush coplanar alignment with one another in a generally vertical plane, and face into the interior space of the building. This second channel 18 is a recessed groove of suitable profile for mating connection with a respective frame extension member, which in the instance of a cased window assembly (i.e. a window assembly with interior trim or casing around its perimeter at the finished interior surface of the wall) and depending on the particular perimeter frame member concerned, may be a side jamb extension 20, a head jamb extension 22, or a sill or stool 24. In the case of a non-cased (i.e. untrimmed) window installation, the frame extensions at the upright sides and top of the window may be drywall returns instead of side and head jamb extensions, in which case such drywall returns reach into drywall return channels that are snap-fit into the second channels 18 of the window's perimeter frame members 12a, 12b, 12c. Whether the frame extension members include jamb extensions or drywall returns, the frame extensions 20, 22, 24 project from the perimeter frame 12 of the existing window 10 on the interior side thereof in generally perpendicular orientation relative to the plane of the existing glass pane 14, and reach into the interior space of the building. The 3D volume delimited between these frame extension members is referred to herein as a window-space.
The multi-pane storm window system of the present invention features

9 two separate storm window units, each having a respectively auxiliary pane.
Figure 3 shows the first storm window unit 26 in its installed position within the window space, prior to the addition of the second storm unit 28 that is subsequently placed in the window space for magnetic coupling to the first unit 26. The first storm window unit 26 features a primary mounting frame 32 having a rectangular box construction made up of four primary frame members connected together end-to-end to extend in series from one another at right-angles to delimit an inner rectangular space between them. Three of the primary frame members are visible in the cross-sectional drawing views at 32a, 32b, 32c. Each primary frame member is made primarily of a closed-cell foam material, for example closed cell PVC, which provides notable thermal insulation value.
An inner edge of each of each primary frame member that faces into the rectangular interior space bound by the four frame members is provided with a recessed channel 34 spanning the full length of this inner edge. The four channels 34 in the four primary frame members receive respective perimeter edges of a first auxiliary pane 36 of the storm window system, which for example may be made of acrylic, or other transparent, or least translucent, material.
A sealant 38, for example silicon, is injected into the channels 34 in a flowable state prior to receipt of the first auxiliary pane 36 therein during factory manufacture of the first storm window unit 26 in order to provide an air tight seal between the first auxiliary pane 36 and the primary mounting frame 32 around a substantial entirety of the first auxiliary pane's perimeter in the finished unit. The channels 34 are intentionally oversized in their depth to accommodate thermal expansion in the height and width dimensions of the first auxiliary pane 36, as allowed by the flexibility that remains in the silicone sealant after curing. Though not shown, glazing tape such as acrylic foam or butyl tape may also be applied along the perimeter

10 of the first auxiliary pane 36, for example on the rear side thereof that faces the existing glass pane 14.
Two or three of the four primary frame members may be seamlessly integral with one another to form a unitary piece spanning a respective two or three sides of the primary mounting frame's finished box structure, with the remaining one or two primary frame members being subsequently adhered to said unitary piece.
That is, the primary frame could be assembled from a single U-shaped foam piece to which the auxiliary pane 36 is assembled by sliding the auxiliary pane 36 into the aligned channels 34 of the three primary frame members 32a, 32b, 32c through the open end of the U-shaped piece, before the fourth primary frame member is subsequently slid over the remaining exposed edge of the auxiliary pane 36 and adhered to the two free ends of the U-shaped piece. Alternatively, the primary frame 32 could be assembled from two L-shaped foam pieces, each of which is slid over two perpendicularly-adjacent perimeter edges of the auxiliary pane 36 to assemble the first storm window unit 26.
On the other hand, the primary frame may be assembled from four separate foam pieces that are respectively fit over a respective perimeter edge of the rectangular auxiliary pane 36, and then adhesively mated together at the four corners of the auxiliary pane 36.
The outer dimensions of the primary mounting frame 32 are determined based on measurement of the window space for which the storm window system is destined, whereby the outer dimensions can be carefully controlled to closely match the measurement of the window space so that insertion of the first storm window unit 26 into the window space will place the outer edge of each primary frame member into abutting contact with, or at least very close proximity to, the inner surface of each frame extension member 20, 22 24 of the existing window assembly 10, as shown in Figure

