Tandem Windows for High Energy Efficiency

Abstract

A configuration of tandem high efficiency primary windows is disclosed as both a structure and method to enhance the energy efficiency of windows. Each of the tandem windows is separately installed, respectively, on the exterior and interior of a building window opening. Each window may be separately operable for opening, closing, and cleaning. The interior window can include a cover, surrounding any part of the frame that protrudes into the interior space, the cover having an air gap for interior air to circulate and remove moisture from the interior surfaces of the interior window and its frame. The space between the windows is vented for removal of water vapor, if necessary, by a tube that extends from the space to the outside or to the cold side of the window opening, the tube having features that prevent the entry of outside into the space between the windows.

Claims

1-33. (canceled)

34. A tandem window assembly for installation in a window opening in a wall, having an interior portion and an exterior portion and a thickness therebetween, comprising: an inner primary window assembly and a separate outer primary window assembly each installed independently of one another on respective interior and exterior portions of said window opening in said wall, said window assemblies, when installed in said window opening, defining an interstitial space between said respective separate window assemblies and surrounded by said window opening in said wall, said interstitial space being of a predetermined depth set by an installer to enable separate operation of said respective windows.

35. A tandem window assembly as in claim 34, further comprising: an extended element mounted with and supporting said inner window assembly along a perimeter of a frame of said inner window assembly, said extended element extending and protruding said inner window assembly toward and into an interior space with respect to said interior surface of said wall so that said interstitial space predetermined depth can exceed said thickness.

36. A tandem window assembly as in claim 35, further comprising: a cover placed around said protruding inner window assembly frame, said cover being spaced from said inner window assembly frame to allow interior air to circulate between said frame and cover and allow for any moisture accumulating on said inner window assembly frame to be removed via said circulating air.

37. A tandem window assembly as in claim 34, further comprising: a vent extending from within said interstitial space downwardly and exteriorly with respect to said interstitial space, said vent including an exterior end facing downwards and positioned below said interstitial space, said tube forming a chamber therein of sufficient size and length to prevent ingress of exterior air into said interstitial space.

38. A tandem window assembly as in claim 34, further comprising a vent extending from within said interstitial space having a removeable plug for insertion into said vent so as to reversibly control the ingress and egress of air from said interstitial space.

39. A method of installing tandem windows in a window opening in a wall to improve the energy efficiency of the window installation, comprising the steps of: installing a first primary outer window assembly to an outer portion of said window opening, selecting a desired separation for installation of a second primary inner window and, thereafter, installing a second separate primary inner window assembly to a second interior portion of said window opening, thereby defining, between said installed windows, an interstitial space of said desired separation that is surrounded by the frames of said primary widows and by said window opening, said interstitial space enabling separate operation of said respective window assemblies, providing access for cleaning, and for other purposes.

40. A method as in claim 39, further comprising: adding an extended element mounted with and supporting said inner window assembly along a perimeter of a frame of said inner window assembly, said extended element extending and protruding said inner window assembly inward into an interior space with respect to said interior surface, and providing any desired separation between the said inner primary window assembly and the said outer primary window assembly

41. A method as in claim 40, further comprising: installing a cover surrounding and onto, and in spaced relation to, a perimeter of said inner window assembly protruding into an interior space before said wall, so as to permit air to circulate between said perimeter and said cover and remove moisture from inner surfaces of said first window assembly.

42. A method as in claim 39, further comprising: providing a vent extending into said interstitial space, said vent extending downwardly and exteriorly with respect to said interstitial space, and said vent having an outer end thereof facing downwardly and being positioned below said interstitial space, said vent forming a chamber therein of sufficient size and length to prevent ingress of exterior air into said interstitial space caused by wind, change of air pressure, or change in temperature.

43. A method as in claim 39, further comprising: a vent extending from within said interstitial space having a removeable plug for insertion into said vent so as to reversibly control the ingress and egress of air from said interstitial space.

Description

DESCRIPTION OF THE DRAWING

[0065] FIG. 1 shows a representative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0066] A primary principle of my invention is the installation of high-efficiency windows in tandem pairs, which is made practical primarily by improvements in the configuration of the frames of the windows.

[0067] The following is a representative embodiment. The embodiment comprises a method of installation, specific features of the frame configuration, improvements in venting to avoid condensation on the panes, and a feature to prevent condensation on the inner frame of the inner window.

[0068] In this embodiment, an increase in separation between the pair of windows is achieved primarily by configuring the frame of the inner window so that it can be attached to the inner wall surfaces of the window opening in a manner that extends the body of the inner window inward. The frame of the outer window may be configured similarly to extend the body of the outer window outward.

