TECHNICAL FIELD

[0001] The present invention relates to a ventilation system for a building having a chimney, for instance a residential building. The present invention further relates to a building including the installed ventilation system, a method of ventilating a building and a method of installing a ventilation system, including retrofitting the ventilation system in a building.

BACKGROUND

[0002] In recent years, it has been recognised that a number of health-related problems can result from poor air quality within buildings. For example, increases in the prevalence of medical conditions including asthma and allergies are attributable to poor air quality in the home or workplace. The presence of harmful pollutants, including volatile organic compounds (VOCs), is known to have a negative impact on health. These are prevalent in cleaning products, paints and plastics materials commonly found in the home and workplace. A high moisture content within air in the home has also been shown to result in an increased occurrence of mould spores and bacterial growths which are harmful to health. Furthermore, studies have shown that airborne dust can act to spread pollutants, mould spores and bacteria around a building, whilst the dust itself can of course be a harmful allergen.

[0003] These problems have been exacerbated by the drive to better insulate buildings, involving for example the installation of double and triple-glazed windows and composite doors, which are sealed relative to building apertures in order to reduce cold air ingress and warm air egress around the window and door frames. In addition, older housing stock in countries such as the United Kingdom frequently comprise chimneys which vent to the exterior of buildings. The drive to improve the insulation of buildings has, in many cases, involved the closing of chimney passages (for example by capping the chimney outlet), and the replacement of old open-hearth fireplaces with gas or electric heaters which block the channel. Whilst this has greatly improved the thermal efficiency of buildings, it has resulted in a reduction of the rate at which stale internal air within buildings is replaced by fresh, external air. This has had the knock-on effect of reducing air quality and increasing moisture content in the air within buildings, with the consequences discussed above.

[0004] This can be mitigated by improving the flow of air into and out of a building. For example, positive pressure ventilation systems have been developed which draw in fresh external air and discharge it into a building, forcing stale air out. Extractor fans are frequently installed in areas where moisture content is high, particularly bathrooms and kitchens in the home. However, the installation of such systems and fans is disruptive, requiring the formation of apertures in the building and/or the installation of ducting. A need to improve the ventilation of existing buildings has therefore been identified, particularly in older housing stock.

[0005] It is an aim of certain examples of the present invention to solve, mitigate or obviate, at least partly, at least one of the problems and/or disadvantages associated with the prior art. Certain examples aim to provide at least one of the advantages described below.

BRIEF SUMMARY OF THE INVENTION

[0006] According to a first aspect of the present invention there is provided a ventilation system for a building comprising a chimney, the ventilation system being configured to be located at least partly within the chimney, wherein the ventilation system defines: a first guide path through which fresh air from outside the building can be drawn into the chimney and discharged into the building; and a second guide path through which stale air from inside the building can be discharged to an exterior of the building via the chimney; wherein the ventilation system comprises a heating device configured to selectively heat fresh air prior to the fresh air being discharged into the building, wherein fresh air can be discharged into the building and stale air exhausted to the exterior of the building regardless of whether the heating device is operating.

[0007] The heating device may be electrically powered. The heating device may be further configured to radiate heat into the interior of the building.

[0008] The ventilation system may further comprise: a housing configured to be positioned at an internal opening of the chimney, the housing containing the heating device. The housing may be configured to be sealed around its periphery to the internal opening of the chimney such that discharged fresh air is not drawn back into the chimney. The housing may further include an outlet for discharging fresh air into the building and an inlet for drawing stale air from the building.

[0009] The ventilation system may further comprise: a heat exchanger configured such that a thermal energy transfer occurs between the stale air in the outlet flow channel and the fresh air in the inlet flow channel prior to the fresh air being discharging into the building. The heat exchanger is included in the housing.

[0010] The ventilation system may further comprise: a pump or fan for drawing fresh air from outside the building; or a pump or fan for drawing stale air from inside the building. At least one pump or fan may be included in the housing.

[0011] The ventilation system may further comprise an inlet conduit for fresh air defining at least part of the first guide path; wherein the inlet conduit is configured to extend along the length of the chimney to a position exterior to the building, or the inlet conduit is configured to open such that an existing passage of the chimney defines at least part of the first guide path; and wherein the inlet conduit passes through or adjacent to the heating device or couples to the heating device such that if the heating device is operating the fresh air in the inlet conduit is heated.

[0012] The ventilation system may further comprise an outlet conduit for stale air defining at least part of the second guide path; wherein the outlet conduit is configured to draw stale air from the building and discharge the stale air from the outlet conduit either directly to the exterior of the building or into a passage of the chimney for subsequent discharge to the exterior of the building.

[0013] According to a second aspect of the present invention there is provided a building comprising: a chimney; and a ventilation system as described above located at least partly within the chimney such that: the ventilation system is configured to draw fresh air from outside the building into the chimney along a first guide path and discharge the fresh air into the building; and the ventilation system is configured to discharge stale air from inside the building to an exterior of the building along a second guide path via the chimney.

[0014] According to a third aspect of the present invention there is provided a method of ventilating a building having a chimney and a ventilation system as described above located at least partly within the chimney, the method comprising: operating the ventilation system to draw fresh external air from outside of the building into the chimney along a first guide path and discharge the air into the building; operating the ventilation system to discharge stale internal air from inside the building to an exterior of the building along a second guide path via the chimney; and selectively heating fresh air prior to the fresh air being discharged into the building, wherein fresh air can be discharged into the building and stale air exhausted to the exterior of the building regardless of whether the heating device is operating.

[0015] According to a fourth aspect of the present invention there is provided a method of installing a ventilation system in a building having a chimney, the method comprising: positioning a ventilation system as described above located at least partly within the chimney such that: the ventilation system is configured to draw fresh air from outside the building into the chimney along a first guide path and discharge the fresh air into the building; and the ventilation system is configured to discharge stale air from inside the building to an exterior of the building along a second guide path via the chimney.

[0016] The method of installing a ventilation system may further comprise: removing any existing heating device from the chimney prior to positioning the ventilation system. [0017] A ventilation system, building or method as described above wherein the building comprises a residential building.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Examples of the invention are further described hereinafter with reference to the accompanying drawings, in which:

Figure 1 is a schematic plan view of a ground-level floor of a conventional residential building of a type comprising a chimney with a heater installed in the chimney;

Figure 2 is a cross-sectional side view of the chimney shown in figure 1 , drawn to a larger scale;

Figure 3 is a view of the chimney which is similar to figure 2 but with the heater removed, and showing a ventilation system according to an embodiment of the present invention positioned within the chimney;

Figure 4 is a view of the chimney which is similar to figure 3, showing a ventilation system according to another embodiment of the present invention positioned within the chimney;

Figure 5 is a view of the chimney which is similar to figure 3, showing a ventilation system according to further embodiment of the present invention positioned within the chimney;

Figure 6 is a view of the chimney which is similar to figure 3, showing a ventilation system according to a still further embodiment of the present invention positioned within the chimney, including an optional heater;

Figure 7 is a view of part of a ventilation system according to a yet further embodiment of the present invention; and

Figure 8 is an alternative to the part of the ventilation system shown in figure 7.

DETAILED DESCRIPTION

[0019] There is disclosed in this document a method of ventilating a residential building having a chimney, the method comprising the steps of: drawing fresh external air into the chimney along a first guide path and discharging the air into the building; and simultaneously drawing stale internal air from the building and into the chimney along a second guide path which is separate from the first guide path, and discharging the air from the chimney to an exterior of the building. A corresponding ventilation system is also disclosed.

[0020] The method advantageously makes use of the existing chimney in the building to provide a pathway for simultaneously (i.e. at the same time or in the same process) drawing stale air out of the building, and supplying fresh external air in. Effective ventilation can therefore be achieved with minimal disruption to the fabric of the building. Known ventilation systems in contrast involve significant disruption to the fabric of a building, particularly in the installation of air ducts within rooms of the building. Use of the chimney can also be advantageous in that fresh external air can be drawn in from a relatively elevated position above the ground. Air quality at such an elevated position may be higher compared to that at a lower level (e.g., ground level), for reasons including the presence of vehicle pollutants.

