GB2304887A

GB2304887A - Roof ventilation duct

Info

Publication number: GB2304887A
Application number: GB9517563A
Authority: GB
Inventors: Neil Rideout
Original assignee: Willan Building Services Ltd
Current assignee: Willan Building Services Ltd
Priority date: 1995-08-26
Filing date: 1995-08-26
Publication date: 1997-03-26
Anticipated expiration: 2015-08-26
Also published as: GB9517563D0; GB2304887B

Abstract

A ventilation system is provided for ventilating closed inter-rafter air spaces. One or more ventilators, such as ventilator tiles, are mounted over one or more of the inter-rafter spaces, and communication is established between these ventilated spaces and adjacent inter-rafter spaces by means of bridging ducts. These ducts may comprise vacuum-formed plastics channel structures 18 which are fixed on top of the rafters (8). The channel structures 18 run along the rafters (8) and are open downwardly and overhang the sides of the rafters so as to define a series of transverse side-by-side channels across the rafter (8). The channel structures 18 may be deformable so that they can be nailed down under tile batten (12) without disturbing the lie of the roof tiles (14).

Description

ROOF VENTILATION SYSTEM This invention relates to a roof ventilation system.

A known kind of insulated roof structure has rafters covered with roofing underlay beneath tiles or other roof covering on the outside of the roof, and sheets of plasterboard on the inner side with insulation material retained between the rafters.

With this known structure it is important to ventilate the air spaces enclosed between the rafters. With a simple, pitched roof with a top ridge, the rafters run up to the ridge and high level ventilation can be achieved between the rafter ends at the ridge using ridge ventilators. In this way good ventilation is possible conveniently and inconspicuously without unduly detracting from the aesthetic appearance of the roof.

In the case of a hipped roof where two inclined parts of the roof have rafters running to an intermediate join (hip tree) extending up the roof to meet the main ridge, and in the case of some ridge constructions, there are problems involved in venting the inter-rafter spaces conveniently and inconspicuously. It is possible to use ventilation tiles at the upper end regions of the rafters, between each pair of adjacent rafters, but this is inconvenient and expensive and may result in a conspicuous and aesthetically displeasing arrangement.

It is also known to drill holes through the rafters to provide air flow communication between adjacent inter-rafter spaces, whereby it is not necessary to provide ventilation tiles for all of the spaces. This is however not a satisfactory solution to the problem. Provision of adequate numbers of drilled holes is inconvenient and time consuming, and may result in weakening of the rafters.

An object of the invention is to overcome the stated problem by providing a ventilation system with which good ventilation of inter-rafter spaces can be achieved in a simple, convenient and inconspicuous manner.

According to one aspect of the invention therefore there is provided a ventilation system for ventilating inter-rafter air spaces in a roof structure, said system comprising at least one ventilator providing communication between at least one said inter-rafter space and the external environment, and characterised by the provision of at least one bridging duct extending over one rafter bounding said ventilated inter-rafter space to provide communication between said space and the next adjacent inter-rafter space.

With this arrangement it is possible to achieve good ventilation of the inter-rafter spaces in a simple, convenient and inexpensive manner with minimal use of conspicuous ventilators.

All or only selected ones of the inter-rafter spaces may be linked with bridging ducts, as desired. Also, there may be only one, or several ventilators in accordance with the manner of interlinking of the spaces and the requirements for ventilation.

With regard to the roof structure, this is preferably as described above, i.e. a hipped roof structure with roofing underlay under tiles or other roof covering on the external surface of the rafters, and plasterboard fixed to the underside of the rafters retaining insulation material on the inner side.

It is however to be understood that the invention is not intended to be restricted to this arrangement. Other suitable structures and materials may also be used.

Also, the ventilator preferably comprises a ventilator tile, that is a structure which is generally of the shape of, or is dimensioned to fit in place of one, or possibly two or other integral number, standard roof tile or tiles, such structure having an external outlet connecting to the external environment, and an internal inlet projecting into the inter-rafter space, preferably with suitable constructions to limit or prevent unwanted passage of rain water, insects etc. Any other suitable form of ventilator may however also be used.

