WO2016010473A1

WO2016010473A1 - A ventilation device and a method for installation of a ventilation device

Info

Publication number: WO2016010473A1
Application number: PCT/SE2015/050820
Authority: WO
Inventors: Karl-Henrik Nilsson; Mattias Svensson
Original assignee: Smartvent Sverige Ab
Priority date: 2014-07-18
Filing date: 2015-07-13
Publication date: 2016-01-21
Also published as: SE541573C2; SE1450899A1

Abstract

A ventilation device (10) comprising a ventilation duct (11) having a longitudinal axis (A), a first end (14), a second end(15) and a duct wall (16), said duct wall extending axially between the first and second ends (14, 15). The duct wall (16) is provided with a first aperture (22) and a second aperture (23), said apertures forming passages for air in a radial direction. The first aperture (22) is provided with a first hood (12), and the second aperture (23) is provided with a second hood (13), the hoods (12, 13) extending through the apertures (22, 23). Each of the hoods (12, 13) are provided with a projection (25) engaging an interior side of the duct wall (16).

Description

A VENTILATION DEVICE AND A METHOD FOR INSTALLATION OF A VENTILATION DEVICE

FIELD OF THE INVENTION

The invention relates to a ventilation device and a method for installation of such a ventilation device. Air in premises, such as rooms in houses, offices, commercial buildings, industrial buildings and other types of buildings, are ventilated to exchange air in one or more of the rooms. For exam- pie, this type of ventilation is residential or domestic ventilation. Fresh air is supplied from an air supply, such as ambient air, i.e. outdoor air, or air from another space, to the rooms through one or more ventilation devices. Further, exhaust air is conveyed from the one or more rooms and, for example, to the outside of the building. This type of ventilation devices comprises a ventilation duct for connecting the air supply, such as outdoor ambient air, and the one or more rooms within the building to enable transport of air between the air supply and the room. Such ventilation devices usually extend through a building wall between an interior side of the wall inside a room and an exterior outdoor side.

BACKGROUND AND PRIOR ART

There are several different types of ventilation devices in the prior art. One such type of ventilation device is disclosed in GB2465029. GB2465029 discloses a vent cover for securing over an end of a vent duct. The cover is made collapsible to enable it to fit through a ventilation duct, so that the cover can be folded and pushed through the ventilation duct from within a building by means of a rod and then unfolded and mounted over the end of the duct by means of said rod. Spring clips are used to secure the cover to the duct. One problem with such ventilation devices according to prior art is that they can be difficult to install.

Another problem with such prior art ventilation devices is that the exterior orifice of the duct is not protected satisfactorily.

Another problem with such prior art ventilation devices is that the venti- lation can be less efficient. Another problem with such prior art ventilation devices is that they are expensive to manufacture, install and maintain.

SUMMARY OF THE INVENTION

An object of the present invention is to avoid the problems of the prior art. The present invention results in a reliable ventilation device being easy to install and which provides efficient ventilation.

The present invention relates to a ventilation device comprising a ven- tilation duct having a longitudinal axis, a first end, a second end and a duct wall, said duct wall extending axially between the first and second ends, characterised in that the duct wall is provided with a first aperture and a second aperture, said apertures forming passages for air in a radial direction, the first aperture is provided with a first hood, and the second aperture is provid- ed with a second hood, the hoods extend through the apertures, and each of the hoods are provided with a projection engaging an interior side of the duct wall. This arrangement of the ventilation device makes it possible to provide safe and reliable ventilation and simple installation from within the building. The ventilation device according to the invention results in the possibility of providing a larger air passage than the cross section of the ventilation duct without moving parts or foldable hoods or covers. Hence, improved protection of the ventilation duct against wind and water is achieved with minimal effect on the ventilation.

Each of the hoods can be dimensioned to fit through the ventilation duct to enable positioning of the hoods at the apertures from said first end. Hence, a person can push one hood at a time from within the building and into the ventilation duct through the first end thereof and position the hood in its aperture in a simple manner. The hoods can be arranged with substantially fixed dimensions and can be non-foldable. Hence, a reliable and durable hood is provided, without moving joints and entirely or substantially without any moving parts. The hoods can be provided with front and back walls and a top and side wall, which top/side wall can extend radially out from the duct wall and then downwards. Hence, the apertures can be arranged laterally and downwards in the ventilation duct, wherein each of the air passages formed by the hoods has an outer orifice extending in a horizontal plane. Hence, an efficient protection against wind and water is provided with minimum impact on the ventilation.

