GB2118991A

GB2118991A - Ventilating roofs

Info

Publication number: GB2118991A
Application number: GB08234860A
Authority: GB
Inventors: Barry Cliff
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-12-07
Filing date: 1982-12-07
Publication date: 1983-11-09
Also published as: GB2118991B

Abstract

A roofspace ventilator unit includes a pair of overlapping barrier plates (13) fitted between successive pairs of rafters (10). The plates are identical but oppositely handed, the amount of overlap between the plates being varied to accommodate variations in the spacing between the rafters. Each plate is divided into an inclined deflector section and a vertical end stop section, the two sections each having a flange (14) nailed to an adjacent rafter. The vertical sections are also nailed to a wallplate (12) and project above the wallplate. When fitted in position the two plates prevent rolls of insulating material laid between the ceiling joists (11) from inadvertently obstructing the air flow into the roofspace. <IMAGE>

Description

SPECIFICATION Roofspace ventilator unit This invention relates to the ventilation of pitched roof structures in which a roofspace is provided between the roof covering and the ceiling of the interior space protected by the roof.

The present need to conserve energy has led to the increased use of additional roof insulation in pitched roof structures. However this increases the likelihood of undesirable condensation occurring in the roofspace unless it is adequately ventilated. Unfortunately the present practice of laying rolls of additional insulating material between the ceiling joists may at least partially block the passage of ventilating air into the roofspace, and thereby aggravate the condensation problem.

In accprdance with one aspect of the present invention there is provided a pitched roof structure in which the roofspace is ventilated through an eaves ventilator, and in which obstruction of the airflow from the ventilator when laying insulating material between successive pairs of ceiling joists is prevented by barrier means disposed in the path of the insulating material between the respective pairs of joists at one end thereof, the air from the ventilator flowing into the roofspace through a gap formed between the roof covering and the barrier means.

The barrier means preferably comprises successive pairs of overlapping members fitted between respective pairs of rafters, the amount of overlap being varied in accordance with the spacing between the joists. In one particular embodiment of the invention the members of each pair are substantially identical but oppositely handed.

Each member preferably includes a first section inclined at an angle generally corresponding to that of the roof pitch for deflecting a layer of insulating material away from the roof covering, the deflector section being spaced beneath the top edges of the rafters to maintain the air gap between the deflector and the roof covering. The member may also include a second substantially vertical section acting as an end stop to prevent further movement of the insulating material. The vertical section is preferably secured to a wallplate supporting the joists, and projects above the wallplate.

The barrier members are preferably derived from a continuous strip, the number of members which can be obtained from a given length of strip being increased if the members consist of discrete prongs or teeth disposed symmetrically about a central spine, the prongs or teeth of successive members meshing with one another along the continuous strip.

Each member may be further adapted to function as a bracket for securing the wallplate to a rafter in a trussed rafter roof construction. This advantageously avoids the present need for skew nailing the rafter to the wallplate.

Moreover, each member may be further provided with means for retaining a sheet of insulating material against the outside surface of the wallplate to prevent the wallplate acting as a cold bridge to the insulated roofspace.

In accordance with another aspect of the present invention there is provided a ventilator unit for fitting between successive pairs of rafters along at least one side of a pitched roof structure, the unit when fitted preventing obstruction of the airflow from an eaves ventilator into the roofspace when additional insulating material is laid or deposited between the ceiling joists, and the unit comprising a pair of overlapping barrier members for blocking and/or deflecting movement of the insulating material, each member having at least one flange for securing to a respective rafter, the flanges being inclined to the respective surfaces of the members such that, when fitted, the respective surfaces lie beneath the top edges of the rafters to maintain an air gap between the member and the roof covering, and the overlap between the two members being varied to accommodate variations in the spacing between the rafters.

By way of example only, several embodiments of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is an isometric detail of a pitched roof structure showing two barrier plates of a ventilator unit fixed in position between a pair of rafters, Fig. 2 is a front elevation of the two barrier plates fitted with minimum overlap, Fig. 3 is a view similar to Fig. 2 showing the plates fitted with maximum overlap, Fig. 4 is an isometric view of one of a pair of alternative barrier plates, Fig. 5 is. a typical soffit section showing the plate of Fig. 4 fitted in position, Fig. 6 is a plan view of one of a pair of barrier components comprising discrete prongs or teeth, and Fig. 7 is an isometric view of one of a pair of barrier plates similar to the plates of Figs. 1 to 3 but with additional features.

Referring first to Fig. 1 the detail illustrates part of the framework of a. trussed rafter pitched roof structure. The framework includes rafters 10, ceiling joists 11, and a wall plate 12. Air is normally admitted into the roofspace through louvred ventilators fitted in the undersurface or soffit of the eaves. This flow of air is indicated by the arrows 'A' in Fig. 1, and normally passes through the gap formed between the roof covering and the top of the wall plate 12.