[0021] The method may comprise the step of positioning an inlet conduit within the chimney, the inlet conduit defining at least part of the first guide path. The method may comprise drawing fresh external air into the inlet conduit and discharging the air from the inlet conduit into the building.

[0022] The method may comprise the step of utilising an existing passage of the chimney to provide an inlet conduit which defines at least part of the first guide path. Fresh external air may therefore be drawn into the chimney passage for discharge into the building. The method may comprise lining the chimney passage so as to define the inlet conduit. Lining may be achieved using a dedicated tubular liner, or by applying a flowable material to an internal wall or walls of the chimney (e.g., a spray or paint-on material).

[0023] The method may comprise drawing the fresh external air into the chimney, optionally into the inlet conduit, at an input location which is spaced along a length of the chimney relative to an output location at which the stale internal air is discharged from the chimney to the building exterior. The input and output locations may be staggered (e.g., vertically). One of the input and output locations may be positioned above the other one of the input and output locations.

[0024] The method may comprise the step of positioning an outlet conduit within the chimney, the outlet conduit defining at least part of the second guide path. The method may comprise drawing stale internal air from the building into the outlet conduit and discharging the air from the outlet conduit directly to the exterior of the building, or into the chimney passage for subsequent discharge to the exterior of the building.

[0025] The step of drawing stale internal air into the chimney may comprise drawing the air into a passage of the chimney. The method may comprise discharging the air from the chimney passage to the exterior of the building.

[0026] Discharge of stale air from the chimney passage may be via an external opening of the chimney. Discharge may be via a dedicated port formed through a wall structure of the chimney, for example a side wall defining part of the chimney passage. [0027] The method may comprise the further steps of: directing the stale internal air through a heat exchanger along an outlet flow channel which communicates with a heat exchange element of the heat exchanger; and directing the fresh external air through the heat exchanger along an inlet flow channel which is separate from the outlet flow channel, the inlet flow channel communicating with the heat exchange element so that a thermal energy transfer occurs between the stale internal air in the outlet flow channel and the fresh external air in the inlet flow channel prior to the fresh external air discharging into the building.

[0028] During operation of the heat exchanger, moisture vapour in the fresh external air may condense out of the air stream within the heat exchanger. The method may comprise collecting condensed liquid water and periodically draining the liquid. The liquid may be manually or automatically drained.

[0029] The outlet flow channel may form part of or may be in the second guide path. The inlet flow channel may form part of or may be in the first guide path.

[0030] Where the method involves positioning an inlet conduit and/or an outlet conduit in the chimney, the method may comprise coupling the heat exchanger to the inlet conduit and/or the outlet conduit.

[0031] The inlet and outlet conduits may take the form of ducts, and may be of a metallic material. The method may comprise arranging the inlet and outlet ducts so that they are adjacent one another, and optionally substantially parallel. The method may comprise providing a main duct assembly comprising adjacent inlet and outlet duct portions, which may be separated by a dividing wall. The method may comprise providing at least one heat exchange zone which forms a heat exchange element between the ducts, and which may be defined by or may comprise a portion of the dividing wall. At least one other portion of the dividing wall may be thermally insulated so as to limit heat exchange primarily to the at least one heat exchange zone. The method may comprise providing a plurality of heat exchange zones spaced out along the lengths of the ducts. In a variation, a side wall of the inlet duct may be arranged in contact with a side wall of the outlet duct. Heat exchange zones may be provided by portions of the side walls of the duct where they contact one another. Alternatively, a heat exchange zone may be provided by a portion of a side wall of one of the ducts. A side wall of the other duct may be provided with an aperture at the heat exchange zone, to facilitate heat exchange.

[0032] The use of a heat exchanger may help to mitigate heat losses which occur with known ventilation systems and extractor fans, involving the discharge of cooler external air into buildings. In particular, in situations in which the temperature of the air within the building is significantly higher than that of the external air (this being common for example during winter periods in the northern hemisphere), the thermal energy transfer effected by the heat exchanger serves to transfer heat from the stale internal air exiting the building to the cooler incoming external air. The fresh external air is therefore heated, by the action on the heat exchange element of the stale internal air, prior to the fresh external air discharging into the building. The method may therefore be a method of providing combined ventilation and heating of a building having a chimney.

[0033] The heat exchanger may also be capable of providing a cooling effect on external air being drawn into the building. This may be beneficial in situations in which the temperature of the air within the building is lower than that of the external air (this being common during summer periods around the world), the thermal energy transfer effected by the heat exchanger serving to transfer heat from the incoming external air to the cooler stale internal air exiting the building. The fresh external air is therefore cooled, by its action on the heat exchange element (transferring thermal energy to the exiting stale air), prior to the fresh external air discharging into the building. As will be understood, the temperature differential between the internal air and the external air could be significant during summer periods in relatively hot countries, particularly where air conditioning systems are employed to cool the air within the building. The method may therefore be a method of providing combined ventilation and cooling of a building having a chimney.

[0034] Since the heating or cooling effect provided is dependent upon the temperature differential between the internal and external air, the method may be a method of providing combined ventilation and heating/cooling of a building having a chimney.

[0035] Reference is made in this document to stale internal air, and to fresh external air. It will be understood that stale internal air is air which has typically been present within the building for an extended period of time, and which may be contaminated with pollutants such as VOCs, mould spores, bacteria and dust; which may have a relatively high CO and/or CO ₂ content; and/or which may have an elevated moisture content, compared to external air. Fresh external air is that which has been drawn from the atmosphere surrounding the building, and which will typically contain lower levels of such pollutants and CO/CO ₂ , and/or may have a lower moisture content.

[0036] Reference is also made in this document to a chimney, and to a building having a chimney. The reference to a chimney should take its standard meaning, typically being that of a structure defining a passage or pipe which can serve to conduct smoke and combustion gases upwardly from a source of combustion (such as a fire, solid fuel burner or gas heater) through a roof or side wall of a building. As is well-known, the chimney may comprise an internal opening adjacent to or incorporating a hearth, and an external opening which is typically provided by a chimney pot, flue or vented cap. The passage communicates with the internal opening and the external opening such that smoke and/or combustion gases flow upwardly along the passage in a direction away from the internal opening towards the external opening, where they exit the building. The chimney will typically be integral to the building (i.e. built-into the structure of the building such as in blockwork of the building). The chimney may be of any suitable type and may be a masonry chimney formed of bricks and/or cement blocks (optionally containing a metallic flue pipe), but could be a flue-type chimney at least partly comprising a metallic pipe.

[0037] The method may comprise the step of positioning the heat exchanger at least partly within the chimney, particularly within a passage of the chimney. The method may comprise positioning the heat exchanger entirely within the chimney, particularly within the chimney passage. This may help to minimise disruption to the fabric of the building during installation of the heat exchanger.

[0038] The method may comprise positioning a majority of the inlet conduit (or the entire inlet conduit) within the chimney, particularly within the chimney passage. The inlet conduit may comprise an input end, and the method may comprise arranging the inlet conduit so that the input end opens to the exterior of the building. The inlet conduit may comprise an output end, and the method may comprise arranging the inlet conduit so that the output end opens to an interior of the building. The inlet conduit may extend from the input end to the output end, for supplying fresh external air from the input end along the conduit to the output end, for discharge into the building. The inlet conduit may comprise an input portion defining or comprising the input end, and the step of coupling the heat exchanger to the inlet conduit may comprise arranging the inlet conduit so that the input portion extends from the input end to the heat exchanger. The inlet conduit may comprise an output portion defining or comprising the output end, and the step of coupling the heat exchanger to the inlet conduit may comprise arranging the inlet conduit so that the output portion extends from the heat exchanger to the output end. The inlet conduit may be arranged so that the first guide path extends from the input portion through the heat exchanger to the output portion.

