EP0059545A1

EP0059545A1 - A window, a method of reducing condensation of water vapour on a window frame structure and a device for use in the method

Info

Publication number: EP0059545A1
Application number: EP82300707A
Authority: EP
Inventors: Stanley Howard Hobbins
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-28
Filing date: 1982-02-12
Publication date: 1982-09-08
Also published as: GB2094382A; GB2094382B

Abstract

An aluminium window frame is heated by energisation of electrical heating elements (43) in glazing channels (27) of the frame or elements comprised by elongated devices (30, 31) mounted on surfaces of the frame. Heating of the frame generally prevents condensation of moisture onto surfaces of the frame exposed at the interior of a building.

Description

From one aspect, the present invention relates to a method of reducing the condensation of water vapour on a window frame structure from air inside a building incorporating the frame structure. The expression "frame structure" as used herein embraces a frame which is fixed in a wall of a building and embraces a frame around a glazing panel, which frame is movable relative to a wall of the building to enable the window to be opened and closed. The term "window" as used herein embraces glazed doors and glazed roofs or glazed parts of roofs.
The invention also relates to a device for use in the method and to a window comprising a frame structure and one or more glazing panels supported by the frame structure.
The frame structure of many windows is made of timber but this material suffers from significant disadvantages, notably shrinkage and warping which lead to a need for considerable maintenance work and may result in a poor fit between relatively movable parts of the window. Steel and aluminium have also been used extensively in the manufacture of window frame structures, these materials avoiding the aforementioned disadvantages of timber but having a relatively high thermal conductivity so that the temperature of the internal surface of the frame structure often falls below the dew point of the atmosphere within the building. This leads to condensation of water vapour on the frame structure which can result in damage to wall and floor coverings and to the growth of organisms on the frame structure. Attempts have been made to reduce condensation on metal window frame structures by incorporating in the frame structure materials having a lower thermal conductivity, for example plastics materials. However, the problem of condensation on window frame structures has not been solved in this way.
According to one aspect of the invention, there is provided a method of reducing the condensation of water vapour on a window frame structure wherein an electrically energisable heating element is applied to the frame structure and an electric current is passed through the heating element.
Energisation of the heating element can conveniently be controlled manually. However, energisation of the heating element may alternatively be controlled automatically in accordance with the temperature at a position on or within the window structure.
There is also provided in accordance with the invention a window comprising a frame structure and one or more glazing panels supported by the frame structure, wherein there is mounted on or in the frame structure adjacent to the periphery of the glazing panel an electrically energisable heating element.
There is also provided according to the invention a heating device for use in a method according to the first aspect and comprising a hollow housing, an electrically energisable heating element disposed within the housing, a further electrical conductor disposed within the housing, first and second parts of a two-part electrical connector mounted at spaced positions in the housing and each having a first electrical connector connected electrically with the heating element and a second electrical connector connected electrically with the further conductor, the connector parts being so arranged that the first part can co-operate with the second connector part of an identical device and the second part can co-operate with the first connector part of a further identical device to connect the heating elements of the three devices electrically in series with one another and to connect the further conductors of the three devices electrically in series with one another.
Examples of windows embodying the invention are illustrated in the accompanying drawings wherein:-

FIGURE 1 shows an elevation of a window;
FIGURE 2 shows on an enlarged scale a fragmentary cross-section on the line II-II of Figure 1;
FIGURE 3 shows a partial cross-section of a modification of the window, on a line corresponding to the line III-III of Figure 1;
FIGURE 4 illustrates diagrammatically an elevation of a further window; and
FIGURE 5 illustrates an end portion of a heating device applied to a frame structure of the window.

