GB2211521A

GB2211521A - Roof insulation location for ventilation

Info

Publication number: GB2211521A
Application number: GB8725201A
Authority: GB
Inventors: George Molyneux
Original assignee: Radway Plastics Ltd
Current assignee: Radway Plastics Ltd
Priority date: 1987-10-28
Filing date: 1987-10-28
Publication date: 1989-07-05
Anticipated expiration: 2007-10-28
Also published as: GB8725201D0; GB2211521B

Abstract

The invention relates to the location of a thick layer of fibrous thermal insulation 28 laid on the ceiling 26 of a pitch roof building, the location being critical in the region of the eaves. In place of the shallow roof trays which are sometimes secured between adjacent roof rafters 20, 22 near to the eaves, the invention provides a pitch roof construction in which an insulation locator 30 is fixed between adjacent rafters and is itself located on part of the wall 12, 24 of the building adjacent to the eaves. The locator provides a receptacle on the inside in which the edge of the insulation is received and located, but the top wall of the receptacle is sufficiently lower than the plane containing the top surfaces of the rafters to provide the essential ventilation gap over the top of the insulation and below the sarking or roof felt. <IMAGE>

Description

Roof Insulation Location It is common, and recommended, practice to provide a thick layer of fibrous thermal insulation laid on the ceiling of a pitch roof building. The insulation material itself may be, for example, mineral wool, and in the United Kingdom, the recommended thickness is 4 inches (100mm). There is however a dilemma associated with the location of the edges of the insulation material at the eaves of a building. On the one hand, if the insulation is forced into the eaves during fitting, there is the probability that it will wedge between the wall plate, or top edge of the wall, and the underside of the sarking or roof felt. This prevents ventilation of the roof space via ventilation openings provided at the eaves detail, which in turn leads to the formation of condensation within the roof space.On the other hand, if part of the ceiling near to the eaves is left uncovered hy the insulation, or if the edges of the insulation are disturbed after fitting, so that part of the ceiling becomes uncovered, this can lead to the formation of condensation on the underside of the uncovered part of the ceiling.

In an attempt to solve this dilemma, shallow roof trays are sometimes secured between adjacent roof rafters near to the eaves. In theory, the insulation can then be packed into the eaves and against the underside of the roof trays, because there should always be a ventilation channel through each tray. However, roof trays do not always provide an adequate solution to the problems.One reason for this is that they will only function properly if they are correctly located along the length of the rafters; but it is practically impossible to provide longitudinal location of a roof tray because it simply comprises a shallow channel open at its end and with lips along the tops of its side walls resting on the top sides of the rafters. (Incidentally, the fitting of roof trays must always prevent ideal-location of the roof slates or tiles because these lips necessarily lift the roof felt away from the rafters.) Moreover, the roof trays provide no means of ensuring the location of the edges of the insulation.

The object of the invention is to provide a roof insulation location structure which is superior to the use of the known roof trays.

According to a first aspect of the invention, in a pitch roof construction wherein thermal insulation material is laid on top of the ceiling below the rafters, an insulation locater is fixed between adjacent rafters and is itself located on part of the wall adjacent to the eaves, the locater providing a receptacle on the inside in which the edge of the insulation is received and thereby located, the top wall of the receptacle being sufficiently lower than the plane containing the top surfaces of the rafters to provide an essential ventilation gap over the insulation and below the sarking or roof felt.

It will be appreciated that the construction in accordance with this aspect of the invention provides the same ventilation effect as should be provided by a roof tray, but the ventilation effect is assured because of the correct location of the insulation locater. Secondly, it provides a more accurate location of the edge of the insulation material because it acts as a receptacle for the edge of the insulation.

Preferably the receptacle provided by the locater is in the form of a pocket open along its inside edge, but closed on the outside edge and having an effective top for engagement with the top of that part of the insulation which enters the receptacle. The receptacle may comprise a plate curved in cross-section from a bottom outer edge to a top inner edge, the space beneath the curved plate constituting the receptacle.

