GB2503778A

GB2503778A - Ventilation assembly

Info

Publication number: GB2503778A
Application number: GB1307972.8A
Authority: GB
Inventors: Colin Biggs
Original assignee: Nuaire Ltd
Current assignee: Nuaire Ltd
Priority date: 2012-05-02
Filing date: 2013-05-02
Publication date: 2014-01-08
Anticipated expiration: 2033-05-02
Also published as: EP2660526A2; GB201207715D0; EP2660526A3; EP2660526B1; GB201307972D0; GB2503778B

Abstract

A ventilation assembly comprises a supply fan and a supply conduit connected to the supply fan for channelling an air supply within a building, and an extract fan and an extract conduit connected to the extract fan for extracting vitiated air from within the building. A plurality of supply outlets supply air to a corresponding plurality of habitable rooms of the building. A plurality of extract inlets corresponding to the plurality of supply outlets (inlet and outlet are common) extract air from the same plurality of habitable rooms. A plurality of independently actuatable closure means (dampers) are associated with the plurality of inlets and outlets. In a first condition one of the closure means closes one of the extract inlets and opens the corresponding supply outlet to permit air to be supplied to the habitable room by the supply fan and prevent air from being extracted via the extract fan. In a second condition the supply outlet is closed and the corresponding extract inlet is opened to permit air to be drawn from the room by the extract fan and prevent air from being supplied by the supply fan.

Description

A VENTILATION APPARATUS

The present invention relates to a ventilation apparatus, and in particular to a ventilation apparatus for providing supply and purge ventilation to habitable rooms of a dwelling.

Ventilation systems may be specified to operate at different flow rates and modes depending on pre-defined conditions within the property being served. This is particularly common in systems specified for residential properties.

As an example of this, the ventilation provision required to satisl the Building Regulations in the UK, currently defines several conditions to be met Firstly, a provision for background ventilation is required. This is defined as the normal condi Lion of operation and requires a continuous supply of fresh air to be made available for all habitable rooms within the property (distributed proportionally with room volume).

For residential systems, this is referred to as the Whole Dwelling Supply rate.

Additionally, a provision for extract ventilation is required from the "wet" rooms (kitchen, utility room, bathroom, toilet) -and this may either be specified as continuous extract at approximately the same overall rates as for the background supply rate (known as the Mininmrn Low rate), or operated intermittently (on demand) at significantly higher rates.

Secondly, for the systems that extract continuously, there is a requirement to boost the extract ventilation rate on demand, to a higher level (known as the Minimum High or Boost rate).

The provisions above may be delivered by a number of different recognised ventilation system types, including exclusively fan based systems, and combinations of passive air inlets and outlets with fans for supply and extract.

Ihere is an increasing tendency for ventilation systems to be more energy efficient, incorporating a means of waste heat recovery (from the extract system), and to provide improved indoor air quality by filtration. Generally these enhancements may only be obtained by using fans for both the supply and extract provision.

There is a third and higher flow rate, referred to as the Rapid or Purge extract ventilation rate, and this rate is required for the habitable rooms for the purpose of quickly removing an occasional excess of pollutants, such as would occur when a room was being decorated.

The purge ventilation rate is set at a rate of four air changes per hour for the room affected This represents an eight-fold increase in the flow rate required when compared to the normal supply rate and a change in ventilation mode from supply to extract.

Ideally, this requirement would be achieved by the use of opening windows of an appropriate free area, but these are not always an acceptable solution due to security risks, and the potential ingress of noise or traffic based pollution. In high rise buildings, adverse wind effects and the risk of falling are other considerations. Some or all of these issues may be cited by the planning authorities to prevent the use of opening windows.

Alternative methods to provide purge ventilation would be to use larger, more powerfid fans and higher capacity ductwork distribution systems to cope with the higher flow rate requirement, or to use additional fan systems, dedicated to the purge ventilation function.

These methods result in significantly increased costs and spatial requirements for the systems as well as compromising the basic efficiency of operation of the system.

