Rehau vs Liniar: Which uPVC Window System Is Better? (UK 2026)

Liniar markets one of the lowest published U-values in UK uPVC, and homeowners comparing it against Rehau often reach us with a single question: is that number real? It is real, but it describes a very specific build that most quotes will not include. This comparison sets the two systems side by side on chambers, corner construction, heritage options and sustainability, and separates the headline figures from what a standard specification actually delivers.

Quick Decision Frame

Choose Rehau if you want factory-integrated EPDM gaskets pre-fitted into the profile, a recycled-content option in the co-extruded TOTAL70c variant, or a matching range that runs from casements through flush sash to inline sliding patio doors.

Choose Liniar if you want the option of Timberweld corner construction, which reads as a mechanical joint outside while remaining welded inside, or you are specifying a double-rebated flush sash and want the deeper 80mm Resurgence frame.

Either works for Part L compliance, PAS 24 security, Secured by Design, a 10-year frame guarantee and FENSA-registered installation.

Company Background

Rehau

Rehau takes a different route to the same goal. The two reach their numbers differently. Liniar's headline figure needs its EnergyPlus upgrade suite; TOTAL70 runs five chambers with steel reinforcement zones as its standard profile construction, and the EPDM gaskets arrive factory-integrated rather than inserted afterwards. Glazing specification still drives the final U-value for both.

Rehau was founded in 1948 in Rehau, Bavaria, and is one of Europe's largest uPVC profile extruders, supplying more than 50 countries. For this comparison the relevant detail is that TOTAL70 needs no separate upgrade suite to reach its published figures, and that a recycled-content route exists through the co-extruded TOTAL70c variant at up to 75% post-consumer material. Rio covers flush casement work and Slinova the inline sliding patio door.

Liniar

Liniar is a British system designer and extruder based in Derbyshire, where it extrudes lead-free uPVC profile and distributes it to a nationwide network of independent fabricators. Liniar states plainly on its own site that it does not manufacture finished glazed products, so the company building your window will always be a separate fabricator.

The range includes a 70mm casement, the 80mm Resurgence flush sash with a 70mm sash, and a 70mm Original Flush Sash with a 50mm sash. Liniar holds a patent on its bubble gasket and describes Resurgence as the UK's first double-rebated uPVC flush sash window.

Chambers and Thermal Performance

Liniar is unusually clear about chamber counts, which is welcome. Its standard profile uses four symmetrical chambers, and the EnergyPlus suite uses six.

| Metric | Rehau TOTAL70 | Liniar 70mm Casement | |---|---|---| | Frame depth | 70mm | 70mm | | Chambers | 5-chamber with steel reinforcement zones | 4 symmetrical, or 6 with the EnergyPlus suite | | Published U-value, double glazing | from 1.2 W/m²K | 1.4 W/m²K, standard suite. No optimised double-glazed figure published | | Published U-value, triple glazing | from 0.8 W/m²K | 0.81 W/m²K with the EnergyPlus suite | | Window Energy Rating | A+ standard | up to A++ | | PAS 24 | Standard | PAS 24, Secured by Design, Part Q | | Corner joints | Welded, with mechanical option on Rio | Welded, Mechanical, or Timberweld | | Acoustic reduction | Specification dependent | up to 33 dB standard double glazing, 37 dB best | | Guarantee | 10-year profile | 10-year frame |

What the 0.81 Figure Actually Requires

This is the part worth reading carefully. Liniar's own Energy Performance specification sheet, dated 21 July 2025, sets out the build required to reach 0.81 W/m²K: the EnergyPlus suite, a small outer frame, PVCu reinforcement, a glazing flipper, a thermal dam, 40mm triple glazing and 90% argon fill.

That is a deliberately optimised window, and very few residential quotes specify all seven elements together.

The same document gives the honest working figure. With the standard suite rather than EnergyPlus, and 28mm double glazing, Liniar records a U-value at or below 1.4 W/m²K for replacement windows and 1.6 for new build, at a band B Window Energy Rating.

So the fair comparison runs in two parts.

At best-case configuration the two are level. Liniar's 0.81 W/m²K sits a hundredth above Rehau's published 0.8 W/m²K triple-glazed figure, which is no difference at all in practice. Both require an optimised build, and the six-chamber EnergyPlus suite is a genuinely high-performance piece of engineering.

On double glazing the comparison is harder to make cleanly, and we should say why. Rehau publishes from 1.2 W/m²K. Liniar publishes 1.4 W/m²K for its standard suite with 28mm double glazing and does not publish an optimised double-glazed equivalent, so the only figures available are our published best against their published standard. That is not a like-for-like comparison and we will not present it as one. Ask any installer quoting Liniar which suite and which glazing unit the figure on your quote refers to, because the difference between those two Liniar builds is larger than the difference between the brands.

Rehau's published figures carry the same caveat in principle. Manufacturer U-values across this market are best-case configurations, and a quote should always state the actual specification rather than the brochure headline.

Corner Joints: Timberweld Is a Genuine Differentiator

On period and conservation properties, the corner detail is usually what a planning officer looks at. A welded corner leaves a diagonal witness line at 45 degrees. A mechanical joint produces a square butt joint much closer to traditional timber.

Liniar offers a third route. Timberweld gives the appearance of a mechanical joint on the outside face while the frame remains welded internally, so you keep the structural continuity of a weld with the aesthetics of a timber-style corner. For a homeowner who wants the heritage look without a fully mechanical frame, that is a real advantage and Rehau has no direct equivalent.

