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Highly insulated composite bifold doors - available with double or triple glazing 

Continuing on from the success of the SF75, the SUNFLEX SF75c has been specifically evolved to offer the best in thermal efficiency – an extremely low U-Value, eco-friendly bifold door system. This market leading system provides the lowest in CO2 emissions associated with reduced energy consumption and considerable savings in heating bills.

The SF75c bifold door represent the best of both worlds. With a thermally broken aluminium bifold doors system blends in with rest of your windows, while the timber clad internally enables to match the look of your room. Enjoy the benefits with the low maintenance and superior thermal efficiency in aluminium combined with the natural beauty and warmth of wood.

Key features

  • One of the most thermally efficient bifold door systems on the market with overall U-Values less than 1.0W/m2K.
  • Revolutionary narrow sight-lines (118mm). Slimmest composite bifold door available.
  • Triple gasket for finger cushioning and tight compression seals. The most weathertight bifold door available.
  • Secured by Design award. Designed and installed to police preferred specification.
  • Severely weather rated with weathered track and unbeatable reassuring test results (900Pa water tightness).
  • Extremely versatile, up to 1,100mm wide panels, 3,500mm high, open in/out flush or weathered track option.
  • Mushroom locking into side jamb coupled with top and bottom metal shoot bolt rods, excellent security. WK2 security package available.
  • Large range of timber types and finishes available along with moulded, square edge or plain internal timber profile choices allowing you to choose the best look for your project.

Versatility in design

The system may be folded to the left or the right, open to the inside or outside. The SF75c can have panels all folding the same way or split with a number folding to each side.

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Whatever your requirements our bespoke range of bifolding doors can provide the solution. All systems can open either to the inside or the outside with panels opening to the left or the right. With all bifolding door systems an odd configuration will provide a single access door, which can stack the same direction or to the opposite side.

In even number configurations, two door panels will open together allowing access between spaces. Once fully open panels will stack neatly at 90o, all to one side or split with a number of panels to the left and right. With our unique stacking catch the doors will then hold themselves open meaning doors will not start to close if there is any breeze.

Our systems are also available with fixed or moveable 90o or 135o angled corner posts making it possible to completely open up corners, bays or even segmented radius curves.


Standard aluminium finishes

As standard we offer the choice of the five colours, silver anodised EV1; white RAL 9016; silver RAL 9006; grey aluminium RAL 9007; or anthracite grey RAL 7016, as shown below. These colours offer our shortest lead times and are included within our quotations. Once we have prepared a quotation we are able to send colour samples for approval prior to progressing with your order.

Standard finishes for the SF75c bi-folding door by IDSystems


Special RAL colours

Over our standard range we are also able to offer the full RAL classic colour range. The range consists of over 200 colours which come in a matt, semi-gloss or full-gloss finish. The colours shown in the swatch will give an indication to the colour shade, however before progressing with an order we can provide aluminium samples for your approval.

RAL colours for the SF75c bi-folding door by IDSystems



RAL swatches for the SF75c bi-folding door by IDSystems

RAL swatches

RAL classic colour swatches can be purchased directly from us for £10.99 (including postage).

The full colour swatch is a great tool to allow you to choose the colour of your doors and windows to complement your internal decoration, external render, brickwork or other features within your project.

To order a RAL swatch you can make a card payment over the phone by calling us on 01603 408804. If you have narrowed down your choice we are able to send a colour sample for your approval when placing an order.



Finishes on meranti

Below are images of our range of standard stain finishes available on our standard hardwood meranti.

  • Standard stain finish for meranti in ash from IDSystems
  • Standard stain finish for meranti in pine from IDSystems
  • Standard stain finish for meranti in old pine from IDSystems
    Old pine
  • Standard stain finish for meranti in light oak from IDSystems
    Light oak
  • Standard stain finish for meranti in dark oak from IDSystems
    Dark oak
  • Standard stain finish for meranti in teak from IDSystems
  • Standard stain finish for meranti in mahogany from IDSystems
  • Standard stain finish for meranti in rosewood from IDSystems
  • Standard stain finish for meranti in walnut from IDSystems
  • Standard stain finish for meranti in ebony from IDSystems


Finishes on pine

Below are images of our range of standard stain finishes available on our standard softwood pine.