The window illustrated in Figure 1 comprises a timber surround 10 which is fixed in an opening in a wall (not shown) of a building. The timber surround extends around the periphery of a frame structure 11 supported by the surround. In turn, the frame structure supports a number of glazing panels which may be formed of glass. The frame structure 11 includes a head 12, sill bar 13, side members 14 and 15 extending between the head and the sill bar, mullions 16 and 17 also extending between the head and the sill bar and transoms 18 and 19 extending each between one of the side members and one of the mullions. All of these parts of the frame structure are fixed with respect to the masonry wall. A glazing panel 20 supported by the sill bar, mullions and the head is also fixed. Below each transom, there is a hinged casement comprising a glazing panel 21 supported in a rectangular frame 22 which constitutes a part of the frame structure. Above each transom, there is a top- hinged rectangular frame 23 supporting a further movable glazing panel 24. The glazing panels shown are double glazing sealed units.
The frame structure 11 is formed mainly of aluminium, being assembled from lengths of aluminium extrusions. As shown in Figure 3, the frame structure further comprises resilient seals mounted on the frames 22 and 23 to seal these frames to the fixed parts of the frame structure when the panels 21 and 24 are closed.
Marginal portions of each of the glazing panels are received in respective glazing channels defined by the frame structure 11. In Figure 3, a glazing channel defined by the mullion 17 is indicated by the reference number 26 and a glazing channel defined by one of the hinged frames 22 is indicated by the reference numeral 27. Glazing gaskets 28 are interposed between the side walls of the glazing channels and the marginal portions of the glazing panels. These gaskets are tapered to facilitate insertion of the gaskets into the glazing channels after the marginal portions of the glazing panels have been received therein. The seals 25 and gaskets 28 are conveniently formed of neoprene rubber. The remainder of the frame structure 11 is formed of aluminium.
On surfaces of certain parts of the frame structure 11 which face towards the interior of the building, there are mounted heating devices. On each of the side members 14 and 15, there is mounted a heating device 29 which extends almost from the lower end of the side member upwardly for a distance approximately equal to one third the height of the side member. On each of the mullions 16 and 17, there is mounted a heating device 30 which extends approximately from the lower end of the mullion to the level of the adjacent transom, a distance which is approximately two thirds the height of the mullion. On the sill bar 13, there are mounted three heating devices 31, 32 and 33, each of which occupies almost one third of the length of the sill bar. Each of the heating devices 29 to 33 is elongated and rectilinear. The heating device 31 is joined to the adjacent heating device 29 by an angle connector 34 and is joined to the heating device 32 and to the adjacent heating device 30 by a connector tee 35. A similar connector and tee are associated with the heating device 33. At the upper ends of the heating devices 30, there are provided end caps 36 and at the upper ends of the heating devices 29 there are provided end caps 37.
As shown in Figure 2, each of the heating devices 29 to 33 comprises an electrical energisable heating element 38 and a further, insulated electrical conductor 39 disposed within a hollow'housing. The housing comprises a base plate 40 and a cover 41 mounted on the base plate. In the particular example illustrated, the surfaces of the frame structure 11 on which the heating devices are mounted are flat and therefore the face of the base 40 which is presented outwardly of the housing is flat.
The heating element 38 is in the form of a length of known heating tape having an electrically conductive core covered by an electrically insulating material. This tape engages the face of the base 40 which is disposed at the interior of the housing and the base is formed of aluminium or other material which is a good conductor of heat. Between the heating element 38 and the cover 41, there is provided a strip 42 of thermally insulating material.
Opposite ends of the housing of each of the devices 29 to 33 are closed by respective plugs which incorporate respective parts of a two-part electrical connector. Each of these parts has a first connector element connected with the core of the heating element 38 and a second connector element connected with the core of the further conductor 39. The pair of connector elements in each plug may comprise, as shown in Figure 5, a projecting pin 44 and an element 45 defining a socket 46 in which an identical pin can engage. Alternatively, the ^-1 connector elements in the plug at one end of a device may be in the form of longitudinally projecting pins whilst the connector elements in the plug at the opposite end of the device are formed with sockets to receive an identical pair of pins. With this alternative arrangement, each of the devices 29 to 33 has a male plug at one end and a female plug at the other end.
Each of the tee connectors 35 comprises a housing containing two similar, insulated electrical conductors connecting together respective connector elements in each of three plugs comprised by the tee connector. The tee connector does not include an electrical heating element. Each of the end caps 36 comprises a single electrical conductor connecting together connector elements in a single plug of the end cap so that the end cap provides an electrical connection between the heating element 38 and the conductor 39 of the adjacent heating device 30. Each of the end caps 37 comprises a pair of terminals by means of which electrical leads which pass through the timber surround 10 can be connected to the heating element 38 and conductor 39 of the adjacent heating device 29. If required, an end cap 37 may be provided on one only of the heating devices 29, an end cap 36 being provided on the other heating device 29.
Each of the heating devices 29 to 33 is secured to the frame structure 11 by means of screws (not shown) passing through holes drilled in the base 40. The connectors 34 and 35 may be secured to the frame structure in a similar way. The tee connectors 35 herein before described connect the heating elements 38 of the heating devices 31, 32 and 33 in series with one another, the conductors 39 of these devices also being in series with one another, but establish parallel connection of the heating devices 30. Alternatively, each tee connector 35 may establish series connection of each of the three adjacent heating devices.
It will be noted that an upper part of the frame structure 11 is devoid of heating elements. The aggregate of the lengths of the heating devices 29 to 33 is less than one half the aggregate of the lengths of the components of the frame structure 11 and is preferably less than one third the latter aggregate.