The ventilation duct can be provided with an internal dividing wall extending axially and dividing the ventilation duct in first and second airflow ducts for supply air and exhaust air, respectively. Hence, the ventilation device can be used for providing a supply airflow and an exhaust airflow at the same time. For example, only a single hole in the building wall is provided for both supply air and exhaust air.

The invention also relates to a method for installation of a ventilation device, the method comprising the steps of

a) arranging a through hole in a building wall,

b) inserting a ventilation duct into the hole from an interior side of the building wall, the ventilation duct having a longitudinal axis, a first end, a second end and a duct wall extending axially between the first and second ends, wherein the second end is arranged to project from an exterior side of the building wall,

c) bringing a first hood to extend through a first aperture of the ventilation duct, and

d) bringing a second hood to extend through a second aperture of the ventila- tion duct.

The hoods can be inserted into the ventilation duct from within the building, wherein the first hood is inserted and installed first and then the second hood is inserted and installed. The hole can be a single through hole. Projections of the hoods can be brought into contact with the interior side of the ventilation duct to fit the hoods in the apertures. Further, the hoods can be secured in the apertures by means of a securing device, such as a flexible projection which can be forced over the edge of the duct wall. After installation of the hoods an internal dividing wall can be inserted axially into the ventilation duct, thereby dividing the ventilation duct in a first airflow duct connected to the first aperture and a second airflow duct connected to the second aperture. Hence, supply air can be transported through the first airflow duct while exhaust air can be transported through the second airflow duct simultaneously. Hence, supply air can be intermittently and alter- natingly transported through the first airflow duct and the second airflow duct. Simultaneously, exhaust air can be intermittently and alternatingly transported though the first and second airflow ducts. This type of ventilation devices can be connected to a regenerative heat exchanger, e.g. comprising at least one heat exchanger and at least one fan, for moving air and recovering thermal energy for reducing energy loss when providing fresh air to the rooms and transporting exhaust air out from the rooms. Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

SHORT DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail with the aid of embodiments and with reference to the appended drawings, in which

Fig. 1 is a schematic perspective view of a ventilation device according to one embodiment, comprising a ventilation duct, a first hood and a second hood seen from above,

Fig. 2 is a schematic view according to Fig. 1 seen from below, Fig. 3 is a schematic perspective view of the ventilation duct according to one embodiment, seen from above and showing a first and second aperture of the ventilation duct, Fig. 4 is a schematic perspective view from above of a hood according to one embodiment,

Fig. 5 is a schematic perspective view illustrating insertion of the ventilation duct according to Fig. 4 into a hole in a building wall from within the building,

Fig. 6 is a schematic perspective view of the ventilation duct inserted into the hole in the building wall seen from an exterior side of the building wall, Figs. 7-1 1 is a series of schematic views illustrating installation of the first hood in the first aperture of the ventilation duct,

Figs. 12-16 is a series of schematic views illustrating installation of the second hood in the second aperture of the ventilation duct,

Fig. 17 is a schematic view from within the building of the ventilation device according to one embodiment, wherein a dividing wall is arranged in the ventilation duct to enable supply airflow and exhaust airflow simultaneously, Fig. 18 is a schematic perspective view of a regenerative heat exchanger unit connected to the interior side of the ventilation duct according to one embodiment,

Fig. 19 is a schematic section view of the regenerative heat exchanger unit of Fig. 18,

Fig. 20a is a schematic perspective view from above of the regenerative heat exchanger unit according to Fig. 18 arranged in a room and illustrating an exhaust airflow and a supply airflow in a first part of a working cycle,

Fig. 20b is a schematic perspective view according to Fig. 20a, illustrating the exhaust airflow and the supply airflow in a second and final part of the working cycle, and Fig. 21 is a schematic perspective view of of the hood according to another embodiment. THE INVENTION

Referring to Fig. 1 and Fig. 2 a ventilation device 10 according to one embodiment is illustrated. The ventilation device 10 is arranged for connecting a room in a building to outdoor ambient air, so that air can be transported between the inside of the building to the outside thereof for ventilating the room in the building. Hence, the ventilation device 10 is arranged for transporting supply air from outside the building to the room and for transporting exhaust air from the room to the outside of the building.