It is further preferred that an angle formation on the locater is engaged with the top outer edge of the wall plate, or a part of the wall, to provide the location of the locater. According to another preferred feature of this aspect of the invention, an insulation retaining strip projects downwardly from a top part of the locater into its receptacle, so that insulation material forced into the receptacle has to contract in thickness to pass under the retaining strip. Insulation material which has thus passed under the retaining strip will recover to nearly its free thickness, so that the retaining strip will key into the insulation material.

The insulation locater is preferably made in water-resistant material and it may for example be made in plastics material, such as unsaturated polyvinyl chloride of the kind conventionally used for building elements such as gutters and fallpipes.

Since the insulation locater may be made of constant cross-section, it lends itself to manufacture hy extrusion, being subsequently cut to the lengths required to substantially fill the width between adjacent rafters.

However, because the locaters will generally all be of the same length, they may be made as injection mouldings.

Fixing holes may be formed in the part of the locater which locates on the wall or roof plate to accept nails or screws. For strengthening purposes, the locater may have integrally moulded laterally extending ribs on the outside (if it is formed as an injection moulding) or alternatively, separate longitudinally spaced support brackets may be attached to the locater.

According to a second aspect of the invention a thermal insulation locater for use in building construction comprises a receptacle open along its inside edge, but closed on its outside edge and having an effective top side, there being angle formation along the bottom outside edge to provide a location for locating the locater on a roof plate of a wall.

All the preferred features of the insulation locater described in the first aspect of the invention may be employed in the second aspect.

Various constructions illustrating both aspects of the invention will now be described by way of examples, with reference to the accompanying drawings, in which: - Figure 1 is a perspective view of the eaves detail of a pitch roof building, Figure 2 is a cross-section through an insulation locater shown in Figure 1, Figure 3 is a perspective view of an injection moulded insulation locater, Figure 4 is a perspective view of another insulation locater, and Figure 5 is a detailed perspective view of a support bracket.

In Figure 1, sufficient of the eaves detail of a pitch roof building has been shown to illustrate the use of the invention. Part of the outer brick leaf of a cavity wall is shown at 10 and the inner breeze block leaf of the wall is shown at 12. In this particular construction, the inner leaf is continued above the top of the outer leaf, and a special cavity closer and ventilation element 14 is provided, resting on the top of the outer leaf and abutting the outer face of the inner leaf. This element is constructed as described in the specifications of patent applications Nos. 8709320 and 8709321 and the description of that element in those Patent Applications is incorporated herein. It is worth noting that a layer of cement 16 is laid in the element 14 to provide --a fire barrier across the top of the cavity, and that there are ventilation openings 18 in the outer face of the element 14 to allow ventilation into the roof space under the rafters, two of which are shown at 20 and 22.

The top edge of the inner leaf 12 is capped by a conventional timber roof plate 24 and again as is conventional, the rafters 20 and 22 rest on the outer top corner of the roof plate 24, the rafters being cut if necessary to fit this corner of the roof plate. A plaster board ceiling 26 is illustrated, and for purposes of thermal insulation a thick layer of mineral wool fibre 28 is laid on top of the ceiling 26, between the joists (not shown). In the United Kingdom, it is recommended that the thermal insulation material should have a depth of approximately 100mm. The purpose of the thermal insulation is to retain heat within the rooms of the building, rather than allowing it to escape into the roof space, and thence out through the roof itself.

It is desirable that the entire ceiling 26 should be covered by the insulation material 28, because if the edges of the insulation material terminate short of the inner leaf 24 of the wall, then a part of the ceiling 26 which is not covered by the insulation material forms a cold bridge to the roof space, and as a result, condensation is very likely to form on the underside of this uncovered part of the ceiling. This frequently leads to the formation of mould growth on the underside of a ceiling adjacent to an external wall of the building.

However, if the relatively thick thermal insulation material 28 were simply forced into the eaves across the top of the roof plate 24, there is a considerable danger, that it would pack up against the underside of the sarking or roof felt (not shown) which is nailed to the top edges of the rafters 20 and 22. If this happens, then it completely blocks the ventilation into the roof space, which then gives rise to the formation of potentially damaging condensation within the roof space.