In Figure 3, there is illustrated a modification of the window shown in Figure 2, from which all of the heating devices 29 to 33 and the connectors and end caps associated therewith are omitted, heating elements 43 being mounted on the frame structure 11 within certain of the glazing channels. The heating elements 43 comprise lengths of known heating tape which lie in face-to-face engagement with walls of the glazing channels. These lengths of heating tape can be inserted in an existing window by removing glazing gaskets 28 at selected positions, inserting the heating elements into the glazing channels and then replacing the gaskets. . Electrical conductors for conveying current to and from the heating elements 43 may pass between the glazing gaskets and the walls of the glazing channels or may extend through apertures drilled in walls of the glazing channels.
As shown in Figure 3, a heating element 43 may be provided in one of the hinged frames 22 arid 23. In this case, there are provided on the frame concerned two connector elements (not shown) of respective two-element separable connectors, the other elements of which are mounted on a fixed part of the frame structure 11 to establish electrical contact with the connector elements on the hinged frame when the panel supported by that frame is closed. The two-element connectors may be of a type known for use in burglar alarm systems.
The number and length of heating elements 43 used may be substantially the same as the number and length of heating elements 38 used in the window illustrated in Figure 1, the heating elements 43 being arranged in corresponding positions. However, I have found that where heating elements arranged as shown in Figure 3 are provided, the aggregate length of the heating elements can be somewhat less than the aggregate length of the heating elements provided in the window shown in Figure 1.
It will be noted that each of the heating elements 43 is disposed in a substantially closed, elongated space defined by the frame structure and the glazing panels. When the heating elements 43 are energised, heat is transferred by conduction to the immediately adjacent wall of the frame structure 11 which is preferably adjacent to the interior of the building. Heat is conducted to further elongated air spaces defined by the frame structure, such as the air space 44 indicated in Figure 3. Heat is also transferred directly to air in the glazing channel containing the heating element. The heated air in these enclosed spaces rises by convection to carry heat to parts of the frame structure remote from the heating elements. Thus, heat is transmitted by convection to parts of the frame structure separated from the directly heated parts by rubber seals or gaskets which do not conduct heat as readily as does the metal of the frame structure. It has been found that the heating elements can be confined to the lower two thirds of a frame structure without impairing the effectiveness of the heating elements to reduce condensation on the frame structure under moderate conditions.
For use under severe conditions, we prefer to provide heating elements of the same form as the heating element 43 around the entire periphery of each glazing panel. Such an arrangement is illustrated in Figure 4, where there is illustrated a window comprising a fixed frame 47 of aluminium defining a glazing channel supporting a fixed glazing panel 48 and also defining an opening which is normally closed by a hinged casement. The hinged casement comprises an aluminium frame 49 supporting a glazing panel 50. A heating element 51 is disposed in the glazing channel defined by the fixed frame 47 and extends around substantially the entire periphery of the glazing panel 48. Opposite ends of the heating element 51 enter a connector block 52 secured on the fixed frame. A further heating element 53 is disposed in a glazing channel of the hinged casement and extends around substantially the entire periphery of the glazing panel 50. The element 53 is in two pieces, respective first ends of which enter a connector block 54 secured on the frame 49 and second ends of which enter a connector block 55 also mounted on the frame 49. Terminals of the connector blocks 52 and 54 are connected together by a two-core cable 56 and terminals of the connector block 55 are connected with a further connector block 56 also by a two-core cable. Terminals of the connector block 56 are connected with a low voltage supply.
In use of the arrangements illustrated in the accompanying drawings, energisation of the heating elements 38, 43 or 51 and 53 may be controlled by a manually operable switch so that the heating elements are energised intermittently or, on occasions when the temperature outside the building is particularly low, continuously. Alternatively, energisation of the heating elements may be controlled by a thermostatic switch (not shown) arranged to sense the temperature at a position which may be outside the building or may be on or in the frame structure 11. The control means may be arranged to energise the heating elements continuously whilst the outside temperature is below a predetermined value. Alternatively, the control means may be arranged to energise the heating elements intermittently in a manner to prevent the temperature of the frame structure falling below a predetermined value. A thermostatic switch mounted on or in the frame structure is preferably situated at the coldest part of the frame structure.
The heating elements are preferably supplied from a low voltage source of electric current, conveniently a transformer connected to the mains supply. The low voltage source may include a switch which enables the power output of the source to be set to a selected one of two or more alternative values. Typically, at the highest power setting, the output is approximately 10 watts per metre of heating element.
In a further modification of the window shown in Figure 1, heating elements similar to the elements 43 are disposed in an elongated cavity defined between the timber surround 10 and the frame structure 11. A single heating tape may extend around the entire periphery of the frame structure.
The invention may be applied to a glazed roof or glazed part of a roof. Glazed roofs commonly comprise a number of rectangular glazing panels which rest on supporting rails adjacent to their longer edges. The cross-sectional shape of the rails is that of an inverted T, with the glazing panels resting on the flanges of the T and at the stem projecting upwardly between adjacent glazing panels. Elastomeric seals are interposed between marginal portions of the glazing panels and the flanges of the rails. These seals may be supported on ribs or other elongated projections which extend from the flanges of the rails towards the glazing panels. To reduce the condensation of moisture onto the rails from within the building, there is applied to each rail an electrical heating element. The heating element may rest on the upwardly facing surface of one flange of the rail.
Alternatively, the exposed, downwardly facing surface of the rail may be covered by a capping strip which is a snap-fit onto the flanges of the rail. With the latter arrangement, an electrical heating element in the form of a tape is trapped between the capping strip and the rail to rest on the upwardly presented, concealed surface of the capping strip. The heating element may be energised continuously or intermittently when the temperature outside the building is low.
It will be noted that, in the arrangement described, a heating element extends along two only edges of each glazing panel.

