GB2503891A

GB2503891A - Inverted roof systems

Info

Publication number: GB2503891A
Application number: GB201212226A
Authority: GB
Inventors: Conrad Stephen Newberry
Original assignee: JABLITE Ltd
Current assignee: JABLITE Ltd
Priority date: 2012-07-10
Filing date: 2012-07-10
Publication date: 2014-01-15
Anticipated expiration: 2032-07-10
Also published as: GB2503891B; GB201212226D0

Abstract

An insulation board for an inverted roof system, where the insulation is above the waterproofing layer, comprises a first face, a second face opposite the first face, a first edge between the first and second faces, and a second edge between the first and second faces, the second edge being opposite the first edge. The distance between the first and second faces at the first edge is less than the distance between the first and second faces at the second edge, so that the board is tapered from the first edge to the second edge. The boards when laid on a flat substrate create a sloped upper surface.

Description

Inverted roof systems

Field of the Invention

The present invention concerns inverted root systems.

More particularly, but not exclusively, the invention concerns insulation boards for use in inverted roof systems, and inverted roof systems incorporating such insulation boards.

Background of the Invention

Inverted roofs, also known as protected membrane roofs, are roof systems in which the main thermal insulating layer is positioned above the waterproof layer. A known inverted roof system 1 is shown in Figure 1. The inverted roof system 1 comprises a roof deck 2, which is the upper part of the building upon which the inverted roof is oonstructed.

On top of the deck 2 is a waterproof membrane 3. An insulating layer 4 comprised of multiple interlocking insulation boards is positioned on top of the waterproof membrane 3, and is overlaid by a water-flow reducing protective layer 5. A ballast layer 6, for example of gravel, covers the protective layer 5.

Thus, the insulated layer 4 is positioned above the waterproof membrane 3, making the roof system 1 an inverted roof. The ballast layer 6 protects and keeps in place the lower layers of the roof system 1, while the protective layer 5 helps prevent rainfall passing through in liquid or vapour form.

Other known inverted roof systems may have as the uppermost layer a layer of pavinq slabs or green roofs, for

example.

Inverted roof systems have many advantages over conventional roof systems. The presence of the insulating layer above the waterproofing membrane has several advantages: damage to the waterproofing membrane by variations in temperature is reduced, it prevents UV degradation, the waterproofing layer can be easily inspected and tested during construction of the roof, and the building can be weatherproofed more quickly, allowing interior work to begin earlier.

UK Building Regulations and Codes of Practices and European statutory and non statutory requirements (for example) recommend that inverted roofs should have an adequate fall (i.e. be sufficiently sloped) to prevent excess water, for example rainwater, building up ("ponding") above the waterproof membrane and/or thermal insulation layer. However, creating a slope on an inverted roof system can be costly and time consuming. Consequently, it is most common for inverted roof systems to be "zero" flat roof (i.e. to have no slope at all), despite the disadvantages this presents.

A known solution is to provide a sloped surface to the roof deck by installing a sloped screed surface on top of the structural roof deck. Screeds are typically supplied semi-dry (i.e. containing free water, not required for cement hydration, which needs to evaporate from the concrete) . Semi-dry screeds typically take 28 days to achieve compressive strength. Further, if rainfall occurs prior to the waterproofing layer being applied, the final screed layer can contain a high level of free water, while the top surface of the screed may appear to be dry. The high heat from application of "hot" waterproofing systems to screeds can then cause the excess free water to be drawn up to create suction spots under the waterproofing layer. Over time, board movement (from thermal expansion and contraction) , foot and plant traffic, and fines from gravel may cause further weakness and potentially (over the long term) membrane issues.

Furthermore, it is common for flat roof decks to be designed to deflect water to a rain water outlet, and unwanted hollows and back-fall areas in the roof can reduce the effectiveness of this.

The present invention seeks to provide a sloped inverted roof system that mitigates the above-mentioned problems. Alternatively and/or additionally, the present invention seeks to provide improved insulation boards for use in an inverted roof system.

