The present invention relates to windows. Windows are extremely useful multi-function devices, which may provide daylight, ventilation, passive solar gain and a means of escape . However, the high overall heat transfer coefficient ("U-value") of conventional windows and glazing systems may contribute significantly to the requirement to heat buildings in winter and/or cool buildings in summer. This may have a significant impact on C0 ₂ emissions from the built environment.

Buildings contribute almost half of the UK's carbon emissions. The UK government has set a target of a 60% reduction in carbon emissions by 2050. Heat lost through windows typically represents around 20% of the total heat loss from an average home. Hence, more efficient window technologies may have a significant role to play in improving energy efficiency, reducing fuel consumption and reducing C0 ₂ emissions. Efficient windows may not only be cost effective, but they may also improve the thermal comfort of occupants of buildings.

As part of the UK government's push to reduce C0 ₂ emissions from the built environment, the Department for Communities and Local Government published a Code for Sustainable Homes in 2006. The Code was introduced to drive a step-change in sustainable home building practice. Compliance with levels 5 and 6 of the Code may not be achievable without improvements in the energy efficiency of glazing.

Thus, there is a need for more efficient windows to be developed, if the UK is to achieve its C0 ₂ emissions reduction target. Under the Code 's assessment procedure, any doors with a large expanse of glazing, such as patio doors are assessed as windows, and conservatories and roof-lights are also classified as windows. In this patent application, the term window should likewise be understood to encompass doors with a large expanse of glazing, conservatories and rooflights, as well as normal windows. It is a non-exclusive object of the invention to provide a window which may be energy efficient.

A first aspect of the invention provides a window comprising a first at least partially transparent or translucent sheet or panel and at least one body located adjacent a major surface of the first sheet or panel, wherein the or each body bounds at least partially one or more enclosed cavities containing a vacuum.

Advantageously, the enclosed cavity containing a vacuum may help to reduce heat transfer through the window.

In an embodiment, the window may further comprise a second at least partially transparent or translucent sheet or panel, wherein the or each body is located between the first sheet or panel and the second sheet or panel. The space between the first sheet or panel and the second sheet or panel may be at least partially evacuated. The first sheet or panel and the second sheet or panel may be coextensive . The spacing between the first sheet or panel may be uniform, e.g. the first sheet or panel and the second sheet or panel may be parallel, or the spacing may vary.

Advantageously, providing a window with a plurality of enclosed cavities containing a vacuum may improve the reliability of the window and increase its useful service life, especially in comparison with a conventional vacuum double glazing window. This is because the window may still perform acceptably well, even after failure or degradation of the vacuum in one (or a small number) of the enclosed cavities, since there may still be a good vacuum maintained in the other enclosed cavities.

Preferably, the or each body may be at least partially transparent or translucent.

In an embodiment, the or each enclosed cavity may be partially bound by a surface of the first sheet or panel. In an embodiment, the or each body may comprise a first element and a second element located at least partially within the first element. The enclosed cavity may be located at least in part between the first element and the second element. In an embodiment, the first element and/or the second element may be tubular. Such tubular elements may have any cross-sectional shape, which may be constant or may vary along the length of the element.

In an embodiment, the first element and the second element may be tubular and the enclosed cavity may be located between an inner wall of the first element and an outer wall of the second element. The distance from the inner wall of the first element to the outer wall of the second element may be 2 mm or more, preferably 3 mm or more, more preferably 5 mm or more . The first element and the second element may be arranged coaxially.

The window may comprise a plurality of bodies. The bodies may be arranged in parallel with one another. The bodies may be spaced apart or they may be touching each other. The bodies may be oriented substantially vertically, horizontally or in any other direction.

The first sheet or panel and/or the or a second sheet or panel may be made from glass. The or each body may be made from glass. Preferably, liner lenses may be provided on the first sheet or panel and/or the or a second sheet or panel, in order to minimise or at least reduce visual distortion caused by the or each body within the window.