The ventilation device 10 comprises a ventilation duct 1 1 , a first hood 12 and a second hood 13. The ventilation duct 1 1 is arranged as a tube or a pipe for transporting the supply air to the room and the exhaust air from the room to the exterior of the building. Hence, the ventilation duct 1 1 is arranged to extend through a building wall, which is described in more detail below. For example, the ventilation duct 1 1 is arranged with circular cross section. For example, the ventilation duct 1 1 is a straight duct arranged without bends, so that the interior of the ventilation duct 1 1 forms a straight cylinder. The ventilation duct 1 1 comprises a longitudinal axis A, a first end 14 and a second end 15. The ventilation duct 1 1 further comprises a duct wall 16 extending axially between the first and second ends 14, 15. The first end 14 forms an interior end of the ventilation device 10 and the second end forms an exterior end of the ventilation device 10. In the illustrated embodiment, the ventilation duct 1 1 comprises an end cover 17 at the second end 15 of the ventilation duct 1 1 , wherein the second end 15 is sealed and substantially non-permeable to air. The end cover 17 extends in a plane perpendicular to the longitudinal axis A. The end cover 17 is, for example, an end wall or a separate cover arranged over the second end 15 of the ventilation duct 1 1 . For example, the first end 14 is provided with an orifice forming an inlet and outlet for air, which orifice extends in a plane perpendicular to the longitudinal axis A, so that air can enter and exit the ventilation duct 1 1 at the first end 14 in a direction along the longitudinal axis A. For example, the first end 14 is arranged to be connected to a heat exchanger unit, such as a regenerative heat exchanger unit, which is described in more detail below. For example, the ventilation duct 1 1 is arranged with a diameter of 100-500 mm or 200-300 mm.

The first and second hoods 12, 13 are arranged at the exterior end of the ventilation device 10, so that the hoods 13, 14 are arranged on the outside of the building to protect exterior inlets and outlets of the ventilation duct 1 1 against wind and water. In the illustrated embodiment, the hoods 13, 14 are arranged close to or at the second end 15 of the ventilation duct 1 1 . The hoods 13, 14 are arranged to form inlets and outlets downward, so that the hoods 13, 14 protect against wind and water from other directions, such as from above, laterally and from the front and back in the axial direction.

Hence, in the illustrated embodiment the hoods 13, 14 are formed with front and back walls 18, 19 and a curved top and side wall 20 extending radially outward and downward from the duct wall 16. The front and back walls 18, 19 and the curved top and side wall 20 are continuous to protect against wind and water. For example, the hoods 13, 14 are also arranged to prevent debris and animals, such as vermin, birds, rodent, etc., from entering the venti- lation duct 1 1. The hoods 13, 14 are, for example, provided with a grating 21 to prevent debris and animals from entering the ventilation duct 1 1 . For example, the grating 21 is arranged in a lower part of the hoods 12, 13.

With reference to Fig. 3 the ventilation duct 1 1 is illustrated without the hoods 13, 14 according to one embodiment. The ventilation duct 1 1 is formed with a first aperture 22 and a second aperture 23 in the duct wall 16, the first and second apertures 22, 23 forming passages for air in the radial direction. Hence, the apertures 22, 23 are arranged coaxially. The first and second apertures 22, 23 are arranged for receiving the first and second hoods 12, 13, respectively. In the illustrated embodiment, the first and second apertures 22, 23 are arranged at the second end 15 of the ventilation duct 1 1 and extend a distance towards the first end 14. In the illustrated embodiment the ventilation duct 1 1 is provided with a fitting 24 at the first end 14 of the ventilation duct 1 1 . For example, the fitting 24 is arranged for fastening the ventilation duct 1 1 to the interior side of the building wall and, for example, also for connecting a heat exchanger unit or another type of ventilation unit to the first end 14 of the ventilation duct 1 1.

With reference to Fig. 4 one of the hoods 12, 13 is illustrated. For example, the first hood 12 and the second hood 13 are similar. For example, the hoods 12, 13 are formed in a plastic material or in sheet metal. For example, the hoods 12, 13 are arranged with fixed dimensions. For example, the hoods 12, 13 are moulded plastic articles.

The hoods 12, 13 comprise at least one projection 25 for engaging the interior side of the duct wall 16 to prevent the hoods 12, 13 from leaving through the apertures 22, 23 in the ventilation duct 1 1 . For example, the at least one projection is arranged in a top part of the hoods 12, 13. For exam- pie, the upper edge of the top and side wall 20 is provided with a first projection 25, wherein a second projection 26 is arranged at the lower part of the hoods 12, 13 or at the edge of the grating 21 . Alternatively, a groove or similar is arranged at the edge of the grating 21 or at the lower part of the hoods 12, 13 for interaction with the edge of the duct wall 16 around the apertures 22, 23. In the illustrated embodiment also the upper part of the front and back walls 18, 19 of the hoods 12, 13 are provided with projections or flanges for engaging the interior side of the duct wall 16, for example to prevent the hoods 12, 13 from exiting through the apertures 22, 23 and provide a sealing between the front and back walls 18, 19 of the hoods 12, 13 and the duct wall 16.