  • Standard stain finish for pine in ash from IDSystems
  • Standard stain finish for pine in pine from IDSystems
  • Standard stain finish for pine in old pine from IDSystems
    Old pine
  • Standard stain finish for pine in light oak from IDSystems
    Light oak
  • Standard stain finish for pine in dark oak from IDSystems
    Dark oak
  • Standard stain finish for pine in teak from IDSystems
  • Standard stain finish for pine in mahogany from IDSystems
  • Standard stain finish for pine in rosewood from IDSystems
  • Standard stain finish for pine in walnut from IDSystems
  • Standard stain finish for pine in ebony from IDSystems


Finishes on oak

Below are images of our range of standard stains and finishes available on oak, which is available over our standard pine or meranti.

  • Standard stain finish for oak in ash from IDSystems
  • Standard stain finish for oak in pine from IDSystems
  • Standard stain finish for oak in old pine from IDSystems
    Old pine
  • Standard stain finish for oak in light oak from IDSystems
    Light oak
  • Standard stain finish for oak in dark oak from IDSystems
    Dark oak
  • Standard stain finish for oak in teak from IDSystems
  • Standard stain finish for oak in mahogany from IDSystems
  • Standard stain finish for oak in rosewood from IDSystems
  • Standard stain finish for oak in walnut from IDSystems
  • Standard stain finish for oak in ebony from IDSystems
  • Standard stain finish for oak in oiled from IDSystems
  • Standard stain finish for oak in clear from IDSystems


Please note that due to the variation of the grain in timber, any colour samples provided are designed only to give an indication of the shade and may not match the finished product.

Glass options

As standard all of our products will be fitted with glazing that exceeds Building Regulations Document N and L which govern safety and thermal efficiency. Over our standard glass there are many options for you to choose from including:

  • Laminated glass: Improved security and UV reduction preventing furniture fading.
  • Tinted anti-sun glass: Reducing solar gain, available in blue, green, grey or bronze.
  • Neutral anti-sun glass: Neutral in colour with reflective properties to reduce solar gain.
  • Self-cleaning glass: Reduces the need to clean the glass, very useful in roofs.
  • Obscure glass: Our satin deco is a stylish solution for areas requiring privacy.
  • Low-iron glass: Improves the light transmittance through glass while providing some free energy. 




Manufacturers recommend panel widths do not exceed 1,100mm, with a maximum height of 3,500mm. Please contact our technical department for advice.

The system can cater for very large openings - up to seven metres in any one direction.


The SF75c bifold door profile is constructed from a strong aluminium extrusion. This has been thermally broken by a 44mm polyamide insulation bar, guaranteeing it maximum resistance to combat heat loss and condensation. The minimal framework is offered as a square edge profile.

The SF75c benefits from the strength and stability that is provided by the aluminium, and combines it with the natural charm and beauty of timber to the inside. This provides the very best of both worlds and with a choice of timber profile shape to suit. The standard timbers are meranti (hardwood) and Nordic pine (knot free-softwood), while other timbers such as American white oak, Larch or Douglas Fir are available by special order. When closed the vertical junction between each pane of glass is just 114mm wide making it one of the slimmest systems available.

Track options

There are two choices of track; a standard weathered track for a severe weather rated system and a low threshold track. The low threshold track complies with Building Regulations Document M for disabled access.

Weathered track

In any exposed location we would always recommend the use of a weathered track. When used with an outward opening door a weathered track can be fully recessed below your internal floor level meaning that there is no threshold to trip over, just a 35mm step down to the outside. An external deck or paving can be brought up to the track on the outside giving a very minimal difference in levels whilst maintaining a weather tight seal.

Low threshold track

The Low threshold track can be recessed into the floor with matching inside and outside floor levels and just a small 14mm upstand on the track. The upstand allows the doors to form a seal, whilst offering a smaller difference in floor level than the weathered track.


Lead door or single pass door fitted as standard with a five-lever key-locking cylinder, incorporating mushroom headed ESPAG bolt and shootbolts top and bottom. A central latch position can be added for convenience with a horizontal stainless steel lever handle. First opening pair (or alternative lead door) consists of a two-point top and bottom shootbolt mechanism. The locking system is incorporated within the framework within each intermediate panel, operated by an internal flush handle.

For improved security, all Sunflex bifolding door systems are internally glazed as standard, with centre secured locking hinge pins and interlocking gaskets.

Where there are an odd number of panels, a five-lever profile cylinder is fitted to the end lead door or to the first opening pair in an even number of panels. It can be fitted to either the inside only or both internally and externally, meeting the requirements of the Association of British Insurers.

The shootbolt rods are manufactured in aluminium and linked by a corrosion resistant cam. In addition they are capped with polyamide cones that prevent any damage to the track when locking, whilst compressing the panels tight against the top and bottom seals.