With regard to the (or each) bridging duct, this may take any suitable form but preferably comprises an elongate structure which can be fixed longitudinally on top of a rafter to provide multiple side-by-side ducts.

The ducts may be of the form of open-sided channels which conveniently may have the open sides facing downwardly to be closed by the top surface of the rafter. Between the channels there may be contact portions for engagement with the top surface of the rafter.

The width of the elongate structure may be slightly greater than the width of the rafter whereby each channel has inlet and outlet ends thereto which overhang opposite sides of the rafter.

Preferably the elongate structure is formed from a semi-stiff or crushable material which can be readily locally compressed whilst retaining its shape in adjoining regions thereof. With this arrangement, the structure can be compressed locally between the rafter and the usual tile batten which is nailed to the rafter thereby avoiding disruption of the lie of the tile battens and tiles.

The elongate structure may be held in position by the above mentioned nailed battens and/or by direct fixing of the structure to the rafter, e.g. at the said contact portions, by nails or by any other means.

Conveniently the elongate structure is formed from vacuum formed plastics, although other materials and forming techniques may also be used.

According to a second aspect of the present invention there is provided a bridging duct structure for use in the above mentioned ventilation system comprising an elongate vacuum-formed semi-stiff plastics structure having multiple side-by-side channels extending transversely across the structure with intermediate contact portions for engagement with and fixing relative to the top surface of a roof rafter, said channel having inlet and outlet ends thereto adapted to overhang opposite sides of the said rafter.

The invention will now be described further by way of example only and with reference to the accompanying drawings in which: Fig. 1 is a diagrammatic plan view of a hipped roof with one form of a ventilation system according to the invention; Fig. 2 is a sectional view of part of the roof showing bridging duct structures according to the invention installed on top of roof rafters; Fig. 3 is a plan view of one section of the bridging duct structure; Fig. 4 is a sectional view on the line IV-IV of Fig. 3; and Fig. 5 is a cut away perspective view showing the ventilation system with a slate-type roof covering.

Referring to Figs. 1 and 2, a roof structure of a domestic house or other building has a main top ridge 1 with pitched sides 2, 3 having rafters 4 running up to the ridge 1. There is also a hipped construction. An inclined end part 5 of the roof meets the sides 2, 3 at joins 6, 7 which run up to the main ridge 1. Rafters 8 of the end part 5 run up to the joins 6, 7 as also do end region rafters 9 of the sides 2, 3.

The rafters 4, 8, 9 are insulated therebetween as shown in Fig. 2 with conventional insulating material 10. Plaster board 11 is fixed to the under sides of the rafters over this material. Fig. 2 only shows the rafters 8 of the end part 5.

Transverse battens 12 are nailed across the top surfaces of the rafters 8 with roof felting 13 of conventional kind trapped underneath the battens 12 over the rafters 8. Tiles 14 are fixed to the battens 12 in the usual way.

Air spaces 15 are enclosed between the plaster board 11 and the roof felting 13 between pairs of adjacent rafters 8.

As shown in Fig. 1 some of these spaces 15 are vented near to the joins 6, 7 by means of conventional ventilation tiles 16 which have outlets connecting to the external environment and downwardly projecting inlets within the inter rafter spaces 15 above the insulating material 10.

The adjoining inter-rafter spaces 1 5 which do not have ventilation tiles 16 are linked to the ventilated spaces 15 by bridging air duct structures 17.

As shown in Figs. 3 and 4, each such structure 17 is an elongate vacuum formed plastics structure having multiple side-by-side downwardly open channels 18 with flat contact portions 19 there between, and downwardly directed side rims 20. There is an upwardly directed strengthening ridge 21 alongside each channel 18, and there are two depressions 22 in each channel 18 which have bottom surfaces level with the contact portion 19. The section shown in Figs. 3 and 4 is repeated along the length of the structure 17.

