Stellar Aluminium Windows Review

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Nick Dardalis

The Stellar aluminium windows review tells you everything you need to know about the new window from Epwin Windows. Comprising casement windows, you’ll also find in the collection, residential doors, sliding doors and bifolding doors. We explain what you get with the system and its features and benefits. We also point out a number of things Epwin, we think, missed out on this new system, as good as it is.

Information about Stellar Windows and Doors

Stellar aluminium windows
modern home extension

Unique window styling and a more distinctive window from the mainstream, Stellar aluminium windows are high quality, secure and energy-efficient with a flush casement design, for new build or refurbishment projects.

Editor's Rating:


  • Well designed with good aesthetics
  • Casement and tilt and turn options
  • Matching flush door
  • Very good energy ratings


  • Handle styling could be better
  • Mullions can look thick and chunky
  • Not as slim as it's marketed

There are claims that that aluminium window and door systems have not really developed with little innovation. We don’t agree.

Epwin Windows also says the same about its new Stellar windows and doors. They’re new, look different from other systems, and come from a very reputable and experienced business. Epwin’s capacity to supply Stellar extrusions is substantial and includes a polyester powder paint plant. They also have the latest machines and innovative ways of streamlining the production of extrusions, such as inserting thermal breaks and gaskets.

So while we don’t agree at the lack of innovation with aluminium windows and doors over the years, one area where aluminium has not developed that well is the improved fabrication and a more ‘fitter-friendly’ installation. Aluminium windows remain mostly hand-crafted products and one of many reasons for choosing them over uPVC.

stellar aluminium windows review

If you’re a homeowner choosing your new windows and doors, how easy your windows and doors are to make or fit isn’t a concern. However, for the fabricator and installer, it matters. The glazing industry respects the views of its installers. If they find a product hard to fix and awkward to glaze, this feedback is invaluable.

The Stellar Product Range

stellar aluminium windows review

We focus on the window product in the Stellar aluminium windows review. Within the entire collection, you will also find residential doors, a sliding door and the existing bifolding door.

The windows and doors, as well as the lift and sliding door, are entirely new. Epwin says the system offers slim sightlines, the manufacturing and installation benefits, reduced waste, improved sightlines and integrates across the various products in the collection.

Stellar Aluminium Doors come designed mainly for the residential market and have the same flush aesthetic. These are suitable for single back or side doors, porch doors and double French doors. Of course, they integrate well with the window suite, creating bigger patio doors such as patio doors with sidelights.

The sliding door offering offers the desirable lift and slide action, and we will be reviewing this product fully at a later date alongside the residential doors.

Stellar Aluminium Windows

Studying the fabrication and technical manual reveals a suite of sections all of which feature a deep thermal break and entirely flat in appearance. Therefore, the Stellar windows collection is very much modern-focused. You won’t find any traditional profiles available across other brands such as Aluk windows or the Smart Systems Alitherm range. Here we think Epwin have missed out on an opportunity.

Integrating more traditional profiles is not difficult to do and we hope this is part of a future update. In fact, many window installers, especially in suburban houses often choose a combination of a profiled outer frame and a flat sash arrangement. It looks good and it works.

With the Stellar range, you get the option of two flush casement window options. One of these has the flush detail on the outside only, with a square stepped detail on the inside. The other has a flush detail internally as well. Epwin says it’s the only fully flush casement window on the market but Origin’s OW-80 has been on the market for several years already.

Available are three different outer frames. WQ01 is the slimmest, with a medium option WQ02 also used as the outer frame in the door. WQ03 is the deepest outer frame. In the real world and especially for window replacements, the medium and deep are the more likely to be used. The slim will only really work in new installs.

You also get two sash options, for the fully flush and the ouside only. Then there are six different mullion options. What you choose depends on aesthetics, window sizes and overall inertia and strength needed.

With six different beads for double or triple glazing, there is also a range of ancillary profiles. These include a good range of cills, bay poles, corner posts, frame extensions for trickle vents and other components needed to suit all manner of installations.

grey stellar window

How slim are Stellar Windows?

