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

Rehau and Deceuninck are two of the most established uPVC systems available to UK homeowners, and both turn up on quotes for the same job. Both are European engineering businesses with decades of UK trading history, both hold the security and energy certifications a premium installation needs, and both offer a heritage flush casement alongside a standard casement range. The differences that actually matter sit in corner-joint construction, published thermal figures, recycled content and where the profile is extruded. This comparison sets them side by side, including a straight answer on which one we fabricate and why.

Quick Decision Frame

Choose Rehau if you want factory-integrated EPDM gaskets pre-fitted into the profile rather than a separately inserted seal, need the stronger published casement U-values in this pairing, or want a single-brand specification that runs from casements (TOTAL70) through flush sash (Rio) to inline sliding patio doors (Slinova).

Choose Deceuninck if UK extrusion matters to you for lead times and long-term parts availability, you want third-party EPD-certified recycled content rather than a manufacturer claim, or you are specifying a conservation-area property where mechanically jointed corners are the starting point rather than an option.

Either works for Building Regulations Part L compliance, PAS 24 security, Secured by Design accreditation, a 10-year profile guarantee, A+ energy ratings on double glazing and FENSA-registered installation.

Company Background

Rehau

Rehau is a German polymer engineering company founded in 1948 in Rehau, Bavaria. It is one of Europe's largest uPVC profile extruders, supplying construction, automotive and industrial markets across more than 50 countries. In the UK its profiles are fabricated by a network of approved partners.

The residential range is built around TOTAL70, a 70mm five-chamber profile with steel reinforcement zones and factory-integrated EPDM gaskets pre-fitted into the profile, so there is no separate gasket to shrink or work loose over time. A co-extruded variant, TOTAL70c, carries up to 75% post-consumer recycled material according to the published Rehau brochure. The Rio flush casement offers a mechanical-joint corner option, which matters where a planning officer is assessing the frame detail on a period property.

Deceuninck

Deceuninck is a Belgian polymer group whose UK subsidiary, Deceuninck Limited, was established in 1981 and operates from Stanier Road, Porte Marsh Industrial Estate, Calne, Wiltshire. UK profiles are extruded domestically rather than imported, which shortens the supply chain for fabricators and for replacement parts years after installation.

The UK residential range centres on the Heritage 2800 sculptured casement and a separate Heritage Flush Sash. Deceuninck publishes dated technical datasheets with document numbers and test-house tables, which makes its figures unusually auditable for this market. Its BIM object for the 2800 C7 casement carries an EPD certification recording 21% recycled content and 59% recyclable content, valid to May 2027.

Thermal Performance: Head to Head

U-value measures heat loss through the window, so lower is better. Building Regulations Part L requires a maximum whole-window U-value of 1.4 W/m²K for replacement windows, or a Window Energy Rating of band C.

Standard Casement

| Metric | Rehau TOTAL70 | Deceuninck Heritage 2800 | |---|---|---| | Frame depth | 70mm | 70mm (55mm and 85mm frame options also available) | | Chambers | 5-chamber with steel reinforcement zones | Multi-chamber. Deceuninck does not publish a chamber count | | Whole window U-value, double glazing | from 1.2 W/m²K | 1.4 W/m²K, down to 1.3 W/m²K with 4/20/4 argon | | Whole window U-value, triple glazing | from 0.8 W/m²K with triple glazed argon sealed units | 0.96 W/m²K, down to 0.89 W/m²K | | Window Energy Rating, double | A+ | A+ (index 12) | | Window Energy Rating, triple | A++ achievable | A++ (index 22) | | PAS 24 | Standard | PAS 24:2022, plus Secured by Design and BSI Kitemark | | Acoustic reduction | Specification dependent | up to Rw 42 dB |

Result: Rehau leads at both glazing levels, at 1.2 against 1.3 W/m²K double and 0.8 against 0.89 triple. Both sets of figures describe optimised configurations rather than what every quote carries, so treat the gap as a genuine but modest edge rather than a decisive one. Across a 20-year ownership the thermal experience would be effectively identical.

One point of honesty on the Deceuninck figures. Its 2021 datasheet records 1.3 W/m²K double and 0.89 triple, while its more recent 2025 BIM object claims as low as 1.2 double and 0.86 triple. The datasheet carries a document number and a test-house table, so it is the more defensible source; the BIM object is the more current. We have quoted the datasheet above.

Heritage and Flush Casement

| Metric | Rehau Rio | Deceuninck Heritage Flush Sash | |---|---|---| | Frame depth | 70mm | 70mm | | Corner joints | Mechanical-joint corner option available | Applicable to both mechanically jointed and welded windows | | Whole window U-value, double | from 1.2 W/m²K | 1.4 W/m²K, down to 1.2 W/m²K | | Whole window U-value, triple | Not separately published for Rio | 0.94 W/m²K, down to 0.90 W/m²K | | Window Energy Rating | A rated | A+ (index 12) double, A++ (index 23) triple | | Acoustic reduction | Specification dependent | up to 43 dB |

Result: the flush sash comparison is close. Rio matches Deceuninck's best double-glazed figure at 1.2 W/m²K and betters its standard 1.4. Rehau does not publish a separate triple-glazed figure for Rio, so we make no claim there; Deceuninck's 0.90 stands unopposed on published data. Both systems offer mechanically jointed corners, which is the detail that decides most conservation-area applications, so for a period property the two are closely matched where it counts.

Corner Joints and Why They Matter

A welded corner fuses the profile at 45 degrees and leaves a small witness line. A mechanical joint bolts the corner instead, producing a square butt joint that reads much closer to a traditional timber window. On Article 4 and conservation-area properties, planning officers are consistently more comfortable with mechanically jointed frames.