In an embodiment, the first sheet or panel and/or the second sheet or panel may be tinted or coloured. The or each body may be tinted or coloured. The first sheet or panel and/or the or a second sheet or panel and/or the or each body may be differently tinted or coloured. Thus, for instance, interesting decorative or aesthetic effects may be achieved. More practically, the window may be designed so that, for instance, it may provide occupants of a room or building with privacy, e.g. via one-way and/or tinted glass or by the use of patterned and/or cloudy glass. A wall of the enclosed cavity may be coated with a layer comprising a getter, e.g. a flashed getter such as barium. Other flashed getters, e.g. aluminium, magnesium, calcium, sodium, strontium, caesium or phosphorus may be suitable .

The or each vacuum may have a pressure of 0.010 Pa or lower, preferably 0.001 Pa or lower.

The first sheet or panel and the or a second sheet or panel may be provided with a photocatalytic coating on a major surface opposite that which is adjacent the or each body. The photocatalytic coating may comprise titanium dioxide . Advantageously, the photocatalytic coating may react with daylight to break down organic dirt on the or each sheet or panel, thereby making the window self-cleaning to at least some extent.

The or each body may comprise a glass evacuated tube . The glass evacuated tube may comprise one tube. Alternatively, the glass evacuated tube may comprise a pair of tubes arranged one inside the other, preferably coaxially, with the gap between the two tubes being evacuated.

The window may further comprise one or more thermoelectric devices.

In an embodiment, the window may further comprise an air-flow channel between the first sheet or panel and the or a second sheet or panel. The air-flow channel may provide fluid communication between an air movement means and at least one opening.

Preferably, the air-flow channel may be tortuous. In an embodiment, the window may be part of a window assembly further comprising the air movement means and/or the at least one opening.

The air movement means may comprise a fan, e.g. an electric fan. The or each opening may be provided with a cover, operable to open or close the opening.

In an embodiment, the window assembly may comprise a first opening on one side of the window and a second opening on an opposite side of the window from the first opening.

In an embodiment, the window or the window assembly may comprise a frame. The frame may house the or an air movement means and/or the or a at least one opening.

A second aspect of the invention provides a window assembly comprising:

• a window comprising a first at least partially transparent or translucent sheet or panel and a second at least partially transparent or translucent sheet or panel, the second sheet or panel at least partially overlapping and being spaced apart from the first sheet or panel;

• an air-flow channel passing between the first sheet or panel and the second sheet or panel;

• an air movement means at a first end of the air-flow channel; and

• a first opening at a second end of the air-flow channel;

wherein the air movement means is operable to cause air to flow through the air-flow channel in a direction either towards or away from the first opening.

In an embodiment, the air-flow channel may be tortuous. In an embodiment, one or more dividers may be located at least in part between the first sheet or panel and the second sheet or panel. The or each divider may at least partially bound a portion of the air-flow channel.

The air-flow channel may pass around and/or through one or more bodies located between the first sheet or panel and the second sheet or panel. The or each body may bound at least partially one or more enclosed cavities containing a vacuum.

The air movement means may comprise a fan, e.g. an electric fan. In an embodiment, the assembly may further comprise a second opening. Preferably, the second opening may be located at the second end of the air-flow channel. The second opening may be on an opposite side of the window from the first opening. The or each opening may be provided with a cover, operable to open or close the opening.

The first sheet or panel and the second sheet or panel may be coextensive . The spacing between the first sheet or panel may be uniform, e.g. the first sheet or panel and the second sheet or panel may be parallel, or the spacing may vary.

A third aspect of the invention provides a method of manufacture of a window comprising:

• arranging one or more bodies adjacent a major surface of a first at least partially transparent or translucent sheet or panel, wherein each body bounds at least partially an enclosed cavity containing a vacuum.

The method may comprise the initial step of manufacturing one or more bodies comprising an enclosed cavity containing a vacuum.

The method may further comprise sandwiching the one or more bodies between the first sheet or panel and a second at least partially transparent or translucent sheet or panel. A fourth aspect of the invention provides a method of manufacture of a window assembly comprising:

• arranging a first at least partially transparent or translucent sheet or panel and a second at least partially transparent or translucent sheet or panel such that the second sheet or panel at least partially overlaps and is spaced apart from the first sheet or panel;

• providing an air-flow channel passing between the first sheet or panel and the second sheet or panel;

• providing an air movement means at a first end of the air-flow channel; and

• providing a first opening at a second end of the air-flow channel; wherein the air movement means is operable to cause air to flow through the air-flow channel in a direction either towards or away from the first opening.