The hoods 12, 13 comprise a securing device 27 for securing the hoods 12, 13 to the ventilation duct 1 1 . For example, the hoods 12, 13 comprise a snap-fit securing device or another type of securing device. In the illustrated embodiment the securing device is formed by at least one flexible protrusion to be forced over the edge of the duct wall 16 at the aperture 22, 23, which protrusion returns to its original position by its inherent flexible properties to engage the exterior side of the duct wall 1 1 and prevent the hoods 12, 13 from being pushed into the apertures 22, 23.

With reference to Figs. 5 to 17 installation of the ventilation device 10 is illustrated according to one embodiment. With reference to Fig. 5 a through hole 28 is provided in a building wall 29. For example, the hole 28 is provided from the interior side of the wall 29. The hole 28 extends from the interior side of the wall 29 to the exterior side and is arranged for receiving the ventilation duct 1 1 . Hence, the diameter of the hole 28 corresponds to the outer diameter of the ventilation duct 1 1 . The ventilation duct 1 1 , without the hoods 12, 13, is inserted into the hole 28 from within the building, which is illustrated by means of the arrow B in Fig. 5. Hence, the ventilation duct 1 1 is installed from within the room and from the interior side of the wall 29. The second end 15 of the ventilation duct 1 1 is inserted into the hole 28 and pushed through the hole 28 until the second end 15 projects from the building wall 29 on the exterior side thereof, so that the second end 15 with the apertures 22, 23 are arranged on the outside of the building wall 29. The exterior side of the building wall 29 with the ventilation duct 1 1 inserted into the hole 28 is illustrated in Fig. 6. Hence, the apertures 22, 23 are arranged on the outside. For example, the ventilation duct 1 1 is installed in the hole 28, so that the apertures 22, 23 are directed substantially downward on the outside of the building.

Then, after insertion of the ventilation duct 1 1 in the hole 28 the first hood 12 is inserted into the ventilation duct 1 1 , which is illustrated in Fig. 7. As illustrated in Fig. 7 the first hood 12 is arranged with dimensions to fit into the ventilation duct 1 1 , so that the first hood 12 can be inserted into the ventilation duct 1 1 through the orifice at the first end 14 and pushed along the longitudinal axis A from the first end 14 to the first aperture 22. The first hood 12 is inserted axially into the ventilation duct 1 1 . Hence, the first hood 12 is inserted into the ventilation duct 1 1 from the inside of the building and is pushed from the inside of the building into position at the first aperture 22. For example, the first hood 12 is arranged with a fixed width and a fixed height to fit through the ventilation duct. For example, the width and height are in a plane perpendicular to the longitudinal axis A. The first hood 12 is positioned at the first aperture 22 from the inside of the ventilation duct 1 1 and is then inserted into the first aperture 22, which is illustrated in Fig. 8. For example, the second projection 26 is brought to engage the interior side of the duct wall 16, wherein the first hood 12 is rotated through the first aperture 22, which is illustrated by means of the arrow C in Fig. 9 until the securing device 27 is pushed over the duct wall edge at the first aperture 22 and the first projection 25 engages the interior side of the duct wall 16, which is illustrated in Fig. 10. Hence, the first hood 12 is positioned at the first aperture 22 and is pushed out through the first aperture 22, for example, by rotation, until the projections 25, 26 engages the interior side of the duct wall 16. In the illustrated embodiment the first hood 12 is secured to the duct wall 16 in its final position extending from the first aperture 22 by means of the securing device 27. In its final position, which is illustrated in Figs. 10 and 1 1 the first hood 12 forms a passage for supply air and exhaust air in the radial direction into and out from the ventilation duct 1 1 .

Alternatively, the first hood 12 is positioned and secured inside the ventilation duct 1 1 at the first aperture 22 in advance and before insertion of the ventilation duct 1 1 into the hole 28, wherein the first hood 12 is released and rotated into position in the first aperture 22 after insertion of the ventila- tion duct 1 1 into the hole 28.

