GB2231398A

GB2231398A - Roof ventilation system

Info

Publication number: GB2231398A
Application number: GB9003189A
Authority: GB
Inventors: Brian Cecil Tubb
Original assignee: SOFFIT VENTILATORS Ltd
Current assignee: SOFFIT VENTILATORS Ltd
Priority date: 1989-04-13
Filing date: 1990-02-13
Publication date: 1990-11-14
Anticipated expiration: 2010-02-13
Also published as: GB8908343D0; GB2231398B; GB9003189D0

Abstract

A roof ventilator strip for fixing to a fascia board (15), consists of a flat strip base (1) having a downwardly projecting locating rib (2) at one edge and a hollow section extending above the base adapted to support an end tile. The hollow section has an upper surface with a downwardly sloping portion (4) which extends beyond the edge of the base on the side carrying the locating rib (2), a perforated outer section (6) sloping inwardly and a substantially vertical perforated inner section (5). The outer section may carry an inwardly and upwardly directed baffle (16) to prevent the passage of wind driven rain. Preferably the perforated outer section is a strip slidably mounted between the outer edge of the downwardly sloping surface and the outer edge of the flat strip base, the strip being perforated with vertical slots. A ventilation system for the attic space of a building comprises incorporating the ventilator strip between the top of the fascia board and the underside of the roof. Preferably the roof liner rests on the downwardly sloping portion of the upper surface. <IMAGE>

Description

ROOF VENTILATION SYSTEM.

This invention relates to a roof ventilation system and to a ventilator strip for use as a building component in such a system.

In order to conserve energy national legislation requires a high degree of thermal insulation between the ceilings of the uppermost floors of a building and the roof void above them; U values not exceeding 0.35 W/m 2oC are required.

As a consequence the roof void or attic space formed under pitched roofs follows the wide variations in external temperature which occur in response to the prevailing climatic conditions. It is found that ventilation of the attic space in such buildings is essential to prevent high humidity conditions arising which lead to condensation. In the United Kingdom the current Building Regulations require cross ventilation by means of permanent vents situated on two opposite sides of the roof. The vents must have an area equivalent to that of a continuous gap along the two sides of width not less than lOmm where the roof pitch exceeds 150.

Various attempts have been made to provide satisfactory ventilation systems. In GB-B-2 115 920 it is proposed that a perforated strip be located between the fascia board and the wall edge, i.e. in the soffit. Such a ventilation system is supplied with warm air rising along the side of the wall of the building. This air carries up moisture, due to evaporation from porous walls such as brick walls, and also insects.

In an alternative approach proposed in GB-B-2 127 060 and GB-A-2 206 405 air is allowed to enter the roof space under the tiles from above the gutter. The air will be cooler than the air rising from along the wall. However the system proposed in the first document is expensive, difficult to install, and liable to obstruction by the roof liner. The system proposed in the second document is more efficient but the slots cause fabrication problems with some polymers and the ventilator strips lack rigidity until fitted which leads to handling problems.

The object of the present invention is to provide a roof space ventilation system which is simple to install. A further object is to provide an ample supply of cool air to the roof space of a building to prevent condensation.

Another object is to provide a ventilator strip which is not subject to obstruction by the roof liner.

According to the present invention there is provided a ventilator strip for fixing to a fascia board consisting of a flat strip base having a downwardly projecting locating rib at one edge and a hollow section extending above the base adapted to support an end tile and carrying apertures to allow the passage of air across the base, characterised in that the hollow section has an upper, surface with a downwardly sloping portion which extends beyond the edge of the base on the side carrying the locating rib, and which is supported by a perforated outer section sloping inwardly on the side carrying carrying the locating rib and a substantially vertical perforated inner section on the opposite side.

There is also provided a method of ventilating the attic space of a building by incorporating a ventilator strip according to the invention between the top of the fascia board and the underside of the roof.

