120mm Celotex XR4120 PIR Insulation Board 2.4m x 1.2m - 2.88m2 per board
120mm Celotex XR4120 is a rigid polyisocyanurate (PIR) insulation board built for cut-to-fit work between and under rafters, and it is the depth Celotex reaches for in loft conversions and room-in-roof builds. At 120mm it pairs with common rafter depths to create a warm, habitable roof space while keeping the insulation inside the slope rather than stealing floor area.
Each board measures 2400mm x 1200mm, covers 2.88m² and is sold individually. A declared thermal conductivity of 0.022 W/mK gives it a thermal resistance of 5.45 m²K/W, one step up the XR4000 range from the 110mm board, at a maximum board weight of around 4.93 kg per square metre. The rigid PIR core carries a low-emissivity aluminium foil on both faces to lift performance against a sealed cavity air space, and the square edges close up tight for a continuous run across rafters and joists.
The value of the 120mm depth is headroom: it reaches a habitable-roof U-value in a single between-and-under-rafter layer, so the conversion keeps its ceiling height instead of losing it to a thicker or doubled build-up, and the warm side stays clear for boarding out.
XR4120 is used between and under rafters in warm pitched roofs and loft conversions, over and between joists in flat roofs, and as a single cut-to-fit layer in solid and suspended floors, masonry walls and timber- and steel-framed systems. Install it in line with the latest Celotex technical guidance, the project specification and current Building Regulations, including fire requirements and the height limit on external wall use. In wall build-ups it should be covered with a fire-rated lining such as 12.5mm plasterboard. Across conversions and new roofs alike, the 120mm board carries the loft U-value target on the rafter line without complicating the build.
Key Benefits of 120mm Celotex XR4120:
- 120mm rigid polyisocyanurate (PIR) board, the thickness Celotex specifies between and under rafters for loft conversions and room-in-roof builds.
- Thermal resistance (R-value) of 5.45 m²K/W, a step up from the 110mm board for tighter U-value targets.
- Declared thermal conductivity of 0.022 W/mK, reaching that resistance in a 120mm depth that suits common rafter sizes.
- Carries a habitable-roof U-value in a single between-and-under-rafter layer, protecting ceiling height in a conversion.
- Works equally as a single cut-to-fit layer in floors, masonry walls and timber- and steel-framed systems.
- Low-emissivity aluminium foil facings on both sides, improving performance against sealed and cavity air spaces.
- Square edges for flush, tight joints and a continuous insulation layer up the slope.
- Manufactured with a blowing agent of zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP), free of CFCs and HCFCs.
- Supplied as a single 2400mm x 1200mm board covering 2.88m², at a maximum board weight of around 4.93 kg per square metre.
- BBA certified (Certificate 25/7318) for defined pitched roof, dry lining and floor applications.
Good to know:
- Boards measure 2400mm x 1200mm and are sold individually, each covering 2.88m².
- The foil facing is printed on one side only: fit the board with the plain face towards the cavity for the rated thermal performance.
- The foil facing is not a vapour control layer; many roof and wall build-ups still need a separate VCL to manage interstitial condensation.
- In wall applications the board should be covered with a fire-rated lining, such as 12.5mm plasterboard.
- Celotex XR4000 should not be used in the external walls of buildings over 11 metres in height; check current Building Regulations for your project.
- PIR is moisture resistant but not waterproof: store boards flat, off the ground, dry and out of prolonged sunlight.
- Insulation UK offers a bespoke cutting service, supplying boards cut to your sizes to reduce waste and on-site mess.
For loft conversions that have to stay warm without losing height, 120mm Celotex XR4120 puts a 5.45 m²K/W layer on the rafter line in one board, keeping the build simple and the room above usable.
Important Notice: Please be aware that during periods of high demand, we reserve the right to provide alternative brands that meet the same specifications and quality standards as the products you originally ordered.
