The inventions in this specification is related to "systems of window assemblies". It is important to make the distinction for the sake of this specification between a "single window assembly" and a "system of window assemblies". A "single window assembly" is as its name suggests a single window assembly typically comprising a frame, a sash connected to said frame and a panel element mounted in said sash. However, manufacturers of window assemblies rarely design or manufacture single window assemblies. Instead they design and manufacture "systems of window assemblies".

A system of window assemblies will comprises at least two different types of window assemblies which are related in some manner. For example, many systems of window assemblies will comprise one window assembly which is side hung, one window assembly which is top hung, and one window assembly which has a fixed panel element. The frame/sash/panel elements in the three different window assemblies will be essentially the same, but the fittings used will be different in the three different window assemblies. This will give a common visual impression to the three different window assemblies and will allow windows of different types to be mixed in a single building project without leading to conflicting visual impressions. Furthermore, from a manufacturing perspective, the manufacturing complexity is reduced by designing and manufacturing a system of window assemblies since there are fewer components to manufacture and stock. In the above example, there are three different functions, but only one type of frame/sash/panel element. One concrete example of a system of window assemblies is the "V200"(™) system of windows produced by Velfac.® The V200 (™) system of window assemblies comprises a large number of different types of window assemblies all sharing the same visual identity. Another concrete example is the "Aldus"® system from Rationel Vinduer A/S. ®
In general, systems of window assemblies can be identified as systems of window assemblies since they will be marketed as systems of window assemblies by the manufacturers. This can be verified by looking at the home pages and/or product catalogues of different window manufacturers. In case where it is not clear whether two window assemblies are part of a system of window assemblies from the manufacturers own marketing material, different ways of identifying a system of window assemblies are provided here. These ways are all equally useful, but it could in the future be decided to weight one or more of the ways more important than others. One way is to define a system of window assemblies as window assemblies having a common exterior visual identity between different types of window assemblies, for example, double glazed, triple glazed, side hung, top hung, reversible, etc. Another way of defining a system of window assemblies, is as window assemblies having a common frame element. Another way of defining a system of window assemblies, is window assemblies having a common fittings cavity. Another way of defining a system of window assemblies, is as window assemblies which use the same fittings. Another way of defining a system of window assemblies, is as window assemblies using the same outer glazing beads.
When designing a system of window assemblies, the main technical design problems lie in designing the frame and sash elements and the fittings such that they can be shared between many different types of window assemblies.
In the last few years, this problem has increased since there are more and more variants which need to be catered for. One example is the demand for different types of panel elements which vary greatly in thickness. Traditionally double glazed window panes with argon gas between the two panes of glass have been used. These types of window panes typically have a thickness of about 24mm. However lately, due to increasing demands to the thermal resistivity of window assemblies, there is a large focus on using triple glazed window panes. Triple glazed window panes are made up to 52mm wide when using argon gas. Traditionally it has not been possible to use these very wide triple glazed panes in wooden windows. Therefore, Krypton gas has been used instead of argon gas. Krypton gas is a much better insulator and allows the gap between the panes of glass to be made smaller. This allows triple glazed windows to be made at a thickness of about 36mm. Window panes of 36mm thickness have been used with wooden windows in the past. However, Krypton is much more expensive than argon gas and triple glazed windows have therefore been very expensive.

It is therefore a first aspect of the inventions of the current specification to provide a system of window assemblies which can accept window panes which vary greatly in thickness. For example, a system of window assemblies which can accept window panes which vary between 24 and 52 mm in thickness.