Epwin says on its website:

“Stellar is at least 30% slimmer than the main competing systems.” And they are right looking at the information provided by the Company.

As this is a flush casement product, it makes sense to compare it against some other flush casement windows on the market.

SightlineStellar WindowOrigin
Smart Systems Alitherm 500
Fixed Light36mm slim frame
54mm medium frame
38mm slim frame
58mm long frame
50mm slim frame
Outer frame &
61.5mm slim frame/flush

75 mm slim frame/full flush

65mm slim frame
85mm long frame
Sash, Mullion, Sash105mm107mm148mm103.5mm
Sash, Mullion, Fixed79.5mm 80mm108mm103mm

We’ve looked at the fabrication and technical manuals for Stellar and other systems. The probable direct competitor to Stellar will be Smart Systems Alitherm 500 window. Stellar is slimmer and offers friction stays where the Alitherm 500 only comes with butt hinges for opening casements. With Alitherm this also has to have the dummy vents. It’s also been pointed out that you can’t glaze this window directly from the fixed frame either.

The Senior Systems Series 2 product is as well but this does depend on the frame combinations chosen. The Senior Systems Ali VU flush casement is 66mm internally and 84mm when used with a frame extension. Reynaers CS68 and SL38 windows also come out slimmer but again depending on the frame combinations.

For balance, Epwin tells us that their claims are based on a CEN standard window. For those that don’t know this is a window style 1230 wide x 1480 high, an opening light next to a fixed pane. Therefore when compared to Origin OW-80 window or the Warmcore product it’s a slimmer window.

Based on this CEN standard window, Stellar is slimmer than the Alitherm 600 and Aluk 58BW windows too. Epwin also tells us that they’ve compared their new window to Alitherm 600 and Aluk 58BW as these are considered the most commonly used competitor systems. And we’d agree with them. Again, for balance, whilst sightlines are important, overall aesthetics matter more to the buyer. And the Stellar aluminium windows collection is an attractive product overall.

The pre-gasketed system

We were sceptical of a pre-gasketed system when Aluk introduced the C70S earlier this year. Epwin has done a far better job of marketing the message and providing more benefits. The pre-inserted gaskets method works well in reducing fabrication time. First of all the windows do not need wedge gasket typical of other systems. This is bound to save a lot of time glazing the window and provides a neater and better-looking window overall.

Another benefit is neater gasket ends and hopefully less unsightly overlapping where vertical and horizontal gaskets meet. Again homeowners only see a possible visual benefit, but largely unaware this feature even exists. Our view is only the glazier benefits in reality. Experienced fabricators (and especially those making more than one system) are used to making different products in different ways. Arguably this isn’t a substantial selling point to them. However, we encourage people to go glaze a Stellar window. The difference over traditional methods is evident.

And all of this also comes down to a brilliantly designed glazing bead. Doing away with the conventional leg found on other casement windows, Stellar beads feature a rounded design above the leg that clips into the frame or vent. We’ve seen this, it works and once again will make a difference in the speed of glazing windows. It’s as easy as putting in a upvc bead. The bottom beads only need fitting with WG10 seal cord which appears to offer protection from water pooling on the bottom bead, given its alternative design to regular window beads.

Other great features of Stellar Windows

When putting together this Stellar aluminium windows review, its difficult to not focus on the benefits of this system to the trade rather than the end-user. The fabrication and fitting benefits do stand out more than the reasons for a homeowner to choose the system.

The locking system comprises fast-to-fit espagnolette locks and therefore don’t need additional shoot bolts. Reduce the hassle of corner ties – you won’t need as many. What’s more, your stock levels will be easier to manage because many parts are consistent across the suite. Be aware the flush sash has the handle fitted after it’s glazed. For those used to getting their window handles fitted on their windows, it’s a change. You’ll need to fit the handle last and also seal the back of the handle to the bead.

The ingenious reverse butt joint on this system means Stellar windows do away with dummy sashes for consistent sightlines. Cleverly designed, they achieve the same look without using additional profiles.  For the trade, it’s simpler to make and cost-effective. Windows with multiple panels will be faster to put together too. There is obviously less stockholding and material handle. For the homeowner, it should work out a cheaper window, using less material than other systems on the market.