Rehau's answer is the Rio flush casement with a mechanical-joint corner option, which is a true mechanical joint rather than an appearance treatment. Which one suits you depends on whether your planning authority is assessing the visible detail or the construction itself.

Flush Sash Options

| Metric | Rehau Rio | Liniar Resurgence | Liniar Original Flush Sash | |---|---|---|---| | Frame depth | 70mm | 80mm frame, 70mm sash | 70mm frame, 50mm sash | | Rebate | Single | Double-rebated | Single | | Corner options | Mechanical joint available | Welded, Mechanical, Timberweld | Welded, Mechanical, Timberweld |

Liniar's Resurgence is the deeper frame of the three and the only double-rebated option, which improves the weather line on exposed elevations. Rehau's Rio is the lighter frame at 70mm throughout.

One caution worth flagging. On Liniar's own product pages, the accreditation list for the 70mm Original Flush Sash, read August 2026, names Secured by Design, BS EN 12608 and ISO 9001 but does not include PAS 24, while the Resurgence page explicitly does. An absence from a published list is not proof the product lacks certification. If PAS 24 matters for your insurance or a Part Q new-build requirement, ask the fabricator to confirm it for the specific flush sash product being quoted rather than assuming it applies across the range.

Sustainability

Rehau offers TOTAL70c, a co-extruded variant carrying up to 75% post-consumer recycled material according to its published brochure. It has to be specified; the standard TOTAL70 profile is not the same product.

Liniar extrudes lead-free uPVC in Derbyshire and its spec tables for the 70mm casement and Resurgence both record "Contains Recycled Material: No". That declaration sits at profile level and may reflect these specific products rather than a company-wide position, so we would not present it as a statement about Liniar's wider sustainability programme. If recycled content is a decision factor, ask both suppliers for a product-level declaration in writing.

Lead-free extrusion is a genuine point in Liniar's favour and is stated clearly on its own product pages.

Security

Both meet the UK benchmark. Liniar publishes PAS 24, Secured by Design and Part Q compliance, certified to BS EN 12608-1 through BSI. Rehau ships PAS 24 as standard with multi-point locking and internal beading. For a standard residential aperture there is no meaningful security difference between them, and the installation quality matters far more than the profile.

Which One We Fabricate, and Why

We fabricate Rehau, so treat this as a declared position rather than an impartial one. Our Uxbridge workshop cuts, machines and assembles Rehau profile into finished units, and our own teams install them.

The decision came down to what a quote can actually promise. A system that needs no separate upgrade suite is easier to quote honestly, because there are fewer conditions between the brochure headline and the window on the order. The glazing unit still governs the final figure, which is why our quotes state it. Consistent sightlines across casements, flush sash and sliding doors on the same job matter to us for the same reason.

Where Liniar wins, it wins clearly. Timberweld is a clever piece of engineering with no Rehau equivalent, the six-chamber EnergyPlus suite is a legitimately high-performance option, and Derbyshire extrusion shortens the supply chain. A homeowner working with a good Liniar fabricator would get a very capable window.

Our installations are FENSA registered and carry a CPA insurance-backed guarantee.

The Verdict

| Category | Winner | |---|---| | Double-glazed published figures | Rehau at 1.2, though against Liniar's standard suite rather than an optimised one | | Best-case optimised thermal performance | Level, 0.8 against 0.81 | | Chamber count at top specification | Liniar, six against five | | Gasket construction | Rehau | | Heritage corner options | Liniar, on Timberweld | | Flush sash weather detail | Liniar, on the double-rebated Resurgence | | Recycled content option | Rehau | | UK extrusion | Liniar | | Published specification clarity | Liniar | | Range coherence across window and door types | Rehau |

Frequently Asked Questions

Is Liniar really 0.81 W/m²K?

Liniar's own specification sheet dated 21 July 2025 confirms 0.81 W/m²K, but only with the EnergyPlus suite, a small outer frame, PVCu reinforcement, a glazing flipper, a thermal dam, 40mm triple glazing and 90% argon fill together. With a standard suite and 28mm double glazing the same document records 1.4 W/m²K or better at band B. Ask which configuration your quote is based on.

How many chambers do Rehau and Liniar windows have?

Rehau TOTAL70 uses five chambers with steel reinforcement zones. Liniar's standard profile uses four symmetrical chambers and its EnergyPlus suite uses six. More chambers generally helps thermal performance, though frame depth, reinforcement and glazing unit all matter as much as the chamber count alone.

What is Timberweld?

Timberweld is Liniar's corner construction that gives the appearance of a mechanical timber-style joint on the outside face while the frame stays welded internally. It suits period properties where the visible corner detail matters. Rehau's equivalent route is the Rio flush casement with a genuine mechanical-joint corner option.

Are Liniar windows made in the UK?

Liniar extrudes its profile in Derbyshire and states on its own site that it does not manufacture finished glazed products. The finished window is built by an independent fabricator from Liniar profile, so the fabricator you choose determines the build quality of the actual unit.

Which is better for a conservation area?

Both can work. Liniar offers Timberweld and a fully mechanical corner across its flush sash range; Rehau offers a mechanical-joint corner option on Rio. Confirm the requirement with your local planning authority first, because Article 4 directions differ between councils and some assess construction rather than appearance.

Do Rehau windows contain recycled material?

The standard TOTAL70 profile is not the recycled-content product. Rehau's co-extruded TOTAL70c variant carries up to 75% post-consumer recycled material per the published brochure, and it has to be specified deliberately. Ask for the product code on your quote if recycled content is a requirement.