Another example of a variant between different window assemblies in a system of window assemblies is that in certain cases it is desired to have a system of window assemblies where one window assembly has a wooden sash and another window assembly has a wooden sash with an exterior "environmental shell", for example a shell of aluminium or composite material mounted on the wooden sash. In order to reduce the number of manufactured components necessary, the window system could be arranged such that the same fittings can be used in both types of window assemblies. In most cases, window assemblies with wooden exteriors and window assemblies with "environmental shell" exteriors are parts of two different window systems since different fittings need to be used for the different exteriors.
It is therefore an aspect of the invention of the current specification to provide a system of wooden window assemblies which can either have a wooden exterior or an "environmental shell" exterior.
Another example of a variant between window assemblies in a system of window assemblies is fixed or openable window assemblies. In openable window assemblies, the window pane can be opened and in fixed window assemblies, the window pane is fixed to the frame such that the window pane can't be opened. In many building projects, fixed and openable window assemblies are mixed and therefore they have to be related visually and constructionally to a certain extent.
It is therefore an aspect of the invention of the current specification to provide a system of window assemblies which comprises both fixed and openable window assemblies. A window assembly according to the preamble of claim 1 and 11 is disclosed by GB 2 283 779 A.

Some of the above mentioned aspects are provided in part by a system of outwardly opening window assemblies according to claim 1. In this way a system of window assemblies can be provided which allows both fixed and openable window assemblies to be mixed in a single system where the number of variants which need to be manufactured and stored are reduced significantly.
It should be noted that an "outwardly opening window assembly" as used in this specification should be understood as a window assembly having a sash mounted in a frame where the sash is arranged to open by swinging or moving in an outward direction. In the open position, the sash is therefore arranged for the most part outside the frame member.

It can also be noted that in this specification, the term "outside" and "inside" refer respectively to the outside and inside of a house in which the window assembly is mounted. It can also be noted that the person skilled in the art will usually be able to identify the outer and inner surfaces of the window assembly, even if the window assembly is not mounted in a house due to the design of the seals and the design of the mounting hardware.

In one embodiment, as mentioned in claim 2, the exterior placement of the window pane can be standardized between fixed and openable window assemblies. This allows, for example the same glazing bead to be used in both fixed and openable window assemblies within the same system of window assemblies.

In another embodiment, a system of window assemblies can be provided which combines fixed, openable double glazed and openable triple glazed window assemblies. According to the features of claim 4, the glazing beads used in all three different window assemblies could be the same.

In certain embodiments, window panes filled with argon gas can be used. In these window panes, the thickness of the triple glazed window panes could be greater than 45 mm and/or up to 52 mm. In general, window thicknesses of between 24 and 52 mm could be used.

In certain embodiments, the sash members and the frame members could be made from wood which allow cutting operations to be used to change the dimensions of the profiles in an easy manner. Different variants of the frame and sash members can therefore be made just before the window is assembled in order to reduce the number of stock profiles necessary.
A compound window assembly and a post for a compound window assembly are also provided.

In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention unnecessarily.

• Figure 1 shows a cross section through one vertical side of an outwardly opening side hung window assembly with a hinge.
• Figures 2(a) and 2(b) show two variants of a first embodiment of a system of outwardly opening window assemblies.
• Figures 3(a) and 3(b) show two variants of a second embodiment of a system of outwardly opening window assemblies.
• Figures 4(a)-4(d) show four different variants of a third embodiment of a system of window assemblies.
• Figures 5(a)-5(d) show four different variants of a fourth embodiment of a system of window assemblies.
• Figure 6 shows a perspective view of a window assembly with one fixed window pane and one openable window pane.
• Figure 7 shows a front view of the window assembly of figure 8.
• Figure 8 shows a cross section view taken along the plane as defined by the line VIII-VIII in figure 7.
• Figure 9 shows an exploded perspective view of the frame of the window assembly of figure 6.
• Figures 10(a) and 10(b) show two different variants of a fifth embodiment of a system of window assemblies.
• Figures 11 (a) and 11 (b) show two different variants of a sixth embodiment of a system of window assemblies.

The cross section of an outwardly opening window assembly 1 shown in figure 1 comprises a window frame element 2, a window sash element 3, a double glazed window pane 4, a glazing bead 5 which holds the window pane in place after the window pane has been placed in the window sash and a mounting fitting 6 in the form of a hinge.