The flexibility of Stellar windows is another bonus. We like how you have the option of mechanical or crimped corners. The components used in the corners are less than other systems.

A range of other Stellar window and door options

Since the system’s launch, Stellar has introduced to accompany Stellar aluminium windows and the bifolding door, a flush casement residential door, and a lift and slide door.

This enables the homeowner or trade installer to provide a complete home solution. And it works, as several established manufacturing companies have now taken on the product as their key product offering for aluminium windows.

Colours and options available with Stellar Windows and Doors

As you’d expect from a modern 70mm deep aluminium window you get all the RAL colours and it’s great that Epwin includes the textured powder-coated finish. Few people buy it due to the lead times, but it’s a great finish.

Standard colours include RAL9003 white which we think is a great choice of white over the very common RAL9910 and RAL 9010. It’s a softer more creamy colour and looks good with the flush design. You’ll also find the expected RAL 7016 popular grey and a grey/white dual colour combination.

Then there are a range of non standard colours such as cream, a lighter and darker grey, brown and black.

The use of Yale hardware (like the Origin OW-80 window) throughout the system is also a good move as it is a familiar security brand for the end-user. The Yale Lifetime Security Guarantee is also a selling point for the homeowner. But! The windows we understand need fitting with the appropriate PAS-24 compliant hardware.

Furthermore, we like how the profiles are designed with flat rebates with fewer grooves for the dirt to get trapped. The window looks pretty on the inside compared to products having a conventional wedge gasket.

There are manufacturing differences between a standard window and one needing a PAS24 specification. The system generally requires the fitting of glazing/bridge packers on glazing. These need positioning at the hinge and locking point positions. Evidently, the tested window is different from a standard model.

Also available with the system is three cill sections at 100mm, 150mm and 200mm. These are deep cills at 36mm and 46mm including the cill upstand at the back. They’re designed to replicate the look of thick timber cills. This they do quite well. Once again the Stellar system designers have thought about the fabrication. You don’t need to machine the cill for drainage.

stellar aluminium windows and doors

Stellar Aluminium Windows Review – Conclusion

We’ve seen the window, we’ve studied the fabrication and technical manuals and it’s an excellent window system and worth considering by fabricators and installers. Glazing the window is a breeze and for the trade, a huge benefit. We’ve not touched much on the colour, security and hardware options in this Stellar aluminium windows review. The reason for this is there is nothing radically different compared to other systems on the market.

We’d like to see more ‘real-world’ published performance figures. Marketing is great at giving the impression of the lowest U-Values and high security. What marketing rarely mentions is what configuration of product and its specification achieves its test results. You won’t yet see this product on the SBD website, but Epwin tells us the product now has the BSI Kitemark, therefore expect to see it listed on the Secured by Design website soon.

However, there are areas where we think Epwin could have done better. The doors and windows don’t go wide or tall enough to accommodate the large floor to ceiling glazing. There is no dedicated steel-look vent/frame option on the windows either. We would have preferred to see a conventional casement design – not everyone loves a flush casement window. It will be interesting to see how installers take to the system, especially as few are loyal to a complete suite. We all know many sell windows from one brand, doors from another.

More information about Stellar Aluminium.

The fenestration sector certainly loves Stellar, winning multiple awards and twice the award for New Product of the Year. Overall, our Stellar aluminium windows review shows this to be a very well designed and attractive windows collection. By far the reverse butt joint finally addresses one headache in making aluminium windows while creating improved slimmer sightlines and thermal performance.

The trained eye sees the fabrication and installation benefits of the product straight away. It is clear the team at Epwin has created a good residential window, given the people behind the product, the company experience and background.

stellar aluminium systemsFabricators and installers will see advantages in making and selling Stellar. There is a lot of competition in terms of service and products from brands such as Origin, Reynaers, Smart Systems and Aluk. Some of these systems companies are outstanding at getting their brand across to the homeowner. We think what Epwin needs to do now is get the retail message across better.