Split your purchase of £60.99 into 3 with no sign-up fees or late fees.
£20.33
today
£20.33
1 month
£20.33
2 months
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Choose PayPal at checkout to pay later with Pay in 3.
Complete your purchase with the first payment today.
Remaining payments are taken automatically.
Pay in 3 is a form of credit, so carefully consider whether the purchase is affordable and how you will make the repayments. Be aware of the possible impact of using Pay in 3 and of missing payments, including making other borrowing more difficult or more expensive. Pay in 3 eligibility is subject to status and approval. 18+ UK residents only. Available for purchases of £30 to £2,000. Terms and conditions apply. PayPal Pay in 3 is a trading name of PayPal (Europe) S.à r.l. et Cie, S.C.A. 22-24 Boulevard Royal L-2449, Luxembourg.
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Klarna's Pay in 30 days is an unregulated credit agreement. Borrowing more than you can afford or paying late may negatively impact your financial status and ability to obtain credit. 18+, UK residents only. Subject to status. T&Cs and late fees apply.
Pay over time
£20.33 Every 30 days
Pay in 3
£20.33
today
£20.33
in 30 days
£20.33
in 60 days
Klarna's Pay in 3 is an unregulated credit agreement. Borrowing more than you can afford or paying late may negatively impact your financial status and ability to obtain credit. 18+, UK residents only. Subject to status. T&Cs and late fees apply.
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At checkout select Klarna.
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Split your purchase of £60.99 into 4 with no sign-up fees or late fees. Your purchase will be split into 4 payments, payable every 2 weeks
£15.25
today
£15.25
second payment
£15.25
third payment
£15.25
fourth payment
How it works
Choose Clearpay at checkout to pay later with Pay in 4.
Complete your purchase with the first payment today.
Remaining payments are taken automatically.
Clearpay is unregulated credit. Use responsibly. 18+, T&Cs and late fees apply at clearpay.co.uk/en-GB
Clearpay lends you a fixed amount of credit so you can pay for your purchase over 4 instalments, due every 2 weeks. Ensure you can make repayments on time. You must be 18+ and a permanent UK resident (excl Channel Islands). Clearpay charges a £6 late fee for each late instalment and a further £6 if it’s still unpaid 7 days later. Late fees are capped at £6 for orders under £24 and the lower of £24 or 25% of the order value for orders over £24. Missed payments may affect your ability to use Clearpay in the future and your details may be passed onto a debt collection agency working on Clearpay’s behalf. Clearpay is credit that is not regulated by the Financial Conduct Authority. T&Cs and other eligibility criteria apply at clearpay.co.uk/terms
Delivery charges vary by product category and order value. Items may ship from different suppliers and arrive separately, so delivery charges can be shown per part of your order at checkout.
Standard (Nationwide) Delivery
Core Products
Core
ORDER VALUE
DELIVERY CHARGE
Under £300
ex. VAT
£30
ex. VAT
Over £300
ex. VAT
FREE
Core Delivery charges apply only when all products in an order that have equivalents are accepted as such. If even one product cannot be substituted with an equivalent, the entire order will not qualify for Core Delivery charges.
Insulation, Plasterboard and Drylining Products
ORDER VALUE
DELIVERY CHARGE
Under
£400
£45
ex. VAT
Over
£400
ex. VAT
FREE
Express Delivery
Express Delivery - Insulation and Plasterboard & Drylining
We work with a nationwide network of trusted suppliers. Items in your basket may be supplied by different suppliers and delivered separately. Where this applies, you will see delivery charges shown at checkout for each part of your order. We always aim to group products from the same supplier to keep delivery costs as low as possible.
Delivery areas
Delivery charges apply to mainland UK, excluding: AB, CA, CF, DD, DG, EH, EX, FK, KA, KW, KY, IV, LA, LD, LL, ML, NP, PA, PH, PL, SA, SY, TR, TQ and TD.
If your address is in one of these areas, we will contact you before processing your order to confirm any additional costs. We do not currently offer delivery outside the UK mainland.
What to expect on delivery day
Deliveries are typically kerbside.
Please ensure someone is on-site to accept delivery. For heavier items, help with offloading may be required.
Many building materials arrive on large vehicles. If access is restricted, a specialist vehicle such as a HIAB may be required and could incur an additional charge.
Why delivery can cost more than typical parcel delivery
Building materials often travel on larger vehicles and usually carry fewer drops per run than parcel networks. That is why delivery charges can be higher than standard e-commerce shipping.
Returns
Returns depend on what you have bought and whether there is anything wrong with it. For full details on eligibility, timeframes, and exclusions, please see our full policy.
Celotex XR4000 PIR Insulation Board with a 2400mm length, 1200mm width, and 150mm thickness. This high-performance thermal insulation board consists of a rigid polyisocyanurate (PIR) core with low-emissivity foil facings on both sides. It is engineered for use in floors, walls, and roofs where high thermal resistance is required to meet stringent Building Regulations. The board provides a durable, moisture-resistant barrier that maintains its structural integrity over the lifespan of the building.