Claims

1. A method of reducing the condensation of water vapour onto a window frame structure wherein there is applied to the frame structure an electrically energisable heating element and electric current is passed through the heating element.

2. A method of reducing the condensation of water vapour onto a frame which supports a glazing panel wherein an electrically energisable heating element is applied to the assembled frame and electric current is passed through the heating element.

3. A method according to Claim 2 wherein the frame defines a glazing channel in which marginal portions of the glazing panel are received and wherein the heating element is placed in the glazing channel.

4. A method according to Claim 1 wherein the heating element is applied to a surface of the frame structure which, prior to application of the heating element, is exposed to the interior of a building.

5. A method according to any preceding claim wherein a fraction only of the frame structure has applied thereto a heating element.

6. A window comprising a frame structure and one or more glazing panels supported by the frame structure, wherein there is mounted on the frame structure an electrically energisable heating element.

7. A window according to Claim 6 wherein the frame structure defines glazing channels in which respective marginal portions of the or each glazing panel are disposed and wherein the or each heating element is disposed in a glazing channel.

8. For use in a method according to Claim 1, a heating device comprising a hollow housing, an electrically energisable heating element disposed within the housing, a further electrical conductor disposed within the housing, first and second parts of a two-part electrical connector mounted at spaced positions in the housing and each having a first connector element connected with the heating element and a second connector element connected with the further conductor, the first connector part being arranged for co-operation with the second part of an identical device and the second part of the connector being arranged for co-operation with the first part of a further identical device to connect the heating elements of three devices electrically in series with one another and to connect the further conductors of the three devices electrically in series with one another.

9. A device according to Claim 8 wherein the housing has a substantially flat external surface and the heating element is adjacent to said surface at the inside of the housing.