GB2206405A - Roof ventilation system - Google Patents

Abstract

A roof ventilation system and a ventilator strip for use as a building component in such a system is described. The ventilator strip, for fixing to the top of a fascia board, consists of a flat strip base having a downwardly projecting locating rib at one edge and a hollow ventilator section extending above the base adapted to support an end tile and carrying apertures to allow the passage of air across the base, the ventilator section having one convex side extending beyond the edge of the base on the side carrying the locating rib. The ventilator strip preferably has a convex deflector rib consisting of an upper sloping portion adapted to support a roof liner and a lower ventilator portion. The ribs can be separated by slots which extend upwardly from the base, the width of the slots being substantially equal to the width of the ribs. The space within the hollow strip may be filled with organic or inorganic fibres to act as a filter. <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 20C 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 10mum 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.

An alternative approach is proposed in GB-B-2 127 060 where 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 proposed system is expensive, difficult to install, and liable to obstruction by the roof liner.

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 ventilator section extending above the base adapted to support an end tile and carrying apertures to allow the passage of air across the base, the ventilator section having one convex side extending beyond the edge of the base on the side carrying the locating rib.

There is also provided a method of ventilating the attic space of a building by incorporating the ventilator strip 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 is continuous however the upper, tile supporting, surface of the hollow ventilator section may be discontinuous and the ventilator section can be formed by a series of upwardly directed ribs which allow sufficient air to pass through the space between them to meet the requirements of the Building Regulations.

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 tube with a central supporting rib. The tube is slotted by transverse saw cuts across its apex down to within a few millimetres of the base.

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 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 ventilator strip, Figure 3 is a cross sectional view of the ventilator strip shown in Figure 2 through the line X-X, and Figure 4 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 Figure 1, consists of a flat strip base 1, having a downwardly projecting locating rib 2, at one edge. A hollow ventilating section is formed by a group of three ribs, 4, 5 and 6, attached to the base 1 and joining to form a common tile support apex 7. The sloping rib 4 and the vertical rib 5 form a rigid frame which carries any vertical load. The convex rib 6 extends beyond the edge of the base 1 carrying the locating rib 2. The opposite edge of the base 1 is pierced by a series of fixing holes 8. The groups of ribs 4, 5 and 6 are separated by gaps 9, see Figure 2, approximately equal to their width which allow the free passage of air but prevent the ingress of birds and rodents.

In use the ventilator strip is fixed to a wooden fascia board 12, see Figure 3, by means of a nail 13 which is driven through the fixing hole 8 into the board 12. The base 1 of the strip is held firmly in position by the combined action of the nail 13 and the rib 2. The convex rib 6 comprises an upper portion 14 and a lower portion 15.

The upper portion 14 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 spaces formed by the gaps between the lower portion 15 of the ribs. The upper portion 14 0 preferably slopes at an angle of 46 to the horizontal so as to accomodate any roof pitch greater than 150.

The roof portion of a building incorporating a ventilator strip according to the invention, see Figure 4, consists of an outer brick wall 16 and an inner brick wall 17, with a cavity 18, between them. The walls 16 and 17 carry the roof load through a series of rafters one of which 19, is shown. The rafter 19 has a series of battens 22 attached to it which retain rows of tiles 20. Under the battens 22 lies a continuous layer of roofing felt 23 whose end emerges under an end tile 21. The fascia board 12 supports a gutter 25 by means of a series of brackets 26.

The space between the bottom of the fascia board 12 and the outer brick wall 16 is closed by a soffit 27.

The ventilator strip is fixed to the fascia board 12 in the manner previously described. The felt 23 extends over the ventilator strip lying on the upper portion 14 of the convex rib 6. The apex of the ventilator strip supports the edge of the end tile -21.

Air can enter the space 24 through the gaps 9 in the lower portions 15 of the convex ribs 6,of the ventilator. The majority of the air entering the ventilator will have passed over the gutter 25 which will cool 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 (15)

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 ventilator section extending above the base adapted to support an end tile and carrying apertures to allow the passage of air across the base, the ventilator section having one convex side extending beyond the edge of the base on the side carrying the locating rib.

2. A ventilator strip as claimed in claim 1 in which the hollow -ventilating section is formed by a group of three ribs, each attached to the base and joined at an apex for supporting a roof end, the group including a sloping rib and a central vertical rib which forming a rigid frame to support the roof end and a convex deflector rib.

3. A ventilator strip as claimed in claim 2 in which the convex deflector rib consists of an upper sloping portion adapted to support a roof liner and a lower ventilator portion.

4. A ventilator strip as claimed in claim 3 in which the upper sloping portion forms an angle of 460 with the horizontal.

5. A ventilator strip as claimed in any of the preceding claims in which the ventilator section carries a series of vertical slots to allow the passage of air across the base.

6. A ventilator strip as claimed in claim 5 in which the slots extend upwardly from the base separating the ribs.

7. A ventilator strip as claimed in claim 6 in which the width of the slots is substantially equal to the width of the ribs.

8. 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.

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

10. 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.

11. A method of ventilating the attic space of a building as claimed in claim 10 wherein the roof liner rests on the top of the ventilator section and is supported by the upper surface of the convex side.

12. 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.

13. Methods of ventilating the attic space of a building as claimed in claim 10 and as herein described.

14. The method of making a ventilator strip as claimed in any of the claims 5 to 7 wherein the strip is formed as a tube and thereafter slotted by transverse saw cuts through the ventilator section.

15. Methods of making a ventilator strip as claimed in claim 1 and as herein described.