Knauf Insulation has launched the Polyfoam® Slimline System, a protected membrane, flat roof insulation system. The new system features a special separation membrane that successfully reduces the effect of moisture cooling on the roof. It means, as a direct result, that the insulation layer can be reduced in thickness – ‘slimmed’ down – to offer designers a range of benefits including a lighter, less expensive, structure.
For the client, protected membrane roofs mean flexibility of use. A protected membrane roof using high performance extruded polystyrene can be used as a balcony, patio, terrace, roof garden or even rooftop car park. For the designer, although these opportunities are strong reasons to use the method, another major influencing factor is a technical advantage. The layer of insulation protects the roof’s waterproof membrane from temperature variations, mechanical damage and UV degradation – all factors that threaten the roof’s watertight integrity.
The theory behind the Polyfoam® Slimline System is simple. On conventional protected membrane roofs, water is free to seep past the insulation to drain away on the waterproof layer beneath it. As it does so, heat washes away with it and this directly affects the specification of the insulation layer as designers have to apply a ‘Rainwater Cooling Penalty’ to compensate. And it’s not just the insulation that may be affected; there can be a significant knock-on effect. For example, as the amount of ballast needed above the insulation is linked to its thickness, the equation can become: thicker insulation = thicker ballast = more weight = a stronger structure = higher costs! Clearly, the answer is to reduce the compensation factor by encouraging more water to drain off the roof above the insulation. The special separation membrane used in the Polyfoam® Slimline System successfully achieves just that.
The system has two key components: the separation membrane and the insulation material. The all-important membrane is a polyethylene, non-woven geotextile that acts to resist the passage of water but remains vapour permeable. Supplied in 100m long, 1.5m wide rolls, it’s laid loose on top of Polyfoam® Roofboard, Knauf Insulation’s high-performance, extruded polystyrene insulation board which forms the system’s insulation component.
Independent trials of the system found that the Polyfoam® Slimline System does significantly reduce the impact of the Rainwater Cooling Penalty. As an example: when calculated using the new ‘fx’ methodology in BS EN6946, a typical 150mm thick concrete roof will achieve the Elemental U-value of 0.25 W/m2K required by ‘Part L’ of the Building Regulations with a layer of insulation just 120mm thick. That’s great news at it means that the Polyfoam® Slimline System could save pounds and dramatically reduce the ‘waste-line’!
Using the Polyfoam® Slimline System makes the option of a protected membrane roof an even more exciting design choice. The reduction of the thickness of the insulation can make the whole construction lighter and less expensive making the concept of a protected membrane roof a much more attractive cost proposition both initially and on a whole-life cost analysis basis. And this, in turn, opens the door for greater design flexibility, better use of roofing areas and creative opportunities for ‘sexy’ applications such as green roofs, patio and terrace areas.
For a free brochure about the Polyfoam® Slimline System, please call 08700 668 660 or e-mail email@example.com quoting ID: PR12604.
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Knauf Insulation is a multinational manufacturer of insulation products with operations in the UK, Europe and the USA and an annual sales revenue of approximately £500 million. Knauf Insulation Limited is insulation market leader in the UK, has four manufacturing plants employing around 500 people and an annual sales revenue of approximately £90 million. The company manufactures a wide range of insulation products to meet the growing demand for energy efficiency and acoustic performance in both new and existing homes and commercial buildings. Products include glass mineral wool, rock mineral wool, expanded polystyrene and extruded polystyrene marketed under the trademarks Crown®, Rocksilk® and Polyfoam®. Knauf Insulation is committed to the environment: its products use recycled and naturally abundant materials.