The ventilator strip according to the invention is placed on the upper surface of the fascia board with its locating rib against one edge of the board. The base strip is conveniently attached to the board by means of nails or screws which pierce the flat strip base at the edge remote from the locating rib. Alternatively clips, adhesives or any other method of attachment may be used.

The base of the ventilator strip and its upper surfaces are continuous however the inwardly sloping outer section and the substantially vertical inner section both carry perforations which allow sufficient air to pass through the space between them to meet the requirements of the Building Regulations. The perforations may take the form of slots, circles, oval or rectangular apertures which have been punched, drilled, sawn or otherwise formed in the inner and outer sections. In a preferred form the aggregate cross sectional area of the two sets of perforations is substantially equal.

In a preferred embodiment the hollow interior of the ventilator strip carries a baffle plate to reduce the ingress of wind driven rain and snow. The baffle plate is attached to the lower edge of the perforated outer section so that any intercepted moisture can flow under the action of gravity out through the perforations. The baffle plate projects inwardly from the lower edge of the outer section and may take the form of a flat plate at an angle, preferably from 300 to 600 from the vertical. Alternatively the baffle plate may have an upwardly curved profile. In either case it is necessary to leave a space between the upper edge of the baffle plate and the underside of the downwardly sloping portion of the upper surface to ensure that the flow of air through the ventilator strip is not obstructed.

The ventilator strip may be formed from a synthetic polymer material or metal. The material used must be resistant to corrosion and capable of resisting temperatures at least in 0 0 the range 70 to -20 Celcius without melting or cracking. Preferred materials are thermo-plastic synthetic polymers such as rigid polyvinyl chloride, high density polyethylene, polypropylene, ABS and polycarbonate.

The materials may contain pigments, fillers, anti-oxidants, stabilizers against the effects of ultra-violet radiation, and other customary addenda. The choice will depend on cost and the method of fabrication chosen.

For convenience of fixing the ventilator strip is preferably made in strips about 2 metres long. The strips should be formed from a material which is easily cut with hand tools so that strips can be assembled to form any required length.

When the ventilator strip is fabricated from a synthetic polymer it may be extruded continuously in tubular form and subsequently perforated or cut to allow ventilation. In a preferred method of manufacture the ventilator strip is extruded as a section having a profile comprising the base, the locating rib the upper surface and vertical inner section.

The underside of the downwardly sloping portion of the upper surface and the upper surface of the base over the locating rib carry retaining grooves or locating ribs.

The outwardly facing section is formed separately as a perforated flat strip and is slotted into the retaining grooves before installation. The strip may be retained after assembly by application of a suitable adhesive or by local heating to form a weld. Alternatively the perforated flat strip may be placed against the locating ribs and retained by the use of an adhesive or welding.

When the outwardly facing section is formed separately the baffle plate may be attached to it at lower edge of the perforations. The unperforated portion below the perforations slots into the retaining grooves and the baffle plate is contained in the hollow interior of the strip. Preferably the baffle plate is formed at the same time as the outwardly facing section as a single extrusion.

The base strip is preferably punched or drilled at regular intervals along one edge to allow fixing nails or screws to be driven through the edge without causing it to crack or split. In the preferred embodiment the fixing holes are located at 75 mm intervals. Further fixing holes may be provided in the central portion of the base strip or at the apex of the strip.

In areas where infestation by insects is likely to occur it is possible to include loose organic or inorganic fibres, such as polyester fibres or glass wool, within the ventilator section of the ventilator strip. The loose fibres act as a filter and prevent the ingress of insects without impeding the free flow of air. The size and shape of the slots or apertures must be small enough to exclude birds, bats, rodents and large beetles but large enough to ensure that the free flow of air meets the requirements of the Building Regulations.

While it is most convenient to form a roof structure using the ventilator strip according to the invention in the construction of new houses, it may also be incorporated into the structure of existing houses with closed eaves.

In such cases the fascia boards must be replaced or have their width reduced to allow for the space taken by the ventilator. The ventilator strip may be used satisfactorily both with fascia boards separated from the house wall and those with fascia boards attached to the wall.