11 3.
To ensure an air tight seal between the exterior of the primary mounting frame 32 and the frame extension members 20, 22 24 when the first storm window unit 26 is inserted in to the window space, a bead of sealant 40 (e.g. clear silicone) can first be applied to the frame extension members 20, 22 24 around the full perimeter of the window space at the depth therein for which the storm window unit is destined, as shown in Figure 2. Turning to Figure 3, in addition to the stability provided by the sealant once cured, the installed position of the first storm window unit 26 may be further secured by driving of threaded screw fasteners 42 outwardly through the primary frame members 32a, 32b, 32c and into the frame extension members 20,22, 24 of the existing window assembly at spaced positions around the primary mounting frame 32 on the interior side of the auxiliary pane 36. This sealed installation of the first storm window unit 26 within the window space provides permanent mounting of the first auxiliary pane 36 within the window space at a distance spaced from the existing window pane 14.
This creates a permanent air gap Gl between the existing glass pane 14 and the first auxiliary pane 16, thus improving the original thermal efficiency of the existing window.
A near entirety of the primary mounting frame 32 is defined by the aforementioned close-cell foam material, which thus forms a constituent body 32a of the primary frame. The closed-cell foam material has notable thermal insulation properties which minimize heat transfer across the first storm window unit.
However, to enable magnetic attachment of the second storm window unit 28 to the first unit 26, the primary mounting frame 32 features a thin band of steel or other ferromagnetic material 44 affixed to the constituent foam body 32a at a front side of the primary mounting frame 32 that faces into the interior space of the building. This ferromagnetic band 44 spans around the entire primary mounting frame 32 to form a magnetically

12 attractable layer over the full area of its front side. This magnetically attractable layer may be adhered to the constituent foam 32a by double sided tape 46, for example by double sided foam tape commercially available from the 3M Company. The ferromagnetic layer 44 is preferably powder coated or otherwise painted or finished to present an aesthetic appearance at its exposed outer surface at the front side of the first storm window so as to maintain an aesthetic appearance of the window insulation even when the magnetically mounted second unit 28 is removed. For example, the ferromagnetic layer 44 may be provided with a white finish to closely match commonly used white PVC window perimeter frames and extensions.
The second storm window unit 28 features a secondary mounting frame 48 assembled from four secondary frame members that surround a second rectangular auxiliary pane 50 on all four sides thereof. Three of the secondary frame members are visible in the cross-sectional drawing views at 48a, 48b, 48c. Each secondary frame member is an elongated member of extruded profile, for example a PVC
extrusion, which includes a first channel 52 opening into the secondary frame member at the inner edge thereof that faces into the open center space delimited between the secondary frame members, and a second channel 54 opening into the secondary frame member at a rear side thereof that faces toward the primary mounting frame 32 in the installed position of the second storm window unit 28. The first channels 52 of the secondary mounting frame receive the four perimeter edges of the second auxiliary pane 50, which again may be made of acrylic, or other transparent, or least translucent, material, while the second channels 54 each receive one or more magnets 56 therein.
With reference to Figure 1, insertion of the second storm window unit 28 into the window space on the interior/front side of the permanently installed first storm window unit 26 moves the recessed magnets 56 in the rear side of the secondary

13 mounting frame 48 into close proximity with the ferromagnetic material 44 at the front side of the primary mounting frame 32. Accordingly, magnetic forces automatically draw the rear side of the secondary mounting frame 48 into abutting contact with the front side of the primary mounting frame 32, thus securing the second auxiliary pane 50 in place within the window space at a spaced distance from the first auxiliary pane 36 to create a second air gap G2 between the first and second auxiliary panes 36, 50.
A contact area of the second storm window unit 28 at the rear side thereof that abuts the front side of the primary mounting frame spans fully around the perimeter of the secondary mounting frame and is entirety flat, as is the ferromagnetic layer 44 at the front side of the primary mounting frame, whereby these planar front and rear contact areas of the primary and secondary mounting frames abut in fully flush planar contact with one another in the magnetically mounted position of the second storm window unit 28. This achieves a substantially air-tight interface between the two storm window units around the perimeter frames thereof to achieve an effectively sealed, air-tight closure of the second air gap G2, The outer dimensions of the secondary mounting frame are selected to closely conform to the outer dimensions of the primary mounting frame, and thus closely conform to the dimensions of the window space. A width of each secondary frame member between its inner and outer edges preferably matches the width of each primary frame member so that in the installed position of the second storm window unit, the front side of the primary mounting frame is completely concealed by the secondary mounting frame, while the inner edges of the two mounting frames are substantially flush with one another, as shown in figure 1.
Instead of being fully isolated from one another, the first and second air gaps are fluidly communicated with one another by an air passage 58 that is drilled or