[0039] The method may comprise positioning a majority of the outlet conduit (or the entire outlet conduit) within the chimney, particularly within the chimney passage. The outlet conduit may comprise an input end, and the method may comprise arranging the outlet conduit so that the input end opens to the interior of the building. The outlet conduit may comprise an output end, and the method may comprise arranging the outlet conduit so that the output end opens to an exterior of the building. The outlet conduit may extend from the input end to the output end, for supplying stale internal air from the input end along the conduit to the output end, for discharge to the building exterior. The outlet conduit may comprise an input portion defining or comprising the input end, and the step of coupling the heat exchanger to the outlet conduit may comprise arranging the outlet conduit so that the input portion extends from the input end to the heat exchanger. The outlet conduit may comprise an output portion defining or comprising the output end, and the step of coupling the heat exchanger to the outlet conduit may comprise arranging the outlet conduit so that the output portion extends from the heat exchanger to the output end. The outlet conduit may be arranged so that the second guide path extends from the input portion through the heat exchanger to the output portion.

[0040] The steps of positioning the inlet and outlet conduits within the chimney may comprise arranging the input end of the inlet conduit so that it is spaced along a length of the chimney relative to the output end of the outlet conduit, and/or staggered (e.g., vertically) relative to said output end. This may help to restrict the possibility of stale air discharged from the outlet conduit being drawn back into the building through the inlet conduit.

[0041] The method may comprise arranging the input end of the inlet conduit and the output end of the outlet conduit so that one of said ends is above (suitably vertically above) the other one of said ends. The method may comprise arranging the input end of the inlet conduit so that it is above (suitably vertically above) the output end of the outlet conduit. This may be beneficial in that the air which is drawn into the inlet conduit through its input end may be of a higher quality (e.g., containing fewer pollutants).

[0042] Alternatively, the method may comprise arranging the output end of the outlet conduit so that it is above (suitably vertically above) the input end of the inlet conduit. The stale air exiting the building through the outlet conduit will typically be at a higher temperature than the external air, and may therefore tend to rise through the body of external air by a convective effect. Positioning said output end above said input end may therefore help to restrict the possibility of the stale air being drawn back into the building through the inlet conduit.

[0043] In another alternative, the method may comprise arranging the output end of the outlet conduit so that it is at substantially the same level (in a vertical sense) as the input end of the inlet conduit. This may help to minimise disruption to the building during installation. For example, said output and input ends may be provided in a common component such as a vented cap, chimney pot or flue pipe on the chimney defining an external opening of the chimney. Said output and input ends would typically be spaced around a perimeter of the cap or the like in order to restrict the possibility of stale air discharged from the outlet conduit being drawn back into the building through the inlet conduit. [0044] The steps of positioning the inlet and outlet conduits within the chimney may comprise arranging the input end of the outlet conduit so that it is spaced (e.g., vertically spaced) relative to the output end of the inlet conduit, and/or staggered (e.g., vertically staggered) relative to said output end. This may help to ensure that fresh external air discharged from the inlet conduit is not drawn quickly back out of the building through the outlet conduit.

[0045] The method may comprise drawing stale internal air from a first room of the building, and discharging fresh external air into the same room. This may help to minimise disruption to the fabric of the building during installation, as it may not then be necessary to route the outlet conduit out of the chimney to another room. Optionally however, the method may comprise drawing stale internal air from a first room of the building, and: discharging fresh external air into the first room and at least one further room of the building; or discharging fresh external air into at least one further room of the building.

This may require the installation of ducting within the building, or connection to an existing ducting system.

[0046] The method may comprise providing a supplementary heater and selectively activating the heater to impart a heating effect to the fresh external air. The chimney may comprise an existing heater, and the method may comprise selectively activating the heater to impart the heating effect. The heater may be of any suitable type, including but not limited to an electrically powered heater, a gas heater, and a solid fuel burner. By “selective” it is meant that the supply of fresh air to the building (and the exhaust of stale air from the building) is not contingent on the heater or heating device being operational. Fresh air may be supplied heated or unheated. Where a heat exchanger is also provided then the heating device is arranged to selectively heat the fresh air in addition to any heat recovery that has taken place.

[0047] The method may comprise passing the fresh external air through a heating chamber of the heater prior to being discharged into the building. The method may comprise positioning the heat exchanger at least partly within the heating chamber. The method may comprise positioning the output portion of the inlet conduit at least partly within the heating chamber. The method may comprise arranging the output portion of the inlet conduit so that the fresh external air is discharged into the heating chamber. The heater may then direct the external air out of the heating chamber and into the building.

[0048] The method may comprise providing one or more pump or fan, and activating the pump or fan to draw in the fresh external air and discharge it into the building, and/or to draw in the stale internal air and discharge it from the building. Separate fans may be provided for drawing in fresh and stale air, respectively. The method may comprise coupling a pump or fan to the inlet conduit and/or to the outlet conduit so as to direct flows of air along the conduit or conduits. The at least one pump or fan may be positioned at least partly within the chimney (suitably within its channel), and may be entirely positioned within the chimney. This may again help to minimise disruption during installation.

[0049] The first and second guide paths may be separate in that the air in the different paths may not mix, at least within the confines of the chimney. The second guide path may therefore be fluidly isolated from the first guide path. This may help to avoid contamination of the fresh external air by pollutants and the like in the stale internal air exiting the building.

[0050] The heat exchanger may be of a known type; may be a parallel flow, counter-flow or cross-flow heat exchanger; and may be a double-pipe type, shell-and-tube type, plate type (single or multiple plate), or plenum box type. Suitable heat exchangers include the MODEL H cross-flow, PCF and REK counter flow air plate, and air to air plate heat exchanger plenum box heat exchangers commercially available from UK Exchangers Ltd in the United Kingdom.

[0051] The fresh external air may be filtered prior to the air being discharged into the building. A filter may be provided on or in the inlet conduit, and may form part of the heater.

[0052] Reference is made in this document to a residential building, which may be one that provides sleeping accommodation for normal residential purposes, typically with cooking and dining facilities. It will be understood that the building may be of any residential type comprising a chimney, and could be a house, flat or apartment.

[0053] There is further disclosed herein a method of retrofitting a ventilation system as described above in a residential building. The ventilation system may thus be termed a retrofit ventilation system. The method may comprise positioning the ventilation system at least partly within a chimney of the building, the ventilation system defining: a first guide path through which fresh external air can be drawn into the chimney and discharged into the building; and a separate second guide path through which stale internal air can be simultaneously drawn from the building into the chimney and discharged to an exterior of the building.

[0054] The heat exchanger may be installed at least partly within the chimney, particularly within a channel of the chimney. The heat exchanger may be installed entirely within the chimney, particularly within the chimney passage.

[0055] The inlet conduit may be configured so that a majority of the conduit (or the entire conduit) can be positioned within the chimney, particularly within the chimney passage. The inlet conduit may comprise an input end, and the inlet conduit may be configured so that the input end can open to the exterior of the building. The inlet conduit may comprise an output end, and inlet conduit may be configured so that the output end can open to an interior of the building. The inlet conduit may extend from the input end to the output end, for supplying fresh external air from the input end along the conduit to the output end, for discharge into the building. The inlet conduit may comprise an input portion defining or comprising the input end, and the heat exchanger may be adapted to be coupled to the inlet conduit so that the input portion extends from the input end to the heat exchanger. The inlet conduit may comprise an output portion defining or comprising the output end, and the heat exchanger may be adapted to be coupled to the inlet conduit so that the output portion extends from the heat exchanger to the output end. The inlet conduit may be arranged so that, in use, the inlet flow path extends from the input portion through the heat exchanger to the output portion.

[0056] The outlet conduit may be configured so that a majority of the conduit (or the entire conduit) can be positioned within the chimney, particularly within the chimney passage. The outlet conduit may comprise an input end, and the outlet conduit may be configured so that the input end can open to the interior of the building. The outlet conduit may comprise an output end, and the outlet conduit may be configured so that the output end can open to an exterior of the building. The outlet conduit may extend from the input end to the output end, for supplying stale internal air from the input end along the conduit to the output end, for discharge to the building exterior. The outlet conduit may comprise an input portion defining or comprising the input end, and the heat exchanger may be adapted to be coupled to the outlet conduit so that the input portion extends from the input end to the heat exchanger. The outlet conduit may comprise an output portion defining or comprising the output end, and the heat exchanger may be adapted to be coupled to the outlet conduit so that the output portion extends from the heat exchanger to the output end. The outlet conduit may be arranged so that, in use, the outlet flow channel extends from the input portion through the heat exchanger to the output portion.