As part of the Celotex range, this 150mm board offers increased depth compared to standard GA4000 100mm insulation, allowing for the achievement of lower U-values within a single layer. The high thickness-to-performance ratio makes it an ideal specification for high-performance envelopes and low-energy builds.
Features & Benefits
Thermal conductivity (0.022 W/m·K): Reduces the thickness required to meet U-value targets.
Low-emissivity foil facings: Reflect radiant heat across cavity air spaces, improving overall efficiency.
XR4000 range (extra resistance): Suited to achieving low U-values with a single layer in roofs, walls, and floors.
Rigid PIR core: Lightweight yet robust, easy to cut and install with standard tools.
Moisture resistance: Closed-cell core prevents water uptake and preserves thermal performance.
Environmental credentials: Zero ODP, low GWP blowing agent, and BRE Green Guide Rating A.
BBA certified (17/5405, 16/5352): Independent assurance of performance across roofs, walls, and floors.
Board size 2400 x 1200mm: Large-format sheets reduce installation time.
Thickness 150mm: Deep-section board for meeting strict U-value targets in high-performance builds.
Applications
Extra resistance: Thick board designed to achieve low U-values in single-layer applications for energy-efficient and low-energy projects.
Beam & Block Floors: Rigid PIR insulation is laid directly over the floor structure to provide high thermal performance in limited floor thicknesses.
Concrete Slab Floors: Boards are installed either above or below the slab to create a continuous thermal barrier and prevent heat loss into the ground.
Suspended Timber Floors: Precision-cut boards are fitted between floor joists to significantly reduce draughts and improve the energy efficiency of the floor.
Upgrading Concrete Slab Floors: The high thermal-to-thickness ratio allows for effective insulation upgrades over existing slabs where floor heights are restricted.
Timber Frame Wall: Insulation is installed within the stud cavity or as a continuous layer to achieve low U-values in modern timber frame constructions.
Between and Over Rafters: Boards are combined within and across the rafters to eliminate thermal bridging and create a high-performance warm roof.
Between and Under Rafters: The insulation is fitted between rafters with a second layer underneath to maximise internal thermal retention in pitched roof spaces.
Pitched Roof Sarking: Large format boards are installed over the rafters to provide a seamless layer of insulation that protects the internal structure.
Loft Insulation: The boards provide a stable, non-compressible surface suitable for supporting typical storage loads when used in conjunction with protective timber boarding and a load-bearing structure.
New Build Roof Insulation: Specified for new build projects where Part L 2021 requires enhanced U-values and achieves optimal thermal performance when combined with additional layers.
Passive House & Low-Energy Builds: Specified in passive house and low-energy building projects where maximum insulation performance per millimetre is essential.
Installation Guidance
Cut and fit tightly: Use a knife or fine-tooth saw; maintain close joints to avoid thermal bypass.
Seal or tape as specified: Ensures continuity with air and vapour control layers.
Fix securely: Mechanical fixings, adhesives, or retention by framing depending on application.
Protect on site: Store boards flat, dry, and covered until required.
Compliance & Performance
Thermal conductivity: 0.022 W/m·K (BS EN 12667).
Compressive strength: ≥140 kPa (BS EN 826).
Reaction to fire: Euroclass E (BS EN 13501-1).
Environmental performance: Zero ODP, low GWP, BRE Green Guide Rating A.
Part L Regulation compliance: High-thickness profile specifically designed to meet the stringent U-value requirements of Approved Document L for new build dwellings and existing extensions.
Fabric energy efficiency: Supports a "fabric first" approach by providing a continuous thermal layer that reduces carbon emissions and improves the overall SAP rating of the build.
Important note: This product must be installed with tightly abutted joints and high-quality foil tape sealing to ensure the continuity of the thermal barrier and maintain compliance with building regulations.
Customer Reviews
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5/5based on 4 reviews
I used this in my roof. Easy to cut and install
Amad A on
Fantastic service. Board came on it's agreed delivery date
Hugh F on
Great PIR insulation board. Used in cavity air spaces and house is now noticeably warmer.
What is the difference between Celotex XR4 and GA4?
The main difference is simply the thickness of the board. Both GA4000 and XR4000 are made from the same high-performance polyisocyanurate (PIR) foam with foil facings and have the same thermal conductivity 0.022 W/mK.
Is 150mm PIR insulation enough for a new build roof?
In many cases, yes. 150mm PIR is the standard starting point, but whether it is enough depends on the specific type of roof and the U-value target set by your Building Designer.
What U-value does 150mm Celotex achieve?
A U-value is a calculation for an entire building element (the whole wall, roof, or floor), so it depends on the other materials in your construction. However, for a single sheet of 150mm Celotex XR4150, the standalone thermal performance is measured by thermal conductivity (0.022 W/mK)
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