After mounting of the first hood 12 at the first aperture 22 the second hood 13 is inserted into the ventilation duct 1 1 from the inside of the building, which is illustrated in Fig. 12. Also the second hood 13 is arranged to fit into the ventilation duct 1 1 , similar to the first hood 12. For example, the first and second hoods 12, 13 are identical or mirror-inverted in relation to each other. Alternatively, the second hood 13 is somewhat smaller than the first hood 12. The second hood 13 is installed in a similar way as the first hood 12. Hence, the second hood 13 is pushed into the ventilation duct 1 1 from within the building and is positioned over the second aperture 23. Then the second pro- jection 26 is brought into contact with the interior of the duct wall 16, wherein the second hood 13 is rotated outwards, which is illustrated by the arrow D in Fig. 13. Hence, the second hood 13 is pushed into the second aperture, as illustrated in Fig. 14 until the first projection 25 engages the interior of the duct wall 1 1 and the securing device 27 secures the second hood 13 in its final position, which is illustrated in Figs. 15 and 16. For example, the first and second hoods 12, 13 are arranged for providing air passages substantially downward. According to one embodiment the ventilation device 10 comprises a dividing wall 30 for dividing the ventilation duct 1 1 into first and second ducts 1 1 a, 1 1 b. Hence, the ventilation device 10 is arranged for directing two airflows simultaneously in opposite directions, i.e. the exhaust airflow and the supply airflow simultaneously. Hence, the ventilation device 10 is arranged for directing both the supply airflow and the exhaust airflow to and from the building simultaneously. The first duct 1 1 a is connected to the first aperture 22 and the second duct 1 1 b is connected to the second aperture 23. The dividing wall 30 is, for example, arranged centrally inside the ventilation duct 1 1 . For example, the dividing wall 30 extends in a vertical plane. The cross section of the ventilation duct 1 1 is, for example, circular, wherein the cross section of the first duct 1 1 a is semi-circular and the cross section of the second duct 1 1 b is semi-circular. The dividing wall 30 is inserted into the ventilation duct 1 1 after installation of the first and second hoods 12, 13. In the illustrated embodiment the dividing wall 30 is provided with flexible top and bot- torn borders 31 , 32, such as rubber strips or similar, for securing the dividing wall 30 inside the ventilation duct 1 1 by means of friction. Hence, the dividing wall 30 with the flexible top and bottom borders 31 , 32 is pushed into the ventilation duct 1 1 in the axial direction through the orifice at the first end for dividing the ventilation duct 1 1 into the first and second ducts 1 a, 1 1 b for simul- taneous transport of air in opposite directions. The hoods 12, 13 facilitate separation of supply air and exhaust air while protecting the ventilation duct 1 1 from wind, water, debris and animals.

With reference to Figs. 18 and 19 a regenerative heat exchanger unit 33 for connection to the first end 14 of the ventilation duct 1 1 is illustrated according to one embodiment. The unit 33 comprises an internal wall 34 dividing the unit 33 into a first compartment 35 and a second compartment 36. In the illustrated embodiment, the first and second compartments 35, 36 are similarly designed and are inverted in relation to each other. The first and second compartments 35, 36, respectively, comprise a first opening 37a, 37b and a second opening 38a, 38b. The first opening 37a, 37b is connected to the first and second ducts 1 1 a, 1 1 b of the ventilation duct 1 1 . The second openings 38a, 38b are arranged for directing exhaust airflow and supply air- flow between the room and the compartments 35, 36 of the unit 33.

Each of the compartments 35, 36 comprise a heat exchanger 39 and a fan 40 for providing the exhaust airflow and the supply airflow alternatingly through the first and second compartments 35, 36. Hence, the first compartment 35 comprises a first heat exchanger 39a and a first fan 40a, wherein the second compartment 36 comprises a second heat exchanger 39b and a second fan 40b. When the exhaust airflow is directed through the first compartment 35, the supply airflow is directed through the second compartment 36 and vice versa, which is illustrated in Figs. 20a and 20b. The striped parts of the arrows illustrate hot air and the plain parts of the arrows illustrate cold air. The heat exchanger 39a, 39b is, for example, a fixed matrix generative heat exchanger having through channels for the airflow.

