Knauf Insulation is gearing up to launch new products that fulfil its promise of providing straightforward insulation solutions to help the industry meet the 2006 version of Part L of the Building Regulations. Two of the products, codenamed ‘DriTherm® 32’ and ‘DriTherm® 34’, are eagerly awaited as they represent Knauf Insulation’s recommended solutions for full-fill cavity wall insulation. The new products ensure that, despite the industry’s fears about the design implications caused by the changes to Part L, cavity widths can remain at 100 mm or less.

The advantages and benefits of full-fill, over part-fill, cavity wall insulation are well known and, if the insulation material used is either glass or rock mineral wool, highly persuasive. Full-fill cavity wall insulation can be installed in both new-build and existing walls. In new-build walls, semi-rigid slabs of either glass or rock mineral wool are simply placed in the cavity as the wall is built. Existing walls, including those newly built, can be retro-insulated by injecting loose mineral wool through holes drilled through one of the leaves. Apart from offering designers an alternative method of installation, the Government’s commitment to reducing greenhouse gas emissions has fuelled the popularity of retro-installation by offering homeowners attractive subsidies.

Installing full-fill cavity wall insulation during construction is quicker and easier than installing part-fill insulation as the fixings needed to hold the insulation against the inner leaf – to create a residual cavity – are not required. Using mineral wool slabs can also result in a better thermal performance as the ‘give’ in their surface overcomes minor imperfections on the face of the cavity. In addition, the edges of mineral wool slabs mesh together, closing joints and preventing cold bridging. In part-fill cavities using rigid board insulation, snots of mortar can force the boards away from the surface of the inner leaf creating air gaps behind and through the insulation. In fact, a DETR report published in 2001 noted significant variations between the measured and calculated U-values of part-fill cavity wall insulation – even across the same wall!

In addition to its thermal performance, mineral wool also has excellent acoustic and fire insulation properties, which mean its use as full-fill cavity wall insulation provides an effective acoustic and fire stop.

“Experience shows that full-fill is, in theory and reality, the least expensive and most cost-effective method of insulating a cavity wall,” said John Gaunt, Knauf Insulation’s Market Manager for the residential sector. “We’ve promised to provide straightforward insulation solutions to help the industry meet or exceed the targets required by the changes to the Building Regulations and, now we know what we’re aiming at, we can fulfil that pledge!”

The new regulations coming into force on 1 April 2006 focus on ‘whole-building’ performance and aim to increase energy standards by between 18 and 27 per cent in new buildings. Although there is flexibility in exactly ‘how’ this is achieved, any shortfall in performance in one variable has to be compensated for elsewhere. The new products are specifically designed to give designers a flying start by ensuring that Elemental U-values between 0.27 and 0.32 W/m2K can be achieved in cavity widths of between 75 mm and 100 mm.

Knauf Insulation’s product range offers solutions for either new-build or retro-installation. Crown® DriTherm® Cavity Slab and Rocksilk® DriTherm® Cavity Slab are semi-rigid slabs of glass and rock mineral wool designed for use as full-fill cavity wall insulation. Measuring 1200 mm long by 455 mm wide (for use with wall ties at a vertical spacing of 450 mm) they are available in a range of thicknesses to maximise design versatility. Crown® SupafilTM Cavity Wall Insulation is a loose, glass mineral wool insulation installed by approved contractors using specialist equipment.

The new products will be available in both the Crown® Glass Mineral Wool and Rocksilk® Rock Mineral Wool ranges. Revised brochures featuring the new products are being published and copies can be ordered in advance by contacting Knauf Insulation’s enquiries hotline.

For further information, please visit Knauf Insulation’s website at www.knaufinsulation.co.uk or call their enquiries hotline on 08700 668 660 quoting CR 405 05.

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