Summary of the Invention

In accordance with a first aspect of the present invention there is provided an insulation board for an inverted roof system comprising: a first face; a second face opposite the first face; a first edge between the first and second faces; a second edge between the first and second faces, the second edge being opposite the first edge; wherein the distance between the first and second faces at the first edge is less than the distance between the first and second faces at the second edge, so that the board is tapered from the first edge to the second edge.

The insulating board thus, when positioned on a flat surface, provides a slope on its upper surface. Using a plurality of such insulating boards of suitable thicknesses (i.e. the distance between the first and second faces), an insulating layer for an inverted roof oan easily be provided that has an overall slope or slopes. Thus, the use of the insulating board allows a sloped inverted roof to be easily provided, with the slope being provided by the insulating layer, without requiring more complex and/or disadvantageous means of providing a slope to the inverted roof being required.

Preferably, the board is made of an insulating polymer.

Advantageously, the board is made of expanded polystyrene.

The panel may ideally be shape moulded or profile cut from a block of expanded polystyrene. Alternatively, the panel may be made of any material from the group of extruded polystyrene, polyurethane or polyisocyanurate. The material may have a thermal conductivity of O.050W/mK or below. The material may have a thermal conductivity of 0.040W/mK or below. Preferably, the material has a thermal conductivity of 0.038W/mK or below. Advantageously, the material has a thermal conductivity of 0.033W/mK or below. The material may have a thermal conductivity of O.O2lW/mK or below.

Advantageously, the board is made of low-water absorption expanded polystyrene. Preferably, the board is made from beads of low-water absorption expanded polystyrene for use in inverted roofs.

Preferably, the board is tapered or wedge shaped. More preferably, the upper surface of the board is flat, in the sense that any cross-section through the upper surface gives a straight line. (The upper surface will of course still provide a slope relative to the lower surface of the board.) Advantageously, at least one edge of the board comprises a joint. This allows the boards to be securely positioned together, and prevents cold bridges forming. The joint may comprise an extended portion for positioning with a corresponding recess in an adjacent insulating board.

Alternatively, the joint comprises a recess for receiving an extended portion of an adjacent insulating board.

In accordance with a second aspect of the present invention there is provided an inverted roof system comprising: a water-resistant layer; an insulating layer above the water-resistant layer; wherein the insulating layer comprises a plurality of insulating boards as claimed in any preceding claims.

Advantageously, the insulating layer further comprises a plurality of insulating boards of uniform thickness. The insulating boards of uniform thickness can be arranged in a layer or layers beneath an upper layer of sloped boards. In this way, sloped inverted roofs of large area can be provided without sloped insulating boards of large thickness being required in order to provide the necessary thickness of the insulating layer.

Advantageously, the insulating layer is arranged so that water falling upon the roof is directed off at least one edge of roof. Alternatively or additionally, the inverted roof system nay further comprise a rainwater outlet, and the insulating layer arranged so that water falling upon at least one area of the roof is directed towards the rainwater outlet.

Preferably, the inverted roof system further comprises a ballast layer above the insulating layer. Advantageously, the inverted roof system further comprises a protective layer above the insulating layer. The protective layer helps prevent rainwater flowing through the insulation joints and reaching the waterproofing layer below and creating a cooling effect. In a preferred embodiment, the protective layer prevent 100% of rainwater. The protective layer also prevents damage to the insulating layer and other layers due to particles from the ballast layer (amongst other things) . The protective layer may be impermeable to water. The protective layer may be impermeable to liquid water but permeable to water vapour. In this way, the protective layer can help prevent the lower layers of the inverted roof system being damaged by water such as rainwater, by reducing the flow of water to lower layers (in other words, the layer is a water-flow reducing layer) while still allowing any moisture in the lower layers to evaporate.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only with reference to the accompanying figures of which: Figure 1 is a cross-section of a known inverted roof system; Figure 2 is a cross-section of an inverted roof tapered board insulation system in accordance with a first embodiment of the invention; Figure 3 is a top view of an insulation board from the inverted roof tapered board insulation system of Figure 2; Figures 4a and 4b are cross-sections of insulation boards from the inverted roof tapered board insulation system of Figure 2; and Figure 5 is a cross-section of the insulating layer of the inverted roof tapered board insulation system of Figure 2.