Throughout the range of Sunflex bifolding door systems you have the option of internal and/or external handles. Handles are fitted to every intermediate door panel and additional locks can be added at these points for higher security.

There are further enhanced security options available and panic locks can be fitted for fire escapes, etc. Sunflex also offers electric latch-release locks and a rollerball latch lock for commercial use.

Weather seals

The system is a severe weather rated system when used with the weathered track option, providing a top and bottom double-rebated seal. Unique triple gaskets provide a finger cushion and eliminate draughts. The system achieves BS EN 12207 air permeability Class 4, water tightness Class 9A (900Pa), wind resistance Class 4.

The triple gasket seals both at the front and the back of the panel are continuous, even behind the hinges, and of superior quality (consisting of long lasting EPDM). The unique design of these triple self-sealing gaskets provides a minimal sightline. Whilst providing a cushion to minimise injury if fingers were to be trapped, in addition to improved weather performance.

Operating system

The stainless steel running mechanism consists of four wheels, manufactured from tough glass fibre reinforced polyamide. And set around a maintenance-free sealed ball-bearing, giving a quiet, smooth operation with optimum resistance to extreme weather and temperatures fluctuations.

The SF75c bifold door can be adjusted to alter height and load of the system to provide a degree of tolerance. The wheels of the running mechanism run in a channel in the sides of the track rather than sitting directly on the bottom. Unlike many inferior systems, this minimises the risk of the operating system fouling, should any dirt or debris be allowed to build up in the bottom of the track.

The unique design of running gear mechanism hinged between the door panels eliminates the need for a sliding post. This achieves smoother operation, slim sightlines and larger glass area.


The SF75c system is available as standard in silver anodised EV1 or polyester powder coated to a semi-gloss finish - white RAL 9016; aluminium RAL 9006; grey aluminium RAL 9007; or anthracite grey RAL 7016.

Single doors fitted as standard with stainless steel lever handles. With first opening pair and intermediate door panels fitted with flush handles are specially designed to complement the door system. Standard colours are white RAL 9016; black RAL 9011; aluminium RAL 9006; grey aluminium RAL 9007; or anthracite grey RAL 7016. Gaskets are in black, with hinges mounted within seal sightline available in white RAL 9016 or black RAL 9011.

Other RAL colours are available with over 200 colours to choose from. You can even have different colours to the inside and outside (dual colour) or different wood grain effects are available for a nominal charge. The RAL colours can be applied to the handles and hinges if required or alternatively there is a stainless steel handle and hinge option. In addition you can specify whether a matt, semi-gloss or full-gloss level of paint finish is required.

A marine environment finish, required to all systems within 5,000m of a shoreline or chemical swimming pool environment, is also available.

The SF75c, in addition to the external aluminium finishes listed above, has the natural character of wood cladding to the inside. Perfectly preserved by using Sikkens micro-porous water based wood stains (ie they contain no harmful solvents) in a variety of stain colours, standard Sunflex timber door systems are fully finished with one basecoat and two topcoats. Clear or oil finishes are available upon request.


Trickle vents with an airflow equivalent to 2500mm2 or 5000mm2 can also be incorporated with the addition of a 35mm add-on head profile. These will be colour coded to suit the frame colour choice.

Panel catch

In the situation of a single access or pass door in an odd number configuration, the panel is fitted with a panel catch. This prevents the door from swinging back around in high winds, and also counter weights the door with the adjacent panel for effortless operation.

Pull handles

When the bifolding door system opens externally the intermediate panels are fitted with a moulded 'D' shaped handle. This is attached to the internal hinge between two even panels, and sits neatly within the gasket line. This enables easy closure of panels against the compression top and bottom gasket seal.


The SF75 bifolding door system is internally glazed and can accommodate triple glazing with a sealed unit of up to 56mm.

Our standard comprises of a 4mm triple glazed unit with a centre pane U-Value of 0.6W/m2K clear toughened glass to exceed all building regulations for safety and thermal efficiency.

All units are BS kite marked, manufactured to BS EN 12600 and BS 5713:1979 standards.

IDSystems offer a wide choice of glazing options, including manual or electrical internal venetian blinds which can be incorporated inside the glazed unit (depending upon glass specification). These are very popular, especially on internally opening systems where curtains are not practical.