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120mm Celotex XR4120 PIR Insulation Board 2.4m x 1.2m - 2.88m2 per board
120mm Celotex XR4120 PIR Insulation Board 2.4m x 1.2m - 2.88m2 per board
120mm Celotex XR4120 is a rigid polyisocyanurate (PIR) insulation board built for cut-to-fit work between and under rafters, and it is the depth Celotex reaches for in loft conversions and room-in-roof builds. At 120mm it pairs with common rafter depths to create a warm, habitable roof space while keeping the insulation inside the slope rather than stealing floor area.
Each board measures 2400mm x 1200mm, covers 2.88m² and is sold individually. A declared thermal conductivity of 0.022 W/mK gives it a thermal resistance of 5.45 m²K/W, one step up the XR4000 range from the 110mm board, at a maximum board weight of around 4.93 kg per square metre. The rigid PIR core carries a low-emissivity aluminium foil on both faces to lift performance against a sealed cavity air space, and the square edges close up tight for a continuous run across rafters and joists.
The value of the 120mm depth is headroom: it reaches a habitable-roof U-value in a single between-and-under-rafter layer, so the conversion keeps its ceiling height instead of losing it to a thicker or doubled build-up, and the warm side stays clear for boarding out.
XR4120 is used between and under rafters in warm pitched roofs and loft conversions, over and between joists in flat roofs, and as a single cut-to-fit layer in solid and suspended floors, masonry walls and timber- and steel-framed systems. Install it in line with the latest Celotex technical guidance, the project specification and current Building Regulations, including fire requirements and the height limit on external wall use. In wall build-ups it should be covered with a fire-rated lining such as 12.5mm plasterboard. Across conversions and new roofs alike, the 120mm board carries the loft U-value target on the rafter line without complicating the build.
Key Benefits of 120mm Celotex XR4120:
- 120mm rigid polyisocyanurate (PIR) board, the thickness Celotex specifies between and under rafters for loft conversions and room-in-roof builds.
- Thermal resistance (R-value) of 5.45 m²K/W, a step up from the 110mm board for tighter U-value targets.
- Declared thermal conductivity of 0.022 W/mK, reaching that resistance in a 120mm depth that suits common rafter sizes.
- Carries a habitable-roof U-value in a single between-and-under-rafter layer, protecting ceiling height in a conversion.
- Works equally as a single cut-to-fit layer in floors, masonry walls and timber- and steel-framed systems.
- Low-emissivity aluminium foil facings on both sides, improving performance against sealed and cavity air spaces.
- Square edges for flush, tight joints and a continuous insulation layer up the slope.
- Manufactured with a blowing agent of zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP), free of CFCs and HCFCs.
- Supplied as a single 2400mm x 1200mm board covering 2.88m², at a maximum board weight of around 4.93 kg per square metre.
- BBA certified (Certificate 25/7318) for defined pitched roof, dry lining and floor applications.
Good to know:
- Boards measure 2400mm x 1200mm and are sold individually, each covering 2.88m².
- The foil facing is printed on one side only: fit the board with the plain face towards the cavity for the rated thermal performance.
- The foil facing is not a vapour control layer; many roof and wall build-ups still need a separate VCL to manage interstitial condensation.
- In wall applications the board should be covered with a fire-rated lining, such as 12.5mm plasterboard.
- Celotex XR4000 should not be used in the external walls of buildings over 11 metres in height; check current Building Regulations for your project.
- PIR is moisture resistant but not waterproof: store boards flat, off the ground, dry and out of prolonged sunlight.
- Insulation UK offers a bespoke cutting service, supplying boards cut to your sizes to reduce waste and on-site mess.
For loft conversions that have to stay warm without losing height, 120mm Celotex XR4120 puts a 5.45 m²K/W layer on the rafter line in one board, keeping the build simple and the room above usable.
Important Notice: Please be aware that during periods of high demand, we reserve the right to provide alternative brands that meet the same specifications and quality standards as the products you originally ordered.
