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

Rehau and Kömmerling are the closest match in this market. Both trace back to German polymer engineering, both build on a 70mm five-chamber platform, and both publish a whole-window U-value of 1.2 W/m²K with double glazing. A homeowner holding two quotes will struggle to separate them on the headline numbers alone. The differences sit in where the profile is extruded, how each states its figures, and how far the published security certification extends.

Quick Decision Frame

Choose Rehau if you want factory-integrated EPDM gaskets pre-fitted into the profile, published Window Energy Ratings to compare against other quotes, or a single-brand range covering casements, flush sash and inline sliding patio doors.

Choose Kömmerling if UK extrusion matters for lead times and long-term parts supply, you want calcium-zinc lead-free profile from a manufacturer that says it was early to abandon lead stabilisers, or you prefer the ovolo decorative edge of the O70 for a period property.

Either works for Part L compliance, a 10-year profile warranty, multi-point locking and FENSA-registered installation.

Company Background

Rehau

Rehau's Bavarian operation dates to 1948 and reaches beyond construction into automotive and industrial polymer, which shows in how much it publishes. That matters in this particular pairing: against Kömmerling, Rehau's advantage is less about the profile itself than about what it publishes.

TOTAL70 is the 70mm five-chamber casement platform with steel reinforcement zones and factory-integrated EPDM gaskets. Alongside it, Rehau publishes Window Energy Ratings, a PAS 24 claim covering windows, and a stated recycled-content figure through TOTAL70c at up to 75% post-consumer material. Rio handles flush casement and Slinova the inline sliding patio door.

Kömmerling

Kömmerling is part of the profine group and trades in the UK as profine UK Ltd. Its profile is extruded and produced at Common Lane, Huthwaite, Nottinghamshire, which puts manufacturing in the UK rather than importing from Europe.

The 70mm platform splits into two aesthetics using similar design parameters. C70 carries a chamfered edge for a modern look. O70 carries an ovolo decorative edge suited to period and cottage properties. The wider range extends to 76mm, 88mm, a vertical slider and a flush sash.

Kömmerling states that it was among the first manufacturers to replace lead-based stabilisers with non-toxic calcium zinc alternatives, and that it was the first to obtain Zero Pellet Loss certification, which addresses plastic pellet escape during manufacture. Both claims appear in its C70 and O70 brochures dated January 2024.

Thermal Performance

| Metric | Rehau TOTAL70 | Kömmerling C70 / O70 | |---|---|---| | System size | 70mm frame depth | 70mm system | | Chambers | 5-chamber with steel reinforcement zones | 5-chamber throughout | | Whole window U-value, double glazing | from 1.2 W/m²K | 1.2 W/m²K as standard | | Whole window U-value, triple glazing | from 0.8 W/m²K with triple glazed argon sealed units | 0.88 W/m²K | | Window Energy Rating | A+ standard | Not published | | Acoustic reduction | Specification dependent | up to 42 dB | | Guarantee | 10-year profile | 10-year PVCu profile warranty |

One distinction favours Kömmerling in a way the raw numbers hide.

Rehau states 1.2 W/m²K as a "from" figure, meaning the best achievable in an optimised configuration. Kömmerling states 1.2 W/m²K "as standard". If both hold in practice, the Kömmerling figure is the more conservative claim and the more useful one for a homeowner comparing quotes, because it describes the normal build rather than the ceiling.

Rehau takes the triple-glazed comparison. Its TOTAL70 brochure publishes from 0.8 W/m²K using triple glazed argon sealed units, against Kömmerling's 0.88. The 0.08 W/m²K margin between them is not something a homeowner would perceive, and both depend on the glazing unit specified rather than the profile alone.

The gap in Kömmerling's disclosure is the Window Energy Rating. It publishes no A, A+ or A++ band on its UK site. WER is the rating most homeowners actually recognise and the one most quotes lead with, so its absence makes direct comparison harder. Ask any installer quoting Kömmerling to state the WER band for the specific window and glazing unit on your quote.

Security: Read the Scope Carefully

This is the one area where the two systems are not documented to the same depth, and it needs stating precisely rather than dramatically.

Rehau ships PAS 24 as standard across its window range, with multi-point locking and internal beading.

Kömmerling's published material states that its doors exceed the standards set out in PAS 24:2022. For its windows, the C70 and O70 brochures dated January 2024 describe multipoint locks, shoot bolts and push-button key locking, but do not carry an equivalent published PAS 24 claim.

An absence of a published claim is not evidence that the windows fail the standard, and it would be unfair to read it that way. Many systems hold certification that is documented through the fabricator rather than the systems house. The practical step is simple: if you need PAS 24 for insurance, for Secured by Design, or to satisfy Part Q on a new build, ask your Kömmerling fabricator for the test certificate covering the specific window configuration you are buying. That is a reasonable request and a good fabricator will provide it without hesitation.

Corner Construction

Rehau offers welded corners across TOTAL70, with a mechanical-joint corner option on the Rio flush casement for heritage applications.

Kömmerling describes variable corner welding options on its windows, and welded corner joints with steel reinforcement on its doors. For a conservation-area property where a planning officer is assessing the corner detail, Rehau's Rio gives a more clearly documented mechanical route. Kömmerling's flush sash sits in the wider range beyond the C70 and O70 platform covered here, so confirm the corner options for that specific product if heritage is your priority.