The invention described below is intended to he used with a conventionally designed and proportioned supply and extract ventilation system (usually with provision for heat recovery), and to provide the normal and boost ventilation rates, and to additionally offer a purge or rapid ventilation solution.

In a supply and extract ventilation system, both fans are beneficially located within a common enclosure (the ventilation unit), and drive supply and extract air across the heat exchanger element also contained within the enclosure.

Fresh air is ducted into the unit from outside. The fresh air passes through the heat exchanger wherein its temperature is increased by the heat transferred from the extract air-stream. The tempered fresh air is then delivered via further dueting to each of the habitable rooms.

S

Vitiated air is extracted from each of the "wet" or service rooms, and ducted to the unit.

Passing through the heat exchanger, heat is transferred to the cooler supply air path, and is then discharged to the outside via further ducting.

In each case, the air supply flow path, and the extract air path are each common at their respective connections to the unit, and then separate from the common duds to each individual room at locations appropriate for both the layout of the property and the containment of the ductwork.

It is therefore desirable to provide an improved ventilation apparatus which addresses the above described problems and/or which offers improvements generally.

According to the present invention there is provided a ventilation apparatus and method of ventilating the habitable rooms of a building as described in the accompanying claims.

The present invention consists of a device or collection of components that provide a connection between each habitable room and both the common supply duct and the common extract duct.

The connection device provides a feature that allows the occupant to select either supply ventilation for the habitable room (the default condition) or extract ventilation at the appropriate purge ventilation rate when required.

At the connection point of the room branch duet to the common supply duet, a changeover damper is provided. When in the default supply ventilation mode, the damper position is such that the connection to the extract system is blocked, and air is supplied directly to the room from the common supply duct. When purge ventilation mode is selected, the damper position changes to close off the connection to the common supply duct and to open the connection to the common extract duct.

The design and proportion of the device are such that the supply airflow to other branch s duct coimections upstream and downstream of the device are un-affected by the operation of the damper.

The operation of the damper is initiated by occupant demand and the damper operation is interfaced with that of the ventilation unit, enabling a simultaneous increase in the overall extract performance to provide the minimum purge ventilation rate required for the room, as well as maintaining the extract rate to the "wet" rooms, I'hc flow rates of alL of the rooms served by the system are set to the appropriate value by relative adjustment of the branch airflow resistance characteristics in a commissioning process known as balancing.

The airflow resistance characteristics of the purge connection device are optimised for the system under consideration, with parasitic energy losses and flow generated noise emissions minimised by the use of elipsoidal profiles for the components in the air streams.

Operation of the damper may be electricaHy or mechanically actuated, and the control interfaces may be sited within each room, or at a central location. For electrical operation, the control connection to the damper actuators may be directly wired or by made by wireless connection.

Operation by manual selection would be typical, but automatic operation via suitable sensors is possible.

In another aspect of the invention there is provided a ventilation assembly comprising: an air supply fan; an air supply conduit connected to the air supply fan for channelling an air supply within a building; an air extract fan; an air extract conduit connected to the air extract fan for extracting vitiated air from within the building; a plurality of supply outlets located along the air supply conduit for connecting the air supply conduit to a corresponding plurality of habitable rooms of the building; a first plurality of extract inlets located corresponding to the plurality of supply outlets along the air extract conduit for connecting the extract conduit to the same plurality of habitable rooms; and a plurality of independently actuatable closure means each arranged to in a first condition close one of the extract inlets and open the corresponding supply outlet to permit air to be supplied to said corresponding habitable room by the air supply fan and prevent air from being extracted via the extract fan and in a second condition close the supply outlet and open the corresponding extract inlet to permit air to be drawn from said corresponding room by the air extract thn and prevent air from being supplied by the supply fan.