Detailed Description

An inverted roof system in accordance with a first embodiment of the invention is now described with reference to Figures 2 to 5.

As with the known inverted roof system of Figure 1, the inverted roof system 100 of the present embodiment comprises a roof deck 2 with a waterproofing membrane 3. On top of the waterproof membrane is an insulating layer 110 comprising insulating boards, as described in more detail below. The insulating layer 110 is overlaid with a prctective layer 5, which is in turn covered by a ballast layer 6, again as with the known inverted roof system of Figure 1.

An insulation board 120 from the insulating layer 110 is shown in Figure 3. The insulating board 120 is formed of rigid, closed cell, shape moulded expanded polystyrene foam insulation, with a water absorption of less than or equal to 2.0% (in accordance with British Standard EN 12087). The insulation board has on the lower part of adjacent edges 121 and 122 an extended portion, and on the lower part of opposing adjacent edges 123 and 124 a corresponding recess.

Each edge 121 to 124 is 1200mm in length.

A cross-section through line A-A in Figure 3 of the insulation board 120 is shown in Figure 4a; the cross-section is identical for any line through the insulation board 120 parallel with A-A. As can be seen, the height of the extended portion of edge 121, and the corresponding recess of edge 123, is 60mm. The portion of the edge 121 above the extended portion is 10mm, giving the edge 121 a total height of 70mm. In contrast, the portion of the edge 123 above the recess is 25mm, giving the edge 123 a total height of 85mm. Therefore, it oan be seen that the insulating board is tapered or wedge-shaped, and when placed on a flat surface the upper face of the insulating board 120 will have a slope or fall of 1:80 from the higher edge 123 to the lower edge 121.

The insulating board 120 shown in Figure 4a is of the minimum thickness used in the insulating layer 110. A cross-section through an insulation board 128 of maximum thickness used in the insulating layer 110 is shown in Figure 4b. The top view of the insulating board 128 is identical to that of the insulating board 120 shown in Figure 3, and again any parallel cross-section through the insulating board 128 is identical. The insulating board 128 has a first edge with an extended portion of height 60mm and a portion above the extended portion of height 130mm, giving a total height of 190mm. The opposite edge 133 has a recess of height 60mm and a portion above the recess of 145mm, giving a total height of 205mm. Therefore, while the overall thickness of the insulating board 128 is greater than that of the insulating board 120 of Figure 4a, the insulating board 128 has the same slope of 1:80 from the higher edge 133 to the lower edge 131.

A cross-section through the insulating layer 110 is shown in Figure 5. The insulating layer 110 comprises a first set of insulating boards 120a to 128a of the type shown in Figures 3, 4a and 4b, with each board (expect the leftmost board 120a) having the extended portion of the lower edge positioned within the corresponding recess of -10 -higher edge of the adjacent board. Further, the height of the higher edge each board is the same as the height of the lower edge of the adjacent board. Thus, the upper surfaces of the boards 120a to 128a provide a continuous flat surface with a slope of 1:80.

The insulating layer further comprises a second set of insulating board 121b to 12gb, similar to the first set of boards 120a to 128a. However, the lower joint edge (the leftmost edge) of the leftmost board l2lb is flat, i.e. it does not comprise an extended portion. The second set of boards 12th to 128b is positioned so that the lower edge of the left-most board 121b of the second set is positioned against the upper part of the rightmost edge of the rightmost board 128a of the first set. Further, a third set of identical insulating boards 150 of uniform height is positioned beneath the second set of boards 121b to 12gb.

The joint edges of the insulating boards 150 have extended portions and recesses similarly to the sloped insulating boards, and again the top view of the insulating boards 150 is identical to that of the insulating board 120 shown in Figure 3. The height of the insulating boards 150 is such that the top of the lower edge of the insulating board 121b meets the top of the higher edge of the insulating board 128a. In practice, this means that the height of the insulating boards 150 is 120mm.

