Bifold windows – the ultimate guide

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Nick Dardalis

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Providing an entirely different window proposition, bifold windows create larger opening windows, open up a room better than other windows, and maximise ventilation whilst providing more glass, additional light and better views. Depending on your house design, these folding windows can create an excellent alternative window with all the features and appeal of a bifold door in a smaller size. This guide to bifold windows explains what they are, the benefits of this window design, how to use them, and some of the available products.

What are bifold windows?

Bifold windows work like folding sliding doors and are essentially bifold doors in a cut-down size. This once more commercially orientated window design is often found in in hotels, restaurants, cafés and trade counters and is now popular in modern home extensions as an alternative to traditional opening outwards windows.

Just like a folding door, bifold windows can fold in one or two directions, open in or out, come with slim sightlines, depending on the model of bifolding window you choose and are fully bespoke in design, your choice of colour, handles and glass. Usually, this window style is used to complement a bifold door on the same or other elevations, giving you matching doors and windows. And with the same benefits as bifolding doors, a property can have folding doors, hinged doors, front doors and bifold windows all made from the same aluminium profiles and a consistent look throughout, even down to the handles.

Other than sliding windows, this folding window design is essentially the only window type letting you open up fully an entire window aperture. Operating the windows is exactly the same as the larger door. At the same time, these folding windows come with the same finger-safe gaskets, attractive door handles, colour options and a choice of modern or classic styling. There are even frameless glass versions and ultra-slim designs.

Designs available with bifolding windows

You can design a folding window starting with just two panels, folding to the left or to the right and with the option of folding inwards or outwards.

When your window opening allows for more than two panels, you then benefit from designing the window with an optional independent opening panel. Just like the traffic door on a set of bifold doors, this is one panel that is hinged to open without having to fold the rest of the panels back. The benefit here is opening just one panel like a regular window for ventilation. If you have four panels, there is no reason these cannot be in the middle of the window set, opening just like a set of French windows. As a result, you get the benefit of opening middle windows for regular use, with the option to fold two panels back on each side when you want the benefit of the full window opening.

You can also create expansive windows ranging from two to eight panels and with many bifold windows going up to 1200mm wide per panel. They are also ideal for smaller window openings, with folding panels as small as 400mm possible with most products.

Depending on the overall building design, it is also possible to make these windows with a fixed or open corner design where you need them on two sides.

If you want privacy and shading, the latest integral glass blinds can be fitted to bifold windows, but do bear in mind these create a picture frame look around the glass, which can give a more bulky look.

Security of folding windows

Most windows in the folding design use the existing hardware of their larger door counterparts. However, the size of the window can affect the number of locking points you get. A full-size bifold door takes advantage of a longer lock body, and you typically get from four up to eight locking points, depending on the brand. Most suppliers will either use an alternative locking system or cut down an existing lock body to suit the bifold window height. You get the same shoot bolt locking at the intermediate panels, securing the middle panels at the top and bottom just like a bifold door.

You also get as standard the glass secured from the inside of the window, a quality key locking cylinder and the same robust and stylish handles of the door versions.

You will need to speak with a professional supplier of these windows to fully understand the security available. Or you can get in touch with us for advice. These windows are by no means unsafe or not secure, but it is unlikely any have been tested to any official security tests and certifications.

Energy-efficiency of bifold windows

Again, because these windows are modified and cut-down bifold doors, you may not easily find official U-Values or window energy ratings. A professional supplier working with the bifold system company can advise on the U-Values you will get.

The thermally insulated frames you get as standard, combined with a high-specification double-glazed or triple-glazed unit, should ensure these windows meet the requirements of current Building Regulations.

Weather performance of folding windows

Bifold windows are sealed and air, wind and weather resistant using the same sealing design and components as folding doors.

Advantages of bifold windows

Compared to conventional windows, choosing a bifold window can provide several benefits in terms of window design and overall functionality.

First is the full opening and folding design, reiterating the point that this is the only window type that can fully open up your window aperture. When fully open, there are no static window mullions or transoms – just the window panels neatly stacked to the side and panoramic views.

Due to their door-inspired design, bifold windows create larger opening windows than other types of opening outwards or inwards windows. At the same time, they offer bigger panes of glass for a more modern window design.

Depending on the bifold window model chosen, sightlines at the middle mullions can be very slim indeed or frameless when choosing a slide-and-turn system. And when combined with bifolding doors, these windows can look great in creating glazing in a room that not only fully opens unlike any other window product, but also creates matching framing throughout.

Disadvantages of bifold windows

Many installations of this window design have them over the sink or kitchen worktops. The disadvantage is that you must reach over the sink to get to the window handle, but this can be no different from opening a regular window.

The other potential functional drawback to a folding window design is when they open outwards. You will probably have to go outside to release the panels in order to close the windows. Whilst this can appear strange, it is worth bearing in mind that many of these windows are designed for occasional use rather than everyday use.

These window types lend themselves better to new window opening and extensions, unless you have a larger than usual existing window opening.

Finally, not all brands are available as bifold windows, with some restricted to a minimum height of about 1600mm-1800mm. This is due to the locking systems available with the product, so you may have to to with an alternative bifold windows brand that can achieve the sizes you want. For example, Cortizo bifolds are very popular as a brand, but these cannot go below 1600mm high. You can get in touch with us for help and advice on the products that can meet your sizes and designs.