In this embodiment, the window frame element 2 and the window sash element 3 are made from wooden profile elements. The profile elements are in this embodiment built up by laminating different pieces of wood together to arrive at a basic profile element. The basic profile element is then run through a profiling machine which removes wood to arrive at the final profile. This method of manufacturing wooden profile elements will be well known to the person skilled in the art. By building the basic profile element such that the cross section of the basic profile element is as close to cross section of the final profile element as possible, the material wastage is reduced to a minimum. However, in certain cases, it will be desired to use solid pieces of wood. This will increase the material wastage, but result in a finer finished product with an attractive visual appearance.

As will also be known to the person skilled in the art, the window sash is built up of four sash members or elements assembled into a rectangular window sash by joining the individual sash elements at the corners of the rectangle. The window frame is also built up of four frame members or elements which are assembled into a rectangular frame by joining the frame elements at the corner of the rectangular frame. Different ways of assembling the frame and the sash are known to the person skilled in the art and the details won't be discussed further here.

In the current embodiment, the four frame elements along the four sides of the window are identical in cross section and the four sash elements along the four sides of the window are identical in cross section. This is true for all the embodiments disclosed in this specification, but many of the teachings of this specification could also be used on window assemblies having non-identical frame and/or sash elements.

As can be seen from the figure, the window pane 4 is held in place in the sash by the glazing bead 5. The glazing bead is in this case mounted to the sash via a clip system (not shown) which attaches to the surface 7 located underneath the window pane. This is useful in this embodiments since the surface 7 does not extend past the outer surface of the window pane. Therefore, it is difficult to mount the glazing bead with traditional fasteners such as nails and screws. However, the glazing bead could be mounted to the sash element directly via screws, nails or other form of fastening mechanism in other cases where the sash element allows this. It should be noted that the surface 7 is sloped about seven degrees. This is to allow moisture which could find its way into the window sash to run out of the sash at the bottom of the sash. In particular it should be noted that the building code of many countries requires this sloped surface on the bottom sash member of a window sash. The same is true for window frames as can be seen from the figures. This sloped surface imposes significant design limitations to the design. Some window manufacturers have therefore decided to make window sashes where the bottom sash member is different from the side and top sash members. For example, the side and top sash members could have a straight surface whereas the bottom sash member has a sloped surface. This is also true for frames. In the current embodiments, in order to save variants, the same frame and sash profile is used on all four sides of the window.

As can be seen from the figure, the window pane is supported on the inner side of the window pane by an outwardly facing "support" surface 8 of the sash element. A seal element 9 is placed between the support surface 8 and the window pane to absorb any tolerances and to provide a water tight seal. As can be seen from the figure, the support surface 8 and the surface 7 to which the glazing bead is mounted are two surfaces of an integrated element 3. This means that the two surfaces are not surfaces of two different distinct elements, but are surfaces of the same element. The outwardly facing "support" surface is therefore an integrated part of the sash element in contrast to the glazing bead which is added to the sash element after the window pane is placed into or set into the window sash. It should be noted that this type of sash could be called a sash where the window pane is mounted from the outside. There are other types of window sashes a support surface integrated with the sash is located on the outside of the window pane. In this case the window pane is mounted from the inside. A removable glazing bead is then mounted on the inside of the window pane to hold the window pane in place. Still other types of sashes are "U" shaped sashes where the window pane is inserted into the sash in a direction parallel to the plane of the window. In these types of constructions, the sash is built up around the outside of the window pane. This is in contrast to the sash type shown in the figures where the sash is assembled into a rectangle first and then the window pane is placed in the sash.

It can also be seen that the sash element could be described as having an "L" form where a first leg of the L extends along the inner surface of the window pane and a second leg of the L extends underneath the window pane. The first leg of the L provides the support surface 8 which provides the sealing interface between the window pane and the sash element. The first leg of the L also provides support for the window pane to prevent it from moving in directions which are towards the inside of the window assembly. The second leg of the L provides a surface to which the glazing bead is fastened. The second leg of the L also provides support to prevent the window pane from moving in directions which are parallel to the plane of the window pane.