Two barrier plates 1 3 are shown fitted between the right hand pair of rafters 1 0. In practice, such plates would be fitted between each successive pair of rafters along the length of the wallplate 12.

The plates 13 are identical (the right hand 'plate being turned through 180 , or oppositely handed, relative to the left hand plate as viewed in Fig. 1) and are formed from metal or plastic sheets. Each plate is bent along its centre line 15 at an angle broadly corresponding to that of the roof pitch, the resulting vertical and inclined sections of the plate each including a flange 14 (only the flanges of the left hand plate being visible in Fig. 1) for nailing to a respective rafter 10 using, for example, plasterboard nails. The flanges 14 are inclined with respect to the faces of the respective sections of the plate so that the plates are always spaced beneath the top edge of the rafter to maintain an air gap through which air can enter the roofspace.

As shown in Figs. 2 and 3, the identical plates 1 3a, 1 3b are each provided with two sets of slots 16 and 1 8 respectively, one set 1 6 being disposed along the longitudinal edge 21 and the other group 18 along the opposing edge 20. The slots 1 6 are set at right angles to the slots 1 8 and are so spaced that when, as shown, plate 1 3b is turned through 1 800 and overlapped with plate 1 3a, the intersection o.' slots 1 6 and 1 8 provide at least one opening through which a nail 1 7 can be driven into the wallplate.

It can be ssen that when the plates are fitted in position the ventilating air from the eaves space is deflected upwardly over the plates and enters the roofspace through the gap between the inclined faces of the plates and the roof covering.

Accordingly, if additional rolls of insulating material are laid between the ceiling joists 11, the plates 13 will maintain ventilation to the roofspace by preventing the rolls of insulating material being pushed into the eaves space to block the flow of air 'A'. In practice the inclined faces of the plates 14 progressively compress the insulating material as it is pushed toward the wallplate 12, and the vertical faces of the plate 14 act as end stops. The end stops would also be effective in the case of granular insulating material.

An identical arrangement can of course be fitted on the opposite side of the roof so that the whole of the roofspace is adequately ventilated and the possibility of condensation forming becomes negiigible.

In a trussed rafter construction the flanges 14 can be fixed directly to the rafters above the wall plate since the gang nail plates securing the ceiling joists to the rafters only cover a portion of the rafter. However, in a conventional pitched roof structure where the ceiling joist extends across the side face of the rafter, it would be necessary to cut the ceiling joist back on the same pitch as the rafter in order to provide space for the flanges 14.

In Fig. 4, the barrier plate 100 is made of metal and corresponds to the plate illustrated in Figs. 2 and 3. In addition, however, the plate includes the stamped out tabs of finger clips 110 which can be bent up and folded over a sheet of insulating material 120 as shown in Fig. 5. This therefore holds the sheet of insulating material 1 20 against the wallplate 1 30 to prevent the wallplate acting as a cold bridge to the insulated roofspace. The sheet of insulating material 120 may consist, for example of a 1 5 mm polystyrene sheet.

Plates 100 are fitted between adjacent pairs of rafters 140 as described with reference to Figs. 2 and 3. Air thus flows from a vent 1 50 in a soffit 1 60 along the arrowed path 1 70. At the same time, the plates 100 prevent roof insulation 1 80 being pushed inadvertently into the eaves space and thereby blocking the airflow 1 70.

As shown in Fig. 4, the plate 100 is provided with holes 1 90 in the end flanges 200 so that the flanges can be nailed or screwed to the rafter 140.

In addition, further holes 210 are provided close to the flanges 200 so that the plate can also be nailed to the wallplate 130 close to the junction of the wallplate 130 with the rafter 140. Only one set of holes 210 is required, the other set being provided so that the plate can be used as a left handed plate or a right handed plate. In this manner the plate acts not only as a barrier to the insulating material but also as a bracket for securing the wallplate 130 to the rafter 140.

The wallplate 1 30 is conventionally mounted on a blockwork lintel 220 at the top of a cavity wall construction.

The barrier member shown in Fig. 6 would be used with other identical members in exactly the same manner as described with reference to Figs.

2 and 3. The only difference is that the member of Fig. 6 is not a continuous plate. Instead the top and bottom portions of a generally rectanguiar plate are each cut away to provide alternate grooves 210 and prongs or teeth 211.

When fitted in position with the prongs 211 a uppermost, the pongs 21 lea will provide a barrier to the rolls of insulating material laid between the joists while one or more of the lower prongs 211 b can be used to hold a sheet of insulating material against the wallplate. The selected lower prongs thus serve the same function as the stamped out tabs or finger clips 110 of the plate illustrated in Fig. 4, the remaining lower prongs being nailed to the wailplate.

The member of Fig. 6 can be used as a left hand or right hand member merely by turning it through 1 800 as described with reference to Figs. 2 and 3.