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
120mm Celotex XR4120 is a rigid polyisocyanurate (PIR) insulation board built for cut-to-fit work between and under rafters, and it is the depth Celotex reaches for in loft conversions and room-in-roof builds. At 120mm it pairs with common rafter depths to create a warm, habitable roof space while keeping the insulation inside the slope rather than stealing floor area.
Each board measures 2400mm x 1200mm, covers 2.88m² and is sold individually. A declared thermal conductivity of 0.022 W/mK gives it a thermal resistance of 5.45 m²K/W, one step up the XR4000 range from the 110mm board, at a maximum board weight of around 4.93 kg per square metre. The rigid PIR core carries a low-emissivity aluminium foil on both faces to lift performance against a sealed cavity air space, and the square edges close up tight for a continuous run across rafters and joists.
The value of the 120mm depth is headroom: it reaches a habitable-roof U-value in a single between-and-under-rafter layer, so the conversion keeps its ceiling height instead of losing it to a thicker or doubled build-up, and the warm side stays clear for boarding out.
XR4120 is used between and under rafters in warm pitched roofs and loft conversions, over and between joists in flat roofs, and as a single cut-to-fit layer in solid and suspended floors, masonry walls and timber- and steel-framed systems. Install it in line with the latest Celotex technical guidance, the project specification and current Building Regulations, including fire requirements and the height limit on external wall use. In wall build-ups it should be covered with a fire-rated lining such as 12.5mm plasterboard. Across conversions and new roofs alike, the 120mm board carries the loft U-value target on the rafter line without complicating the build.
Key Benefits of 120mm Celotex XR4120:
- 120mm rigid polyisocyanurate (PIR) board, the thickness Celotex specifies between and under rafters for loft conversions and room-in-roof builds.
- Thermal resistance (R-value) of 5.45 m²K/W, a step up from the 110mm board for tighter U-value targets.
- Declared thermal conductivity of 0.022 W/mK, reaching that resistance in a 120mm depth that suits common rafter sizes.
- Carries a habitable-roof U-value in a single between-and-under-rafter layer, protecting ceiling height in a conversion.
- Works equally as a single cut-to-fit layer in floors, masonry walls and timber- and steel-framed systems.
- Low-emissivity aluminium foil facings on both sides, improving performance against sealed and cavity air spaces.
- Square edges for flush, tight joints and a continuous insulation layer up the slope.
- Manufactured with a blowing agent of zero Ozone Depletion Potential (ODP) and low Global Warming Potential (GWP), free of CFCs and HCFCs.
- Supplied as a single 2400mm x 1200mm board covering 2.88m², at a maximum board weight of around 4.93 kg per square metre.
- BBA certified (Certificate 25/7318) for defined pitched roof, dry lining and floor applications.
Good to know:
- Boards measure 2400mm x 1200mm and are sold individually, each covering 2.88m².
- The foil facing is printed on one side only: fit the board with the plain face towards the cavity for the rated thermal performance.
- The foil facing is not a vapour control layer; many roof and wall build-ups still need a separate VCL to manage interstitial condensation.
- In wall applications the board should be covered with a fire-rated lining, such as 12.5mm plasterboard.
- Celotex XR4000 should not be used in the external walls of buildings over 11 metres in height; check current Building Regulations for your project.
- PIR is moisture resistant but not waterproof: store boards flat, off the ground, dry and out of prolonged sunlight.
- Insulation UK offers a bespoke cutting service, supplying boards cut to your sizes to reduce waste and on-site mess.
For loft conversions that have to stay warm without losing height, 120mm Celotex XR4120 puts a 5.45 m²K/W layer on the rafter line in one board, keeping the build simple and the room above usable.
Important Notice: Please be aware that during periods of high demand, we reserve the right to provide alternative brands that meet the same specifications and quality standards as the products you originally ordered.
