Reynaers SlimLine 38 Windows Review

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Nick Dardalis

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Reynaers Slimline 38 windows are some of the best-designed steel-look aluminium windows on the market because they provide frame options replicating original steel profiles better than other aluminium steel-look windows on the market. This great styling comes with the well-known Reynaers profile quality, design, excellent specifications and the premium brand name. The downside is the difficulty in viewing these windows in a showroom as they are very hard to locate.

In this review, we take a look at what makes Reynaers SlimLine 38 windows an excellent new or replacement windows solution in the steel-look and worthy of consideration against the established Crittall® style windows like Aluco, Alitherm Heritage, airMOD, Duration Royale and Aluk ST.

Reynaers SlimLine 38
steel look black window

Well designed and engineered with slimline profiles and several frame styling options. Reynaers SlimLine 38 windows are attractive, high-performance windows available as fully glazed or in the desirable steel look.

Editor's Rating:


  • The excellent Reynaers brand.
  • Mimics original steel windows well.
  • Opening in and out versions.
  • Openings windows up to 2.8m.


  • Hard to find in showrooms
  • Expensive

What is the Reynaers SlimLine 38 windows suite

The Reynaers aluminium windows range is substantial, offering many types of aluminium windows working with the door ranges. These windows range from simpler open out casement windows for most residential projects, through to the advanced Masterline 8 and CS77 windows, designed for those with more demanding designs and specifications.

Reynaers SlimLine 38 windows are premium aluminium windows designed to provide an industrial, Crittall® style and heritage window solution.

reynaers slimline 38 windows aluminium in a black colour in a modern house

The steel-inspired Reynaers SL 38 windows suite is the company’s latest product joining the popular steel-look systems currently available. Although the choice of homeowners isn’t that extensive.

Some brands like Origin, Senior, Stellar, and Sheerline use a more straightforward method of bars applied to otherwise standard windows. Their systems aren’t designed from the outside in the steel look. If you like their styling, any of these windows look fine with bars applied to the glass. Products by these systems companies are, of course, perfectly suitable as replacement or new windows. It’s also true many customers don’t mind buying them if the styling works for them and still regard them as a steel-look window.

Then you have products by Smart Systems, Aluk, Schuco, Aluco Aluminium, aïrMOD and Reynaers designing a dedicated system. These systems differ from the brands mentioned above because they’ve taken inspiration from how original steel window profiles are designed.

Original steel windows came in several styling versions and whilst nothing beats a genuine Crittall® or other steel window, aluminium offers an alternative and cheaper version. When you want a much cheaper product, this is where these aluminium windows work best.

Reynaers has done an excellent job of replicating the features of old steel windows. The system doesn’t claim to match Crittall or any of the other steel windows made by companies from the 1920’s onwards. It tries to give you the styling hues of old metal windows, and Reynaers SlimLine 38 does this very well.

The steel-look designs with Reynaers SlimLine 38 Windows

The three variants possible are Classic, Cubic and Ferro. All come with the latest in thermal insulation and the option of double or triple glazing. There are several immediate advantages these windows bring.

First of all is how their styling takes on some similarity to the W20, S30 and SMW profiles used in steel windows. The projecting bar of the Ferro style, the putty line of the Classic or the more minimal look of the Cubic.

Next how they retain the slimline appearance regardless of whether you choose double and triple glazed. Designed as a fixed light the frame dimension is just 33.5 increasing to around 56mm when you add an opening vent. As a result they retain their thin and elegant proportions. There are slimmer windows on the market, but they don’t come with this distinctive styling.

Another nice design feature is the lack of drainage caps. All aluminium windows need machined holes designed to drain any water entering the chambers to the outside. And most using this face-drained method rely on plastic clip-on caps to mask these essential drainage holes. Reynaers SL 38 windows are designed without the need for drainage caps making the windows look altogether sleeker. Clever.

The option of an opening inwards window or tilt and turn is another benefit and not usually available with other dedicated steel-look systems and brands. Yes, most aluminium systems offer a tilt and turn, but only Reynaers, Alitherm and the aïrMOD windows offer a steel-look or heritage tilt and turn option. Of course, you can take a standard tilt and turn and add the bars if you wish. And Reynaers have gone further with their steel-look tilt and turn in offering the windows from what we can see with no visible internal hinge that you find on every other tilt and turn window.

The Classic systems is a more traditional looking window. At the bottom of each vent and outer frame is a loping section very much like a weather bar. But this does not detract from the contemporary lines and slim aluminium profiles.

The Cubic variant of the Reynaers window is a much more flatline in appearance window. This we think is the best looking of the three products.

The Ferro we think is designed to replicate the old W series Crittall Windows. At the bottom of the vent is a projecting ‘bar’ section typical of windows such as the old W20. The outer frame like the Cubic remains flat in profile.

The best applied bars on an aluminium steel-look window

Most aluminium steel-look windows come with a couple of options when it comes to creating the grid-like appearance of classic metal windows.