In the construction which is illustrated in Figure 1, a special insulation locater 30 is fitted between each adjacent pair of rafters such as the rafters 20 and 22. The purpose of this locater is to receive and locate the marginal portion of the thermal insulation material 28, as will be described in more detail.

Turning to Figure 2, the insulation locater 30 in this construction is made as an extrusion in unsaturated polyvinylchloride material of the grade commonly used for the manufacture of building elements such as guttering and fallpipes. Because of the extrusion process, the locater material can be produced in long strips, which can then be cut on site if necessary, into the short lengths (usually about 300mm long) required to occupy the width between adjacent pairs of rafters.

Essentially, the locater comprises a curved plate 32, which extends through an angle of 900 from a bottom outer edge to a top inner edge; an angle location part 34, the horizontal flange of which extends from the bottom outer edge of the plate 32, and the vertical flange of which depends from the horizontal flange, and an inwardly and downwardly extending retaining flange 36 which depends from the top inner edge of the plate 32. As illustrated in both Figures 1 and 2, the angle strip 34 of the locater is itself located on the top outer corner of the wall plate 24, and then it is secured to the wall plate by nails 38 passing through clearance holes 40 which are formed in the horizontal flange of the angle strip 34 after the extrusion has been completed.In fact, since the angle strip 34 is of relatively thin construction, it may not be necessary to provide clearance holes 40, it being sufficient to simply drive the nails through the horizontal flange of the angle location strip.

It will be appreciated, that once the angle strip 34 has been secured to the wall plate 24, the entire insulation locater 30 is fixed in a stationary location, and this is an important feature of the invention, because it ensures that the joiner will always secure the locater in precisely the correct position. This is in contradistinction with what happens with so-called cavity trays, where the joiner can fit the tray over a wide range of positions, some of which may not provide the correct effect. Once the locater is fixed in position, the curved plate 32 provides in effect a receptacle bounded on the underside by the top face 42 of the wall plate 24, and on the outside and top side by the curved plate 32. This receptacle may be regarded as a pocket open on the inside edge. However, the retaining flange 36 projects downwardly into the upper portion of the pocket or receptacle.

It is an important feature of the invention, that the dimensions of the locater 30 are such that when the locater is fixed in position, the tangent to the outside of the curved plate 32 which tangent is parallel with the top edge of the rafters, must be spaced below the plane containing the top edges of the rafters. In Figure 1, this is indicated by the dimension "X". In a practical situation, this dimension will be not less than 30mm.

In use, once the locater has been fitted, then the thermal insulation material 28 can be laid on the ceiling 26, and the edges of that material can be pushed by the fitter into the receptacle provided by the locater. Moreover, this fitting of the edges of the insulation material can in effect be a stuffing operation to ensure that the insulation material provides a good cover over the marginal portion of the ceiling 26, and indeed extends part way over the roof plate 24 as is clear from Figure 1. During this stuffing operation, as the insulation material passes under the retaining flange 36, it will be temporarily compressed in thickness, but that material which passes to the outside of the retaining flange 36 will then substantially recover its original thickness, thus filling the space on the inside of the locater.From then on, the retaining flange 36 effectively acts as a key against the subsequent withdrawal of the material stuffed into the locater. Only if considerable force were applied to the insulation material could it be pulled past the retaining strip 36.

This keying effect is enhanced by the downwward and outward inclination of the retaining flange.

Once the fitting has been completed, as illustrated in Figure 1, then besides providing proper thermal insulation for the ceiling 26, adequate ventilation of the roof space is ensured, because air entering through the openings 18 in the element 14 and entering the roof space can pass between the top side of the locater 30 and the underside of the sarking or roof felt which is nailed to the top edges of the rafters 20 and 22 through the gap illustrated at Figure 1 at "X".

Turning now to Figure 3, there is illustrated an insulation locater 40 which is made as an injection moulding to a length approximately equal to the standard distance between adjacent rafters of a pitch roof.

Essentially, this locater has the same features as the locater 30, namely a curved plate 42, an angle location strip 44 and a retaining flange 46. However, in order to strengthen the locater, it is also formed with two hollow strengthening ribs 48 which are spaced apart longitudinally, but have the same generally arcuate form as the plate 42.

