GB2075565A - Ventilating insulated roofspaces - Google Patents

Abstract

Open ended trays 1 are attached to the rafters 8 to provide ventilation channels 21 or 24 between the underside of the roof and insulation material 18 or 23 which is located directly over the ceiling 17 or 22. The tray may be of wire mesh or stamped from a metal strip. <IMAGE>

Description

SPECIFICATION Improvements in roof construction The invention is related to building construction, and more especially to the construction, or post-constructional modification of, roofing structures incorporated into the insulation and ventilation environment known as a "cold roof".

A "cold roof" is a roof in which the inner surface of the skin (or composite skin e.g. tiles and felt) is not in contact with a heat-insulating layer.

Because of this, it must be adequately ventilated by a moving layer of air since the warm air inside the building, when it rises will otherwise contact the cold roof skin and deposit any excess water vapour as condensation on the skin and adjacent structure, leading eventually to rot and corrosion.

One form of "cold roof" is common in residential building; beneath the eaves over part of all of their length there is an air gap for ventilation, and the thermal insulating layer is of course on the floor of the loft. Alternatively, for those buildings with rooms in the roof, a layer of thermal insulation material follows the contours of, but is spaced from, the inner surface of the skin of the roof, being supported on the effective sloping ceiling material of the rooms. Ventilation of the inner surface is effected by movement of cooler air in the air gap In recent building practice there has been a move towards the use of thicker layers of thermal insulating material, and indeed the standard specification has now moved towards use of an 80mm layer, in these locations discussed above, in place of the previously specified 25mm layer.

I have now realised that this use of thicker thermal insulation can lead to characteristic ventilation and condensation problems. The present invention sets out to overcome these problems.

The present invention provides a "cold roof" structure wherein the necessary spacing between the inner surface of the weather resistant skin of the roof, and an adjacent layer of thermal insulation is maintained by preformed spacer members fixed to structural members of the roof.

Alternatively stated, the invention provides a roof structure of the type wherein inclined roof structural members such as rafters or roof trusses support a weather resistant skin, in which one or more preformed spacer members having coplanar marginal regions separated by a depressed area beneath the plane of and extending the whole length of the marginal regions is located at the underside of the roof, over a supporting wall, with its marginal regions fixed one to each of adjacent roof structural members at the upper surfaces thereof so that a predetermined air space is defined and maintained between the depressed area and the inner surface of the roof skin.

The preformed spacer member while capable of embodiment in a wide range of shapes is preferably generally rectangular in shape. It could be, for example, a rectangle of fairly stiff material e.g. building grade p.v.c., generally in one plane but with a continuous and deformation-resistant channel extending the whole width i.e. separating and defining the margins. More usually it will be traylike, having raised walls with outwardly extending coplanar margins along the short edges but with no raised walls on the long edges. Such a tray can be integral and imperforate, or can be perforated to save material. It can alternatively be a wire framework defining a tray shape, as above.

It will be appreciated that the above construction is preferably assembled as the roof is initially built. This in another aspect of the invention consists in a method of constructing a roof in which between erecting of the roof structural members and affixing a weather resistant skin thereto a spacer member is fixed to lie between adjacent roof structural members, the spacer member having coplanar marginal regions separated by a depressed area beneath the plane of and extending the whole length of the marginal regions and being fixed by its marginal regions to the upper surfaces of the adjacent structural members.

The function of the spacer member is to prevent insulation from contacting the inner surface of the roof skin. Thus, in another aspect the invention consists in the assembly of (a) a vertical supporting wall and a ceiling supported thereby (b) an inclined roof overlying the wall with its weather resistant skin spaced therefrom (c) a preformed spacer member fixed to adjacent roof structural members to define and maintain a space with the inner surface of the roof skin and (d) a layer of resilient thermally insulating material over the ceiling with one edge located generally over the wall but held from contact with the skin of the roof by the spacer.

The spacer members itself also constitutes a separate vendible article and another aspect of the invention, and may be embodied as described above, as separate articles, or possibly as a continuous series of articles in a length or roll.

The invention will be further described with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a spacer member in the form of a wire traylike framework; Fig. 2 shows a detail of an alternative embodiment of traylike spacer member; Fig. 3 is a cross-section through part of a roof structure showing a spacer member in use; Fig. 4 is a cross-section through an alternative roof structure showing a spacer member in use.

In Fig. 1 a traylike member 1 is formed of three parallel wires 2 (e.g. of number 10 gauge) and four cross wires 3, spot-welded at their intersections.

Each end of a wire 2 has an upwardly extending portion 4, an outwardly extending portion 5 and a downwardly extending portion 6 terminating in a pointed end 7. The overall shape is therefore traylike, with marginal regions defined by the various portions 5 collectively, with the main body of the "tray" depressed between them at a lower level.

In use the pointed ends 7 are driven into adjacent trusses or rafters 8, for a purpose described in more detail below.

Fig. 2 shows a corner of a different embodiment of traylike spacer member 9.

Upstanding wall 10 and marginal region 11 are located along each edge of depressed area 12.