You’ll find flat bars, cut to size and professionally applied with any steel-look window. Depending on the design, the bar appearance may also come from using slim mullions and transoms.

These windows also come with a fully extruded bar profile for both sides of the glass. The inside of the window comprises a proper aluminium section with raised edges. It’s more prominent yet altogether better-engineered than the simple stick-on flat bar design.

For outside the glass and matching the styling of the three window versions are two separate aluminium extrusions for the grid pattern. One replicates the Ferro design, the other intended for the Classic. They look absolutely on-point compared to the flat bar offering of other systems with pleasing 30mm sightlines.

Matching the framing system are two transom options. One is a flat profile and another matches the sightlines of the Classic. It’s very well thought out and typical of the design excellence you get with Reynaers. So your bars will look like the frame styling options shown above.

Specifications of the Reynaers SL 38 Windows.

Reynaers SL 38 Windows have the typical high insulation, weather performance and security credentials many Reynaers products have as standard. You can find the full technical details on the Reynaers SlimLine 38 page, although some of the figures quoted very much depend on the frame profiles and glass combination used.

Advanced thermal breaks combine with high quality aluminium extrusions and the glass units. Using glass having a soft-coat low-emissivity coating, warm edge spacer bars and argon gas fill, these windows easily surpass the requirements of Building Regulations for insulation and U-Values get as low as 1.4Wm2K. Triple glazing goes up to 55mm thick.

All feature a highly insulated three-chamber system. You can choose from an outward opening casement with the classic variant as well as tilt and turn or turn and tilt options with Ferro and Cubic.

Operating opening elements are high-quality European locking systems and the windows have PAS24 and Secured by Design certification.

Weather performance as you would expect from a modern aluminium window is on a par with other good systems. The windows will achieve airtightness of Class 4 (600Pa) and water tightness Class 9A (600Pa).

Other products to consider with Reynaers SL 38 windows

Aluco Aluminium

Based on the Alitherm Heritage system, Aluco aluminium windows are some of the best known from an independent manufacturer. They are accompanied by arguably the best interior steel-look sliding and hinged doors on the market. Whilst no other steel-look window comes with the same frame styling as Reynaers SlimLine 38, these are worth considering as a brilliantly made, hand-finished window range.

Alitherm Heritage Windows

The Alitherm Heritage product is the best known and most widely used. It comes in several alternative brands such as Sunflex Heritage, REAL Aluminium, and other manufacturers nationwide. Alitherm windows are widely available, tried and tested and the door range is equally good.

airMOD Heritage

Everglade Windows have a great windows collection with the aïrMOD range and it comes in some great steel-look designs. You won’t get the exact styling of the Reynaers SL 38 but it’s certainly a product worth seeing for it’s slim lines and styling. The heritage flush sash and tilt and turn models are especially pleasing on sightlines.

Schuco AWS 70 ST Windows

With Reynaers, Schuco is one of the best aluminium brands and they too offer a steel-styled version of their very well priced AWS70 ST model.

These too come with the projecting bar of W20 steel profiles as well as other versions and you of course, get a premium brand of windows.

Decalu aluminium by Deceuninck

The Decalu aluminium windows from Deceuninck is quite recent with this PVCu systems company now branching out with Aluminium in the UK. As usual, systems companies designing new windows are more interested in finding manufacturers to make windows and sell profile to. Then they want installers to buy them marketing how easy their windows and doors are to fit. They also appear to forget that it’s homeonwers that choose the windows based on styling and how much they cost.

Decalu are good windows with genuine installer and manufacturer benefits – two things of little or no interest to the end-user customer. That said, Decalu windows come in a similar style to Reynaers SL 38 with their Decalu 94 Retro and Decalu 110 Steel, as well as the Decalu 88 New Steel versions. So on a styling comparison, these are also worth checking out, but you might struggle to find these in showrooms right now.

Reynaers SL 38 Windows Review – summary and conclusion

reynaers sl 38 windows in an architectural illustration of a modern house

Reynaers SlimLine 38 windows promise you quality-made windows with excellent specifications and you are certainly improving any property with one of the best aluminium brands. These windows are capable of large or standard window sizes with windows as tall as 2.8m high, making them ideal for new build projects wanting the steel look and the most amount of glass.

Reynaers SL 38 Windows meet the Art-Deco, industrial, steel-look, Scandi, or Hygge look very well, and we see these as especially suitable for general and old metal window replacements and equally good in a new build extension with matching doors. They’re great as a contemporary window as well as a classically styled one. The frame options and especially the better-designed and thoughtful applied steel-look bars really make these windows stand out, and they come highly recommended as a steel-inspired window in aluminium. You’ll also find this brand of windows one of the slimmest among the leading window brands.

If you also need steel-look single or French doors, Reynaers do offer some products but they aren’t anywhere near as well styled as the doors by Smart Systems, Aluco and airMOD that look significantly better as Crittall style doors. But there is no reason why you can’t have your windows from one brand and your doors in another.

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