The member may be cut from a continuous strip of material with the prongs 211 of one member meshing with the prongs of the next member along the strip. This increases the number of members which can be cut from a given length of strip.

The plate shown in Fig. 7 is similar to that of Figs. 1 to 3 and like reference numerals have been used to denot like parts. In addition, the plate is provided with longitudinal stiffening ribs 30, and with truncated wedge-shaped protruberances 31 which prevent sagging of the sarking felt, only one of the protruberances being effective dependent on the orientation of the plate. Moreover, the lower section of the illustrated left hand plate includes a serrated tongue 32 which can be pressed out of the plate and engaged in a slot 33 of the right hand plate (not shown), the right hand plate corresponding to the left hand plate but turned through 1800. This clips the two plates to one another while allowing a variable overlap.

In certain circumstances the two sections of the plate could be opened out to form a flat tray, both flanges 14 then being secured to the rafter at an angle corresponding to the pitch of the roof. This arrangement would not be satisfactory for use with granular insulating material but could provide a sufficient crimping or squeezing effect on the end of a roll of insulating material to maintain an air gap and prevent the end of the roll being pushed too far beyond the wallplate.

Claims

1. A pitched roof structure in which the roofspace is ventilated through an eaves ventilator, and in which obstruction of the airflow from the ventilator when laying insulating material between successive pairs of ceiling joists is prevented by barrier means disposed in the path of the insulating material between the respective pairs of joists at one end thereof, the air from the ventilator flowing into the roofspace through a gap formed between the roof covering and the barrier means.

2. A structure according to claim 1 further comprising means for varying the width of the barrier in accordance with the spacing between the rafters.

3. A structure according to claim 2 in which the width is adjusted by varying the amount of overlap between overlapping members of the barrier means.

4. A structure according to claim 3 in which the barrier means comprises successive pairs of overlapping plates.

5. A structure according to claim 4 in which the two plates of each pair are substantially identical but oppositely handed.

6. A structure according to any one of the preceding claims in which the barrier includes a first deflector section inclined at an angle generally corresponding to that of the roof pitch for deflecting a layer of insulating material out of the path of the air flow, the said section being spaced beneath the top edges of the rafters to maintain the said air gap between the deflector and the roof covering.

7. A structure according to claim 6 in which the barrier further includes a second substantially vertical section acting as an end stop to prevent further movement of the layer of insulating material.

8. A structure according to any one of the preceding claims in which the said end of each joist rests on a wallplate, and in which the barrier means projects above the wall plate and is secured thereto.

9. A trussed rafter roof structure according to claim 8 as dependent on claim 3 in which each barrier member is secured to the wallplate close to the junction of the wallplate and a rafter whereby each barrier member further serves as a bracket for securing the wallplate to the rafter.

10. A structure according to claim 8 in which the barrier means is further provided with means - for retaining a sheet of insulating material against the outside surface of the wallplate to prevent the wallplate acting as a cold bridge to the insulated roofspace.

11. A structure according to any one of the preceding claims in which the barrier means comprises discrete prongs.

12. A structure according to any one of the claims 1 to 10 in which the barrier means presents a continuous barrier surface.

13. A ventilator unit for fitting between successive pairs of rafters along at least one side of a pitched roof structure, the unit when fitted preventing obstruction of the airflow from an eaves ventilator into the roofspace when additional insulating material is laid or deposited between the ceiling joists, and the unit comprising a pair of overlapping barrier members for blocking and/or deflecting movement of the insulating material, each member having at least one flange for securing to a respective rafter, the flanges being inclined to the respective surfaces of the members such that, when fitted, the respective surfaces lie beneath the top edges of the rafters to maintain an air gap between the member and the roof covering, and the overlap between the two members being varied to accommodate variations in the spacing between the rafters.

14. A ventilator unit according to claim 1 3 further comprising means for fastening one member to the other while permitting variation of the overlap.

15. A ventilator unit according to claim 14 in which the fastening means comprises a serrated tongue pressed out of one member and a corresponding slot for receiving the tongue in the other member.

1 6. A ventilator unit according to any one of the claims 13 to 15 in which the two members are substantially identical but oppositely handed.

1 7. A ventilator unit according to any one of the claims 1 3 to 1 6 in which each member comprises two generally rectangular plate sections, the end of each section along one side of the member having a flange inclined to the surface of its respective section for securing the plate to a rafter.

18. A unit according to claim 1 7 in which the two plate sections are inclined to one another.

1 9. A ventilator unit substantially as herein described with reference to Figs. 1 to 3 of the accompanying drawings.

20. A ventilator unit substantially as herein described with reference to Figs. 4 and 5 of the accompanying drawings.

21. A ventilator unit substantially as herein described with reference to Fig. 6 of the accompanying drawings.

22. A ventilator unit substantially as herein described with reference to Fig. 7 of the accompanying drawings.