Marginal region 11 can be provided if necessary with formed holes 1 3 for suitable loose fixing such as screws or nails, but of course if the member is formed in metal these could be replaced or supplemented by suitable shape toothed edges.

For manufacturing simpiicity, such traylike members can be stamped or pressed from a common roll or strip, as shown in dotted lines at 14.

As shown by the vertical line 1 5, the upstanding wall 10 can be at a small angle to the vertical so that trays can be stacked for transport or storage.

Of course, various other shapes of spacer members, traylike or not, can be envisaged, providing that they define and maintain an air space.

One useful mode of effecting this is shown in Fig. 3.

In Fig. 3 a wall 16 supports a ceiling layer 17 covered by fibrous resilient thermal insulation material 1 8 such as fibre glass. Previously, if this were 25mm in thickness, any excess length would merely hang over the outer edge 1 9 of the wall.

However, I have realised that the growing use of 80mm insulation (for example) will, with excess length 1 8a, tend to block the ventilation air gap, it being understood that excess length is always more likely than insufficient length because of the general awareness of the need to avoid cold spots at the edges of the ceiling.

The spacer member 1 or 9 (for example) when fixed as shown in Fig. 1 presses down at 20 upon any excess length 1 8a of insulation material 1 8 as shown in Fig. 3 and thus defines and maintains predetermined air gap 21 with ventilating air currents as shown by the arrow A.

Fig. 4 shows a different "cold roof" construction with sloping ceiling 22 supporting fibrous insulation layer 23 spaced at 24 from the skin of the roof 25. Hitherto, with a 25mm insulating layer (for example) there has been little tendency for any inaccuracies of installation to occur to an extent sufficient to block gap 24.

I have now realised that the more effective thicker insulation, in this structure also, can with relatively little distortion, lead to blocking of the air gap. However, a succession of spacer members 1 or 9, installed as at 26 define and maintain a predetermined continuous air gap 27 for ventilation as shown by arrow B.

Various modifications may be made in the shape, construction and installation of the spacer members, provided that they are deformationresistant enough to maintain the necessary air gap against the pressure exerted by the resilient insulating layer.

Claims (14)

1. A "cold roof" structure wherein the spacing between the inner surface of the weather-resistant skin of the roof and an adjacent layer of thermal insulation is maintained by preformed spacer members fixed to structural members of the roof.

2. A roof structure of the type wherein inclined roof structural members support a weather- resistant skin, in which one or more preformed spacer members having coplanar marginal portions or regions separated by a depression zone or like depressed area beneath the plane of, and extending the whole length defined by, the marginal portions or regions is located at the underside of the roof, over a supporting wall, with its marginal portions or regions fixed one to each of adjacent roof structural members at the upper surface thereof so that a predetermined air space is defined and maintained between the depression zone or like depressed area and the inner surface of the roof skin.

3. A roof structure as claimed in Claim 2 in which the spacer member is generally rectangular in shape.

4. A roof structure as claimed in Claim 3 in which the spacer member is formed with at least one continuous and deformation-resistant channel separating the marginal portions or regions.

5. A roof structure as claimed in Claim 3 in which the spacer member is formed with a continuous and deformation-resistant channel t extending across the whole width thereof and thereby separating and defining the margins.

6. A roof structure as claimed in Claim 3 in which the spacer member is tray-like having, along its edges only, raised walls with outwardly extending coplanar margins,

7. A roof structure as claimed in Claim 6 in which the tray-like member is a wire framework.

8. A method of constructing a roof in which, between erecting of the roof structure members and fixing a weather-resistant skin thereto, a spacer member is fixed to lie between adjacent roof structural members, the spacer member having coplanar marginal regions or portions separated by a depression zone or like, depressed area beneath the plane of, and extending the whole length of, the marginal regions, and being fixed by its marginal regions or portions to the upper surfaces of the adjacent structural members.

9. The structural assembly of (a) a vertical supporting wail and a ceiling supported thereby (b) an inclined roof overlying the wall with a weather-resistant skin spaced therefrom (c) a preformed spacer member fixed to adjacent roof structural members to define and maintain a space with the inner surface of the roof skin and (d) a layer of resilient thermally insulating material extending over the ceiling with one edge located generally over the wall but held from contact with the skin of the roof by the spacer member.

10. A spacer member, for use to provide a ventilation space in a roof structure, of rectangular form having at the shorter edges outwardly extending marginal portions or regions coplanar with each other and lying in a plane parallel to but spaced from another coplanar region defined by the member.

11. A spacer member for use in a roof structure, of tray-like rectangular form having raised walls which extend only from the shorter edges and possess outwardly extending coplanar margins.

12. A spacer member as claimed in Claim 11 in which the tray-like member is formed as a wire framework.

13. A spacer member as claimed in Claim 12 formed as a wire grid, the end of the longer members of which extend upwards at right angles to the plane of the grid and then outwardly parallel to the plane of the grid.

14. A spacer member as claimed in Claim 13 in which the outwardly extending portions of the longer grid members are finally downwardly directed to serve as fixing means.