[0057] The system may comprise a supplementary heater which is selectively activatable to impart a heating effect to the fresh external air.

[0058] The system may be configurable so that the fresh external air passes through a heating chamber of the heater prior to being discharged into the building. The heat exchanger may be located at least partly within the heating chamber. The output portion of the inlet conduit may be located at least partly within the heating chamber. The output portion of the inlet conduit may be configurable so that the fresh external air is discharged into the heating chamber, and the heater may be adapted to direct the external air out of the heating chamber and into the building. The heater may be deactivated when heat recovered from the internal air is deemed sufficient, and may be selectively activated with the aim of heating the fresh external air when needed. A control system may be provided for controlling the operation of the heater depending on factors such as the desired heat within the building and the heat applied to the incoming fresh external air.

[0059] The system may comprise a visual effect heater for providing a visual heating effect, or the heater may be adapted to provide a visual heating effect. The visual heating effect may be a flame effect, for example where the heater is electrically operated.

[0060] The system may comprise one or more pump or fan for drawing in the fresh external air and discharging it into the building. The system may comprise one or more pump or fan for drawing in the stale internal air and discharging it from the building. A pump or fan may be adapted to be coupled to the inlet conduit and/or to the outlet conduit so as to direct flows of air along the conduit or conduits. The at least one pump or fan may be located at least partly within the chimney (suitably within its passage), and may be located entirely within the chimney.

[0061] The system may be a retrofit combined heating and ventilation system, a retrofit combined cooling and ventilation system, or a retrofit combined heating/cooling and ventilation system, for a building comprising a chimney.

[0062] Embodiments of the present invention include a residential building comprising a chimney and the ventilation system described above disposed at least partly within the chimney.

[0063] There is further disclosed a heater for a residential building comprising a chimney, the heater comprising: a housing adapted to be positioned at an internal opening of the chimney; a heating device located within the housing; an inlet duct for directing fresh external air from the chimney and into the building along a first guide path which communicates with the heating device; and an outlet duct for directing stale internal air from the building and into the chimney along a second guide path, for subsequent discharge from the chimney; in which the second guide path is separate from the first guide path; and in which the heating device is selectively operable to impart a heating effect on the fresh external air prior to the air being discharged into the building.

[0064] There is further disclosed a visual effect heater for a residential building, the visual effect heater comprising: a housing adapted to be positioned at an internal opening of a chimney of the building; a display device located within the housing, the display device being operable to provide a visual heating effect; an inlet duct for directing fresh external air from the chimney and into the building along a first guide path; and an outlet duct for directing stale internal air from the building and into the chimney along a second guide path, for subsequent discharge from the chimney, the second guide path being separate from the first guide path.

[0065] The housing may contain or support further components of the ventilation system in addition to a heating device or a display device. Such components include one or more of a pump or fan for fresh or stale air, a heat exchanger, a condensate collection or storage device, ducting, a heating device, an air conditioning device, or a filter. In some cases while the generic term housing is used, the ventilation may comprise more than one housing or housing part located within the chimney opening and configured to be coupled together. In some cases one or more component may be concealed behind a housing, but not actually contained within it.

[0066] The heater may comprise a filter disposed in the first fluid guide path, for filtering the fresh external air. The heater may be coupled to the filter or may be mounted in the housing. The filter may be accessible from an exterior of the heater, suitably from within a room of the building containing the heater. This may facilitate maintenance or replacement of the filter.

[0067] Suitable visual heating effects can include a fire or flame effect.

[0068] Options for the display device include a display screen arranged to display one or more different fire or flame effects, or an artificial fire type display device comprising for example an artificial flame and/or smoke effect.

[0069] The housing may be adapted to be positioned at the chimney internal opening in that it may be located within the opening, and/or so that it closes or covers the opening. However, the housing may be located adjacent or near to the internal opening, for example on a wall above the opening.

[0070] There is further disclosed a display device comprising a housing adapted to be positioned adjacent an internal opening of a chimney of the building; a display device located within the housing; an inlet duct for directing fresh external air from the chimney and into the building along a first guide path; and an outlet duct for directing stale internal air from the building and into the chimney along a second guide path, for subsequent discharge from the chimney, the second guide path being separate from the first guide path.

[0071] The display device may be operable to display televisual signals or programs and may be an audio-visual display device such as a television screen.

[0072] Turning firstly to figure 1 , there is shown a schematic plan view of a ground-level floor 10 of a conventional building 12 of a type comprising a chimney 14 with a heater 16 installed in the chimney. The building 12 shown in the drawings is a residential property in the form of a detached house. It will be understood however that the building 12 may be of any type comprising a chimney, and could be an alternative type of house such as semidetached or terraced, or a flat/apartment. Indeed the present invention is not limited to the building being a house at all, so long as it has a chimney.

[0073] The chimney 14 is shown separately in the cross-sectional side view of figure 2, and is also of a conventional type. The chimney 14 is provided on a side wall 18 of the building 12, and extends upwardly from the ground-level floor 10 through an edge region of a roof (not shown) of the building. The chimney 14 is an integral part of the building structure, and so is built into the side wall 18, suitably being formed by blockwork (bricks, cement blocks) of the building. The chimney 14 comprises a passage 20 which can serve to conduct smoke and/or combustion gases upwardly from the heater 16 and through the roof of the building, which would be a requirement in the case of a heater such as a solid fuel burner, and potentially also a gas heater. In the illustrated example however, the heater 16 is electrically powered, taking the form of a fan-type electrical resistance heater, in which there is no requirement to conduct away combustion gases or smoke.

[0074] The chimney 14 comprises an internal opening 22 adjacent to or incorporating a hearth 24, and an external opening 26. Traditionally, in older housing stock, the external opening 26 is provided by a chimney pot, flue or vented cap (not shown). In the illustrated example however, the external opening 26 has been covered and sealed using a capping plate 28, and the channel 20 has been blocked near the heater using a sealing or cover plate 29 which is secured to a chimney baffle 30.

[0075] Closing of the chimney 14 using the capping and sealing plates 28 and 29 has improved the thermal efficiency of the building 12, by reducing the ingress of external air into a room 32 which communicates with the internal opening 22 of the chimney.

However, capping and sealing of the chimney has also had the effect of closing off an entry point for fresh external air into the building 12, with the disadvantages discussed in detail above. These and other disadvantages are addressed by the present invention, as will now be described.

[0076] Referring therefore to figure 3, there is shown a view of the chimney 14 which is similar to figure 2, but with the heater 16 removed, and a ventilation system according to an embodiment of the present invention positioned within the chimney. The ventilation system, in the illustrated embodiment, takes the form of a retrofit ventilation system and is indicated generally by reference numeral 34.

[0077] Features of the ventilation system 34 and its method of operation will be described in this document. The invention however encompasses a method of ventilating a residential building having a chimney; a method of retrofitting a ventilation system in a residential building having a chimney; and a residential building comprising a chimney and a ventilation system disposed at least partly within the chimney. The invention further encompasses a ventilation system of the type described but installed in a newly constructed building/chimney (and so not a retrofit). Heaters according to further embodiments of the invention are also disclosed. The features of the methods, building, system and heaters will be evident from the following description.

[0078] In the illustrated embodiment, the ventilation system 34 generally comprises an inlet conduit 36, an outlet conduit 38 and an optional heat exchanger 40. The inlet and outlet conduits 36 and 38 are typically simple metallic ducts or pipes of any suitable crosssection. The inlet conduit 36 is positioned within the chimney 14 and serves for drawing fresh external air into the chimney along a first guide path (indicated generally by numeral 48), and discharging the air into the building 12. The outlet conduit 38 is also positioned within the chimney 14 and serves for drawing stale internal air from the building 12 into the chimney 14 along a second guide path (indicated generally by numeral 46), and discharging the air to an exterior 42 of the building. As described in detail above, the stale internal air can contain harmful pollutants, mould spores and bacteria, and can have relatively high moisture and CO2 content. The first guide path 48 is separate from the second guide path 46 so that the air in the different flow paths does not mix. The second guide path 46 is therefore fluidly isolated from the first guide path 48, which helps to avoid contamination of the fresh external air by pollutants and the like in the stale internal air exiting the building.

