The present invention is concerned with minimising heat transfer via roofing systems from and to the interior of buildings.

Typically, roof cladding sheets are roll-formed from painted or unpainted steel strip and include one or more parallel ribs, pan sections, and side edge formations that enable the sheets to be positioned side by side in overlapping relationship.

It is known to secure cladding sheets to an underlying roof support structure, such as roof purlins, by fastening the sheets directly to the underlying structure using fasteners, such as roofing nails, that pierce the sheets and penetrate the underlying structure.

It is also known to secure cladding sheets to an underlying structure by using clip assemblies that include clips that are secured to the structure by fasteners and are formed to extend into the ribs and engage re-entrant portions of the ribs and thereby retain the sheets to the clips. These clip assemblies are often preferred over nails because they enable concealed fixing of cladding sheets to an underlying structure.

There are a number of known concealed fixing retaining clips. The clips include a so-called WG clip disclosed in Australian patent 457099 in the name of Comalco Limited, a clip disclosed in UK patent application in the name of Stramit Industries Limited, and a clip

disclosed in Australian patent 685102 and other Australian patents and patent applications in the name of Stramit Corporation.

In warm climates there is considerable cost in keeping the inside of buildings cool compared to the outside.

Many modern buildings are air-conditioned and the cost of air-conditioning is an important cost consideration.

In cool climates there is considerable cost in keeping the inside of buildings warm compared to the outside. Many modern buildings are heated and the cost of heating is an important cost consideration.

By far the largest amount of heat transfer from and to the interior of a building is through the roofing system of the building. Thus, a roofing system that minimises heat transfer is one option for reducing air- conditioning and heating costs.

The present invention is concerned with providing a roofing system for a building that minimises heat transfer via the roofing system from and to the interior of the building.

The present invention is also concerned with providing a clip assembly of a roofing system for a building that minimises heat transfer via the clip assembly from and to the interior of the building.

The present invention provides a roofing system for a building that includes: a plurality of roof cladding sheets in overlapping relationship, each cladding sheet having at least one rib and pans ; and a plurality of

concealed clip assemblies that retain the cladding sheets to an underlying roof support structure, each clip assembly including: (a) an elongate strap member ; (b) a plurality of clips mounted to an upper surface of the strap member and engaging re-entrant portions of the ribs of one or more sheets ; and (c) a plurality of spacer members made of thermally insulating material mounted to a lower surface of the strap member in alignment with the clips and spacing the clips above the underlying structure.

The present invention also provides a roofing system for a building that includes: a plurality of roof cladding sheets in overlapping relationship, each cladding sheet having at least one rib and pans; and a plurality of concealed clip assemblies that retain the cladding sheets to an underlying roof support structure, each clip assembly including: (a) a clip that engages re-entrant portions of the rib ; and (b) a spacer member that spaces the clip above the underlying structure.

Spacing the clips above the underlying structure by means of the thermally insulating spacer members prevents direct contact between the clips and the structure and this of itself increases the thermal resistance of the clip assembly per se and the roofing system as a whole.

Spacing the clips above the underlying structure also has the effect of spacing the cladding sheets further above the underlying structure than would normally be the case. The additional space may be filled with thermal insulation material or left as an air gap. In either case, there is a contribution to the thermal resistance of the roofing system.

Preferably the roofing system includes: (a) a layer of thermal insulation material, such as batts of fibreglass insulation, on the underlying structure ; and (b) an air gap between the layer and the cladding sheets.

The spacer member may be any suitable member for supporting the clip above the underlying structure.

Suitable members include members that have C-shaped and Z- shaped transverse sections and are formed by folding metal sheet material.

Preferably the spacer members are blocks of thermally insulating material.

Preferably the thermally insulating material has a high density to provide support against downward loads.

Preferably the height of the spacer members is at least 3 cm.

More preferably the height of the spacer member is at least 4 cm.

Preferably the roofing system includes a

plurality of fastening assemblies that secure the clip assemblies to the underlying structure.

Preferably each fastening assembly includes a fastener, such as a screw, that has a head and a shank that extends through aligned openings in each of the clip, the strap member, and the spacer member of one of the clip assemblies and into the underlying structure.

Preferably the fastener has a small diameter shank.

Preferably the clip has a base and the clip opening is in the base and the fastening assembly includes a washer formed from a thermally insulating material that is positioned between the fastener head and the base of the clip.

Preferably the washer includes a downwardly depending sleeve that extends into the opening in the base of the clip and separates the fastener shank from the base.

Preferably each clip includes a pair of cladding sheet retaining members that extend upwardly from opposite sides of the base.