A plurality of j unction elements corresponding to the plurality of first extract inlets and supply outlets, wherein the junction elements are located along and contiguous with the supply conduit. Each junction element comprises a plurality of walls forming a hollow ducting enclosure; a supply flow path defined within the ducting enclosure having an inlet and first and second outlets; an extract flow path defined within the ducting enclosure having an extract inlet and an extract outlet; wherein the supply flow path and extract flow path are fluidly isolated within the ducting enclosure, and the second supply flow path outlet and extract flow path inlet are fluidly connected to the common vent with the closure means being arranged to in the first condition close the extract flow path inlet and open the supply flow path outlet to permit air to be supplied to said corresponding habitable rooni from the junction element and in a second condition close the second supply flow path outlet and open the extract flow path inlet to permit air to be drawii into the junction element from said corresponding room.

Each junction element may comprise a partition arranged to fluidly isolate the supply flow path and the extract flow path.

The extract flow path may be arranged substantially transverse to the supply flow path S between the supply inlet and first outlet of the junction element. This enables the extract flow path to be passed transversely beneath the supply flow path to connect with the extract conduit arranged parallel to the supply conduit, thereby providing a very space efficient arrangement.

The junction element may comprise a first internal surface and a second internal surface spaced from the first surface with the partition being located between the first and second internal surfaces, the partition is secured and sealed to the first surface proximate the inlet and first outlet of the supply flow path with the supply flow path being defined between the partition and the second surface and the extract flow path being defined between the first flow path and the partition.

The partition preferably defines curved ramp sections leading towards the inlet and first outlet of the supply flow path. The curved ramp section define a curved leading edge and trailing edge to the partition which minimises turbulence within the supply flow path due to the presence of the partition.

The common vent duct element may extend from and form part of the junction element.

The extract flow path outlet may be fluidly connected with the extract conduit such that air extracted from the habitable room via is drawn into the extract conduit via the junction element. In a preferred arrangement the extract conduit is arranged adjacent and parall& to the supply conduit with each having a corresponding aligned and sealed aperture to permit extract air to pass from the extract flow path to the extract conduit.

Preferably the first and second internal surfaces define the roof and base of the enclosure and wherein the partition comprises a planar member extending between the side walls of the junction element and located vertically between the base and the roof of the junction element. The terms roof and base are relative and are not limited to the roof being vertically above the base in use.

Preferably the damper members are elongate members having a substantially ellipsoidal cross section thereby optimising flow into and out of the junction.

Controls means are preferably provided which are configured to control the fan to vary its operation when one or more extract inlets are opened to increase the extract flow volume.

In another aspect of the invention ajunction element for a ventilation assembly as described above comprises a plurality of walls forming a hollow ducting enclosure; a supply flow path defined within the ducting enclosure having an inlet and a first outlet arranged to form a contiguous part of a ducting supply conduit, and a second outlet; an extract flow path defined within the ducting enclosure having an extract inlet and an extract outlet; a common vent connected to the enclosure for connecting the junction element to a habitable room of a building; a closure means located within the common vent wherein the supply flow path and extract flow path are fluidly isolated within the ducting enclosure, and the second supply flow path outlet and extraci flow patti inlet are Iluidly connected to the common vent and the closure means is arranged to in a first condition close the extract flow path inlet and opcn the supply flow path outlet to permit air to be supplied from the junction element via the common duct and in a second condition close the second supply flow path outlet and open the extract flow path inlet to permit air lo be drawn into the junction element from said habitable room via the common duct, This junction assembly optimises space and enables the supply and extract air flows to be channelled through a single ducting element rather than requiring additional costly and space consuming dusting elements.

The junction element preferably comprises a partition arranged to fluidly isolate the supply flow path and the extract flow path enabling dual flow within the single ducting element.

The extract flow path is preferably arranged substantially transverse to the supply flow path.

The junction element preferably comprises a first internal surface and a second internal surface spaced from the first surface with the partition being located between the first and second internal surfaces, the partition is secured and sealed to the first surface proximate the inlet and first outlet of the supply flow path with the supply flow path being defined between the partition and the second surface and the extract flow path being defined between the first flow path and the partition.

The partition may bc shaped to form curved ramp sections leading towards the inlet and first outlet of the supply flow path.