[0079] In most buildings there is a need to ventilate a chimney in order to prevent it from becoming damp or mouldy. In some embodiments of the present invention this may suitably be achieved by providing one or more breather holes in the outlet conduit 38 such that stale air exhausted from the living quarters of the building may ventilate the chimney. It will be understood that this ventilation method is possible as the inlet conduit 36 extends all the way to roof level so that fresh air and stale air are kept separate even if stale air is partially exhausted into the chimney through a breather hole.

[0080] The optional heat exchanger 40 is coupled to the inlet conduit 36 and the outlet conduit 38, and comprises a heat exchange element indicated schematically by reference numeral 44. The outlet conduit 38 is arranged so that stale internal air which has entered the conduit from the room 32 flows through the heat exchanger 40 along an outlet flow channel 46a which communicates with the heat exchange element 44. The outlet flow channel 46a is within or forms part of the second guide path 46. The inlet conduit 36 is arranged so that fresh external air which has entered the conduit flows through the heat exchanger 40 along an inlet flow channel 48a which is separate from the outlet flow channel 48a. The inlet flow channel 48a is within or forms part of the first guide path 48. The inlet flow channel 48a similarly communicates with the heat exchange element 44 so that a thermal energy transfer occurs between the stale internal air in the outlet flow channel 46a and the fresh external air in the inlet flow channel, the heat transfer occurring prior to the fresh external air exiting the inlet conduit 36 and discharging into the building 12.

[0081] As can be seen therefore, the present invention advantageously makes use of the existing chimney 14 in the building 12 to provide a pathway for drawing stale air out of the building, and supplying fresh external air into the building. This helps to minimise disruption to the fabric of the building 12 during installation of the system, in particular the inlet and outlet conduits 36 and 38, and the optional heat exchanger 40. Additionally, and as will be described below, use of the chimney 14 also enables fresh external air to be drawn in from a relatively elevated position above the ground.

[0082] Furthermore, the optional heat exchanger 40 helps to mitigate the heat losses which can occur with known ventilation systems and extractor fans, involving the discharge of cooler external air into buildings, by effectively applying heat to the incoming fresh air. In particular, in situations in which the temperature of the air within the building 12 is significantly higher than that of the external air (this being common for example during winter periods in the northern hemisphere), the thermal energy transfer effected by the heat exchanger 40 serves to transfer heat from the stale internal air exiting the building to the cooler incoming external air. The fresh external air is therefore heated, by the action on the heat exchange element 44 of the stale internal air, prior to the fresh external air exiting the inlet conduit 36 and discharging into the building 12.

[0083] The heat exchanger 40 may however be capable of providing a cooling effect on external air being drawn into the building 12. This may be beneficial in situations in which the temperature of the air within the building 12 is lower than that of the external air (this being common during summer periods in many parts of the world), the thermal energy transfer effected by the heat exchanger serving to transfer heat from the incoming external air to the cooler stale internal air exiting the building. The fresh external air is therefore cooled, by its action on the heat exchange element 44 (transferring thermal energy to the exiting stale air), prior to the fresh external air exiting the inlet conduit 36 and discharging into the building 12.

[0084] An installation method for the ventilation system 34 involves removing the existing heater 16 from its location at the chimney hearth 24. However, the system could be retrofitted in a chimney which does not already contain such a heater. The capping and sealing plates 28 and 29 are also removed in order to reopen the chimney passage 20. The inlet and outlet conduits 36 and 38 can then be located within the chimney 12, extending upwardly along the chimney passage 20 towards the external opening 26. The heat exchanger 40 is also positioned within the chimney passage 20, and the inlet and outlet conduits 36 and 38 are connected to the heat exchanger to provide the required outlet and inlet flow paths 46 and 48.

[0085] Stale internal air is drawn from the room 32 into an input end 50 of the outlet conduit 34, as shown by the arrow 52. The stale air passes to the heat exchanger 40, flowing through the heat exchanger along the outlet flow channel 46a, where it comes into contact with the heat exchange element 44. The air then flows upwardly away from the heat exchanger 40, as indicated by the arrow 53, exiting the outlet conduit 38 through an output end 54 and flowing to the exterior 42 of the building, as indicated by the arrow 56.

[0086] Fresh external air is drawn from the exterior 42 into an input end 58 of the inlet conduit 36, as shown by the arrow 60. The fresh air passes to the heat exchanger 40, flowing through the heat exchanger along the inlet flow channel 48a, where it similarly comes into contact with the heat exchange element 44. The air then flows away from the heat exchanger 40, as indicated by the arrow 61 , exiting the inlet conduit 36 through an output end 62 and flowing into the room 32, as indicated by the arrow 64. A filter 65 is optionally provided at the output end 62, for filtering the incoming fresh air to remove contaminants, such as particulates. The filter 65 is suitably positioned so that it can be accessed from within the room 32, for maintenance and/or replacement.

[0087] The heat exchanger 40 is positioned within the chimney passage 20, and suitably entirely within the passage as shown in the drawing. In the same way as for the inlet and outlet conduits 36 and 38, this helps to minimise disruption to the fabric of the building 12 during installation of the heat exchanger. The ventilation system 34 also comprises a (supplementary) heater 66, which takes the form of an electrically powered heater, but which could be of any other suitable type (including solid fuel and gas powered). The heater 66 is sealed within the chimney passage 20 via seals 71 and 73 to ensure against air leakage around its perimeter. The heater 66 is selectively activated to impart a further heating effect to the fresh external air if desired, prior to the air being discharged into the room 32. However, given the use of pumps or fans to drive the flow of fresh air (and optionally also stale air) the heater need not be activated for fresh air to be supplied. This may serve for bringing the air up to a higher desired temperature, above that of the fresh air exiting the heat exchanger 40. The heater 66 comprises a heating chamber 68 in which the heat exchanger 40 is located, so that the fresh air exiting the heat exchanger is heated prior to discharge. As will be described below, this is achieved by arranging an output portion 74 of the inlet conduit 36 adjacent to the heater 66 so that radiant heat outputted by the heater (indicated by arrows 70) also serves to warm the fresh air in the output portion prior to discharge.

[0088] The entire inlet conduit 36 is suitably positioned within the chimney 14, particularly within the chimney passage 20. The inlet conduit 36 is arranged so that its input end 58 opens to the building exterior 42, and so that its output end 62 opens to the building interior (room 32). The inlet conduit 36 extends from the input end 58 to the output end 62, for supplying fresh external air from the input end along the conduit to the output end, for discharge into the building 12. The inlet conduit 36 comprises an input portion 72 defining the input end 58, which extends from the input end to the heat exchanger 40. The inlet conduit also comprises the output portion 74, which defines the output end 62 and extends from the heat exchanger 40 to the output end. The inlet conduit 36 is arranged so that the first guide path 48 extends from the input portion 72 through the heat exchanger 40 to the output portion 74 (where the air is heated by the heater 66, if activated).

[0089] The entire outlet conduit 38 is also suitably positioned within the chimney 14, particularly within the chimney passage 20. The outlet conduit 38 is arranged so that its input end 50 opens to the interior of the building 12 (room 32). The outlet conduit 38 is also arranged so that its output end 54 opens to the building exterior 42. The outlet conduit 38 extends from the input end 50 to the output end 54, for supplying stale internal air from the input end along the conduit to the output end, for discharge to the building exterior 42. The outlet conduit 38 comprises an input portion 76 defining the input end 50, which extends from the input end to the heat exchanger 40. The outlet conduit 38 also comprises an output portion 78 defining the output end 54, which extends from the heat exchanger 40 to the output end. The outlet conduit 38 is arranged so that the second guide path 46 extends from the input portion 76 through the heat exchanger 40 to the output portion 78.

[0090] Although the illustrated embodiment includes the heat exchanger 40, in situations in which a heat exchanger is not required, the conduits 36 and 38 may simply extend along the chimney passage 20 between the chimney openings 22 and 26, to provide the required air flows.