Sustainability

| Measure | Rehau | Kömmerling | |---|---|---| | Recycled content | up to 75% post-consumer in the TOTAL70c variant, per published brochure | Recycled material in the profile core through its UK recycling programme. No percentage published | | Lead-free | Lead stabilisers are no longer used in current UK profile | Calcium zinc stabilisers, which Kömmerling states it adopted early | | Manufacturing certification | Not published in this comparison | Zero Pellet Loss certification, which Kömmerling states it obtained first (its claim, Jan 2024 brochures) |

Rehau publishes a number and Kömmerling does not, which makes Rehau easier to specify against a sustainability requirement. Kömmerling's position is stronger on process: calcium-zinc stabilisers and Zero Pellet Loss certification address the manufacturing footprint rather than the content percentage. The two claims answer different questions and neither cancels the other.

UK Manufacturing

Kömmerling extrudes and produces at Huthwaite, Nottinghamshire. Rehau extrudes in Europe with UK fabrication. For most homeowners the finished window is identical either way, but UK extrusion shortens lead times on volume work and makes matching a profile for a repair easier a decade later. Kömmerling holds that advantage.

C70 or O70: Which Aesthetic

The two share design parameters and differ on the visible edge.

C70 uses a chamfered edge, which reads clean and contemporary and suits modern housing and extensions.

O70 uses an ovolo decorative edge, a softer moulded profile that sits more comfortably on cottages, period terraces and traditional elevations where a hard chamfer looks wrong.

Rehau's equivalent decision is between the standard TOTAL70 casement and the Rio flush casement, though Rio changes the sash geometry rather than only the edge detail.

Which One We Fabricate, and Why

Our workshop in Uxbridge fabricates Rehau. We cut, machine and assemble the profile into finished units and install them with our own teams, which makes this a declared preference rather than a neutral judgement.

Documentation drove the choice more than the profile did. When a customer asks whether a window meets PAS 24, or what energy band it carries, we want to answer from published certification rather than a fabricator's assurance. Rehau publishes both across its window range. That is a smaller engineering distinction than it sounds and a large practical one when a building control officer or an insurer asks the question.

Kömmerling's strengths are real. Nottinghamshire extrusion is a genuine supply-chain advantage, the calcium-zinc and Zero Pellet Loss credentials are ahead of much of the market, and stating 1.2 W/m²K as standard rather than as a best case is the more honest way to publish a figure. A homeowner with a good Kömmerling fabricator would get an excellent window.

We install as a FENSA registered company, with a CPA insurance-backed guarantee on every job.

The Verdict

| Category | Winner | |---|---| | Double-glazed thermal performance | Tied at 1.2 W/m²K, with Kömmerling stating it as standard | | Triple-glazed thermal performance | Rehau, at 0.8 against 0.88 on published figures | | Energy rating transparency | Rehau, since Kömmerling publishes no WER | | Published security scope | Rehau, whose PAS 24 claim covers windows | | Gasket construction | Rehau | | Heritage corner detail | Rehau, on the Rio mechanical joint | | Recycled content disclosure | Rehau | | Manufacturing process credentials | Kömmerling | | UK extrusion | Kömmerling | | Period aesthetic options | Kömmerling, on the O70 ovolo edge |

These are two closely matched German-engineered systems. The installer will affect the outcome more than the choice between them.

Frequently Asked Questions

Is Kömmerling as good as Rehau?

On the headline double-glazed U-value they are level at 1.2 W/m²K, and Kömmerling states that figure as standard rather than as a best case. Rehau takes the triple-glazed comparison at 0.8 against 0.88, per its published TOTAL70 brochure. Rehau answers on documentation, publishing Window Energy Ratings where Kömmerling does not and carrying a PAS 24 claim that covers windows. On the profile itself these two are as close as any pairing in UK uPVC.

Where are Kömmerling windows made?

Kömmerling profile is extruded and produced at Common Lane, Huthwaite, Nottinghamshire, by profine UK Ltd. The profile is then fabricated into finished windows by independent fabricators, so the company building your window is separate from the company making the profile.

Are Kömmerling windows PAS 24 certified?

Kömmerling's published material states that its doors exceed PAS 24:2022. For windows the brochures describe the locking hardware but do not carry an equivalent published claim. That is not evidence the windows fail the standard. If you need PAS 24 for insurance, Secured by Design or Part Q, ask your fabricator for the test certificate covering your specific window configuration.

What is the difference between C70 and O70?

Both use similar design parameters on the same 70mm platform and differ in the visible edge. C70 has a chamfered edge for a contemporary look. O70 has an ovolo decorative edge better suited to period and cottage properties. The performance figures published for the two are the same.

Which system is better for a period property?

Kömmerling's O70 offers the ovolo edge detail that suits traditional elevations. Rehau's Rio flush casement offers a mechanical-joint corner option, which is usually what a planning officer assesses in a conservation area. If the constraint is planning consent rather than appearance alone, the mechanical corner tends to carry more weight. Check with your local authority before ordering.

Do both come with a 10-year guarantee?

Both systems houses provide a 10-year warranty on the PVCu profile itself. Glass, hardware and installation are covered separately by the fabricator and installer, which is why the company fitting the window matters as much as the profile brand. Our installations are FENSA registered with a CPA insurance-backed guarantee.