The frame member 2 of the current embodiment could also be described as having an "L" form where a first leg of the L provides a support surface for the primary sealing interface 10 and the second leg of the L provides an attachment surface for the mounting fittings. The second leg of the L also provides support for a fixed window pane as will be shown in, for example, figures 4c and 4d. The area between the two legs of the L which is "missing" from the frame member, can be called a frame recess as will be discussed further later on. As can be seen from figure 1, the area between the frame and the sash form a "fittings cavity" which provides room for mounting the fittings of the window assembly. This fittings cavity is essentially constant for different window assemblies in some systems of window assemblies. By providing a constant fittings cavity between different window assemblies, the same fittings can be used in different window assemblies.

In order to seal the window assembly, a primary sealing interface 10 is provided between the window frame and the window sash. According to this specification the "primary sealing interface" should be understood as being the main sealing interface between the frame and the sash. In this embodiment there are two sealing interfaces. The first sealing interface is the innermost sealing interface 10 and the other is an outer sealing interface 11 located at the outer periphery of the window assembly. In this case, it is clear that the innermost sealing interface is the "primary" sealing interface as it is the sealing interface which gives the best sealing interface. In other cases where there are more than one sealing interfaces located between the frame and the sash and where it is not clear which one is the primary sealing interface, then the innermost sealing interface is to be chosen as the primary sealing interface for the sake of this specification.

In the following discussion, a number of dimensions will be discussed. The first dimension which is of interest is the distance "t" from the primary sealing interface 10 to the innermost surface 12 of the frame element. According to this specification, when measuring to the primary sealing interface, it is meant to measure to the middle of the sealing interface. The second dimension which is of interest is the distance "u" from the primary sealing interface 10 to the outermost surface 13 of the frame element. This distance "u" could be called the depth or width of the frame recess. The third dimension is the distance "v" from the primary sealing interface to the outermost surface 14 of the sash element. In this example, the distance "v" is slightly smaller than the distance "u", but it could be imagined that these two distances were identical or essentially identical. The fourth dimension is the distance "w" from the primary sealing interface to the outer surface 15 of the window pane. The fifth dimension is the distance "x" from the innermost surface 17 of the sash element to the innermost surface 16 of the window pane. The sixth dimension is the distance "y" from the primary sealing interface 10 to the innermost surface 17 of the sash element. The seventh dimension is the distance "z" from the primary sealing interface 10 to the middle of the fitting groove 18. It can be noted that as the frame member had a frame recess with dimension "u", the sash has a sash recess with a dimension which is equal to "v+y-x".

The two window assemblies shown in figures 2a and 2b are two outwardly opening window assemblies of a first example of a system of window assemblies. The first window assembly 1, shown in figure 2a, is the same as was shown in figure 1. The second window assembly 20, shown in figure 2b, is almost the same as the one shown in figure 1, but has a triple glazed window pane 21 instead of a double glazed window pane as was the case with figure 2a. The only other difference is the sash element 22 of figure 2b which is different than the sash element 3 of figure 1 (and figure 2a). The same reference numerals will be used for the same features as in figure 1.

As can be seen from the figures, even though the first window assembly 1 has a double glazed window pane and the second window assembly 20 has a triple glazed window pane, the dimension t is the same in both figures, the dimension u is the same in both figures, the dimension v is the same in both figures, the dimension w (see w_2a and w_2b) is the same in both figures, the dimension y is the same in both figures and the dimension z is the same in both figures. The only dimension which is different is x, see x_2a and x_2b. For simplicities sake only x_2a, x_2b, w_2a and w_2b are shown on the figures.