[0091] The output end 54 of the outlet conduit 38 is arranged so that it is at substantially the same level as the input end 58 of the inlet conduit 36 (in a vertical sense or plane). This can help to minimise disruption to the building during installation of the system. In particular, and as shown in the drawing, the output end 54 and input end 58 are provided in a common component, which takes the form of a vented cap 80 that is sealed to the chimney 14 at its external opening 26. The inlet and outlet conduits 36 and 38 pass through a base 81 of the cap 80 and are sealed relative to the base so that air flow into and out of the chimney 14 is via the conduits. The output end 54 and input end 58 are however spaced around a perimeter of the cap in order to restrict the possibility of stale air discharged from the outlet conduit 38 being drawn back into the building 12 through the inlet conduit 36.

[0092] In a variation, the output end 54 and input end 58 need not be located at the same level. In one example the input end 58 of the fresh air inlet conduit 36 may be located within a building loft or attic space (below the roof) such that the fresh air that is drawn in is warmer than the ambient air surrounding the building (this may be especially the case during winter where some heat lost from the living quarters of a building is trapped in the loft or attic). A loft space may also be insulated to maintain a higher temperature than the surrounding ambient environment. This may be achieved by punching a hole through the wall of the chimney 14 through which the inlet conduit 36 is passed into the loft or attic. In some embodiments a fan or pump to drive fresh air into the building may be located in the loft space

[0093] In a further variation, the output end 54 and input end 58 may be selectively coupled to first and second openings (not illustrated), one opening being located on the sunny side of the building and the other opening being provided on the shady side of the building, where typically the air temperature is lower. During winter where maximum heating of the incoming fresh air is desired, the fresh air may be drawn into the inlet 36 on the sunny side of the building such that the air is the maximum available temperature before it is further heated. This may be combined with the above described variation of having an inlet in the loft or attic of a building so that in winter fresh air is selectively drawn in from that location. Stale air may be discharged to the shady side of the building. Conversely in summer where it is desired to cool incoming air, the coupling to the openings may be reversed so that fresh air is drawn in from the cooler, shady side of the building.

[0094] In a further variation, the inlet 36 and outlet 38 conduits may be positioned within the chimney 12 so that the input end 58 of the inlet conduit is spaced along a length of the chimney relative to the output end 54 of the outlet conduit, and may be vertically staggered relative to the output end. This may help to restrict the possibility of stale air discharged from the outlet conduit 38 being drawn back into the building through the inlet conduit 36. For example, the input end 58 of the inlet conduit 36 may be positioned vertically above the output end 54 of the outlet conduit 38. This may be beneficial in that the air which is drawn into the inlet conduit through its input end may be of a higher quality (e.g., containing fewer pollutants such as those derived from vehicular emissions). This may be achieved by forming an aperture or port 82 in a side wall 84 of the chimney 14, and positioning the output end 54 within the port so that stale air is ejected from a lower position, relative to the input end 58. Alternatively however, the output end 54 of the outlet conduit 38 may be arranged so that it is vertically above the input end 58 of the inlet conduit 36, for example by positioning the input end in the port 82. The stale air exiting the building through the outlet conduit 38 will typically be at a higher temperature than the external air, and may therefore tend to rise through the body of external air by a convective effect. Positioning the output end 54 above the input end 58 may therefore help to restrict the possibility of the stale air being drawn back into the building 12 through the inlet conduit 36.

[0095] The inlet 36 and outlet 38 conduits are also arranged so that the input end 50 of the outlet conduit is vertically spaced relative to the output end 60 of the inlet conduit, and so staggered relative to the output end. This helps to ensure that fresh external air discharged into the room 32 by the inlet conduit 36 is not drawn quickly back out of the building through the outlet conduit 38.

[0096] In the illustrated embodiment, the stale internal air is drawn from the room 32 of the building 12, and fresh external air is discharged into the same room. Particularly, fresh air is discharged into the room vertically above and spaced apart from the point where stale air is drawn from the room. This helps to minimise disruption to the fabric of the building 12 during installation, as it is not necessary to route the outlet conduit 38 out of the chimney 14 to another room. Optionally however, the stale internal air can be discharged back into the first room 32 and to at least one further room of the building 12 (such as an upstairs room e.g., a bedroom, or a further ground-level room), or all of the air can be discharged into a further room or rooms of the building. It will be understood that this requires the installation of ducting (not shown) within the building 12, or connection to an existing ducting system within it.

[0097] The ventilation system 34 may comprise a pump or fan for each of the inlet and outlet conduits 36 and 38, for drawing in the respective flows of air and directing them along the conduits. An inlet pump 86 is provided for the inlet conduit 36, and an outlet pump 88 for the outlet conduit 38. However, in other embodiments only an inlet pump 86 may be provided to force fresh air into the building, with the exhaust of stale air being driven by a positive pressure differential between inside the building and outside the building as a result of the pumped fresh air. In the following embodiments of figure 4 to 6 the same may apply: where an outlet pump is illustrated, this may be optional. The or each pump may be located in any suitable location, including inline along the inlet and outlet conduits 36, 38, or in a housing in the chimney aperture 22 (along with, optionally, one or more other working component of the ventilation system, such as a heat exchanger, filter, heater or other similar equipment). The pumps 86 and 88 (and indeed the heater 66) are typically electrically powered, suitably via the electrical main in the building 12. The pumps 86 and 88 are similarly positioned within the chimney passage in order to minimise disruption during installation. Suitably, the fans can be located within a housing in the chimney internal opening 22, along with the heat exchanger 40 and heater 66 (if present) so that it is in an easier to access location for maintenance.

[0098] The heat exchanger 40 can of a known type, and may be a parallel flow, counterflow or cross-flow heat exchanger. The heat exchanger 40 could be of a double-pipe, shell-and-tube or plate type construction (single or multiple plate). The heat exchanger 40 can be of a known type, and may be a parallel flow, counter-flow or cross-flow heat exchanger. The heat exchanger 40 could be of a double-pipe, shell-and-tube, plate (single or multiple plate) or plenum box type. Suitable heat exchangers include the MODEL H cross-flow, PCF and REK counter flow air plate, and air to air plate heat exchanger plenum box heat exchangers commercially available from UK Exchangers Ltd in the United Kingdom.

[0099] During use of the heat exchanger 40, liquid water may condense from the outgoing stale internal air, due to the cooling effect on the air which occurs as thermal energy is transferred to the incoming fresh external air. The liquid water may condense within the exchanger 40, and require to be drained. The liquid water may be manually or automatically drained (for example on a continuing or periodic basis), for example via a drain port 49 which may be directed to a collection point or drain line (not shown). Alternatively, liquid water may be drained via an aperture in the chimney, such aperture 82a described below in connection with figure 4. In a further alternative, collected liquid water may be heated and thus evaporated such that it is expelled along with stale air. Or the evaporated water may be used to humidify fresh air supplied via conduit 36 if there is a need to humidify the air.

[00100] The inlet and outlet conduits 36 and 38 are positioned within the chimney passage 20 via suitable mountings or fixings, such as mounting brackets indicated schematically by numerals 90 and 92, which are secured to an internal wall 94 of the chimney and to the conduits. Additionally or alternatively, the input portion 72 of the inlet conduit 36, and the output portion 78 of the outlet conduit 38, can be suspended within the chimney from the vented cap 80. The pumps 86 and 88 may also be mounted to the chimney wall 94. Couplings (not shown) are provided for coupling the heat exchanger 40 to the inlet and outlet conduits 36 and 38. Coupling parts may be provided on the inlet conduit 36 and the outlet conduit 38, for mating with corresponding coupling parts on the heat exchanger 40.

[00101] Typical existing heat exchangers are known to be up to around 90% efficient at transferring thermal energy between two fluid streams. For example, assuming an external air temperature of around 8°C (typical during a northern hemisphere winter), and an internal building temperature of around 20°C (a typical comfortable temperature provided by a heating system), it has been shown that known heat exchangers can enable a thermal energy transfer that can boost the temperature of the incoming fresh air to around 18°C. Thus a temperature differential of perhaps only 2°C between the stale air exiting the room and the fresh external air exiting the heat exchanger can be achieved.

[00102] A typical volumetric throughput for known heat exchangers in order to achieve this level of thermal energy transfer can be around 1 m ³ /hour, providing an effective circulation of stale air out of the building. It will be understood however that the thermal energy transfer to the incoming fresh air must be balanced with a desired circulation rate of stale air out of the building. For example, a higher volumetric flow rate would provide enhanced air quality but a lower reside time of the air streams on the heat exchanger element, and so a lower thermal energy transfer.