14 cut in the primary mounting frame 32 so that each end of this passage 58 opens into a respective one of the two air gaps. Should elevations in temperature in the first air gap increase the pressure between the existing glass pane 14 and the first auxiliary pane 36, air from the first air gap can breathe into the second air gap via the passage 58 in order to equalize the pressure between the two air gaps.
This limits or prevents pressure-induced deflection of the first auxiliary pane 36, particularly in the case of relatively flexible acrylic panes, thus preventing bending or blowout of the first auxiliary pane by preventing a notable pressure differential thereacross. In the illustrated embodiment, the air passage 58 is provided in the form of a cross-channel that reaches forwardly from the rear side of the primary frame 32 and spans perpendicularly across the channel 34 in one of the primary frame members 32b. The cross-channel reaches toward, but stops short of, the opposing ferromagnetically-covered front side of the primary mounting frame 32. The cross-channel is of equal or greater depth to the channel 34 that it crosses, and during manufacture of the first storm window unit 26, care is taken during placement of the sealant 38 to ensure that the bottom of the cross-channel is left unobstructed so that air can flow around the respective perimeter edge of the first auxiliary pane 36 through this open bottom space of the cross-channel. It will be appreciated however that the particular use of a cross-channel is just one option for creating an air passage by which air can flow between the two air gaps. Other possible constructions of the air passage include drilling a bore of larger diameter than the channel-width into the inner edge of the primary frame member at a select location along the channel 34 to create a widened area of the channel at which the bottom of the bore is left unobstructed by sealant 38, or drilling a pair of perpendicularly intersecting bores from the rear side and inner edge of the primary frame member in a manner defining the air passage completely

15 independently of the pane-receiving channels 34 of the primary frame members.
The purely magnetic retention of the second storm window unit, without any additional mechanical catch or latching means, provides a self-activated pressure relief function at the second air gap. That is, should a force exerted on the second auxiliary pane 50 by the equalized pressures in the two air gaps exceed a threshold value corresponding to the magnetic retention force that normally holds the secondary mounting frame 48 in place against primary mounting frame 32, this excess internal pressure in the second air gap of the storm window system will momentarily push at least a partial area of the magnetically retained secondary mounting frame 48 out of its abutting contact with the front side of the primary mounting frame 32, thereby opening up a momentary exhaust space through which air from the second air gap is exhausted into the interior space of the building. This drops the pressure inside the second air gap, thus dropping the pressure-induced force on the second auxiliary pane back below the threshold, whereupon the magnetic attraction force is once again sufficient to snap the secondary mounting frame back into its flush abutment with the primary mounting frame. This momentary pressure relief or "burping" of the second air gap avoids buildup of excess pressures that might otherwise cause bending or blowout of the second auxiliary pane if the secondary air gap was not momentarily openable.
Accordingly, the novel use of a permanently mounted first storm window unit 26 fastened to the frame extensions 20, 22, 24 of an existing window 10 and a readily removable second storm window unit 28 magnetically mounted to the first unit 26 enables installation of a multi-pane storm window using acrylic or other non-glass panes of more thermally expansive material than heavier, costlier glass panes.
This provides the thermal effectiveness of a thermal storm window unit with normally-sealed, but momentarily self-openable, air chambers without the risk of pane-deflection or

16 breakage that would otherwise occur in a fully-sealed unit using such flexible, expansion-prone acrylic panes.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims (21)

CLAIMS:

1. A
multi-pane interior storm window system for interior installation over on an existing window of a building that has one or more existing panes surrounded by a perimeter frame from which frame extensions project on an interior side of said existing window to reach into an interior space of said building, said interior storm window system comprising:
a first storm window unit comprising:
a first auxiliary pane;
a primary mounting frame spanning around a perimeter of the first auxiliary pane, outer dimensions of said primary mounting frame being sized for placement thereof within a window space bound by the frame extension of the existing window in a manner placing sides of the primary mounting frame respectively adjacent said frame extensions for subsequent securement thereto to hold said first auxiliary pane in overlying relation to the one or more existing panes, thereby creating a first air gap between said first auxiliary pane and said one or more existing panes;
a second storm window unit comprising:
a second auxiliary pane; and a secondary mounting frame spanning around a perimeter of the second auxiliary pane, outer dimensions of said secondary mounting frame being sized for placement thereof in at least partially overlapping relationship with the primary mounting frame on an interior side thereof opposite the perimeter frame of the existing window; and a magnetic mounting mechanism comprising magnetic elements and magnetically attractable elements disposed oppositely of one another on the primary and secondary mounting frames such that placement of the secondary mounting frame into the at least partially overlapping relationship with the primary mounting frame on the interior side thereof magnetically couples said secondary mounting frame to the primary mounting frame to hold said second auxiliary pane in overlying relation to the first auxiliary pane, thereby creating a second air gap between said first and second auxiliary panes.

2. A
multi-pane interior storm window system for an existing window of a building that has one or more existing panes surrounded by a perimeter frame from which frame extensions project on an interior side of said existing window to reach into an interior space of said building, said interior storm window system comprising:
a first storm window unit comprising:
a first auxiliary pane; and a primary mounting frame spanning around a perimeter of the first auxiliary pane within a window space bound by the frame extensions of the existing window, with sides of the primary mounting frame being respectively attached to frame extensions and holding said first auxiliary pane in overlying relation to the one or more existing panes at a spaced distance therefrom within said window space, thereby creating a first air gap between said first auxiliary pane and said one or more existing panes; and a second storm window unit comprising:
a second auxiliary pane; and a secondary mounting frame spanning around a perimeter of the second auxiliary pane within the window space on an interior side of the primary mounting frame opposite the perimeter frame of the existing window, the secondary mounting frame at least partially overlapping the primary mounting frame and being magnetically coupled thereto, and thereby holding said second auxiliary pane in overlying relation to the first auxiliary pane at a distance therefrom within said window space, thereby creating a second air gap between said first and second auxiliary panes.