In this example, the frame element 2 is the same in both window assemblies 1, 20. Also the sash elements 3 and 22 are almost identical, except for the difference in the dimension x_2a and x_2b. This difference is formed by removing more material from the basic profile element for the sash element 22 of figure 2b than sash element 3 of figure 2a. This could also be described as cutting a deeper sash recess in the second window assembly than in the first window assembly. The result is that the surface 24 which supports the inner surface of the window pane 21 of the second window assembly is placed closer to the inside of the window assembly than the surface 8 of the sash which supports the inner surface of the window pane 4 of the first window assembly.

As should be clear to the person skilled in the art when comparing figures 2a and 2b, the same fittings can be used for both window assemblies. This significantly reduces the number of fitting variants which have to be stocked. It can also be seen that the fitting cavity between the sash and the frame is the same for the two window assemblies. It can also be seen that the visual impression of the two windows from the outside are identical.

The window assembly examples 30, 31 of figures 3a and 3b are very similar in concept to the window assembly examples 1, 20 shown in figures 2a and 2b. The difference in this case is that the frame 32 and sash elements 33,34 have aluminium environmental shells 35, 36 mounted on the outside of the frame and sash elements respectively in order to provide a exterior maintenance free window assembly. However, the distances as discussed in relation to figures 2a and 2b are the same as for figures 3a and 3b.

Figures 4a and 4c illustrate the invention of this specification. Claims related to the invention are defined in the claims section.

The invention relates to a system of window assemblies where a first window assembly 1 has an openable window sash 2 and a second window assembly 40 has a fixed window pane 4. Figure 4a shows a first window assembly 1 which is the same as the window assembly shown in figures 1 and 2a. Figure 4c shows a fixed window assembly 40. Both window assemblies comprise double glazed window panes 4. The window panes 4 of both window assemblies are held in place by an identical glazing bead 5. In the first window assembly 1, the glazing bead is mounted to the openable window sash 2 and in the second window assembly 40, the glazing bead is mounted to the frame 41. As was the case with the openable window assembly, the glazing bead of the second window assembly is in the current embodiment mounted to the frame member via a clip system (not shown). However, other forms of mounting, such as glue, nails, screws, etc could be imagined in other window assembly geometries as will be known to the person skilled in the art.

In figure 4a, the window pane 4 is in sealed contact with the window sash which is in sealed contact in the closed position of the window assembly with the window frame. In figure 4c, the window pane is in direct sealing contact with the window frame via a seal 42. For window assemblies of the type exemplified by the second window assembly, the primary sealing interface for the sake of this specification can be defined as the seal between the window pane and the window frame.

As can be seen from the figures the distance w4a from the primary sealing interface 10 of the first window assembly to the outside surface 15 of the window pane 4 is greater than the distance w4c from the primary sealing interface 42 of the second window assembly to the outside surface 15 of the window pane 4. This is achieved by providing two frame elements 2, 41 which have different frame recess or frame groove dimensions. In the first window assembly, the frame recess is much deeper than in the second window assembly. However, besides the dimension of the recess, the remaining geometry of the frame members of the first and second frame members are the same.

By arranging the frame members as shown in figures 4a and 4c, the dimension s_4a and s_4c from the outer surface of the window pane to the outer surface of the sash element are the same in both the first and the second window assemblies. This allows the same glazing bead 5 to be used in both the fixed and the openable window assemblies. Since the form of the glazing bead to a certain extent defines the exterior visual impression of a window assembly, openable and fixed windows of the type shown in figures 4a and 4c will provide to a great extent a similar exterior visual impression.

Figures 4b and 4d show two other examples of a system of window assemblies comprising both an openable window assembly 20 and a fixed window assembly 50. In most aspects the window assemblies of 4b and 4d are the same as the window assemblies of 4a and 4c, except that the window assemblies of 4b and 4d have triple glazed windows 21 instead of double glazed windows 4.