The common vent duct clement may extend from and fomis part of the junction element, with the common vent arranged substantially perpendicular to the supply flow path.

The extract flow path outlet may be fluidly connected with the extract conduit such that air extracted from the habitable room via is drawn into the extract conduit via the junction element.

The first and second internal surfaces preferably define the roof and base of the enclosure and wherein the partition comprises a plaiiar member extending laterally between the side walls of the junction element and located vertically between the base and the roof of the junction element.

The supply flow path is preferably defined between the upper surface of the partition and the roof of the enclosure, and the extract flow path is defined between the lower surface of the partition and the base of the enclosure, with the partition being sealed to the base proximate the supply inlet and first outlet to isolate the supply flow path from the extract flow path.

The closure means may be a pivoted damper member. Preferably the damper member is an elongate member having a substantially ellipsoidal cross section.

The present invention will now be described by way of example only with reference to the following illustrative figures in which: Figure 1 shows a section of a ventilation system according to an embodiment of the present invention; Figure 2 shows ajunetion section and a section of the extract ducting of the system of Figure 1; Figure 3 shows the arrangement of Figure 1 from an alternative perspective with the damper in the raised second condition; and Figure 4 shows and internal view of the junction arrangement of Figure 3.

A ventilation system 1 comprises a supply duct 2 for supplying fresh air to habitable rooms of a building and an extract duct 4 for transferring vitiated air to the outside of the building.

The inlet duct 2 Comprises a plurality of hollow dot sections 6 comprising a plurality of walls 8 defining an enclosure having open ends. The duct sections 6 are interconnected to form an air supply flow path 10. The air supply at flow path 10 is connected at one end to an air inlet in fluid connection with the external atmosphere. The air supply flow path is 10 connected upstream of the air inlet to a fan which is arranged to draw air through the air supply flow path from the air intake, The fan (not shown) is preferably contained within a ventilaLion unit. A plurality of supply vents 12 are provided along the length of the air supply flow path. Each supply vent 12 is a modular component forming part of the supply duct air pathway 2.

Each supply vent 12 comprises a body section 14 a projecting spigot section 16 configured to extend to and interconnect the supply duct 12 with a corresponding supply duct aperture in the wall of a habitable room to be supplied. The spigot 16 comprises a peripheral wall section 18 extending from a side wall of the body section 14 and defines a channel having an open end 20 at its distal end and a corresponding opening at its proximal end in open connection with the hollow interior of the body section 14. The spigot section 16 is preferably elongated and rectangular in configuration and corresponding shape to the corresponding apertures in the wall to which it is connected. A further linking duct section may be provided between the spigot section 16 and the conned duel aperture in the wall of the habitable room if required.

As shown in Figure 2, the body section 14 includes an inlet 20, an outlet 22 which connects to a further section of the supply duct 2, and a supply oullet 24 defined by the distal aperture of the spigot section 16.

Thc room supply duct section 12 which is configured as a substantially "T" shaped branch section includes an inlet 20 which is supplied with air from outside the building via the upstream sections of the supply duct 2 and an outlet 22 through which supply air travels onwardly to further sections of the supply duct 2. The room supply duct 12 further includes a second outlet 24 at the distal end of the spigot 1 6 for supplying air to thc associated habitable room. The branch duct section 14 comprises an inner wall section 26. The wall section 26 extends transversely between the side walls 28 and 30 of the branch duct 14 and longitudinally substantially along the entire length of the branch section 14, The wall section 26 comprises a plainer section 32 arranged substantially parallel to the base and the roof of the branch duct 14 and located vertically at the mid point between the base and the roof At its ends approximately inlet 20 and outlet 22 the wall section 26 comprises curved portions which curve downwardly to the base of the branch duct 14. The curved section 34 approximately inlet 20 defines a curved leading edge to the wall section 26 to minimise air flow suction as the supply air passes over the upper surface of the wall 10 section. In this way the wall section 26 fonns a partition defining two separate airflow channels within the branch duct 14.

