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40mm Celotex TB4040 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
40mm Celotex TB4040 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.
£20.68£24.82 Ex VATInc VAT£7.18£8.62 Per M2 Add to cart -
40mm Ecotherm Eco-Versal PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
40mm 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.
£21.21£25.45 Ex VATInc VAT£7.36£8.83 Per M2 Add to cart -
40mm Jablite HP+ 70E External Wall Insulation Board 1200mm x 600mm (4′ X 2′) Pack of 15 (10.80m2)
40mm Jablite HP+ 70E External Wall Insulation Board is designed to enhance thermal efficiency for external walls. It can be bonded or mechanically fixed, providing reliable insulation solution.
£54.58£65.50 Ex VATInc VAT£5.05£6.06 Per M2 Add to cart -
40mm Kingspan GreenGuard GG300 R Rigid Extruded Polystyrene Insulation Board 1250mm x 600mm Pack of 10 (7.50m2)
40mm 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 thermal conductivities as low as 0.033 W/m·K
£65.35£78.42 Ex VATInc VAT£8.71£10.45 Per M2 Add to cart -
40mm Kingspan Kooltherm K103 Insulation Floorboard 2400mm x1200mm Pack of 8 (23.04m2)
40mm Kooltherm K103 is a premium phenolic core floor insulation solution, designed to deliver exceptional performance with solid concrete or suspended timber floors.
£385.51£462.61 Ex VATInc VAT£16.73£20.08 Per M2 Add to cart -
40mm Recticel Eurothane GP PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
40mm 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.
£19.72£23.66 Ex VATInc VAT£6.85£8.22 Per M2 Add to cart -
40mm Rockwool Ductslab Insulation 1000mm x 600mm 6m2 Pack
40mm Rockwool Ductslab Insulation is a high-performance, non-combustible stone wool solution designed to provide thermal, acoustic and fire resistance for rectangular ductwork in HVAC systems.
£86.29£103.55 Ex VATInc VAT£14.38£17.26 Per M2 Add to cart -
40mm Rockwool Ductwrap Insulation Wrap 4000mm x 1000mm 8m2
40mm Rockwool Ductwrap 4000mm x 1000mm is a high-performance insulation blanket designed to snugly wrap around ductwork, delivering great thermal protection.
£67.39£80.87 Ex VATInc VAT Add to cart -
40mm Rockwool FirePro Pipe Collar CE
40mm FirePro Pipe Collar CE delivers powerful fire-activated expansion that seals plastic pipe penetrations from fire smoke and spread.
£9.97£11.96 Ex VATInc VAT Add to cart -
40mm Thick 21mm Pipe Diameter Rockwool Rocklap Aluminium Foil Faced Pipe Lagging 1000mm
40mm Thick 21mm Pipe Diameter Rockwool Rocklap Aluminium Foil Faced Pipe Lagging (length – 1000mm) is a premium thermal insulation material engineered to improve energy efficiency and minimise heat loss in pipe systems.
£10.39£12.47 Ex VATInc VAT Add to cart
40mm Insulation
40mm insulation is a thin insulation layer used to improve thermal control in areas with limited space. It is often specified to address specific thermal detailing requirements rather than to meet whole-element U-value requirements on its own. It fine-tunes heat performance, reduces cold surfaces, and supports a wider build-up.
What is 40mm insulation thickness?
40mm insulation thickness means the material measures exactly 40 millimetres from the warm side to the cold side. The dimension matters because heat loss calculations depend on thickness and thermal conductivity, not just material type.
At this depth, insulation slows heat movement but does not stop it entirely. The actual performance depends heavily on the material’s thermal conductivity (lambda value). High-performance foam materials deliver greater resistance at 40mm than fibrous products.
This size is commonly used where adding more depth would interfere with fixings, floor heights, or detailing.
What is 40mm thick insulation used for?
40mm thick insulation is usually added to improve comfort and efficiency. In most cases, it does not meet UK Building Regulations on its own.
Typical applications include:
- Internal wall upgrades that aim to keep space loss minimal.
- Floors where height build-up is tightly controlled.
- Roof refurbishments where rafters cannot be deepened.
- Thermal breaks around steel, concrete, or structural junctions.
In many builds, thick 40mm insulation works as a supporting layer alongside thicker insulation elsewhere.
Types of insulation 40mm thick
There are several insulation types available at insulation 40mm thickness:
Rigid foam boards
- PIR Insulation: High thermal efficiency for its depth. Often chosen when maximum performance is needed in minimum space. Joints should be fully sealed to minimise air leakage.
- Phenolic Insulation: Offers slightly better thermal performance than PIR. More brittle, so best handled carefully.
- EPS Insulation: Lower performance but stable, lightweight, and cost-effective. Common under floors.
- XPS Insulation: Stronger and more moisture-resistant than EPS. Often used where compression or damp exposure is a concern.
EPS/XPS offers limited thermal benefits at 40mm thickness unless paired with thicker layers.
Mineral wool
- Glass mineral wool: Flexible and easy to fit. Thermal performance at this thickness is modest. Mainly used for sound control, not thermal protection.
- Rock mineral wool: Denser than glass wool. Offers better acoustic and fire performance.
Advanced products
- VIP (Vacuum Insulated Panels): Extremely high performance at very thin depths. Used only where space is critical, as they cannot be cut.
Some aerogel products are available at similar thin dimensions, though they are specialised and costly.
Need bulk insulation quantities or help choosing the right material? Get a fast quote from our team and secure the right 40mm solution for your build.
FAQ
Where to buy 40mm insulation?
You can buy insulation 40mm thick online from Insulation Wholesale. We stock a wide range of materials, so you can choose based on performance, space, and budget. We offer reliable lead times and support both trade and one-off projects. Our ordering process is straightforward, and we handle all bulk quantities properly.
How to fix 40mm insulation?
The fixing method depends on the material and surface:
- Rigid boards are usually bonded with adhesive, mechanically fixed, or both.
- Floors often rely on compression and perimeter restraint.
- Timber frames may use friction fit or fixings through battens.
The key rule is to ensure full contact with the surface or space. Gaps reduce performance more at thin depths than at thick ones.
How to cut 40mm insulation?
- Foam boards: Cut with a fine-tooth saw or insulation knife.
- Mineral wool: Cut a little oversized (so it friction-fits) with a long-blade knife.
- VIP panels: Do not cut – order exact sizes.
Measure accurately because a poor cut wastes more performance at 40mm than at larger thicknesses.
