Knauf Insulation’s latest high-performance product, Crown® Rafter Roll 32, is being used throughout Belturbet Properties’ exclusive, Cornadarragh Forest Park development in County Cavan, Ireland. The design of the luxurious holiday homes called for a warm roof construction with no under rafter insulation. Crown® Rafter Roll 32 was specified as its low thermal conductivity – just 0.032 W/mK – allowed the designers to hit the target U-value of 0.20 W/m²K well within the depth of the rafters. Problem solved!
Belturbet Properties’ prestigious Cornadarragh Forest Park lies on the banks of the River Erne, two kilometres from Belturbet in County Cavan, Ireland’s ‘Lake Country’ and offers holiday-makers immediate access to the area’s amenities. Set in a wooded park, the development comprises a U-shaped courtyard surrounded by 18, individually designed homes with a further 23, 2-bedroom detached lodges and 15, 3 and 4-bedroom family homes scattered throughout the park. In keeping with the setting, the lodges and family homes follow a Scandinavian log-cabin style and are of timber frame construction with coloured, concrete tile roofs. All have been specified to an exceptionally high standard and designed to take full advantage of the stunning location and tranquil setting.
Roof insulation throughout the development was specified and supplied by Insulation Distributors Ltd of Dublin. Technical Guidance Document L of the Irish Building Regulations requires an elemental U-value of 0.20 W/m²K for new-build pitched roofs and, to hit this target, Insulation Distributors faced two challenges. First, to allow the loft space in the cabins to be used as living space, a warm roof construction was necessary and, secondly, to maximise headroom, no under-rafter insulation was to be used.
“In fact the decision to use Crown® Rafter Roll 32 was an easy one!” said Dermot Kearns, Insulation Distributors’ Sales Manager. “We needed something that would meet the thermal insulation target, be confined to the void between the rafters and be compatible with a breather membrane. That pointed to a high-performance mineral wool product and Rafter Roll 32 looked the best option. We recommended two, 85mm thick layers as the combined total of 170mm met the U-value target and was well within the 225mm depth of the rafters. And, as a bonus, mineral wool also gives acoustic insulation and is completely firesafe.”
Crown® Rafter Roll 32 is a glass mineral wool roll with an exceptionally low thermal conductivity of just 0.032 W/mK. The material has the same characteristics as a semi-rigid slab of glass mineral wool insulation but is supplied in roll form for easy storage and handling. Three thicknesses are available – 75mm thick in rolls 5.40m long, and 85mm and 100mm thick in rolls 2.70m long – and in a width of 200mm which means they can be cut to fit between rafters spaced at either 400 mm or 600 mm centres. The material is very easy to cut using a hand-saw – in fact it’s recommended to cut the material to width while it’s still rolled. Installation is just as quick and easy as the material’s semi-rigid nature allows it to friction-fit between the rafters with its ‘scrunchiness’ overcoming timber variations and preventing air gaps.
And the benefits don’t stop there! Although designed as a high-performance thermal insulation material, Crown® Rafter Roll 32 also offers other important insulation properties. Glass mineral wool is a highly effective acoustic insulation material and is also totally non-combustible; a fact recognised by it having a Euroclass A1 fire classification, the highest rating possible.
Further information about Crown® Rafter Roll 32 is available in two Knauf Insulation brochures – Pitched Roofs: New Build & Upgrade and Loft Conversions – which are available free on request. For copies, or to get information about other Knauf Insulation products, please visit www.knaufinsulation.co.uk or call 08700 668 660 quoting KR 242 04. Insulation Distributors can be contacted on + (0)1 623 4541 and further information about the Cornadarragh Forest Park development can be found on their website at www.cornadarragh.com.
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