-
120mm Celotex XR4120 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Celotex XR4120 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£51.94£62.33 Ex VATInc VAT£18.03£21.64 Per M2 Add to cart -
120mm Ecotherm Eco-Versal Rigid PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Ecotherm Eco-Versal is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Ecotherm Eco-Versal is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£52.08£62.50 Ex VATInc VAT£18.08£21.70 Per M2 Add to cart -
120mm Kingspan GreenGuard GG300 R Rigid Extruded Polystyrene Insulation Board 1250mm x 600mm Pack of 3 (2.25m2)
120mm Kingspan GreenGuard GG300 is a high performance rigid extruded polystyrene insulation. It is used to insulate inverted roofs, basements, car park decks, and heavy-duty commercial, industrial and cold store flooring offering a thermal conductivities as low as 0.033 W/m·K
£59.33£71.20 Ex VATInc VAT£26.37£31.64 Per M2 Add to cart -
120mm Kingspan Kooltherm K103 Insulation Floorboard 2400mm x1200mm Pack of 2 (5.76m2)
120mm Kooltherm K103 is a premium phenolic core floor insulation solution, designed to deliver exceptional performance with solid concrete or suspended timber floors.
£265.38£318.46 Ex VATInc VAT£46.07£55.28 Per M2 Add to cart -
120mm Kingspan Kooltherm K107 Pitched Roof Board 2400mm x 1200mm Pack of 2 (5.76m2)
120mm Kingspan Kooltherm K107 Pitched Roof Board is a premium performance insulation with a fibre-free rigid thermoset phenolic core. It is used to insulate pitched roofs and attic spaces, and has a thermal conductivity of just 0.019 W/m.K across all thicknesses.
£265.38£318.46 Ex VATInc VAT£46.07£55.28 Per M2 Add to cart -
120mm Kingspan Kooltherm K112 Framing Insulation Board 2400mm x 1200mm Pack of 2 (5.76m2)
120mm Kingspan Kooltherm K112 Framing Board is a premium performance insulation with a fibre-free rigid thermoset phenolic core. It is used to insulate timber and steel framing systems with thermal conductivity of just 0.019 W/mK across all thicknesses.
£333.92£400.70 Ex VATInc VAT£57.97£69.56 Per M2 Add to cart -
120mm Kingspan Thermaroof TR24 Flat Roof PIR Insulation Board 1200mm x 600mm Pack of 4 (2.88m2)
120mm Kingspan Thermaroof TR24 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. Kingspan Thermaroof is suitable for flat roofs waterproofed with partially bonded torch applied multi-layer bituminous waterproofing.
£114.93£137.92 Ex VATInc VAT£39.91£47.89 Per M2 Add to cart -
120mm Kingspan Thermaroof TR26 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 2 (5.76m2)
120mm Kingspan TR26 Thermaroof is high-performance insulation that has a fiber-free rigid thermoset polyisocyanurate (PIR) core. Suitable for flat roof application waterproofed with mechanically fixed single-ply waterproofing.
£200.81£240.97 Ex VATInc VAT£34.86£41.83 Per M2 Add to cart -
120mm Kingspan Thermaroof TR27 PIR Insulation Board 1200mm x 1200mm Pack of 4 (5.76m2)
120mm Kingspan Thermaroof TR27 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. It is used to insulate flat roofs waterproofed with fully adhered single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing.
£205.95£247.14 Ex VATInc VAT£35.76£42.91 Per M2 Add to cart -
120mm Recticel Eurothane GP PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Recticel Eurothane GP is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Recticel is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£49.31£59.17 Ex VATInc VAT£17.12£20.54 Per M2 Add to cart
120mm Insulation
120mm insulation is a relatively deep insulation layer used when a building requires a high level of heat control, not just a small improvement. It is a thickness typically specified when energy targets matter, and where the construction allows sufficient build-up depth.
What is 120mm thick insulation?
120mm thick insulation means the material measures 120 millimetres when installed at its nominal thickness. It reduces heat transfer in two primary ways: Soft materials trap lots of still air, and rigid boards resist heat transmission through dense foam, helping retain internal heat during winter and limiting heat gain during summer.
What is 120mm insulation thickness used for?
120mm insulation thickness is used when building regulations, occupant comfort, or running energy costs require higher performance.
It is often installed in external walls, roofs, and floor constructions where heat loss would otherwise be high.
It is common in new builds, extensions, and upgraded thermal envelopes where long-term performance outweighs minimal space savings.
Types of 120mm insulation
Insulation 120mm is available in two broad forms. The choice on what to use depends on the application, performance requirements and available space:
- Rigid (hard) insulation: This includes PIR Insulation, phenolic Insulation, EPS, and XPS Insulation boards. They have high thermal efficiency per millimetre, but are less tolerant of installation gaps or inaccuracies. Boards must be cut cleanly and fitted tightly for optimal performance.
- Soft insulation: Includes mineral wool Insulation and glass wool Insulation products. These insulating materials are thick, air-filled and compressible, allowing them to fill gaps well and accommodate uneven stud or joist spacing.
Both insulation types can meet UK thermal performance targets when specified as part of a suitable build-up.
Benefits of insulation 120mm
Below are the advantages of using insulation 120mm thickness:
- Much lower heat loss than mid-range depths
- Better indoor comfort across seasons
- Easier compliance with modern energy standards
- Fewer cold spots in walls, roofs, and floors
This thickness delivers a meaningful contribution to overall thermal performance.
FAQ
Where to buy 120mm insulation?
We stock 120mm insulation at Insulation Wholesale, available in both soft and rigid formats. Our shop is built for trade and DIYers, with clear product data, competitive pricing, and fast delivery. Our team can help match insulation to the actual build detail, not just the thickness on paper, so you get the most suitable product for your specific build.
How to cut 120mm insulation?
- For soft insulation 120mm thick: Use a long knife or saw. Cut slightly oversize so it grips the space without gaps.
- For rigid boards: Score deeply and snap, or saw for clean edges.
Accuracy matters more at this depth because gaps significantly reduce thermal performance.