However, it is of interest to note that the distance w4b and w4d are the same. This is because the window pane shown in the window assemblies of figures 4b and 4d is the thickest window pane for which the window assemblies are designed for. In this position, the innermost surface of the window pane of the openable window assembly is flush with the primary sealing interface. However, for window pane thicknesses which are smaller than that shown in figures 4b and 4d, the dimension from the primary sealing interface between the frame and the window pane to the outer surface of the window pane for fixed window assemblies will be smaller than the dimension from the primary sealing interface between the frame and an openable sash to the outer surface of the window pane for openable window assemblies.

It can also be noted that the window assemblies 1, 20 and 40 could all be part of a single system of window assemblies. In this case, the system of window assemblies comprises a first window assembly which has a double glazed window pane mounted in an openable sash, a second window assembly with a double glazed window pane fixedly mounted to the window frame and a third window assembly with a triple glazed window pane mounted in an openable sash. In this system of window assemblies, the distances w4a and w4b are the same, even though one window has a double glazed window pane and the other has a triple glazed window pane.

A system of window assemblies according to the invention could be manufactured by providing a basic frame element which is the same for all window assemblies in the system of window assemblies. Then in the profiling step, different amounts of material could be removed depending on which type of window assembly was to be made. If a double glazed openable window assembly was made, the frame recess would be greater than if a double glazed fixed window assembly was made.

A method claim to the invention could also be drafted as follows: A method of manufacturing a system of window assemblies characterized in that the method comprises the steps of building a first outwardly opening window assembly with a double or triple glazed window pane arranged in a window sash which is displaceably connected with a window frame and building a second window assembly with a double or triple glazed window pane identical with the window pane of the first window assembly and where the window pane of the second window assembly is mounted directly to the frame member of the second window assembly, characterized in that the step of manufacturing the frame member of the first window assembly comprises the step of providing a frame recess having a depth X1 and in that the step of manufacturing the frame member of the second window assembly comprises the step of providing a frame recess having a depth X2 and where the depth X1 is greater than the depth X2.

A method of manufacturing a system of window assemblies according to a previous claim, characterized in that the window sash and the window frame of the first window assembly and the window frame of the second window assembly are made from wooden profile elements and in that the depths X1 and X2 are provided by removing more or less material in a cutting operation from identical base profile frame elements.

Figures 5a-5d are for the most part the same as figures 4a-4d. The main difference is that the dimensions of the sash and frame elements are slightly different and that an aluminium environmental shell has been added to the outside of the window frame and the window sash. The person skilled in the art will see the similarities between figures 4a-4d and figures 5a-5d so these figures will not be discussed in more detail here but are provided to a show additional embodiments of systems of window assemblies. For example the window assemblies of figures 5a and 5c form a system, as do the window assemblies of figures 5a, 5b and 5c and as do the window assemblies of figures 5a, 5b, 5c and 5d.

Figures 6-9 show different views of a window assembly 80 which comprises a single window frame 81 split into two areas, a fixed window 82 area on the left of figure 6 and an openable window 83 area on the right of figure 6. The fixed window pane is not shown in the figures in order to simplify the figures, but is for the most part similar to that shown in figure 4c. The two window areas are separated by a post 84. In the current embodiment, the post is mounted in between two opposing window frame members. This type of window assembly is well known in the prior art and is in some cases called a "compound window assembly" since it is assembled from multiple window areas, each area possibly comprising a different function. For example a compound window might have, as in the current example, a fixed and an openable window area. Another example is compound window with a side hung, a top hung and a fixed window area. In the case of a three part compound window, there are two posts, a first post between two opposing frame members and a second post between a frame member and the first post. Compound windows can also be made with fourt, five, etc areas. The examples are limitless.