U-Values and heat losses

A U-Value is a calculation of the amount of heat lost through a building material. The calculation of U-Values can be quite complex as it is measured as the amount of heat loss through a 1m2 of material for every degree difference in temperature either side of the material. It is indicated in units of watts per square metre per degree Kelvin or W/m2K. The simplest way to approach U-Values is the lower the U-Value the more thermally efficient a product is.

A U-Value of a door or window is calculated by working out by determining the U-Value of the frame and the area of the glass and is then quoted as an overall U-Value. Beware that some manufacturers may just be providing the U-Value of the glass alone which gives a false overall value. All of our systems have been thermally simulated in accordance with CE standards to BS EN ISO 10077. 

Building Regulations approval will be required on all extensions and new builds to which we are able to provide CE data showing compliance. Any replacement works we are able to cover being a member of FENSA and a certificate would be provided on completion of our installation.

Double or triple glazing

Double glazing is a minimum requirement for external doors and windows. Our standard double glazed units consist of a soft-coat Low-E (low emissivity) pane and an argon gas filled cavity which provides a centre pane U-Value of 1.2W/m2K. Over the standard we can provide super insulated double glazed units providing a centre pane U-Value of 1.0W/m2K whilst providing solar control.

Triple glazing is becoming increasingly popular, especially in total new builds, as it provides the lowest U-Values possible and can be up to 40% more efficient than double glazing. Combining two panes of Low-E glass and two gas filled cavities glazing U-Values as low as 0.5W/m2K are possible with the added benefit of great sound reduction.

For more information on our huge range of glazing options or for help in specifying the correct glass for your project contact our technical sales department on 01603 408804.

Solar control and the benefits of solar gain

With the standard glass specification retaining as much heat as possible you may wish to consider reducing the heat transfer from outside which is known as solar gain. Solar gain can make glass roofs, conservatories or south facing elevations quite uncomfortable in the height of summer months.

A solar control glass is a glass with a either a special coating or a body tint to reduce the amount of heat entering a building either by reflecting or absorbing heat. Using a solar control glass can reduce the need for air conditioning and blinds. Whilst the solar control glasses are great at reducing the heat they will also reduce light transmittance.

Building control often recognise the benefits of solar gain in modern buildings as large areas of glass will work as a source of free energy during cooler months and increased solar gains are recommended. The use of low-iron glass can increase the heat and light transmittance to provide further solar gains during the autumn and winter months. Many modern designs incorporate overhangs to cast shadows over glazing during the summer combatting the solar gains. Thus allowing solar gains as the sun gets lower in the sky later in the year reducing the need for heating.

Safety glass

When required we fit toughened glass to comply with Building Regulations Document N as an alternate method of compliance we are able to fit laminated glass. Both options have their pros and cons.

Toughened glass

Toughened glass has been heat tempered to increasing its strength over ordinary annealed glass by up to five times. Other than the strength the advantage of toughened glass is that should it break it would shatter into non-sharp pieces. It is also available with the widest variety of coatings and can be supplied in larger sheets than equivalent thickness laminated glass.

When the glass is toughened it can suffer from some visual distortion making, meaning the face of the glass is not perfectly flat distorting some reflections.

Laminated glass

Laminated glass is manufactured by bonding two panes of annealed glass with a clear plastic interlayer. The benefit of laminated glass is that if it’s broken the glass will crack rather than shattering, improving security. In addition, laminated glass reduces bleaching of carpets, curtains and furniture by filtering UV rays that would usually penetrate the glass.

The drawback of laminated glass is that extreme heat or cold can cause invisible defects in the glass to form a crack due to the two panes expanding and contracting independently. As the laminated glass is not toughened is does not suffer from the visual distortion that can occur to toughened glass during the toughening process.

Custom designs

As well as offering full height clear glass we can also provide a more traditional style of glazing by incorporating glazing bars, Georgian grids or lead work. Please contact us for further information.

Cat flaps

Often neglected when planning your new build or extension is where a suitable space may be for your feline friend, we have the ideal solution. It is possible to have a cat flap fitted into a glazed panel by cutting a circular hole into the toughened glass unit for you to fit an in-glazed cat flap.

Venetian blinds

We are able to fit venetian blinds within the glazed unit, ensuring a totally dust-free environment which requires no cleaning or maintenance. These are very popular, especially on internally opening systems where curtains are not practical.

Integrated blinds can be tilted to help prevent the build-up of excessive heat and glare of the sun during the daytime and provide privacy when closed. Blind units can be manually operated with an ingenious magnetic control device or electronically operated via remote control. Please visit our dedicated blinds pages for further information.

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