[0069] The term inner window refers to the window that is mounted toward the inside of the enclosed space. The term outer window refers to the window that is mounted toward the outside of the enclosed space.

[0070] FIG. 1 shows the elements of the embodiment as follows: [0071] a window opening in wall 100 [0072] an openable outer window 200, having a conventional arrangement for opening the window for ventilation, comprising one fixed sash with double panes and one horizontally sliding sash with double panes [0073] a frame 210 for window 200 [0074] a flange 220 that surrounds frame 210 and is an integral part of frame 210, that provides for attachment of the outer window 200 to the outer surface of wall 100 [0075] an openable inner window 300, having a conventional arrangement for opening the window for ventilation, comprising one fixed sash with double panes and one horizontally sliding sash with double panes [0076] a frame 310 for window 300 [0077] a novel extension 320 of frame 310 that extends the body of window 300 inward [0078] a flange 330 that is part of the novel frame extension 320, which provides for attachment of the inner window 300 to the inner surface of wall 100 [0079] an interstitial space 400 between window 200 and window 300, which is wide enough to allow convenient opening and closing of the outer window from inside the space, to allow convenient operation of any latching and locking devices on the outer window from inside the space, and to allow convenient cleaning of all the surfaces facing into interstitial space 400 [0080] the frame 210 of window 200 being configured to project the window toward the outside, and the frame 310 of window 300 being configured to project the window toward the inside, to provide the desired width of interstitial space 400 [0081] a vent tube 500 that is incorporated into the bottom of the frame 210 of outer window 200, comprising a path for venting water vapor from interstitial space 400 to the outside [0082] the vent tube 500 being sloped continuously downward toward the outside [0083] the vent tube 500 being sealed to frame 210 to prevent any leakage of air around the outside of vent tube 500 [0084] the vent tube 500 being extended downward on the outside by the distance 510 between the bottom of interstitial space 400 and the bottom of vent tube 500, and the volume of the lower portion of vent tube 500 being great enough, to prevent entry of outside air into space 400 as a result of temperature changes, atmospheric pressure changes, and wind pressure [0085] the bottom opening of vent tube 500 being horizontal to minimize the velocity pressure of wind within the vent tube [0086] a plug 520 that may be inserted or removed at the end of vent tube 500 that is located within interstitial space 400 [0087] a cover 600 over the inner portion of frame 310 of the inner window 300, that provides decoration, protects the inner portion of the frame 310 of the inner window, and protects against impact with the sharp inward facing portions of frame 310 [0088] a continuous vent space 610 that separates the cover 600 from the window frame 310 and from the interior surfaces of wall 100, which allows air in the interior space to circulate between the cover 600, the frame 310, and the adjacent surfaces of wall 100, warming the frame and adjacent wall surfaces, thereby inhibiting the condensation of moisture on the frame, and allowing any moisture that may condense on the window frame to evaporate freely into the interior space.

[0089] For brevity in describing the inventions, it is assumed that the interior of the space is warmer than the outside, so that the inner window is warmer than the outer window. However, my invention applies equally when the outside is warmer than the inside, as for example, with a refrigerated enclosure. In the latter case, the venting of moisture from the interstitial space between the inner and outer windows is directed toward the interior of the enclosure.

[0090] The materials and manufacturing methods of the windows are well known to the window manufacturing industry and to those with ordinary skill in the related arts.

Frame Configuration to Increase Separation Between the Inner and Outer Windows

[0091] My invention makes it practical and convenient to compound the desirable characteristics of contemporary window technology (such as multiple panes, hermetic seals between panes, and insulating gases between panes), especially for energy efficiency. For example, if installation of individual windows is constrained by a weight limit, two windows of that weight can be installed independently of each other within the window opening. Thereby, it becomes practical for the R-value of the paired window assembly to be more than double the R-value that is achievable by a single window.

[0092] The modification of the frame of the inner window makes it practical and convenient to mount a high-efficiency window on the inside of the window opening in a manner that is fully compatible with the installation of a high-efficiency window on the outside of the window opening.

[0093] Another efficiency benefit of my invention is that by maximizing the separation between the inner and outer windows, the path that escaping heat must travel through the surrounding structure of the window opening is lengthened, reducing the heat loss.

[0094] For pairs of tandem windows that are openable, the enhanced separation between the inner and outer windows that is provided by the invention allows: [0095] convenient opening of the inner and outer windows together, [0096] convenient operation of the latching and locking devices of the inner and outer windows [0097] convenient access to the surfaces in the interstitial space between the windows for cleaning.