3. The system of claim 2 wherein said primary mounting frame is attached to the frame extensions of the existing window in an air-tight manner by a seal spanning fully around said primary mounting frame.

4. The system of claim 2 or 3 comprising fasteners driven outwardly through said primary mounting frame into the frame extensions of the existing window to secure said primary mounting frame in place within the window space.

5. The system of any preceding claim wherein the primary mounting frame comprises closed-cell foam.

6. The system of any preceding claim wherein the primary mounting frame comprises a recessed channel running along an inner edge of each side thereof, and perimeter edges of the first auxiliary pane are received within said recessed channels of the primary mounting frame such that said primary mounting frame embraces around each perimeter edge of the first auxiliary pane.

7. The system of claim 6 comprising sealant received within said recessed channels of the primary mounting frame and providing an air-tight seal between the primary mounting frame and there first auxiliary pane fully around a substantial entirety thereof.

8. The system of any preceding claim wherein the primary mounting frame comprises a layer of magnetically attractable material affixed to a materially distinct constituent body of the primary mounting frame at a front face thereof that faces into the interior space of the building in an installed state of the primary mounting frame to enable the magnetic coupling of the secondary mounting frame to said layer of magnetically attractable material.

9. The system of claim 8 wherein said layer of magnetically attractable material has a finished outer surface facing away from the constituent body to leave an aesthetic appearance at said front face of the primary mounting frame when the secondary mounting frame is removed therefrom.

10. The system of claim 9 wherein the finished outer surface of said magnetically attractable material is powder coated.

11. The system of any one of claims 8 to 10 wherein said layer of magnetically attractable material is adhered to said constituent body.

12. The system of claim 11 wherein said layer of magnetically attractable material is adhered to said constituent body by double sided tape.

13. The system of any preceding claim comprising an air passage in the primary mounting frame that crosses a plane occupied by the first auxiliary pane to fluidly communicate the first and second air gaps with one another to enable airflow therebetween.

14. A method of installing a multi-pane interior storm window system, said method comprising:
(a) installing a first storm window unit of said system within an window space bound between frame extensions of the existing window that project to an interior side of one or more existing panes of said existing window into an interior space of a building, including attaching respective sides of a primary mounting frame of said first storm window unit to the frame extensions of the existing window to support a first auxiliary pane of said first storm window unit in an installed position overlying the one or more existing panes at a distance therefrom within said window space to create a first air gap between said first auxiliary pane and said one or more existing panes; and (b) removably installing a second storm window unit of said system by magnetically coupling a secondary mounting frame of said second storm window unit to the primary mounting frame of the first storm window unit, thereby removably securing a second auxiliary pane of said second storm window unit in a mounted position overlying the first auxiliary pane at a distance therefrom to create a second air gap between said first and second auxiliary panes.

15. The method of claim 14 wherein step (a) comprises applying a bead of sealant spanning fully around the window space to form an air-tight seal between the primary mounting frame and the frame extensions of the existing window.

16. The method of claim 14 or 15 wherein step (a) comprises driving fasteners outwardly through said primary mounting frame into the frame extensions of the existing window.

17. The method of any one of claims 14 to 16 wherein the primary mounting frame comprises closed-cell foam.

18. The method of any one of claims 14 to 17 wherein the first storm window unit is a prefabricated unit in which the primary mounting frame is pre-assembled to the first auxiliary pane in a positioning spanning fully around a perimeter thereof.

19. The method of any one of claims 14 to 18 wherein the system is configured according to any one of claims 5 to 12.

20. A method of using the system of anyone of claims 1 to 12 comprising, in the event of a pressure buildup in the second air gap, using a force exerted on the second auxiliary pane by said pressure buildup to momentarily overcome a magnetic attraction force between the primary and secondary frames and thereby momentarily displace said secondary frame away from the primary frame to open a momentary exhaust space therebetween and relieve said pressure buildup by releasing air from the second gap via said momentary exhaust space.

21. A
method of relieving excess pressure from an air gap in an interior storm window installation with an auxiliary pane whose frame is normally held in a default position by magnetic attraction, said method comprising using a force exerted on said pane by said excess pressure to momentarily overcome said magnetic attraction, thereby momentarily displacing said frame out of the default position and opening up a momentary exhaust space through which air is released from said air gap to relieve said excess pressure.