The first channel is defmed above the upper surface of the wall section 26. This first flow channel is open connection and is contiguous with the supply flow path of the supply duct 2. A second flow channel is defined beneath the wall section 26 and extends transversely to the longitudinal direction of the first flow channel. The lower channel opens at one end to the supply aperture 24 of the spigot section 16. At its opposing end the lower channel connects to an aperture formed in the side wall 30 of the branch duct 14 and extends into the extract duet connector section 34. As shown in Figure 3 the aperture 36 extends into and defines a flow connection with the connector duct 34 to permit air to flow from the lower channel into the extract duct 4. The aperture 36 is defined entirely within the lower channel beneath the partition defined by the wall 26. The aperture 36 does not extend into and is fluidly isolated from the supper channel. As such, air from the lower channel is not able to mix with the air from the upper channel.

A movable damper or buffer 40 is provided within the spigot section 16 to selectively close the supply outlet 24. The damper 40 is pivotally mounted along its inner longitudinal edge relative to the wall section 24. The damper 40 pivots between a first position as shown in Figure 2 in which the lower channel is closed and fluid is prevented from flowing between the lower channel and the supply opening 24. In this first position the upper channel is open to the supply outlet 24 such that supply is able to flow from the upper channel out of' the supply outlets 24 and into the corresponding habitable room. The damper 40 comprises curved faces and is preferably ellipsoidal in cross-section. As such, the damper 40 provides a curved edge for the air to flow over to minimise any disruption of the airflow. The buffer is movable to a second position which is pivoted from the first position to close the upper channel from the supply outlets 24 and provide an open connection between the outlets 24 and the lower channel. When in the second extract position the opening 24 is in open flow to connection with the extract duct 4. As such, air is drawn from the room into the supply outlet 24 and into the extract duct 4 via the lower channel.

Each of the dampers 40 located in the multiple supply outlets is independently operable.

Each damper may therefore be independently operated to connect each corresponding room to the extract duct in an independent maimer.

With the damper in the first supply position fresh air is ducted into the ventilation ducting system from outside the building. The fresh air passes through the heat exchanger where its temperature is increased by heat transferred from extracted air within the extractor 4 extracted from a wet room within the building. The tempered fresh air is then delivered onwardly downstream in the supply duct flow path 2 by a supply fan within the heat exchange unit. Simultaneously vitiated air is extracted from each of the "wet" or service rooms by an extractor fan within the heat exchange unit and drawn through the heat exchanger where its heat is transferred to the supply air. The cooled extract air is then discharged to the outside via further extra outlet ducting. A single common extract ducting section connects to the heat exchanger unit which is supplied each of the extract vents S within the building. Similarly, the heat exchange units supplies heated fresh air to a single common supply duct which then passes the air to each of the supply vents 24 via the supply dueting system 2.

When in the default supply ventilation mode, the damper 40 is located in the first position such that connection to the lower extract channel from the rooms in question is blocked and the upper supply channel is an open connection with the supply outlet 24 to supply the fresh air to the room from the common supply duct 2. When the purge ventilation mode is selected, the position of the damper 40 in the relevant outlet 24 of the relevant room is moved to the second extract position to close off connection to the common supply duct 2 is and open connection to the common extract duct 4 via the lower extract channel. At the same time the additional supply vents 24 continue in the open supply position and continue supplying fresh air to the relevant rooms.

The operation of the damper 40 is initiated by occupant demand. Operation of the damper 41) is in one embodiment mechanically actuated, with a lever, switch or other manual activation device being provided to enable the user to manually move the damper between the first supply position and the second extract position as and when purge of the room is req uired. Alternatively, operation of the damper may be electrically actuated with the ventilation duct unit including an electrical actuator. For electrical opcration, the control connection to the damper actuators may be directly wired or may be made by wireless connection. In the further embodiment the dampers may be linked to sensors for detecting air condition within the room and operating the damper automatically when pre-determined air condition indicators are detected, 3 0 The ventilation unit including the extractor fan is linked to the dampers and control means provided to increase the overall extract performance of the ventilation units when one or more of the dampers 40 has moved through the second extractor position to provide a minimum purge ventilation rate to that room as well as maintaining the base line extract rates to the "wet" room. The ventilation unit may include a control for determining the number of dampers operated and calculating and affecting the required increase in extract rate accordingly.

