GB2154624A - Exterior thermal insulation for roofs - Google Patents

Abstract

The insulation for a roof (1) with a substantially plane, tight, water- impermeable membrane (2), comprises blocks (3) of a foamed or expanded plastics material placed in close relationship and a layer of a ballast on top of the blocks (3). In order to improve the insulating properties for a given specific weight of insulating material per unit of area, the ballast consists of slabs (4) of mineral wool with fibres bonded at their intersections by means of a bonding agent. <IMAGE>

Description

SPECIFICATION Exterior thermal insulation for roofs This invention relates to an exterior thermal insulation for roofs and of the kind having a substantially plane, tight, water-impermeable membrane and comprising blocks of foamed or expanded plastics material and a layer of ballast on top of the blocks.

Usually, an exterior or reverse insulation of roofs is provided with a layer of pebbles or fine shingle on top of the insulating blocks as ballast. This ballast layer serves two purposes, namely firstly to prevent a vacuum above the roof from lifting off the blocks and secondly to reduce the eroding effect from sunlight on the plastics material of the blocks. The ballast layer does not contribute to the thermal insulation.

The present invention aims to provide a roof insulation of the above kind in which the ballast layer besides its known functions also contributes substantially to the thermal insulation of the roof.

According to the invention, there is provided exterior thermal insulation for roofs with a substantially plane, tight, water-impermeable membrane and comprising blocks of foamed or expanded plastics material and a layer of ballast on top of the blocks, wherein the layer of ballast comprises slabs consisting of mineral wool with fibres, which in at least some of their intersections are bonded by means of a bonding agent.

Slabs of mineral wool are able to equalize pressure differences due to their fibre structure. The mineral wool will therefore act as ballast and add weight to the blocks of plastic material beneath thus preventing them from being lifted in case of a vacuum present on top of the roof. The bonded mineral wool is resistant to weathering and is not decomposed by sunlight, and it is therefore fulfills the usual requirements of a ballast layer. In reality the mineral wool could be used along as thermal insulation in a reverse roof insulation, but its insulating properties are reduced by 25-40% owing to the fibre structure which is open to diffusion.The combination of mineral wool and diffusion-tight foamed or expanded plastics material provides a susbstantial reduction of the diffusion losses in the mineral wool, which then results in insulating properties close to the theoretical value.

Preferably, the mineral wool slabs are glued to the blocks of foamed or expanded plastics material and have substantially the same length and width.

This arrangement simplifies the handling during construction and if the blocks are to be removed for example during inspection of the water-impermeable membrane.

The invention will now be further described, by way of example, with reference to the drawing which shows a section through an exterior thermal insulation according to one embodiment of the invention.

On a load carrying structure 1, for example a concrete deck or roof, a water-impermeable mem brane 2, for example a roofing felt, has been laid out. This structure is by no means limiting the invention, and the above examples are just conventional construction materials in the building industry. There is no restriction to the type of the structure 1 or the water-impermeable membrane 2 apart from their ability to carry normal loads and water-tightness. Upon the structure 1 and the membrane 2 a thermal insulation block 3 is placed consisting of foamed or expanded plastics material. This layer possesses a high degree of impermeability to water vapour and it is not hygroscopic. Suitable materials are foamed polyurethane with closed cells or possibly a compressed granulate of expanded polystyrene.In order to prevent a vacuum above the structure from lifting off the foamed blocks 3, a ballast layer with pressureequalizing properties is provided on the blocks. According to the invention, this layer consists of slabs 4 of mineral wool with fibres that are bonded at their intersections by means of a bonding agent.

It is preferred that a mineral wool of sufficient mechanical strength for carrying a person walking in soft shoes thereon, be used. This requirement is met by a mineral wool with a specific vieight of 150kg/m3, which will provide a ballasting of 20keg.' m3 by means of a slab of 135mm thickness. The mineral wool protects the foamed plastics insulation against sunlight, while the foamed plastics insulation protects the mineral wool against vapourdiffusion, whereby both insulating materials will have approximately the theoretical insulating capacity in practice.

It is possible to lay out the two layers of insulating material with unaligned joints, but an inspection of the watertight membrane 2 is simpler, if the joints in the two layers are mutually in line, and especially if the mineral wool and the foamed plastic are glued together in a double-layer block.

1. Exterior thermal insulation for roofs with a substantially plane, tight, water-impermeabte membrane and comprising blocks of foamed or ?X- panded plastics material and a layer of ballast on top of the blocks, wherein the layer of ballast comprises slabs consisting of mineral wool with fibres, which in at least some of their intersections are bonded by means of a bonding agent.