[00103] Figure 4 shows the chimney 14 with a ventilation system according to another embodiment of the present invention positioned within it, the ventilation system indicated generally by reference numeral 134. Like components of the ventilation system 134 with the system 34 shown in figure 3 share the same reference numerals incremented by 100. Only the substantial differences between the two systems will be described here.

[00104] The ventilation system 134 of this embodiment comprises an inlet conduit 136 arranged in the same way as the inlet conduit 36 of the system 34. Fresh external air flows through the inlet conduit 136 along a first guide path 148 and into the room 32. The ventilation system 134 differs in that the chimney passage 20 itself is used for discharging stale internal air, and so does not require an outlet conduit extending along the chimney passage. As shown in the drawing, stale air flowing along a second guide path 146 (as indicated by arrow 152) is discharged from an optional heat exchanger 140 and into the chimney passage 20.

[00105] A baffle plate 95 (which may also be referred to as a sealing plate) is mounted within the chimney passage 20 and isolates an upper part 20a of the chimney passage from a lower part 20b. The baffle plate 95 may be insulated to prevent heat from the heat exchanger or the heater (if present) from being lost to the upper part 20a of the chimney passage. The stale external air is discharged into the lower part 20b, and forced out through a port 82a in the chimney sidewall 84, under the positive differential pressure in the chimney imparted by the system. The inlet conduit 136 passes through the baffle plate 95, which is sealed relative to the chimney wall 84 and to the inlet conduit to restrict fluid leakage between the upper and lower passage parts 20a and 20b.

[00106] Although the embodiment of figure 3 does not illustrate a baffle plate as the inlet and outlet ducts 36, 38 extend all the way to roof level, one may be provided with passages for both ducts in order to seal off the chimney. This may be desirable to prevent chimney debris interfering with the housing and operable components in the chimney opening. Breather holes may be provided for ventilating the chimney in the embodiment of figure 3, either in the baffle plate if provided or in the stale air exhaust duct.

[00107] In some embodiments the baffle plate 95 may incorporate one or more breather holes so that some of the stale air from the lower part 20b may pass into the upper part to ventilate the chimney and prevent damp and mould build up.

[00108] Fresh external air exits the heat exchanger 140 and flows into the room 32 through an output portion 174 of the inlet conduit 136 in the same way as the system 34. An input duct 176 of an outlet line connects to the heat exchanger 140, and an output duct 178 extends from the heat exchanger and includes an output end 154 through which stale air is discharged into the chimney passage part 20b. An outlet pump 188 is operable to draw stale air from the room 32 and to discharge it from the output end 154. The input pump 186 may either be provided as illustrated in the upper passage part 20a or may be provided within the housing in the lower part of 20b (the housing including the heat exchanger and the heater) so that it may be easier to access for maintenance. If a heat exchanger is not included then the duct 176 will simply discharge into the lower passage part 20b. An optional heater 166 is also provided, which can be activated to impart further heat to the fresh external air prior to its discharge into the room 32.

[00109] In a variation on the illustrated system 134, an outlet conduit could be provided extending to the chimney cap 80 for discharge of stale internal air, and an inlet duct could communicate with the lower passage part 20b, for drawing fresh external air in through the chimney port 82a.

[00110] Figure 5 shows the chimney 14 with a ventilation system according to a further embodiment of the present invention positioned within it, the ventilation system indicated generally by reference numeral 234. Like components of the ventilation system 234 with the system 34 shown in figure 3, or the system 134 shown in figure 4, share the same reference numerals incremented by 200 or 100 respectively. Only the substantial differences between the systems will be described here. [00111] In the ventilation system 234 of this embodiment, the upper passage 20a itself is used for drawing fresh external air into the building 12. Fresh external air can enter the upper passage part 20a, the air being drawn-in by an input pump 286. The fresh external air enters an optional heat exchanger 240 through an input duct 272 and flows into the room 32 through an output duct 274. An input duct 276 of an outlet line connects to the heat exchanger 140, and an output duct 278 extends from the heat exchanger and includes an output end 254, in the same way as the system 134.

[00112] A baffle plate 295 is mounted within the chimney passage 20, and similarly isolates the upper part 20a of the chimney passage from the lower part 20b. The stale external air is discharged into the lower part 20b, and forced out through port 82a. The inlet duct 272 passes through the baffle plate 295, which is sealed relative to the chimney wall 84 and to the inlet duct to restrict fluid leakage between the upper and lower passage parts 20a and 20b. An optional heater 266 is also provided, which can be activated to impart further heat to the fresh external air prior to its discharge into the room 32.

[00113] In this embodiment as the fresh air is drawn through the upper passage 20a of the chimney itself (that is, without separate ducting), it will be understood that the baffle plate 296 cannot incorporate breather holes for stale air. However, the passage of fresh air itself serves to ventilate the chimney.

[00114] The chimney passage 20, in particular the upper part 20a, may be lined with a suitable tubular liner (e.g., of a polymeric or metallic material), or by a spray-on coating of a suitable material. This may serve to promote air flow into the inlet duct 272, for example by sealing or blocking any leaks in brick or mortar of the chimney, and/or may shield the air from contaminants present in the chimney such as sooty deposits on the chimney wall.

[00115] In a variation on the illustrated system 234, the outlet duct 278 of the outlet line can be arranged to discharge stale internal air into the upper passage part 20a, and the inlet duct 272 of the inlet line can be arranged to communicate with the lower passage part 20b, for drawing fresh external air in through the chimney port 82a.

[00116] In the embodiment of figure 5 a housing contains the heat exchanger 240, heater 266 and inlet 286 and outlet 288 pumps (if each are present) such that all key components of the ventilation system are readily accessible in the internal chimney aperture 22 for maintenance.

[00117] In the preceding figures no housing is explicitly illustrated, though it will be appreciated that in each embodiment of the invention a housing may be provided to contain the various components of the ventilation system and to close off the internal chimney aperture 22. [00118] Figure 6 shows the chimney 14 with a ventilation system according to a still further embodiment of the present invention positioned within it, the ventilation system indicated generally by reference numeral 334. Like components of the ventilation system 334 with the system 34 shown in figure 3, or the system 134 shown in figure 4, share the same reference numerals incremented by 300 or 200 respectively. Only the substantial differences between the systems will be described here.

[00119] The ventilation system 334 is of like construction and operation to the system 134, save that it includes a supplementary heater 366 according to another embodiment of the invention, which is separate to an optional heat exchanger 340 of the system. The heater 366 comprises a housing 96 which can be positioned at the internal chimney opening (hearth 24). A heating device 97 of a suitable type is located within the housing, and can take the form of an electrical resistance heater. The heater 366 also comprises an inlet duct 98 for directing fresh external air from the chimney 14 and into the building 12 along a first guide path 348 which communicates with the heating device 97. An outlet duct 99 is also provided, for directing stale internal air from the building 12 and into the chimney 14 along a second guide path 346, for subsequent discharge from the chimney. The second guide path 346 is separate from the first guide path 348 to prevent mixing of the air streams. The heating device 366 is selectively operable to impart a heating effect on the fresh external air in the inlet duct 98 prior to the air being discharged into the building 12.

[00120] The inlet duct 336 includes a pump 286 which is illustrated as being above the baffle plate 395, however it may be provided below for ease of maintenance. The inlet duct 98 is connected to an output portion 374 of an inlet conduit 336, for example via a flanged connection 35. The outlet duct 99 is similarly connected to an input portion 376 of an outlet conduit 338, again for example via a flanged connection 37. In this way, the heater 366 can be provided separately from other parts of the ventilation system 334, in particular the heat exchanger 340, plus the inlet and outlet conduits 336 and 338. Seals 371 and 373 seal the heater 366 within the chimney passage 20 to ensure against air leakage around the perimeter of the housing 96.

[00121] As for baffle plate 95 of figure 4, baffle plate 395 may incorporate one or more breather holes so that stale air can ventilate the chimney.