[0098] In prior art, in the case of high-efficiency windows with flanged frames, the window is mounted on the outside in order to exploit the rain shedding capability of the flanged design. In the case of window frames without flanges, a high-efficiency window must be installed somewhere within the width of the wall opening so that it can be held in place by stops that are attached to the inner structure of the window opening. The typical thickness of contemporary walls forestalls the possibility of installing two high-efficiency windows within the same wall opening, especially in a manner that allows convenient operation and cleaning of both windows.

Improved Venting to Prevent Condensation in the Interstitial Space

[0099] The embodiment of FIG. 1 illustrates several improvements to venting of the interstitial space 400 between the inner and outer windows of the tandem pair.

[0100] In this embodiment, the vent path is a tube that passes through the frame structure, as illustrated by vent tube 500 in FIG. 1.

[0101] This embodiment minimizes the infiltration of outside air through the vent tube by locating the outer opening of the vent tube below the level of the bottom of the interstitial space by a distance that is sufficient to prevent convective entry of outside air into the interstitial space, and to prevent the forcing of outside air into the interstitial space by wind pressure. Extension of the exit (outer) end of the vent tube below the level of the bottom of the interstitial space is illustrated by the distance 510 in FIG. 1.

[0102] The volume of the external portion of the vent tube 500 is determined by the change in the volume of the air within the interstitial space 400 that may result from changes in temperature, atmospheric pressure, and wind, which induce flow of outside air through the vent tube. The length and volume of the vent tube are great enough so that outside air cannot flow all the way from the exterior opening of the vent tube to the interior portion of the vent tube.

[0103] The open outer end of the vent tube is shielded from the velocity pressure of wind by facing the exterior opening of the vent tube downward.

[0104] Generally, a moisture vent for the interstitial space is unnecessary if the air leakage rate of the inner window is sufficiently less than the air leakage rate of the outer window so that condensation within the interstitial space cannot occur. In such circumstances, the vent may be closed, eliminating any efficiency loss resulting from the use of a moisture vent. In this embodiment, the capability of closing the vent tube is provided by a plug 520, as illustrated in FIG. 1.

Vented Cover of the Interior Frame

[0105] The frame of an inner window that protrudes into the interior space may create an unusual appearance, and it may pose a risk of impact on sharp corners of the frame. To avoid these problems, a cover or molding may be installed around the protruding portion of the inner frame.

[0106] However, a frame cover may cause condensation on the frame and adjacent wall surfaces if the cover is installed directly over the frame material. In such a case, the cover would act as insulation that would keep the frame cooler than it would be if it were exposed to the indoor space temperature. If water vapor in the air on the warm side of the window can penetrate past the molding to the window frame, it may condense there and accumulate. Persistent moisture promotes the formation of mildew, deterioration of surrounding structural or trim materials, and corrosion of any vulnerable metals.

[0107] This embodiment introduces a solution to this potential problem by using a cover over the interior surface of the frame that is vented all around the frame. The venting allows free convective circulation of indoor air between the cover, the window frame, and the adjacent wall surfaces. The air circulation warms the inner frame surface, thereby reducing the tendency to condensation, and it allows free evaporation of any condensation that may occur. This embodiment of the vented cover is illustrated by cover 600 and cover vent space 610 in FIG. 1.

Independence of Window Installation

[0108] The inner and the outer windows may be installed independently of each other, so that the combination does not increase the difficulty of installation.

[0109] The pair of windows may be installed at one time, or an inner or an outer window may be installed on a retrofit basis to form a compatible pair with the originally installed window.

[0110] In a retrofit installation, the novel extension of the frame allows the window that is installed later to have virtually any characteristics that are compatible with the originally installed window.

Further Embodiments

[0111] Further embodiments are possible, including but not limited to the following: [0112] The vent path from the interstitial space to the outside can be installed independently of either window. For example, a vent tube similar to vent 500 in FIG. 1 is embedded in a slot that is located in the bottom of the window opening before installation of the outer window. [0113] The opening of the vent path may be made adjustable, for example, by using a needle valve in the vent path. In window pairs that are openable, the valve may be installed either inside the space between the windows or in the exit side of the vent. In windows that are not openable, the valve may be installed on the exit side of the vent. [0114] Moisture may be vented from the interstitial space using a hollow channel within the frame, separate from the rest of the frame, that has one or more openings to collect water vapor from the space between the two windows, and that discharges the water vapor to the outside through a conduit that extends below the bottom of the interstitial space. [0115] The vented cover for the frame of the inner window may be used to attach window treatments, for example, curtains and blinds.