The structures 17 are slightly wider than the rafters 8 and are fixed directly to the top surfaces thereof, e.g. with nails, so that the ends of the channels 18 and the rims 20 overhang opposite sides of the rafters 8.

These structures 17 are fitted beneath the battens 12 and the roof felting 13 and may extend only along upper end regions of the rafters 8 as shown in Fig. 1.

The plastics material is semi-stiff and is crushed locally immediately beneath the battens 12. This prevents disruption of the lie of the battens 1 2 and tiles 14. Between the battens 12, the plastics material is not crushed and provides free air-flow ducts over the top surface of the rafters between the adjoining inter-rafter spaces 15.

With this arrangement, air can flow from all inter-rafter spaces 1 5 to the ventilation tiles 16. Good ventilation of all inter-rafter spaces 15 can therefore be ensured despite the use of only a small number of ventilation tiles 16.

Good ventilation can be achieved without requiring conspicuous, aesthetically displeasing structures.

The ducts are simple and inexpensive to manufacture, and quick and convenient to install.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims

1. A ventilation system for ventilating inter-rafter air spaces in a roof structure, said system comprising at least one ventilator providing communication between at least one said inter-rafter space and the external environment, and characterised by the provision of at least one bridging duct extending over one rafter bounding said ventilated inter-rafter space to provide communication between said space and the next adjacent inter-rafter space.

2. A system according to claim 1 wherein multiple inter-rafter spaces are linked with said bridging ducts.

3. A system according to claim 2 wherein multiple said ventilators are provided.

4. A system according to any one of claims 1 to 3 wherein the roof structured is a hipped roof structure with roofing underlay under roof covering on the extemal surface of the rafters, and plasterboard fixed to the underside of the rafters retaining insulation material on the inner side.

5. A system according to claim 4 wherein the roof covering comprises tiles.

6. A system according to any one of claims 1 to 5 wherein the (or each) ventilator comprises a ventilator tile.

7. A system according to claim 6 wherein the ventilator tile is a structure which is dimensioned to fit in place of an integral number of roof tiles and has an external outlet connecting to the external environment and an internal inlet projecting into the inter rafter space, and said structure is provided with constructions to limit or prevent passage of rain water and insects.

8. A system according to any one of claims 1 to 7 wherein the (or each) bridging duct comprises an elongate structure which can be fixed longitudinally on top of a rafter to provide multiple side-by-side channels.

9. A system according to claim 8 wherein the side-by-side channels are open sided channels.

10. A system according to claim 9 wherein the open sided channels have open sides facing downwardly to be closed by the top surface of the rafter.

11. A system according to claim 10 wherein between the channels there are contact portions for engagement with the top surface of the rafter.

12. A system according to any one of claims 9 to 11 wherein the width of the elongate structure is slightly greater than the width of the rafter so that each channel has inlet and outlet ends thereto which overhang opposite sides of the rafter.

13. . A system according to any one of claims 8 to 11 wherein the elongate structure is formed from a semi-stiff or crushable material which can be readily locally compressed whilst retaining its shape in adjoining regions thereof.

14. A system according to claim 13 wherein the elongate structure is compressed locally between the rafter and a tile batten which is nailed to the rafter.

15. A system according to any one of claims 8 to 14 wherein the elongate structure is directly fixed to the rafter.

16. A system according to any one of claims 8 to 15 wherein the elongate structure is a vacuum-formed plastics structure.

17. A bridging duct structure for use in the system of claim 1 comprising an elongate vacuum-formed semi-stiff plastics structure having multiple sideby-side channels extending transversely across the structure with intermediate contact portions for engagement with and fixing relative to the top surface of a roof rafter, said channel having inlet and outlet ends thereto adapted to overhang opposite sides of the said rafter.

18. A system according to claim 1 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. A bridging duct structure according to claim 17 substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.