In Figure 4, a locater 50 is illustrated which is very similar to the locater 30 shown in Figures 1 and 2, and indeed it may be formed as an extrusion. However, at longitudinally spaced positions along the length of the locater 50, there are support brackets 52 one of which is illustrated separately in Figure 5. Each support bracket comprises an arcuate strap 54, an angle retainer 56 at the bottom of the strap, and a retaining tab 58 at the top of the arcuate strap. The support bracket is made so that it is a snap-on fit on the outside of the arcuate plate portion of the locater 50, and there may be provision for fixing rivets such as that shown at 60 in Figure 4. A web 62 is formed integral with the bracket, and extends between the angle locater 56 and the outside of the curved strap 54 to provide reinforcing for the curved plate portion of the locater.

Claims

CLAIMS:

1. A pitch roof construction in which thermal insulation material is laid on top of the ceiling below the rafters, and in which an insulation locator is fixed between adjacent rafters and is itself located on part of the wall adjacent to the eaves, the locator providing a receptacle on the inside in which the edge of the insulation is received and thereby located, the top wall of the receptacle being sufficiently lower than the plane containing the top surfaces of the rafters to provide an essential ventilation gap over the insulation and below the sarking or roof felt.

2. A pitch roof construction as claimed in Claim l, in which the receptacle provided by the locator is in the form of a pocket open its inside edge, but closed on the outside edge and having an effective top for engagement with the top of that part of the insulation which enters the receptacle.

3. A pitch roof construction as claimed in Claim 2, in which the receptacle comprises a plate curved in cross-section from a bottom outer edge to a top inner edge, the space beneath the curved plate constituting the receptacle.

4. A pitch roof construction as claimed in any one of Claims 1 to 3, in which an angle formation on the locator is engaged with the top outer edge of the wall plate, or a part of the wall, to provide the location of the locator.

5. A pitch roof construction as claimed in any one of Claims l to 4, in which an insulation retaining strip projects downwardly from a top part of the locator into its receptacle, so that insulation material forced into the receptacle has to contract in thickness to pass under the retaining strip.

6. A pitch roof construction as claimed in any one of Claims l to 5, in which the insulation locator is made in water-resistant material.

7. A pitch roof construction as claimed in any one of Claims l to 6, in which the insulation locator is of constant cross-section and is manufactured by extrusion.

8. A pitch roof construction as claimed in any one of Claims 1 to 6, in which the insulation locator is made as an injection moulding.

9. A pitch roof construction as claimed in any one of Claims l to 8, in which fixing holes are formed in the part of the locator which locates on the wall or roof plate to accept nails or screws.

10. A pitch roof construction as claimed in Claim 7, in which the locator has integrally moulded laterally extending ribs on the outside.

11. A thermal insulation locator for use in building construction comprising a receptacle open along its inside edge, but closed on its outside edge and having an effective top side, there being an angle formation along the bottom outside edge to provide a location for locating a locator on a roof plate of a wall.

12. A thermal insulation locator as claimed in Claim ll, in which an insulation retaining strip projects downwardly from a top part of the locator into its receptacle, so that insulation material forced into the receptacle has to contract in thickness to pass under the retaining strip.

13. A thermal insulation locator as claimed in Claim 11 or Claim 12, which is made in water-resistant material.

14. A thermal insulation locator as claimed in any one of Claims 11 to 13, in which the insulation locator is made of constant cross-section, by an extrusion process.

15. A thermal insulation locator as claimed in any one of Claims 11 to 13, in which the locator is made as an injection moulding.

16. A thermal insulation locator as claimed in any one of Claims 11 to 15, in which fixing holes are formed in the part of the locator which locates on the wall or roof plate to accept nails or screws.

17. A thermal insulation locator as claimed in Claim 15, in which the locator has integrally moulded laterally extending ribs on the outside.

18. A pitch roof construction substantially as herein described with reference to figures 1 to 3 or Figures l and 2 as modified by Figure 4 or Figure 5 of the accompanying drawings.

19. A thermal insulation locator for use in building construction substantially as herein described with reference to Figures 1 to 3 or Figures A and 2 as modified by Figures 4 or 5 of the accompanying drawings.