Preferably each cladding sheet retaining member includes an outwardly-turned top flange that has a central upper section and two outer sections that extend downwardly from opposite ends of the upper section, whereby the outer sections of the top flanges of the retaining members contact the re-entrant portions of the rib of the cladding sheet and secure the sheet to the clip.

Preferably each cladding sheet retaining member

includes a main wall element that extends upwardly from the base and terminates in the top flange.

Preferably the main wall elements extend transversely to a longitudinal direction of the rib.

Preferably the base and the retaining members define a generally U-shape.

Preferably each outer section of the flanges of the retaining members has a free edge that contacts one of the re-entrant portions of the rib and secures the cladding sheet to the clip.

Preferably each outer section of the flanges of the retaining members extends downwardly and outwardly beyond an upper section of one of the main wall elements and the outer section includes a downwardly facing shoulder that connects the outer section to the main wall element.

Preferably each cladding sheet includes a plurality of ribs separated by pans.

The present invention also provides a clip assembly of a roofing system for a building as described above, which clip assembly includes: (a) an elongate strap member having an upper surface and a lower surface, the upper surfaces including a plurality of platforms for clips for engaging cladding sheets ; and (b) a plurality of spacer members made of thermally insulating material mounted to the lower surface of the strap member at locations that are aligned with the clip

platforms on the upper surface.

According to the present invention there is also provided a clip assembly for a roofing system as described in the preceding paragraph and a plurality of clips for engaging cladding sheets mounted on the platforms.

The present invention is described further by way of example with reference to the accompanying drawings, of which: Figure 1 is a partially cross-sectional side elevation of part of one embodiment of a roofing system in accordance with one embodiment of the present invention ; Figure 2 is a side elevation of an embodiment of a clip assembly of a roof assembly of the type shown in Figure 1 ; Figure 3 is a top plan view of the clip assembly shown in Figure 2 ; Figure 4 is an exploded section of the part of the clip assembly of the roofing system shown in Figure 1 ; Figure 5 is a perspective view of the cladding sheet of the roofing system shown in Figure 1 ; Figure 6 is an end elevation of the cladding sheet shown in Figure 5 ; and Figure 7 is an end elevation of the central rib of the cladding sheet shown in Figures 5 and 6.

The roofing system shown in the figures includes: (a) a plurality of roof cladding sheets 7 (only

one of which is shown in the Figure 1) ; (b) a plurality of concealed fixing clip assemblies (only one of which is shown in Figures 1 to 4) retaining the cladding sheets to roof support purlins 5 ; and (c) a layer of fibreglass insulation material 57 (Figure 1 only) occupying part of the roof cavity defined by the cladding sheets 7 and the roof purlins 5.

Each concealed fixing clip assembly includes: (a) an elongate strap 71 ; (b) a plurality of clips 3 mounted to an upper surface of the strap 71 and engaging the cladding sheets 7 ; and (c) spacer members in the form of high density polystyrene blocks 55 mounted to a lower surface of the strap 71 and spacing the clips 3 above the purlins 5.

The straps 71 are a convenient means of mounting a plurality of the clips 3 and the spacer members 55 and thereafter locating the clips 3 at required spacings for engaging the cladding sheets.

Each strap 71 is formed from sheet steel and includes a flat central section 77 and downwardly folded sides 79. Each strap 71 includes a series of spaced apart mounting platforms 81 for the clips 3. The mounting platforms 81 are flattened sections on which the clips 3 can be mounted.

The high density polystyrene block spacer members 55 are mounted to the lower surface of the straps 71, for example by means of adhesive or adhesive-backed tape. The spacer members 55 are positioned to be aligned with the clips 3.

The spacer members 55 provide support for the cladding sheets 7 against downward loads and have substantially the same insulating properties as the surrounding fibreglass insulation material. Thus, the spacer members 55 provide resistance to heat transfer.

In addition, the spacer members 55 space the cladding sheets 7 above the layer of fibreglass insulation material 57 so that the roofing system further includes an air gap 59 (Figure 1 only) in the roof cavity between the cladding sheets 7 and the fibreglass insulation material, and thus further improves the resistance to heat transfer provided by the roofing system.

The roof system also includes fastening assemblies securing the clip assemblies to the purlins 5.

Each fastening assembly includes a fastener in the form of a small diameter screw 51 that secures a clip 3 to a purlin 5. The shank of the screw 51 extends through the clip 3, and then successively through the underlying mounting platform of the strap 71 and the aligned spacer member 55, and then into the purlin 5.

Each fastening assembly also includes a washer 65 that is formed from a thermally insulating material, such as rubber. The washer 65 prevents direct contact between the clip 3 and the head of the screw 51.