Rehau offers the mechanical-joint corner as an option on the Rio flush casement. Deceuninck's 2800 C7 casement object specifies fully mechanically jointed corners, with welded transoms and mullions as standard and mechanical available, and its Flush Sash is explicitly available in both constructions.

Both give you a credible heritage answer. Deceuninck arguably makes it easier to reach, since the mechanical detail sits at the centre of the 2800 C7 rather than as an upgrade path.

Sustainability and Recycled Content

These two brands publish recycled-content claims that measure different things, so comparing the headline numbers directly would mislead.

| Measure | Rehau | Deceuninck | |---|---|---| | Recycled content claim | up to 75% post-consumer recycled material in the TOTAL70c co-extruded variant | 21% recycled content, 59% recyclable content | | Verification | Manufacturer brochure | Third-party EPD certification, valid to May 2027 | | Applies to | The specific TOTAL70c product | The 2800 casement as documented in its EPD |

Rehau's number is far higher, but it applies to a particular co-extruded variant that must be specified. Deceuninck's is lower and applies more broadly, and it carries independent EPD verification rather than resting on a brochure. If third-party verification is the thing you care about, Deceuninck has the stronger position despite the smaller percentage.

Security

Both systems meet the UK benchmark. Deceuninck publishes PAS 24:2022 with Secured by Design and a BSI Kitemark. Rehau ships PAS 24 as standard with multi-point locking and internal beading. For a standard residential aperture the security outcome is the same, and the quality of installation matters considerably more than the choice between these two profiles.

UK Manufacturing and Supply

Deceuninck extrudes in Calne, Wiltshire. Rehau profiles are extruded in Europe and fabricated in the UK. For a homeowner this rarely changes the finished window, but it can affect lead times on volume work and the ease of sourcing a matching profile for a repair a decade later. Deceuninck holds the advantage here, in the same way Veka does through its Burnley plant.

Expected service life is comparable. Deceuninck publishes 35 years for the 2800, with air permeability Class 4 at 600 Pa and wind resistance Class A5 at 2000 Pa.

Which One We Fabricate, and Why

We are a Rehau fabricator. We cut, machine and assemble Rehau profile into finished windows and doors at our Uxbridge workshop, then install them ourselves. We do not fabricate Deceuninck, so treat this section as a stated position rather than a neutral verdict.

The reasoning is straightforward. Rehau's factory-integrated EPDM gaskets remove a long-term failure point, since a gasket that is pre-fitted into the profile cannot shrink back or fall out the way a separately inserted seal can. The published casement figures are the stronger of the two. And the range coheres: TOTAL70 casements, Rio flush sash and Slinova inline sliding doors let us specify a whole house from one system with matching sightlines and colour.

Where Deceuninck genuinely wins, we would say so. Its UK extrusion is a real supply-chain advantage, its EPD certification is better evidence than a brochure claim, and its flush sash publishes a triple-glazed figure where Rio does not. A homeowner who chose a good Deceuninck installer would get an excellent window.

We install as a FENSA registered company and every job carries a CPA insurance-backed guarantee.

The Verdict

| Category | Winner | |---|---| | Casement thermal performance | Rehau, at both glazing levels on the 2021 datasheet figures | | Flush sash, double glazing | Tied at 1.2 W/m²K | | Flush sash, triple glazing | Deceuninck, the only published figure | | Heritage corner detail | Deceuninck, marginally, on ease of specification | | Gasket construction | Rehau | | Recycled content headline | Rehau | | Recycled content verification | Deceuninck | | UK supply chain | Deceuninck | | Published spec transparency | Deceuninck | | Range coherence across window and door types | Rehau |

The engineering is close enough that the installer matters more than the badge. Both systems will comfortably outlive their 10-year guarantees when fitted properly, and both will fail early when fitted badly.

Frequently Asked Questions

Is Rehau better than Deceuninck?

Rehau holds the better published double-glazed U-value on standard casements, at 1.2 W/m²K against Deceuninck's 1.3, and its factory-integrated gaskets remove a long-term maintenance point. Deceuninck answers with UK extrusion, EPD-verified recycled content and the only published triple-glazed figure on the flush sash pairing. Neither is decisively better across the board.

Are Deceuninck windows made in the UK?

Deceuninck extrudes its UK profiles at Stanier Road, Calne, Wiltshire, where its UK subsidiary has operated since 1981. The profile is then fabricated into finished windows by a network of independent fabricators, so the company that makes your actual window will be a local business rather than Deceuninck itself.

Which system is better for a conservation area?

Both offer mechanically jointed corners, which is the detail most planning officers assess. Deceuninck's Heritage 2800 C7 specifies fully mechanically jointed corners and its Flush Sash is available mechanically jointed or welded. Rehau offers the mechanical-joint corner as an option on the Rio flush casement. Confirm the requirement with your local planning authority before ordering, since Article 4 directions vary between councils.

How many chambers does a Deceuninck window have?

Deceuninck describes its profiles as multi-chamber but does not publish a chamber count in its technical datasheets or BIM objects. Rehau publishes five chambers for TOTAL70. Treat any specific chamber figure quoted for Deceuninck by a third party with caution unless it is sourced.

Do both systems meet Building Regulations?

Both comfortably meet the Part L requirement of 1.4 W/m²K or a band C Window Energy Rating for replacement windows. Deceuninck's 2800 achieves A+ with double glazing and A++ with triple; Rehau TOTAL70 achieves A+ as standard. Compliance is not a differentiator between them.

What guarantee do you get?

Both carry a 10-year profile guarantee from the systems company. That covers the profile itself. The glass, hardware and the installation are covered separately by the fabricator and installer, which is why the company fitting the window matters as much as the brand on it. Our installations are FENSA registered with a CPA insurance-backed guarantee.