With reference to Fig. 21 another embodiment of the hood 12 is illustrated. According to the embodiment of Fig. 21 the securing device 27 for securing the hoods 12, 13 to the ventilation duct 1 1 is arranged in the front wall 18 and back wall 19 of the hood 12. The securing device 27 is formed as a flexible part of the front and back walls 18, 19, respectively, having a flange 41 , which is forced over the edge of the duct wall 16 at the aperture 22, 23, wherein the flexible securing device 27 returns to its original position by its inherent flexible properties so that the flange 41 engages the exterior side of the duct wall 1 1 and prevent the hood 12 from being pushed into the apertures 22, 23. The securing device 27 is formed by arranging a notch 42 from the edge of the front and back walls 18, 19 and a distance into said walls 18, 19, wherein the flange 41 is arranged to pass the edge of the duct wall 16 and engage the exterior side thereof while the projection 25 engages the in- terior side of the duct wall 16 to provide a snap-fit lock. For example, the outer side of the flange of the securing device 27 is inclined in relation to the duct wall 16 to facilitate the securing device 27 to be pushed over the edge of the duct wall 16.

Claims

1 . A ventilation device (10) comprising a ventilation duct (1 1 ) having a longitudinal axis (A), a first end (14), a second end (15) and a duct wall (16), said duct wall (16) extending coaxially between the first and second ends (14, 15), c h a r a c t e ri s e d in that

the duct wall (16) is provided with a first aperture (22) and a second aperture (23), said apertures (22, 23) forming passages for air in a radial direction, the first aperture (22) is provided with a first hood (12), and the second aper- ture (23) is provided with a second hood (13),

the hoods (12, 13) extend through the apertures (22, 23), and

each of the hoods (12, 13) are provided with a projection (25) engaging an interior side of the duct wall (16).

2. A ventilation device according to claim 1 , wherein each of the hoods (12, 13) are dimensioned to fit through the ventilation duct (1 1 ) to enable positioning of the hoods (12, 13) at the apertures (22, 23) from said first end (14).

3. A ventilation device according to claim 2, wherein a fixed width and a fixed height of each of the hoods (12, 13) are dimensioned to fit through the ventilation duct (1 1 ).

4. A ventilation device according to any of the preceding claims, wherein the hoods (12, 13) are provided with a securing device (27) for securing the hoods (12, 13) to the ventilation duct (1 1 ) at the first and second apertures (22, 23), respectively.

5. A ventilation device according to any of the preceding claims, wherein the first and second hoods (12, 13) form downward directed passages for air.

6. A ventilation device according to any of the preceding claims, wherein the second end (15) is provided with a substantially air impermeable end cover (17).

7. A ventilation device according to any of the preceding claims, wherein the ventilation duct (1 1 ) is provided with an internal dividing wall (30) extending axially and dividing the ventilation duct (1 1 ) in first and second airflow ducts (1 1 a, 1 1 b) for supply air and exhaust air, and wherein the first aperture (22) is connected to the first airflow duct (1 1 a) and the second aperture (23) is connected to the second airflow duct (1 1 b).

8. A method for installation of a ventilation device (10), comprising the steps of

a) arranging a through hole (28) in a building wall (29),

b) inserting a ventilation duct (1 1 ) into the hole (28) from an interior side of the building wall (29), the ventilation duct (1 1 ) having a longitudinal axis (A), a first end (14), a second end (15) and a duct wall (16) extending coaxially between the first and second ends(14, 15), wherein the second end (15) is arranged to project from an exterior side of the building wall (29),

c) bringing a first hood (12) to extend through a first aperture (22) of the ventilation duct (1 1 ), and

d) bringing a second hood (13) to extend through a second aperture (23) of the ventilation duct (1 1 ).

9. A method according to claim 8, comprising the steps of

- inserting the first hood (12) into the ventilation duct (1 1 ) from the first end (14) thereof and from the interior side of the building wall (29),

- fitting the first hood (12) into the first aperture (22) of the ventilation duct (1 1 ) and bringing a projection (25) of the first hood (12) into engagement with an interior side of the duct wall (16),

- inserting the second hood (13) into the ventilation duct (1 1 ) from the first end (14) thereof and from the interior side of the building wall (29), and

- fitting the second hood (13) into the second aperture (23) of the ventilation duct (1 1 ) and bringing a projection (25) of the second hood (13) into engagement with the interior side of the duct wall (16).

10. A method according to claim 8 or 9, comprising the step of - after step d, inserting an internal dividing wall (30) axially into the ventilation duct (1 1 ) and thereby dividing the ventilation duct (1 1 ) in a first airflow duct (1 1 a) connected to the first aperture (22) and a second airflow duct (1 1 b) connected to the second aperture(23).