This invention relates to a ventilation unit that is suitable particularly, although not exclusively, for mounting at the ridge of a roof.

In tropical regions and the warmer seasons of other regions, hot air created by solar energy and heat generated within a building rises and becomes trapped at the top of the building. There is thus a need to exhaust such hot air into the atmosphere to avoid an uncomfortable temperature build-up inside. Desirably, a ventilation unit that performs such a task operates without requiring electric supply and has no moving parts, This simplifies installation and minimizes the need for maintenance; as well as making the unit en vironmentally friendly.

US-A-4,545, 292 discloses a ridge ventilation apparatus for use between spaced apart ridge tiles that are positioned over the rid ge of a roof which has an upwardly directed air duct at its ridge for exhausting air from therebelow. The apparatus includes a top frame that consists of two sections joined above the ridge by a hinge. The two sections include el ongate outer exhaust ports disposed on either side of the peak of the frame. Tfie apparatus further includes a pair of lower frames, arranged in a symmetrical -fashion, that form respective chambers with the two top frame sections. The lower frames include inner exhaust ports that allow air from the air duct to pass into the chambers and out through the top frame exhaust ports.

In operation, air flow substantially tangentially over the sides of the top frame sections creates areas of negative pressure adjacent the outer exhaust ports. As a result, air is drawn out into the atmosphere. It can be seen that while this prior art apparatus does not require electric power, its performance is dependent on the presence of wind for creation of the .negative pressure areas. However, wind is not guaranteed and depends on the location of the building and the prevailing weather conditions. Indeed, the hottest and most stifling weather is often associated with a lack of. natural air movement.

Accordingly, there remains an unfulfilled need for a roof ventilation unit that requires no electric power source, has no moving parts and needs minimal maintenance, yet can operate with or without the presence of wind. The present invention aims to meet this need.

In a principal aspect, the invention provides a ventilation unit adapted for mounting at the ridge of a roof, the unit comprising a shell of substantially semicircular section that is elongate in the ridge direction and has outer edges angled so as to be seated and secured on respective opposite slopes of the roof, and at least one air outlet aperture that extends in the ridge direction over a portion of the shell .length .and is located at . the peak of the shell, wherein the whole of the shell, apart from the aperture, comprises thermal insulation material whereby, in use, a region of lower temperature and thereby lower pressure is formed within the shell as compared with the ambient temperature and pressure, so that hot air from within the building is drawn up to said region and exhausted to the outside through said at least one air outlet aperture, the internal configuration of the shell providing a path of least resistance to the air to be exhausted.

The above arrangement creates the necessary low pressure region by means of a thermally insulated shell and so is not dependent on the presence of any wind for effective operation. By providing the shell with a substantially semi-circular section and locating the or each exhaust aperture at the top of it, a path of least resistance is advantageously offered to the hot air to be exhausted. Moreover, the location of the or each exhaust aperture at the peak of the shell minimizes any adverse effect on air exhaustion by atmospheric wind.

In a preferred embodiment, the shell comprises an outer layer of weather- resistant material, a core layer of said thermal insulation material, and an inner layer that supports the core layer.

Preferably, the ventilation unit further comprises a rainwater drain plate that is mounted within the shell and beneath said aperture. The drain plate is suitably oversized relative to said aperture and has an arcuate section with. a peak below said aperture. These features provide for effective collection and drainage of rain.

In a preferred embodiment, the drain plate comprises thermal insulation material. The insulation material is conveniently the same as used for the main shell. Suitable materials includes silicone RTV foam, expanded polyurethane filler foam, polycarbonate, expanded polystyrene (EPS), rockwool, fiberglass wool, and the like.

Similarly to the main shell, the drain plate may comprise an outer layer of weather-resistant material, a core layer of said thermal insulation material, and an inner layer that supports the core layer.

A preferred embodiment further includes a mesh associated with said drain plate, for breaking up heavy rain drops and reducing splashing.

A preferred embodiment further includes a guard that prevents bird and other matter from entering the unit through said aperture. Application of the invention is not confined to ridged roofs. The ventilation unit can also be installed on flat roofs. For this purpose, there is provided a mounting frame adapted for mounting on a flat roof and having inclined ledges to which said outer edges of the ventilation unit shell are secured.

For convenience of manufacture and flexibility of installation, a ventilation unit in accordance with the invention preferably comprises a plurality of modules arranged end-to-end, the modules including at least one main module having said at least one air outlet aperture and at least one extension module without said aperture. The ends of the outermost modules are sealed by end wall caps having the same profile as the shell section. The number of main modules is chosen based on the ventilation requirements of the particular building on which the unit is to be installed.

Thus, in another aspect, the invention provides a main module for use in the aforesaid modular ventilation unit.

In a further aspect, the invention provides an extension module for use in the aforesaid modular ventilation unit.

