Welcome to the Unilin category on Insulation4less. For those who might not be aware, the brand previously known as Xtratherm has transitioned to Unilin, keeping its commitment to quality intact. Let's dive into understanding the range of products under this category and how they can cater to your insulation needs.

Unilin Insulation: Thin-R, Safe-R and Xtratherm Explained

Xtratherm joined the Unilin Group in 2016 and the manufacturer rebranded as Unilin Insulation from 2023. That is why specifications, merchant listings and older drawings may use Xtratherm, Unilin Xtratherm or Unilin for closely related product families. For a replacement board, work from the product code and declared performance rather than the logo printed on an older pack.

The collection at Insulation4Less is centred on foil-faced Thin-R PIR boards, with a Safe-R phenolic option also listed. Thin-R XT/PR-UF is a rigid PIR board designed for applications including ground-supported and suspended floors and pitched roofs. The manufacturer declares 0.022 W/mK thermal conductivity for XT/PR-UF. All full boards in this collection are 2400 x 1200mm, so one board covers 2.88m² before cutting waste.

Unilin Thin-R thickness and thermal resistance

Thermal resistance increases with insulation thickness. The figures below are single-layer R-values from Unilin manufacturer data for XT/PR-UF; they are not whole-element U-values. A floor, wall or roof U-value must be calculated from the complete build-up, including the structure, cavities, surfaces and thermal bridges.

Unilin Thin-R PIR Range

Unilin Thin-R PIR products are available in a variety of thicknesses to cater to a wide range of insulation requirements:

Low-Thickness Insulation (25mm-40mm): Perfect for minor upgrades or where space is a constraint. These are often chosen for retrofitting projects where you want to enhance insulation without a major overhaul.

Medium-Thickness Insulation (50mm-90mm): Suitable for a balanced combination of insulation and space conservation. These thicknesses are frequently selected for new constructions or major renovation projects.

High-Thickness Insulation (100mm-150mm): Best for maximum insulation and energy savings. These are ideal for spaces where you want to ensure minimal heat loss and are not much constrained by space.

Safe-R Range

The Safe-R 2.4m x 1.2m insulation board is versatile and fits a multitude of applications. This product range doesn't specify thickness in the list provided, so it's best to call and enquire about your specific needs. This could be an excellent choice if you are looking for a more custom solution.

Unilin Thin-R General Range

The Unilin Thin-R 2.4m x 1.2m range encompasses all sizes, presumably offering a complete solution for those who are looking for an all-encompassing insulation approach. It's always wise to understand the full range available to make an informed decision based on your project's needs.

Is Unilin as good as Celotex or Kingspan?

This is one of the main comparison questions around the brand. For common foil-faced PIR boards, the useful comparison is declared performance and suitability rather than the badge. Unilin Thin-R XT/PR-UF is declared at 0.022 W/mK. Kingspan Therma TP10 is also declared at 0.022 W/mK. Comparable PIR products can therefore deliver similar thermal resistance at the same thickness, but that does not make every board interchangeable.

If a project simply calls for a foil-faced PIR board with a specified lambda and thickness, Unilin may be compared directly with suitable Celotex or Kingspan alternatives. If the architect, warranty provider or calculation names a particular product, check before changing it. A lower merchant price is not a technical approval for substitution.

How much Unilin insulation should I order?

A 2400 x 1200mm board covers 2.88m². Divide the net area by 2.88 to get the theoretical board count, then round up to whole boards and allow for cutting. Simple open floors may create little waste; roofs, dormers, openings and irregular wall areas create more. Measure each plane separately rather than using the building footprint for every application.

What did Unilin insulation used to be called?

Unilin Insulation was previously known as Xtratherm in the UK and Ireland. The manufacturer states that Xtratherm became part of the Unilin family in 2016 and rebranded as Unilin Insulation from 2023. Older specifications, invoices and site drawings can therefore still refer to Xtratherm, while current manufacturer documents carry the Unilin name.