2. Exterior thermal insulation for roofs according to claim 1, wherein the mineral wool slabs are glued to the blocks of foamed or expanded plastics material and have substantially the same length and width.

3. Exterior thermal insulation for roofs substantially as described herein with reference to the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Exterior thermal insulation for roofs This invention relates to an exterior thermal insulation for roofs and of the kind having a substantially plane, tight, water-impermeable membrane and comprising blocks of foamed or expanded plastics material and a layer of ballast on top of the blocks. Usually, an exterior or reverse insulation of roofs is provided with a layer of pebbles or fine shingle on top of the insulating blocks as ballast. This ballast layer serves two purposes, namely firstly to prevent a vacuum above the roof from lifting off the blocks and secondly to reduce the eroding effect from sunlight on the plastics material of the blocks. The ballast layer does not contribute to the thermal insulation. The present invention aims to provide a roof insulation of the above kind in which the ballast layer besides its known functions also contributes substantially to the thermal insulation of the roof. According to the invention, there is provided exterior thermal insulation for roofs with a substantially plane, tight, water-impermeable membrane and comprising blocks of foamed or expanded plastics material and a layer of ballast on top of the blocks, wherein the layer of ballast comprises slabs consisting of mineral wool with fibres, which in at least some of their intersections are bonded by means of a bonding agent. Slabs of mineral wool are able to equalize pressure differences due to their fibre structure. The mineral wool will therefore act as ballast and add weight to the blocks of plastic material beneath thus preventing them from being lifted in case of a vacuum present on top of the roof. The bonded mineral wool is resistant to weathering and is not decomposed by sunlight, and it is therefore fulfills the usual requirements of a ballast layer. In reality the mineral wool could be used along as thermal insulation in a reverse roof insulation, but its insulating properties are reduced by 25-40% owing to the fibre structure which is open to diffusion.The combination of mineral wool and diffusion-tight foamed or expanded plastics material provides a susbstantial reduction of the diffusion losses in the mineral wool, which then results in insulating properties close to the theoretical value. Preferably, the mineral wool slabs are glued to the blocks of foamed or expanded plastics material and have substantially the same length and width. This arrangement simplifies the handling during construction and if the blocks are to be removed for example during inspection of the water-impermeable membrane. The invention will now be further described, by way of example, with reference to the drawing which shows a section through an exterior thermal insulation according to one embodiment of the invention. On a load carrying structure 1, for example a concrete deck or roof, a water-impermeable mem brane 2, for example a roofing felt, has been laid out. This structure is by no means limiting the invention, and the above examples are just conventional construction materials in the building industry. There is no restriction to the type of the structure 1 or the water-impermeable membrane 2 apart from their ability to carry normal loads and water-tightness. Upon the structure 1 and the membrane 2 a thermal insulation block 3 is placed consisting of foamed or expanded plastics material. This layer possesses a high degree of impermeability to water vapour and it is not hygroscopic. Suitable materials are foamed polyurethane with closed cells or possibly a compressed granulate of expanded polystyrene.In order to prevent a vacuum above the structure from lifting off the foamed blocks 3, a ballast layer with pressureequalizing properties is provided on the blocks. According to the invention, this layer consists of slabs 4 of mineral wool with fibres that are bonded at their intersections by means of a bonding agent. It is preferred that a mineral wool of sufficient mechanical strength for carrying a person walking in soft shoes thereon, be used. This requirement is met by a mineral wool with a specific vieight of 150kg/m3, which will provide a ballasting of 20keg.' m3 by means of a slab of 135mm thickness. The mineral wool protects the foamed plastics insulation against sunlight, while the foamed plastics insulation protects the mineral wool against vapourdiffusion, whereby both insulating materials will have approximately the theoretical insulating capacity in practice. It is possible to lay out the two layers of insulating material with unaligned joints, but an inspection of the watertight membrane 2 is simpler, if the joints in the two layers are mutually in line, and especially if the mineral wool and the foamed plastic are glued together in a double-layer block. CLAIMS

1. Exterior thermal insulation for roofs with a substantially plane, tight, water-impermeabte membrane and comprising blocks of foamed or ?X- panded plastics material and a layer of ballast on top of the blocks, wherein the layer of ballast comprises slabs consisting of mineral wool with fibres, which in at least some of their intersections are bonded by means of a bonding agent.

2. Exterior thermal insulation for roofs according to claim 1, wherein the mineral wool slabs are glued to the blocks of foamed or expanded plastics material and have substantially the same length and width.

3. Exterior thermal insulation for roofs substantially as described herein with reference to the drawings.