In summary, the invention provides a ventilation unit that is cost effective to manufacture and' convenient to install, operates effectively without requiring the presence of wind, consumes no power and has minimal maintenance need. The unit is also aesthetically pleasing as its outer appearance blends in with the rest of the roof structure and the exhaust apertures, being located at the top of the shell, are out of sight from ground level. The invention is described, although not limited, by the following description of preferred embodiments, given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a first exemplary configuration of a ventilation unit; Fig. 2 is a perspective view of a second exemplary configuration of a ventilation unit; Fig. 3 is a perspective view of a third exemplary configuration of a ventilation unit; Fig. 4 is an exploded view of the ventilation unit of Fig. 1; Fig. 5 is a see-through view of the assembled ventilation unit of Fig. 1 ; Fig. 6 is a top view of the ventilation unit of Fig. 1; Fig. 7 is a sectional view on line AA of Fig. 6; - Fig. 8 is a sectional view on line BB of Fig. 6; Fig. 9 is a top view of the ventilation unit of Fig. 2; Fig. 10 is a sectional view on line CC of Fig. 9; Fig. 11 is a sectional view on line DD of Fig. 9; and Fig. 12 is a perspective view of an adaptor frame that allows the ventilation unit o be mounted on a flat roof. Referring to the drawings, Figs. 1 to 3 show three different exemplary configurations of a modular ventilation unit mounted at the ridge of a roof 10. Each unit has at least one main module 12 and at least one extension module 14. The modules 12, 14 are arranged end-to-end in the ridge direction. The number of main modules 12 depends on the ventilation requirements. It is not essential that the main and extension modules are arranged alternately, although this is a preferred arrangement A modular construction is preferred as it allows flexibility of using the same types of module for different applications, as well as the easier prefabrication and transport of smaller modules. However, in certain applications, the ventilation unit may be realized integrally, without departing from the scope of this. invention.

Figs. 4 and 5 show the construction of the ventilation unit of Fig. 1 in greater detail. The main module 12 comprises a shell of substantially semicircular section that is generally elongate in the ridge direction. The outer, depending edges of the shell are angled downwardly so as to allow the unit to be seated on and secured to respective opposite slopes of the roof. The unit may be secured by any of a variety of fastening means, including by using steel cable, wire or flat metal bars, roofing nails or screws, for attachment to the wooden structure of a house or other dwelling. For larger, industrial or commercial buildings, the unit may be fastened by bolts and nuts or by welding, dependent on the building design. The angled footings prevent water seeping in when rain is coupled with high wind, and also provide a stable seating on the top of the roof. The shell includes an air outlet aperture 16 that extends in the ridge direction over a portion of the shell length. The aperture 16 is located at the peak of the shell.

The aperture 16 is protected by a guard, such as a grill 22 that prevents bird and other matter from entering the unit through the aperture 16, without interfering with the passage of air exiting the aperture. A rainwater drain .plate 18 is mounted within the shell and beneath the aperture 16. The drain plate 18 is oversized relative to the aperture and acts as a cover for the roof opening. In this embodiment, the drain plate 18 has an upwardly arcuate section with the peak below the aperture 16. A mesh 20, such as a wire or plastic netting is preferably mounted over the drain plate 18. This helps to break up large rain drops and reduce splashing. The mesh 20 is optional, but desirable for residential buildings. The drain plate 18 is mounted within the shell by means of corner feet that are fastened, for example by bolts and nuts, to correspondly-located lugs on the inside of the shell. The drain plate 18 may be extended when the mesh 20 is not used.

The extension module 14 has the same basic structure as the main module 12, except that the aperture 16 and drain plate 18 are omitted. As an alternative, the same structural component as for the shell of the main module could be used with the aperture closed off by a plate insert.

The join between adjacent modules is sealed by the means of a connecting bracket or clip 24, which acts as linkage and fastening device.

The exposed ends of the two outermost modules are closed off by end wall caps 26.

Figs. 7 and 8 show sectional views of the main module 12 and extension module 14, on lines A-A and B-B of Fig. 6, respectively.

As seen in Fig. 7, the shell and drain plate each comprise a sandwich structure. An outer layer 28, 34 is made of weather-resistant material that can withstand corrosion from solar energy and rainwater attack. The outer layer 28, 34 suitably consists of aluminium, stainless steel, polycarbonate, or any metal, ceramic or other roofing sheet material. A core layer 30, 36 consists of thermal insulation material of the kind mentioned previously. The core layer 30 extends over the whole of .the shell apart from the aperture. The core layer 36 extends over substantially the whole of the drain plate 18. Finally, an inner layer 32, 38 serves to support the respective core layer and prevent attack by rats and the like. The inner layer 32, 38 suitably consists of PVC, polycarbonate, aluminium, stainless steel or the like.

The shell of the extension module 14, as per Fig. 8, has the same sandwich structure (28, 30, 32) as that of the main module 12.

The materials for all three layers are chosen based on usual design factors such as the manufacturing process, cost and the building design.

Figs. 10 and 11 show sectional views of the ventilation unit of Fig. 2 on lines C-C and D-D of Fig. 9, respectively. The arrows in Figs. 10 and 11 illustrate the air flow. As can be seen, the main module acts as an exit for high pressure, hot air into the atmosphere through the aperture 16. The thermal insulation material 30, 36 in the main and extension modules is instrumental in creating a low temperature, low pressure zone to which hot air from within the building is drawn. The exhaust aperture being located at the top of the unit takes advantage of the principle that hot air rises. As long as there is a temperature difference between the inside and outside of the building, air exchange will take place due to pressure equalization. The internal semicircular shape of the unit forms a path of minimum resistance for the air to be exhausted, so that it becomes possible to handle large volumes of exhaust air when the temperature rises. On the outside, the same shape of the unit offers low resistance to wind and so allows the unit to withstand high wind velocity. Also, minimum obstruction to the opening avoids the formation of an invisible air curtain over the opening.

Fig. 12 shows a mounting frame 40 that allows the ventilation unit of the invention to be installed even on a flat-roofed building. The frame 40 has a flat base that can be secured to the roof and inclined ledges 42 to which the outer edges of the shell are secured.

The ventilation unit of the invention can be used on both old and new building structures. Any building having a ceiling would require ventilation openings to be provided in the ceiling. The ventilation unit does not require any new or special machinery for its manufacture. Smaller units for residential use can be factory- made as a completely built-up unit. Larger units for industrial and commercial buildings may be prefabricated in a factory or built on site according to the building design.

The invention may be embodied in ways other than those specifically described herein without departing from the scope thereof.