In order that the invention may be clearly understood it will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of a ventilator strip according to the invention, Figure 2 is a side view of the outwardly facing side of the ventilator strip shown in Figure 1, Figure 3 is a side view of the inwardly facing side of the ventilator strip shown in Figure 1, Figure 4 is a cross sectional view of the ventilator strip shown in Figure 2 through the line X-X, Figure 5 is a cross sectional view of an alternative embodiment of the ventilator strip including a baffle plate, and Figure 6 is a schematic cross-sectional view of a roof arrangement incorporating the ventilator strip shown in Figure 1.

The ventilator strip according to the invention, see Figures 1 to 4, consists of a flat strip base 1, having a downwardly projecting locating rib 2. at one edge. A hollow section is formed by an upper surface 3 having a downwardly sloping portion 4. a vertical inner section 5, the inside of the base 1 and an inwardly sloping outer section 6. The upper surface 3 has a tile supporting apex 7 close to the top of the vertical section 5. Downward forces on the apex 7 are directed to the base 1 through the inner and outer sections 5 and 6.

To provide passage of air through the hollow section the sections 5 and 6 are both perforated. In Figure 1 the perforations in the vertical section 5 are shown as circular apertures 8 while those in the section 6 are shown as vertical slots 9. The slots 9 and the spaces between them are approximately equal which allows the passage of free air but prevents the ingress of birds and rodents.

Preferably the aggregate cross sectional area of the apertures 8 and the slots 9 is equal. The downwardly sloping portion 4 of the upper surface 3 extends beyond the edge of the base 1 on the side carrying the locating rib 2.

In the illustrated embodiment the the outer section 6 is shown as a separate component of the ventilator strip which is retained in position by a pair of grooves 11 and 12.

The groove 11 is formed on the upper surface of the base 1 above the rib 2. The groove 12 is formed on the lower surface of the downwardly sloping portion 4 of the upper suface 3. To assist fixing the inner edge of the base 1 carries a series of holes. These may be used, see Figure 4. to attach the strip to a fascia board 15 by means of a nail 16.

The downwardly sloping portion 4 of the upper surface 3 supports the loose end of the roofing felt or other lining material laid under the tiles of a roof. This prevents the lining material impeding the free flow of air through the slots 9. The sloping portion 4 preferably slopes at an angle of 460 to the horizontal so as to accomodate any roof pitch greater than 150 In an alternative embodiment, see Figure 5, the interior of the ventilator strip contains a baffle plate 16. The baffle plate 16 is attached to the lower edge of the perforated outer section 6 at the base of the slots 9.

While the baffle plate 16 is shown with a curved profile it may take the form of a flat plate projecting inwardly.

The majority of any rain driven through the slots 9 by wind will be intercepted by the baffle plate and flow downwards and outwards through the slots 9.

A ventilator strip 20 is shown incorporated in the roof portion of a building in Figure 6. The building has an outer brick wall 21 and an inner brick wall 22, with a cavity 23, between them. The walls 22 and 23 carry the roof load through a series of rafters one of which 24, is shown. The rafter 24 has a series of battens 25 attached to it which retain rows of tiles 26. Under the battens 25 lies a continuous layer of roofing felt 27 whose end emerges under an end tile 28. A fascia board 29 supports a gutter 31 by means of a series of brackets 32. The space between the bottom of the fascia board 29 and ths outer brick wall 21 is closed by a soffit 33. Enclosed by the board 29, the soffit 33 and the felt 27 is an air space 34.

The ventilator strip is fixed to the fascia board 29 in the manner previously described. The felt 27 extends over the ventilator strip 20 lying on the downwardly sloping portion of the upper surface 3 of the ventilator strip. The apex 7 of the ventilator strip supports the edge of the end tile 28.

Air can enter the space 34 by flowing through the ventilator 20. The majority of the air entering the ventilator will have passed over the gutter 31 which will have cooled it.