Flow rates of all the rooms sewed by the supply system are set to the appropriate value by relative adjustment of the branch airflow resistance characteristics in a commissioning process known as "balancing", The airflow resistance characteristics of the purge connection device branch connector 14 are optimised for the system under consideration, with parasitic energy losses and low generated noise emissions minimised by the use of the elliptical profile of the dampers 40 and the curved leading and trailing edges of the wall section 26.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to andtor shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A ventilation assembly comprising: an air supply fan; an air supply conduit connected to the air supply fan for channelling an air supply within a building; an air extract fan; an air extract conduit connected to the air extract fan for extracting vitiated air from within the building; a plurality of supply outlets located along the air supply conduit for connecting the air supply conduit to a corresponding plurality of habitable rooms of the building; a first plurality of extract inlets corresponding to the plurality of supply outlets are located along the air extract conduit for connecting the extract conduit to the same plurality of habitable rooms; and a plurality of independently acLuatable closure means each arranged to in a first condition close one of the extract inlets and open the corresponding supply outlet to permit air to be supplied to said corresponding habitable room by the air supply fan and prevent air from being extracted via the extract fan and in a second condition close the supply outlet and open the corresponding extract inlet to permit air to be drawn from said corresponding room by the air extract fan and prevent air from being supplied by the supply fan.
2. A ventilation assembly according to claim 1 wherein the air extract conduit comprises at least one further extract inlet for connection to at least one wet room of the building to draw vitiated air from the at least one wet room, wherein the apparatus is configured to draw air through said at least one ifirther extract inlet independently of the first plurality extract inlets.
3. A ventilation assembly according to claim 1 or 2 wherein each corresponding first extract inlet and supply outlet are connected to a common vent duct for connecting the extract inlet and supply outlet to a corresponding habitable room and the corresponding closure means is operable to selectively close one of the s extract inlet and supply outlet to open a fluid pathway between the habitable room and the other of the extract inlet and supply outlet via the vent duct.
4. A ventilation assembly according to claim 3 wherein the closure means is located within the vent duct.
5. A ventilation assembly according to claim 4 wherein the closure means comprises a movable damper which in a first position closes the extract inlet and opens the supply outlet to pemiit fluid flow to the habitable room from the supply outlet via the vent duct element and in a second position closes the supply outlet and opens the extract inlet to allow fluid flow from die habitable room to the air extract conduit via the vent duct element.
6. A ventilation assembly according to claims 5 comprising a plurality ofjunction elements corresponding to the plurality of first extract inlets and supply outlets, wherein the junction elements are located along and contiguous with the supply conduit and each junction element comprises: a plurality of walls forming a hollow ducting enclosure; a supply flow path defincd within the ducting enclosure having an inlet and first and second outlets; an extract flow path defined within the dueting enclosure having an extract inlet and an extract outlet; wherein the supply flow path and extract flow path are fluidly isolated within the ducting enclosure, and the second supply flow path outlet and extract flow path inlet are fluidly connected to the common vent with the closure means being arranged to in the first condition close the extract flow path inlet and open the supply flow path outlet to permit air to be supplied to said corresponding habitable room from the junction element and in a second condition close the second supply flow path outlet and open the extract flow path inlet to permit air to he drawn into the junction element from said corresponding room.
7. A ventilation assembly according to claim 6 wherein the junction element 3 comprises a partition arranged to fluidly isolate the supply flow path and the extract flow path.
8. A ventilation assembly according to claim 7 wherein the exLract flow path is arranged substantially transverse to the supply flow path between the supply inlet and first outlet of the junction element.
9. A ventilation assembly according to claim 8 wherein the junction element comprises a first internal surface and a second internal surface spaced from the first surface with the partition being located between the first and second internal surfaces, the partition is secured and sealed to the first surface proximate the inlet and first outlet of the supply flow path with the supply flow path being defined between the partition and the second surface and the extract flow path being defined between the first flow path and the partition.