As was discussed in relation to figures 4a and 4c, when mixing fixed and openable windows in the system of window assemblies, the frame recess has different dimensions depending on whether it was a fixed window assembly (figure 4c) or an openable (figure 4a) window assembly. This is the same in the current compound window assembly 80. However, since the two windows 81,82 of the window assembly 80 shown in figures 8-11 share a common frame 81, the frame recess is "stepped". This is best shown in figure 9. As can be seen, the frame recess 85 at the fixed window area 81 is not as wide as the frame recess 86 for the openable window area 82. This results in a step 87 in the frame recess at the transition between the openable window area 82 and the fixed window area 81. This step 87 is covered by the post 84 and cannot be seen when the window assembly 80 is assembled. The difference in the width of the frame recess 85,86 can also be seen, from the cross section shown in figure 8. From this cross section, it can also be seen that the post is arranged with two different recess depths on its two sides. On the side of the post 84 facing the fixed window area 82, the recess 85 is not as wide as the recess 86 on the side of the post facing the openable window area 83.

It should be noted that in this specification, the term "frame recess" is used to describe the groove which is formed in the frame and in which a window sash or a fixed window pane is arranged. One surface of the frame recess faces outside and forms one part of the primary sealing interface, either between a window sash and the window frame or between a fixed window pane and the window frame. It can also be mentioned that when the "depth" or the "width" of the frame recess is used, the dimension which is being referred to is the dimension which is perpendicular to the plane of the window assembly.

Figures 6-9 have been drawn rather schematically without any great details of the fixed window pane or the openable window sash. However, the person skilled in the art should be able to fill in the missing details. For example, the cross sections marked A in figure 7 will to a great extend look like the cross section of figure 4a when the window sash, window pane and glazing bead are mounted properly. Also, the cross sections marked C in figure 7 will to a great extent look like the cross section shown in figure 4c when the fixed window pane and the glazing bead are mounted properly. Furthermore, it could be imagined that the cross section marked B will look like the cross section of figure 4c on its left and like the cross section of figure 4a on its right, however with the frame members being replaced by the cross section of the post as shown in figure 8.

It should be noted that the figures 10a-10b are described quite quickly without too many details as many of the details have already been described with respect to previous figures. For example figure 10a is the same as figure 1, 2a and 4a. Figure 10a is the same as figure 3a and 5a. The person skilled in the art will be able to see the similarities between the different embodiments and be able to fill in any missing details.

As can be seen from the figures, figure 10a shows a first double glazed openable window assembly in a wood exterior and figure 10b shows a second double glazed openable window assembly an aluminium exterior "environmental shell". It should be noted that the phrase "environmental shell" is used to describe a shell of material which is added to the outside of a window frame/sash element in order to protect the main material of the window frame/sash from the outside environment. This reduces the need for frequent exterior maintenance. For example, windows having a wooden exterior need to be painted regularly in order to increase their lifetime. By adding a shell of aluminium to the outside of the wooden window, the aluminium protects the underlying wooden material and reduces the need for maintenance. While aluminium is currently being used for many applications, many other materials would also be suitable for example glass fiber or other composite materials.

As can be seen from the figures the distance v10a from the primary sealing interface 10 of the first window assembly 1 to the outer surface 14 of the window sash 3 of the first window assembly is the same as the distance v10b from the primary sealing interface 10 of the second window assembly 30 to the outer surface 37 of the environmental shell 36 of the window sash 33 of the second window assembly. By keeping this distance constant, the same fittings can be used for both window assemblies. This reduces the number of different fittings which need to be manufactured. In order to keep the distances as mentioned above the same, material is removed from the front of the frame and sash elements before the aluminium environmental shells are mounted on the outwardly facing surfaces of the sash and frame elements. The frame member 32 of the second window assembly 30 is essentially the same as the frame member 2 of the first window assembly 1 with the only difference being the length of the "nose" of the frame member. In the second window assembly, the "nose" of the frame member has been cut off in order to make room for the environmental shell. The same can also be said for the difference between the sash member 33 of the second window assembly and the sash member 3 of the first window assembly.

This is in contrast to prior art solutions where window assemblies with wooden exteriors and window assemblies with environmental shell exteriors were typically parts of two different systems of window assemblies which could not be mixed.

Figures 11a and 11b show the same as figures 10a and 10b but with triple glazed window panes instead of double glazed window panes.