It is found that when an attic space is ventilated in the manner described according to the invention the effect of wind is reduced as compared with ventilation produced by apertures in the soffits.

It is usually necessary to insulate the floor of the attic space of a building to obtain the necessary U factor to meet the requirements of the current building regulations.

Many forms of insulation are used but glass fibre mats up to 80mm thick are most frequently employed. When laying such mats it is not unusual for the ends to extend over the ends of the inner and outer walls so that the space between the top of the wall and the bottom of the roofing felt liner is partially or completely blocked. For this reason the ventilator strips according to the invention are preferably used in conjunction with ducting trays placed between the rafters to allow air to circulate freely from the ventilator strip into the attic space above the insulation. Such ducting trays are well known and described in GB 2 127 060 and US 4 096 790.

While the roof ventilation system according to the invention has been described with reference to roofs having flat tiles over a liner it may also be used with roofs comprising pantiles or other tiles having a corrugated surface. In such roofs the roofing felt liner will hang over the tile support apex of the ventilator section of the ventilator strip and rest on the upper portion of the convex rib. The cavities formed between the underside of the tiles and the liner should be filled or obstructed to prevent the ingress of bats and birds.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

1. A ventilator strip for fixing to a fascia board consisting of a flat strip base having a downwardly projecting locating rib at one edge and a hollow section extending above the base adapted to support an end tile and carrying apertures to allow the passage of air across the base, characterised in that the hollow section has an upper, surface with a downwardly sloping portion which extends beyond the edge of the base on the side carrying the locating rib, and which is supported by a perforated outer section sloping inwardly on the side carrying carrying the locating rib and a substantially vertical perforated inner section on the opposite side.

2. A ventilator strip as claimed in claim 1 in which a baffle plate projects inwardly and upwardly from the lower edge of the perforations in the outer section into the hollow section.

3. A ventilator strip as claimed in claim 2 in which the baffle plate has an upwardly curved profile.

4. A ventilator strip as claimed in claim 2 in which the baffle plate takes the form of a flat plate set at an angle from 300 to 600 from the vertical.

5. A ventilator strip as claimed in any of the preceding claims in which the perforated outer section is attached between the outer edge of the downwardly sloping surface and the outer edge of the flat strip base.

6. A ventilator strip as claimed in claim 5 in which the perforated outer section is slidably mounted between the outer edge of the downwardly sloping surface and the outer edge of the flat strip base.

7. A ventilator strip as claimed in claim 6 in which the perforated outer section carries a baffle plate attached at the lower edge of the perforations.

8. A ventilator strip as claimed in claims 5 or 6 in which the perforated outer section is located between the outer edge of the downwardly sloping surface and the outer edge of the flat strip base by means of ribs and retained by welding or an adhesive.

9. A ventilator strip as claimed in any of the preceding claims in which the perforated outer section is perforated with vertical slots.

10. A ventilator strip as claimed in any of the preceeding claims in which the perforated area of the inner section is substantially the same as the perforated area of the outer section.

11. A ventilator strip as claimed in any of the preceeding claims in which the upper sloping surface forms an angle of 0 46 with the horizontal.

12. A ventilator strip as claimed in any of the preceding claims in which the edge of the flat base strip remote from the locating rib carries a series of fixing holes.

13. A ventilator strip as claimed in claim 1 and as herein described.

14. A method of ventilating the attic space of a building comprising incorporating a ventilator strip. as claimed in any of the preceding claims, between the top of the fascia board and the underside of the roof.

15. A method of ventilating the attic space of a building as claimed in claim 10 wherein the roof liner rests on the downwardly sloping portion of the upper surface.

16. A method of ventilating the attic space of a building as claimed in claims 10 or 11 wherein an air ducting device is located on the underside of the roof to ensure that air passing through the ventilator strip can enter the attic space freely.

17. Methods of ventilating the attic space of a building as claimed in claim 14 and as herein described.