10. A ventilation assembly according to claim 9 wherein the partition defines curved ramp sections leading towards the inlet and first outlet of the supply flow path.
II. A ventilation assembly according to claim 10 wherein the common vent duct element extends from and forms part of the junction element.
12. A ventilation assembly according to any one of claims 6 to 11 wherein the extract flow path outlet is fluidly connected with the extract conduit such that air extracted from the habitable room via is drawn into the extract conduit via the junction element.
13. A ventilation assembly according to claim 12 wherein the first and second internal surfaces define the roof and base of the enclosure and wherein the partition comprises a planar member extending between the side walls of the junction element and located vertically between the base and the roof of the junction element.
14. A ventilation assembly according to claimS wherein the damper members are elongate members having a substantially ellipsoidal cross section.
15. A ventilation assembly according to any preceding claim comprising controls means configured to control the fan to vary its operation when one or more extract inlets are opened to increase the extract flow volume.
16. A junction element for a ventilation assembly according to any preceding claim comprising: a plurality of walls forming a hollow ducting enclosure; a supply flow path defined within the ducting enclosure having an inlet and a first outlet arranged to form a contiguous part of a ducting supply conduit, and a second outlet; an extract flow path defined within the ducting enclosure having an extract inlet and an extract outlet; a common vent connected to the enclosure for connecting the junction element to a habitable room of a building; a closure means located within the common vent wherein the supply flow path and extract flow path are fluidly isolated within the ducting enclosure, and the second supply flow path outlet and extract flow path inlet are fluidly connected to the common vent and the closure means is arranged to in a first condition close the extract flow path inlet and open the supply flow path outlet to permit air to be supplied from the junction element via the common duct and in a second condition close the second supply flow path outlet and open the extract flow path inlet to permit air to be drawn into the junction element from said habitable room via the common duct.
17. A junction element according to claim 16 wherein the junction element comprises a partition arranged to fluidly isolate the supply flow path and the extract flow path.
18. A junction element according to claim 16 or 17 wheTein the extract flow path is arranged substantiaLly transverse to the supply flow path.
19. A junction element according to claim 18 wherein the junction element comprises a first internal surface and a second internal surface spaced from the first surface with the partition being located between the first and second internal surfaces, the partition is secured and sealed to the first surface proximate the inlet and first outlet of the supply flow path with the supply flow path being defined between the partition and the second surface and the extract flow path being defined between the first flow path and the partition.
20, A junction element according to claim 19 wherein the partition is shaped to form curved ramp sections leading towards the inlet and first outlet of the supply flow path.
21. A junction element according to claim 20 wherein the common vent duct element extends from and forms part of the junction element, with the common vent arranged substantially perpendicular to the supply flow path.
22. A junction clement according to any one of claims 16 to 21 wherein the extract flow path outlet is fluidly connected with the extract conduit such that air extractcd from the habitable room via is drawn into the extract conduit via the junction element.
23. A junction element according to claim 22 wherein the first and second internal surfaces define the roof and base of the enclosure and wherein the partition comprises a planar member extending laterally between die side walls of the -19 junction element and located vertically between the base and the roof of the junction element.
24. A junction clement according to claim 23 wherein the supply flow path is defined between the upper surface of the partition and the roof of the enclosure, and the extract flow path is defined between the lower surface of the partition and the base of the enclosure, with the partition being scaled to the base proximate the supply inlet and first outlet to isolate the supply flow path from the extract flow path.
25. A junction element according to any one of claims 16 to 24 wherein the closure means is pivoted damper member.
26. A junction element according to claim 25 wherein the damper member is an elongate member having a substantially ellipsoidal cross section.26. A junction element according to any one of claims 16 to 26 comprising controls means configured to control thc fan to vary its operation when one or more extract inlets are opened to increase the extract flow volume.