A Knauf Insulation roofing system has been specified by architects, the Stanley Bragg Partnership Ltd, for use on a new primary school in Great Dunmow, Essex. The system uses Polyfoam® Pitched Roofboard, Polyfoam® Raftersqueeze and Knauf Breatheline to form an insulated pitched roof. Roofing contractors, Lodge Roofing, were impressed with the system, giving it top marks for both ease and speed of installation.
Great Dunmow’s new primary school will be the seat of learning for around 400 pupils when it opens its doors for the new school year in September 2005. The 14 classrooms, two halls, library, kitchen, offices, toilets and ancillary rooms are laid out in two blocks linked to form an L-shaped building. Designed by Colchester architects, the Stanley Bragg Partnership Ltd, the school is being built by Haymills (Contractors) Ltd for the Governors of Great Dunmow Primary School.
Around 2,300m2 of the roof is of insulated, pitched roof design using Glulam trusses and timber rafters finished with an outer skin of natural Spanish slate. Being an insulated roof means installing insulation at rafter level and, to meet the Building Regulation’s Elemental U-value of 0.20W/m2K, the architects chose Knauf Insulation’s Polyfoam® Pitched Roof Insulation System.
The system uses three Knauf Insulation products. Two layers of 50mm thick Polyfoam® Raftersqueeze were specified between the rafters with a single layer of 60mm thick Polyfoam® Pitched Roofboard laid over them. Knauf Breatheline was used to provide an underlay and vapour permeable breather membrane between the roofboard and slates.
Polyfoam® Raftersqueeze is a rigid board designed to fit between rafters irrespective of their designed or actual spacing. The secret of its success lies in the deep grooves formed parallel to its long edges which allow a degree of lateral compression. Having been cut roughly to size, the board can be easily push-fitted – ‘squeezed’ – between the rafters, giving immediate retention and overcoming irregularities in the timber.
Polyfoam® Pitched Roofboard was specifically designed for use in pitched roof construction. Its strength, combined with rebated, shiplap edges on all four sides, means that joints between individual boards do not have to coincide with supporting timbers. This makes it ideal for over-rafter, pitched roof insulation as reducing the amount of cutting makes installation very quick: the boards are simply laid across the rafters and secured with spiral-type fixings.
Phil Lodge, Managing Director of Newmarket-based roofing contractor, Lodge Roofing, was impressed with the system, saying, “We hadn’t used Raftersqueeze before and were intrigued, and a little sceptical, about the concept. When it arrived on site, I immediately took a piece up on the roof, trimmed it roughly to size and stuffed it between two rafters to see if it worked. It did – in fact it was quite a job to get it out again! We’re very impressed with it and would certainly use it again as it really did speed up fixing the insulation between the rafters.”
Polyfoam® Insulation products are made from high performance, 100% ozone friendly, extruded polystyrene. The rigid boards have excellent insulation properties and a high compressive strength yet remain lightweight and both easy and quick to cut and install. Polyfoam® Raftersqueeze has a thermal conductivity of 0.030W/mK and is available in three thicknesses – 50mm, 65mm and 75mm – and comes as a standard size board of 1200mm x 600mm. Polyfoam® Pitched Roofboard has a thermal conductivity of 0.029W/mK and is available in a range of thicknesses from 35mm to 75mm and in a standard size of 1250mm x 600mm.
Knauf Breatheline is a strong, lightweight polypropylene non-woven fabric with excellent tear and drape characteristics. Classified as a breather membrane, it offers little resistance to the passage of water vapour, has been independently tested and holds three BBA Certificates together with their IAB equivalents.
More information about Knauf Insulation’s products can be found at www.knaufinsulation.co.uk or by calling 08700 668 660. Please quote PR 310 05.
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Knauf Insulation is a multinational manufacturer of insulation products with operations in the UK, Europe and the USA. Knauf Insulation Limited is insulation market leader in the UK and employs around 500 people at its four manufacturing plants at St. Helens, Queensferry, Cwmbran and Hartlepool. 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.