A fifth aspect of the invention provides a building, e.g. a house, or a vehicle, e.g. a car, a bus, a boat, a train or an aircraft, comprising a window according to the first aspect of the invention and/or a window assembly according to the second aspect of the invention.

In order that the invention may be well understood, it will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 shows a front elevation of an embodiment of a window according to the present invention; Figure 2 shows a section along line A-A of Figure 1 ;

Figure 3 is a photograph of a window according to the invention;

Figure 4 shows an elevation of another embodiment of a window according to the invention;

Figure 5 shows a section along line A-A of Figure 4; and

Figure 6 shows a section along line B-B of Figure 4.

Figure 1 shows a front elevation of an embodiment of a window according to the present invention. The window comprises a rectangular frame 1 , which is set within a wall or door 2. The frame 1 surrounds a first glass panel 3. Eight glass tubes 4 are located behind the first glass panel 3. As shown in Figure 1 , each glass tube 4 extends from the top to the bottom of the window. The glass tubes 4 are arranged in parallel at substantially regular intervals across the window.

Figure 2 shows section through the window of Figure 1 along line A-A. As can be seen from Figure 2, the glass tubes 4 are located between the first glass panel 3 and a second glass panel 6. Arranged coaxially within each glass tube 4 is an inner glass tube 5. The annular cavities between the glass tubes 4, 5 are evacuated.

As shown in Figures 1 and 2, each evacuated tube may comprise two glass tubes 4, 5. The outer tube 4 is made of extremely strong transparent glass that is able to resist a large impact. The inner tube 5 is also made of glass.

During manufacture, air is withdrawn (evacuated) from the space between the two glass tubes 4, 5 to form a vacuum, which substantially eliminates conductive and convective heat loss. In order to maintain the vacuum between the two glass tubes 4, 5 a barium getter is used. During manufacture, this getter is exposed to high temperatures which cause the bottom of the evacuated tube to be coated with a pure layer of barium (not shown). This barium layer absorbs any CO, C0 ₂ , N ₂ , 0 ₂ , H ₂ 0 and H ₂ out-gassed from the tube during storage and operation, thus helping to maintain the vacuum. The barium layer may also provide a clear visual indicator of the vacuum status, since the silver coloured barium layer will turn white, if the vacuum is lost. This may make it easy to determine whether or not a tube is operating correctly.

The vacuum tubes are enclosed within a frame as shown in Figure 2. The tubes are covered with two sheets of glass with liner lenses to minimise vision distortion. For obscure or tinted glass, the vacuum tubes and/or one or more of the sheets of glass can be coated using different colours. A vacuum level of 0.001 Pa or lower can be maintained between the two glass tube layers and the insulation cavity can be 5 mm or more. Advantageously, the vacuum tubes may provide a much lower U-value than conventional vacuum glazing.

Figure 3 is a photograph of a window according to the invention. The window shown in Figure 3 comprises a frame 7, a front glass panel 9, a rear glass panel (not shown) and a plurality of evacuated glass tubes 8 located between the front glass panel 9 and the rear glass panel. As in the window shown in Figure 1 , the evacuated glass tubes 8 comprise a pair of coaxial glass tubes, the annular gap between them being evacuated to provide a vacuum. The evacuated glass tubes 8 may be manufactured substantially as described above. Figure 4 shows a front elevation of another embodiment of a window 10 according to the invention. The window 10 comprises a frame 1 1. The frame 1 1 has two sides 1 1a, 1 lb, a bottom 1 lc and a top 1 Id. The sides 1 la, 1 lb, bottom 1 1 c and top 1 Id of the frame 1 1 surround a pair of spaced apart and coextensive glass sheets (not shown) between which are located a plurality of evacuated glass tubes 13. The evacuated glass tubes 13 are arranged in parallel and extend in a vertical direction.