Choosing the right material: Wood, Aluminum or PVCu for your Bifold Windows

Bifold windows are available in aluminium, PVCu and wood. Aluminium will always give you the slimmer window, especially at the mullions where the bifold panels meet.

Timber windows are also available and provide a natural, warm-to-the-touch alternative with superb insulation and very long service life. You will read on many websites that timber windows are high-maintenance and not worth considering. This is not true. Modern design, coatings, treatments and paints, with a quality build, make timber windows just as good as other materials. The high-maintenance message around timber windows involves repairing the paint finish should it get damaged. You would also need to repair the powder-coated finish on an aluminium window to avoid corrosion and deterioration of the bare metal. So if you like the longevity, quality and natural feel of real wood, you can consider them, because today you get some fantastic products if you love wood.

PVCu bifold windows in the right location provide the most affordable bifold window option. Historically bifold doors in PVCu have been prone to operational issues, which is why aluminium is widely regarded as the better material. PVCu expands around two and a half times more than aluminium, and this material may not be suitable on west or south elevations. PVCu will always give you thicker styling and sightlines, so do bear this in mind, despite their lower prices.

Choosing some of the best bifold windows

We can help you find folding windows and these are available with most bifolding doors, modified and cut down to window sizes. As a result choosing the best need not be difficult. Here are our top selections.

Frameless Glass Curtains

bifold windows in a kent country property

If you like the idea of a near-frameless bifold window at the mullions, Frameless Glass Curtains based in Kent and working nationwide, provide a spectacular product that is unlike any other on the market.

FGC’s product uses the slide and turn design, double glazed, sealed, secure and energy-efficient with no aluminium at the panel mullions, creating a near-frameless design.

Schüco AS FD 75 and Schüco AS FD 90.HI

Highly recommended for their ultra-slim sightlines, quality and engineering are the newest Schüco bifold doors, also available as folding windows.

The AS FD 75 provides 90mm mullion dimensions and low U-Values capable of panels as small as 500mm wide and 660mm high. Or there is the enhanced AS FD 90.HI model with the same slim mullion sightlines improving the U-Value down to an impressive 0.8Wm2K depending on the design and the glass specification chosen. Fixed and open corner designs are available with both models in the Schüco bifolding doors range.

Origin bifolding windows

Using the OB-72 bifold door model, Origin has made these windows for a number of years, and Origin’s products continue to come with excellent quality and all manner of personalisation options. If you require bifold windows from a great brand without the premium price tag of other brands, get in touch for more information.

Sunflex UK bifold windows

sunflex bifold window showing little boy walking through a set of doors

Sunflex bifold doors are some of the best on the market, made in Germany and with excellent specifications, design and quality. These have also been available as windows for several years and provide highly engineered windows with modern design and excellent styling. Sunflex bifold windows can transform the indoor-outdoor living experience.

More information about buying and choosing bifold windows

If your home design suits a folding window, then these are a great investment, provide a unique window proposition and can make more of your home in the summer, combined with your existing or new patio doors.

Contact us for product information, project help and where to buy the right bifolding windows from the right suppliers.

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16:42 30 Oct 23
Nick responded incredibly quickly to my enquiry (on a Saturday too!), and was able to offer invaluable advice on both aluminum systems and manufacturer / suppliers. Thanks Nick!
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16:18 09 Oct 23
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19:55 13 Sep 23
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07:03 11 Sep 23
Update - A second email to nick for help on bifolds resulted in a detailed informative reply even on a Sunday ! This guy is so knowledgable and helpful .I approached Nick for an independent view on sliding doors v bifold and the different brand options . His reply was extremely detailed and prompt and allowed me to navigate this often confusing world in a much more informed way . Thanks so much Nick
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20:24 26 Jul 23
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17:25 19 Jul 23
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12:28 14 May 23
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10:06 04 May 23
Nick is very helpful indeed. Extremely knowledgeable on bifolds which was in relation to my query. Great website as well, some very useful articles. Particularly appreciated the article that lists all the major bifold options in order of their sightlines! Thank you!
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20:21 22 Feb 23
I dropped Nick at Aluminium Trade Supply an email re high security slim sightline bi-folds and their alternatives and he responded that quickly (and so comprehensively) that I felt bad I’d not paid him for his time!Nick Sir your product knowledge is outstanding and you are providing a level of service that goes wayyyy above and beyond expectations. I’ll definitely make sure I mention Aluminium Trade Supply to anyone I encounter looking for a fenestration solution 🙏🏼
15:13 13 Feb 23
We are looking to replace some old UPVC patios doors with aluminium ones. The ATS website is a great source of advice in an area where clear information is sorely lacking. Having used the website, I then followed this up with a number of specific questions relating to our search, and Nick came back very quickly with clear, detailed and very useful advice.I have been very impressed with both the website and with Nick's advice. My only regret is that I didn't come across ATS before replacing various windows in 2021 - I'm sure it would have saved me a lot of grief and money! Thanks again Nick.
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Nick was super fast to respond and provided some great recommendations. I would recommend this website to anyone looking to find bifold or sliding aluminium doors.
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