[00122] A filter 365 is incorporated into the heater 366, suitably mounted in the housing 96, and serves for filtering the fresh external air prior to discharge into the room 32. Again, the filter 365 may be readily accessible from within the room 32, for maintenance or replacement. In the illustrated embodiment, the heater 366 relies on pumps 386 and 388 of the ventilation system 334 for motivating the different air streams in the inlet and outlet conduits 336 and 338. It will be understood however that the pumps 386 and 388 may be provided as part of the heater 366 itself, and so optionally within the housing 96.

[00123] Providing the heater 366 separately may facilitate subsequent maintenance on the heater or other parts of the ventilation system 334, as well as replacement of the heater if desired or required.

[00124] In each of the embodiments of figures 3 to 6 it will be appreciated that is may be required to seal the internal chimney aperture 22. This may be achieved through the use of a housing and one or more seals about the aperture 22, such as seals 371 and 373 shown in figure 6. Suitably, this housing may contain at least one, some or all of the operable parts of the ventilations system, including one or more of a pump, a heat exchanger, a filter, a heater or a display device, together with the required ducts. The housing may further include one or more air conditioning components for cooling incoming fresh air (beyond any cooling effect achieved through the heat exchange with stale air). In some cases all working parts may be included in a single housing. In other cases the housing may be in several parts that may be separable, such as through the flanged connections 35, 37 in figure 6. Or some parts may be located behind the housing (and not directly contained in any housing at all). In each case though it may be that multiple working parts of the ventilation system may be collocated in the chimney aperture.

[00125] In a variation on the illustrated embodiment, the heater 366 may additionally or alternatively be a visual effect heater, comprising a display device 397 located within the housing 96, the display device being operable to provide a visual heating effect. Suitable visual heating effects can include a fire or flame effect. Options for the display device include a display screen arranged to display one or more different fire or flame effects, or an artificial fire type display device comprising for example an artificial flame and/or smoke effect. Suitable display devices will be well known by persons skilled in the field of the invention. Optionally, the heater 366 may be capable of both imparting heat to the incoming fresh air, and of providing a visual heating effect. This may be desirable for example if the heating device 97 is of the electrical resistance type. These functions may be provided independently or in combination according to the desire of a user.

[00126] In a further variation, the display device could be an audio-visual display device such as a television screen, configured to display televisual signals.

[00127] Figure 7 illustrates part of a ventilation system according to a further embodiment of the present invention, the ventilation system indicated generally by reference numeral 434. The ventilation system 434 is of like construction and operation to the system 34 shown in figure 3, save that it includes a different arrangement of inlet and outlet ducts, and heat exchanger. Only these features are shown in the drawing. Like components of the system 434 with the system 34 shown in figure 3 share the same reference numerals incremented by 400. The remainder of the system 434 is therefore common to the system 34 shown in figure 3, and is not shown in the drawing.

[00128] In this embodiment, the ventilation system 434 comprises inlet and outlet conduits 436 and 438 which take the form of ducts, suitably of a metallic material. The inlet and outlet ducts 436 and 438 are arranged so that they are adjacent one another, and suitably substantially parallel as shown in the drawing. A main duct assembly 39 of the system 434 comprises adjacent inlet and outlet duct portions 436a and 438a, which are separated by a dividing wall 41 . The duct portions 436a and 438a therefore share a common side wall, which is provided by the dividing wall 41 . The main duct assembly 39 may be insulated about its outer circumference to minimise heat transfer into the chimney. Outlet duct 438 (or a chimney baffle plate if provided) may include one or more breather holes so that stale air can ventilate the chimney.

[00129] In this embodiment, a heat exchanger is provided by heat exchange zones in the main duct assembly 39, two such zones being shown and given the numerals 43a and 43b. The heat exchange zones 43a and 43b are spaced along the lengths of the duct portions 436a and 438a, as shown in the drawing. The heat exchange zones 43a and 43b are defined by the dividing wall 41 , and essentially comprise sections or portions of the dividing wall itself. These heat exchange zones 43a and 43b form heat exchange elements between the duct portions 436a and 438a, for transferring thermal energy between stale internal air flowing along the outlet duct portion 438a, and fresh external air flowing along the inlet duct portion 436a (as indicated by the arrows 456 and 460). Constructing the main duct assembly 39 from a metallic material of suitable thermal conductivity may facilitate the thermal energy transfer.

[00130] At least one other portion of the dividing wall 41 may be thermally insulated, to limit heat exchange primarily to the one heat exchange zones 43a and 43b. Suitably an entire remaining portion of the dividing wall 41 is insulated. Three such insulated zones 45a-c are shown in the drawing, and can take any suitable form such as an insulating panel or coating applied to the dividing wall 41 . It will be understood that the remainder of the main duct assembly 39 may be similarly insulated, such as with a coating 47 applied to the exterior of the assembly. In some examples at least the upper and lower portions 45a and 45b may be thermally insulated to avoid thermal bridging along the length of the dividing wall 41 , as illustrated in the variant of figure 8.

[00131] In a variation on the illustrated embodiment, a side wall of the inlet duct portion 436a may be arranged in contact with a side wall of the outlet duct portion 438a. Heat exchange zones may be provided by portions of the side walls of the ducts where they contact one another. Alternatively, a heat exchange zone may be provided by a portion of a side wall of one of the duct portions 436a, 438a. A side wall of the other duct may be provided with an aperture at the heat exchange zone, to facilitate heat exchange.

[00132] Various modifications may be made to the foregoing without departing from the spirit or scope of the present invention.

[00133] For example, the output portion of the inlet conduit may be arranged so that the fresh external air is discharged into the heating chamber of the heater, where it may be heated further prior to discharge from an outlet of or defined by the heater. The heater may therefore direct the external air out of the heating chamber and into the building.

[00134] The chimney may be of any other suitable type, and may contain a metallic flue pipe in which the inlet and outlet conduits can be disposed (and optionally the heat exchanger and other parts of the system), but could be a flue-type chimney at least partly comprising a metallic pipe.

[00135] Reference is made in this document to a method of ventilating a building having a chimney; a method of retrofitting a combined ventilation and heating system in a building having a chimney; a retrofit ventilation system for a building comprising a chimney; and a building comprising a chimney and a ventilation system disposed at least partly within the chimney. It will be understood however that the principles of the invention, and in particular the disclosed methods and system, may have a use in buildings which do not specifically comprise a chimney. In particular, the methods and system may have a use in buildings which comprise an alternative pre-existing void (such as a shaft or channel), which will typically extend upwardly from a lower position within the building to a higher position. The void may for example be an access, maintenance, ventilation and/or services shaft or channel provided within a building. It will be understood that relevant components or parts employed in the disclosed methods and system (including but not limited to the inlet conduit, the outlet conduit and optionally the heat exchanger) would then be positioned within the alternative void.

[00136] Further aspects and/or embodiments of the invention may combine the features of one or more aspect and/or embodiment disclosed in this document. Accordingly, such further aspects and/or embodiments may comprise one or more feature selected from one or more aspect or embodiment of the invention disclosed in this document.

[00137] Unless explicitly implied by context or stated in the document, the features of any method or process disclosed in this document need not necessarily be performed in the precise order set out in the relevant text and/or drawings. Accordingly, any method or process disclosed in this document may be capable of being performed in an order other than that specifically set out in the relevant text/dowings, if circumstances permit.

[00138] Features disclosed in this document (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Accordingly, features disclosed in this document may represent only one example of a generic series of equivalent or similar features.

[00139] Throughout this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components, integers or steps. Throughout this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Throughout this specification, the term “about” is used to provide flexibility to a range endpoint by providing that a given value may be “a little above” or “a little below” the endpoint. The degree of flexibility of this term can be dictated by the particular variable and can be determined based on experience and the associated description herein.

[00140] Features, integers or characteristics described in conjunction with a particular aspect or example of the invention are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification, and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing examples. The invention extends to any novel feature or combination of features disclosed in this specification. It will be also be appreciated that, throughout this specification, language in the general form of “X for Y” (where Y is some action, activity or step and X is some means for carrying out that action, activity or step) encompasses means X adapted or arranged specifically, but not exclusively, to do Y. [00141] Each feature disclosed in this specification may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[00142] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.