The top l id of the frame 1 1 protrudes beyond the sides of the frame. The top l id is hollow and has an internal chamber 16 extending along almost its entire length. An electric fan 12 is housed at a first end of the top 1 Id and there is an opening 17 at the opposite end of the top 1 Id.

As shown in Figure 5 and substantially as described previously, the evacuated glass tubes 13 each comprise an outer tube 14 arranged coaxially with an inner tube 18, the annular gap between the two being evacuated and sealed. As shown in Figures 4 and 5, a divider 15 is present within each inner tube 18 and divides the space within the inner tube 18 into two approximately equal portions. As can be seen from Figure 4, each divider 15 extends from near the bottom of the evacuated glass tube 13 in which it is located to beyond the top of the evacuated glass tube 13 and into the chamber 16. The dividers 15 divide the chamber 16 into portions.

The dividers 15 may be made from any suitable material. Preferably, one or more of the dividers may be at least partially transparent or translucent. In some embodiments, one or more of the dividers may be opaque .

Referring now to the upper drawing in Figure 6, this shows the chamber 16 within the top l id of the frame . The chamber 16 communicates with the first opening 17 and with a second opening 19 located opposite the first opening 17. As shown in the upper drawing in Figure 6, the second opening 19 is open, because a cover 20 is in its open position. The first opening 17 is closed.

In the lower drawing in Figure 6, the situation is reversed: the first opening 17 is open, because a cover 21 is in its open position. The second opening 17 is closed. Operation of the window shown in Figures 4, 5 and 6 will now be described. The window 10 may be installed in an exterior wall (not shown) of a house (not shown), such that the first opening 17 leads indoors and the second opening 19 leads outdoors. As shown in Figure 4, operation of the fan 12 draws air into the window 10. The air flows as indicated by the arrows in Figure 4, along a tortuous channel whose path is dictated by the dividers 15. The channel passes along the inside of each inner tube 18 in two directions and in and out of the portions of the chamber 16. The air will then flow out of whichever of the first and second openings 17, 19 is open, i.e . not covered by its respective cover 21 , 20.

In summer, as shown in the upper drawing in Figure 6, it may be preferred to operate the window 10 such that air passes out of the house, i.e. through the second opening 19. Thus, the fan 12 draws air from inside the house and through the window 10 such that it is released outside, thereby extracting warm air from the house . When the fan 12 is not in operation, the second opening 19 may be open, thereby allowing fresh air to flow into the house through the window 10 by natural convection.

In winter, as shown in the lower drawing in Figure 6, it may be preferred to operate the window 10 such that air remains inside the house. Thus, with the first opening 17 open and the second opening 19 closed, the fan 12 may draw air through the window and release it back into the room. When the fan 12 is not in operation, air may pass through the window in either direction by natural convection.

The window shown in Figures 4, 5 and 6 may also be advantageous in kitchens and bathrooms, where it could be used to help to extract moist and/or odorous air out of the room. Advantageously, the installation of such a window may avoid having to provide or fit a separate extractor fan.

Advantageously, the window 10 may further comprise filtering means and/or perfuming means arranged to treat the air as it passes through the window 10.

Advantageously, windows according to the present invention may be compatible with the higher levels of the Code for Sustainable Homes (80% C0 ₂ reduction and 100% C0 ₂ reduction respectively for levels 5 and 6) and the future requirements of commercial buildings. In addition, the windows may comprise thermoelectric devices and may, for example, be used for heating in winter and electricity generation in summer.

Windows according to the invention may be coated with a photocatalytic compound comprising titanium dioxide and consequently may act as a self-cleaning glass. The photocatalytic coating may react with daylight to break down organic dirt.

The invention may provide a window technology incorporating evacuated bodies, e.g. glass evacuated tubes.

Advantageously, windows according to the invention comprising air movement means, e.g. a fan, may be reduce the need for separate window fan units.

While the invention has been described principally with respect to buildings and the built environment, it will be appreciated that it may find utility in other fields, e.g. in vehicles, in particular passenger-carrying vehicles, such as cars, trains, buses, boats or aeroplanes.