It will be appreciated that the insulating layer is made up of several parallel rows of insulating boards as shown in Figure 5, with the extended portions of the first adjacent sides positioned within the recesses of the second adjacent sides.

-11 -Thus, the parallel rows of the first, second and third sets of insulating boards together provide a solid layer of insulation, with the interlocking extended portions and recesses preventing cold bridging (i.e. areas where the insulation has gaps in it so allowing heat tn be lost more easily) . Further, the solid layer is tapered from the lower edge of the leftmost insulating board l2Oa of the first set with a height of 70mm, to the higher edge of the rightmost insulating board 128b of the second set and rightmost insulating board 150 of the third set, with a combined height of 325mm. In this way, the inverted roof system 100 is provided with a slope of 1:80 by virtue of the tapering of the insulating layer 110.

It will be appreciated that inverted ronfs of larger area could be constructed by placing insulating boards 150 beneath an upper layer of sloped insulating boards to create an overall desired fall.

It will be appreciated that inverted roofs with lower U-values (overall heat transfer coefficients, or heat loss measures) could be constructed by increasing the thickness of the insulation boards 150 beneath an increased thickness upper layer of sloped insulating boards.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. For example, it will be apparent that the invention is egually applicable to boards with different sizes or shapes, and to inverted roofs with different slopes, for example slopes of 1:100, 1:60, -12 - 1:40 or 1:20. Further, the invention is applicable to an inverted roof that tapers towards a corner of the roof (i.e. comprises insulating boards that taper towards a corner) , an inverted roof that tapers towards opposite edges of the rocf from a peak between the edges, or any other suitably sloped construction. Further again, the invention is equally applicable to an inverted roof that tapers towards a point or points within the perimeter of the roof, for example towards the centre of the roof so that rainwater is directed to a rainwater outlet positioned in the centre of the roof.

Further, the invention is applicable to a range of inverted roof U-value reguirements.

Claims

-13 -Cia iris 1. An insulation board for an inverted roof system comprising: a first face; a second face opposite the first face; a first edge between the first and second faces; a second edge between the first and second faces, the second edge being opposite the first edge; wherein the distance between the first and second faces at the first edge is less than the distance between the first and second faces at the second edge, so that the board is tapered from the first edge to the second edge.
2. An insulating board as ciaimed in claim 1, wherein the board is made of an insulating poiymer.
3. An insulating board as claimed in claim 2, wherein the board is made of expanded polystyrene.
4. An insulating board as claimed in claim 3, wherein the board is made of low-water absorption expanded polystyrene.
5. An insulating board as claimed in any preceding claim, wherein the board is shaped in the form of a taper or is wedge shaped.
6. An insulating board as ciaimed in any preceding claim, wherein at least one edge of the board comprises a joint.

-14 -
7. An insulating board as claimed in claim 6, wherein the joint comprises an extended portion for positioning with a corresponding recess in an adjacent insulating board.
8. An insulating board as claimed in claim 6, wherein the joint comprises a recess for receiving an extended portion of an adjacent insulating board.
9. An inverted rcof system comprising: a water-resistant layer; a insulating layer above the water-resistant layer; wherein the Insulating layer comprises a plurality of insulating boards as claimed in any preceding claims.
10. An inverted roof system as claimed in claim 9, wherein the insulating layer further comprises a plurality of insulating boards of uniform thickness.
11. An inverted roof system as claimed in claim 9 or 10, wherein the insulating layer is arranged so that water falling upon the roof is directed off at least one edge of roof.
12. An inverted roof system as claimed in any of claims 9 to 11, further comprising a rainwater outlet, and wherein the insulating layer is arranged so that water falling upon at least one area of the roof is directed towards the rainwater outlet.

-15 -
13. An inverted roof system as claimed in any of claims 9 to 11, further comprising a protective layer above the insulating layer.
14. An inverted roof system as claimed in any of claims 9 to 11, further comprising a ballast layer above the insulating layer.