25mm Insulation Board

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Why 25mm Insulation? 25mm insulation is one of the most specified rigid board thicknesses in the UK wherever build-up depth is tight. At this thickness, boards earn their place as a thermal break in framed walls, a top-up layer over existing insulation, or a slim solution beneath underfloor heating systems where every millimetre below the finished floor level counts. Here is what the range covers: PIR boards at 25mm achieve 0.022 W/mK thermal conductivity in one of the thinnest practical board formats. Phenolic boards at 25mm outperform PIR with a lambda as low as 0.019 W/mK for the tightest U-value targets. EPS options available from 0.030 to 0.038 W/mK for cost-effective floor and below-ground applications. Purpose-built thermal bridging strips such as the Celotex TB4000 range, designed specifically for stud and frame junctions. Available as half boards for smaller areas, awkward cuts and last-minute top-ups. 25mm PIR Insulation Boards PIR is the most commonly specified material for 25mm rigid insulation in the UK. Foil-faced, lightweight and easy to cut, 25mm PIR boards are suitable for thermal break applications in timber and steel framed walls, as a top-up layer over existing insulation and beneath underfloor heating systems where minimal thickness is essential. All boards achieve a thermal conductivity of 0.022 W/mK and are non-water absorbent, meaning performance is maintained across damp or humid environments. Celotex TB4025 The Celotex TB4025 is one of the most frequently ordered 25mm insulation boards in the UK. Purpose-built for thermal bridging applications, it is fitted between studs and the internal lining board in timber and steel framed walls to reduce heat loss at junctions. BBA certified, lightweight and simple to install, it is the standard specification wherever a slim thermal break is required. Browse the full Celotex insulation range for all board types and thicknesses. Ecotherm and Unilin Ecotherm Eco-Versal and Unilin PIR complete the 25mm PI