Bi-fold door specification made clear

When it comes to buying bi-fold doors, there are various factors to bear in mind before laying out cash on such an important purchase. Solarlux breaks down the key areas to consider

It may not seem so to the casual observer, but bi-folding doors are not all built equal: the quality and finish can vary enormously and there is no substitute for seeing, operating and ‘feeling’ the product for yourself. The mechanism and ease of use can vary drastically between brands.

A bi-folding door can be superb addition to your home, adding value and saleability for many years; however some brands use cheaper parts which could result in a shorter lifespan and demand more upkeep. For example, nylon runners are far less effective and not as long lasting in comparison to their more robust stainless steel counterparts.

Weather resistance

High quality manufacturers produce secure systems which don’t rattle in the wind and offer extensive noise reduction from both weather and traffic noise – an important factor for any door.

With a good quality bi-fold door you can achieve a noise reduction of 44 dB and full protection from the elements during inclement weather, while still allowing natural light to flood through the property, bringing a homely warmth to relax and unwind in.

Sometimes people ask ‘how can I determine whether a bi-fold system meets my requirements?’ Michelle Spangehl, marketing manager at Solarlux, explains: “I have come across this question many times during exhibitions. My advice is to ask for certificates that indicate the system’s performance. For instance, DIN EN regulations for protection against driving rain, resistance to wind load and air permeability.

“As an example Solarlux always tests its systems to the highest standards so that we’re able to achieve protection against driving rain up to class 9A, wind load B4 and air permeability class 3 according to DIN EN regulations. Another tip is to ask for cross sections of the doors. The more sophisticatedly engineered the profiles and floor tracks the better the performance – be it weather resistance, security or thermal efficiency.”

Thermal performance

Although bi-folding doors are all about creating open spaces, they also need to perform when closed. Many manufacturers now offer triple glazed doors and are pushing this product option. However, it’s not necessarily all about triple or double glazing – if the profiles are of high quality triple glazing won’t be necessary to reach the key Uw value for window thermal performance of 1.1. If the door’s frame is of poor quality triple glazing will not offset the difference.

It’s worth keeping in mind that the quality of a bi-fold door is also determined by what you cannot see. Generally, heat is lost via the profiles, so high quality manufacturers incorporate precisely engineered thermal breaks (air chambers) in order to reach a low U-value and prevent condensation. When comparing Uw values ask manufacturers if they have considered the profile and frame within their calculation – often they refer to the glass only.

Previously to achieve a Passivhaus standard you had to choose a system manufactured with a combination of timber and aluminium; however, this has now changed. The Bi-Fold Door by Solarlux is believed to be the first aluminium system to achieve thermal transmittance values corresponding to the guidelines for Passivhaus suitability, with a Uw value as low as 0.8 W/m2K. Achieving good thermal performance doesn’t mean compromising on current contemporary design trends.

Be security aware

With bi-folding doors featuring so much glass and making your house open for all to see, you may fear it could attract uninvited guests. Three point locking is a must, and five point is even better.

Glass should be toughened and a minimum of 4 mm thick – you may even choose laminated glass as an upgraded safer option.

The optional security specification RC2 for bi-folds and RC3 for sliders is a European security upgrade which is similar to Secured by Design, the certification preferred by the British police. This means that the system will withstand a prolonged attempted break-in and it comprises additional covers for various door components, making them even less accessible for burglars. These additional security specifications are available for selected aluminium systems only, but generally high quality bi-folds will provide good security as standard.

Sliding vs folding

The alternative to bi-folding doors is sliding doors. Subject to design and type, they are often the more expensive option. Sliding doors are usually made up of two, three or four panels with one or two panels fixed. When closed, you can enjoy uninterrupted views outside due to the fact there are less vertical profiles than with bi-folds; however, there is always an occupied area reducing the overall usable opening width.

Martijn Venema, managing director of Solarlux generally advises: “Sliding doors work best closed, bi-folds work best open. A solution should be chosen depending on the room and the situation. For example, adult-only and pet-free families can choose either, whereas families with busy lifestyles, pets and or children can rather choose a bi- folding door.”

Where the space is often used a bi- folding door is recommended, as it is typically easier to open as one panel can serve as a traffic door. Kitchens especially are where the family and friends often gather, so a bi-fold enables maximum access to the garden. However, large houses with fantastic views might rather choose a sliding door to enjoy an almost completely uninterrupted view.

Both sliding and folding doors can create a seamless transition from house to garden and can be combined with a glass or brick extension. Consult your local dealer, compare the doors’ features and test and try the systems to find your own bespoke product solution that suits your personal needs.