In addition, the washer 65 includes a downwardly extending sleeve 69 that extends into the opening 63 in

the clip 3 and separates the shank of the screw 51 from the clip 3.

The applicant has found in experimental work that the combination of the above-described features of the spacer members 55, the air gap 59, the small diameter screws 51, and the washers 65 formed from thermally insulating material reduces heat transfer from the cladding sheets 7 to the purlins 5 and thereby to the interior of a building and vice versa.

Each cladding sheet 7 is roll-formed from sheet steel and includes a leading edge 8, a trailing edge 10, a central lengthwise extending rib, generally identified by the numeral 11, and pair of lengthwise extending pans 13 on opposite sides of the rib 11.

The cladding sheet 7 may be of any suitable length and width and may include any suitable number of ribs 11 separated by pans 3.

The rib 11 of the cladding sheet 7 includes an upper clip retaining section, generally identified by the numeral 15, and two downwardly extending shoulders 17 that interconnect the upper clip retaining section 15 and the pans 13.

With particular reference to Figure 7, the upper clip retaining section 15 includes a flat upper section 19 that separates two sides, generally identified by the numeral 21. Each side 21 includes a first section 41 that extends outwardly and downwardly from the upper section 19, a second section 43 that extends downwardly and inwardly from the lower edge of the first section 41, and a third section 45 that extends downwardly and outwardly from the second section 43 and merges with the shoulder 17.

The second sections 43 of each upper retaining clip section 15 define opposed re-entrant portions of the rib 13 and are hereinafter referred to as"re-entrant portions 43".

Each shoulder 17 includes a first part 17a that extends upwardly from the pan 13 and a second section 17b that extends from the first section 17a to the clip retaining section 15. The first part 17a has a steeper slope than the second part 17b. In overall terms, the shoulders 17 are a significant component of the total size of the rib 11.

The leading and trailing edges 8,10 of the cladding sheet 7 are formed as partially-completed ribs in order to facilitate interlocking of successive cladding sheets. These partially-completed ribs are hereinafter referred to as"leading edge formations 8"and"trailing edge formations 10".

Each clip 3 is formed by folding a flat metal blank into the configuration shown the Figures.

With particular reference to Figure 4, each clip 3 includes: (a) a flat base 21 ; and (b) a pair of retaining members, generally identified by the numeral 23, extending upwardly on opposite sides of the base 21, whereby the base 21 and the retaining members 23 form a generally U-shaped member.

Each retaining member 23 includes an upstanding

main wall element 61 that terminates in an outwardly extending top flange 25.

Each top flange 25 includes a central upper section 27 and two opposed sections 29 that slope downwardly from the upper section 27.

The downwardly sloping sections 29 terminate in lower edges 31.

The downwardly sloping sections 29 extend outwardly and downwardly beyond the upper sections of the main wall elements 61. The sections 29 include downwardly facing shoulders 57 that connect the sections 29 to the main wall elements 61.

Each clip 3 also includes an opening 63 to facilitate securing the clip 3 to a purlin 5.

In use, a plurality of the clip assemblies is fastened to purlins 5 at spaced intervals along the length of the purlins 5 using the screws 51 of the fastening assemblies.

Batts of fibreglass insulation material are then positioned on the purlins 5 and arranged to extend beneath the straps 71 to form the layer 57 of insulation material shown in Figure 1.

Thereafter, cladding sheets 7 are successively placed over the purlins 5 in overlapping relationship. The cladding sheets 7 are positioned so that the longitudinal direction of the ribs 11 is perpendicular to the planes of the main wall elements 61 of the clips 3.

The cladding sheets 7 are then progressively engaged with the clips 3 as the sheets are successively

placed over the purlins 5.

This is achieved by successively pressing the leading edge formations 8, the ribs 11, and the trailing edge formations 10 of the sheets 7 onto the clips 3 so that the leading edge formations 8, the ribs 11, and the trailing edge formations 10 deflect outwardly and the top flanges 25 of the clips 3 deflect inwardly.

This movement allows the leading edge formations 8, the ribs 11, and the trailing edge formations 10 to be positioned on the clips 3 with the lower edges 31 and the shoulders 57 of the flanges 25 engaging the re-entrant portions 43 of the ribs 11 so that the cladding sheets 7 are secured to the clips 3.

Many modifications may be made to the preferred embodiment of the roofing system described above without departing from the spirit and scope of the present invention.

In the above-described preferred embodiment of the roofing system there is an air gap 59 in the roof cavity. The present invention is not limited to this arrangement and extends to arrangements in which the air gap is filled with insulation material.