This matters when sourcing replacements. Do not reject a current Unilin product just because an older drawing says Xtratherm. Match the original product code, application, thickness and declared characteristics against the current Unilin literature. Product families can also be updated over time, so the current Declaration of Performance or certification should take priority over an old merchant description.

Fitting Thin-R PIR cleanly

PIR performance depends on continuity. Measure each bay accurately and cut boards with a fine-toothed saw or suitable insulation saw on a stable surface. Keep joints tight and stagger joints where the specified build-up requires it. At floors, pay particular attention to perimeter insulation and junctions. At roofs and walls, avoid leaving open gaps around timbers, penetrations and changes of plane.

Follow the relevant Unilin installation guide for the exact product and application. Do not copy a fixing pattern from a different board or build-up. Where the design needs a vapour control layer, airtightness layer or taped foil system, detail it as part of the complete construction rather than assuming the foil face alone resolves every moisture or airtightness requirement.

Frequently asked questions

Is Unilin the same as Xtratherm?

Unilin Insulation is the current name of the business previously known as Xtratherm in the UK and Ireland. Xtratherm joined the Unilin Group in 2016 and the insulation business rebranded from 2023. Older Xtratherm specifications should be matched to current Unilin product codes and technical documents before ordering.

What is the thermal conductivity of Unilin Thin-R?

Unilin declares a thermal conductivity of 0.022 W/mK for Thin-R XT/PR-UF PIR insulation. Thermal resistance then depends on thickness: manufacturer data gives 2.25 m²K/W at 50mm and 4.50 m²K/W at 100mm. A complete floor, wall or roof requires a separate U-value calculation.

What size are Unilin insulation boards?

The Thin-R boards listed in this Insulation4Less collection are 2400 x 1200mm. Each full board therefore covers 2.88m² before cutting. The live collection currently filters from 25mm to 150mm thickness, although the number of available products varies by thickness and product family.

Can Unilin Thin-R be used under floors?

Unilin Thin-R XT/PR-UF is manufactured for ground-supported and suspended floor applications. Unilin declares 0.022 W/mK thermal conductivity and CS(10Y)140 compressive strength for the floor product, and states that it is suitable for underfloor heating. Follow the specified floor build-up and perimeter detailing.

Can Unilin PIR be used between rafters?

Unilin has Thin-R products intended for pitched-roof applications, but the correct product and thickness must suit the roof design. Confirm rafter depth, ventilation strategy, insulation position and the complete roof U-value before ordering. Keep cut boards tight to the construction and follow the current manufacturer installation guidance.

How many Unilin boards do I need?

A standard 2400 x 1200mm Unilin board covers 2.88m². Divide the net area to insulate by 2.88 and round up to whole boards, then add an allowance for cuts and waste. Measure separate roof slopes, floor zones and wall areas individually, deducting openings only where appropriate.

What thickness of Unilin insulation should I use?

The correct thickness comes from the required U-value and the complete construction, not from a universal minimum board depth. Unilin Thin-R provides higher thermal resistance as thickness increases; for example, manufacturer data gives 4.50 m²K/W at 100mm. Use the project calculation or obtain a U-value calculation for the full build-up.

Is Unilin Thin-R a PIR board?

Yes. Thin-R XT/PR-UF is a rigid polyisocyanurate, or PIR, insulation board with composite foil facings. The current Insulation4Less Unilin collection lists 16 PIR products and one phenolic product. Use the material filter and product title to distinguish Thin-R PIR from Safe-R phenolic insulation.

Can I replace an old Xtratherm board with Unilin?

A current Unilin product may be the successor to an older Xtratherm product, but replacement should be based on the exact code, application and declared characteristics. Check thickness, lambda value, facing, edge profile, strength and certification. For specified or warrantied work, obtain approval before substituting a different product.

What is the difference between PIR and Safe-R phenolic insulation?

Thin-R is Unilin’s PIR insulation family, while Safe-R is a phenolic insulation family. Phenolic products can offer lower declared thermal conductivity in particular ranges, allowing a target thermal resistance to be achieved with a different thickness. Always compare the exact Safe-R product code because application, lambda value and certification vary across the range.