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Bi-folding doors opened in garden

If you’re just starting out with your research into bi-folding doors, it’s normal to have some reservations about the insulation they can provide. After all, you’re replacing a brick wall with, essentially, glass.

So, can bi-folding doors be as thermally efficient as a solid material like brick? The short answer is ‘yes’, but it depends on a few factors – energy rating, u-value, material and glazing.

How do you avoid buying draughty units which will ruin your winter? We explain everything you need to know, so you can make a more informed decision when buying your bi-folding doors.

What is U-value and what does it measure?

The U-value measures how well a building material insulates a building – the higher the U-value the poorer the insulation is of that material.

The U-value of a doors is essential to making a decision when buying bi-folding doors, as that’s what will determine the rate of heat transmission. Usually, manufacturers advertise the U-value of the centre pane as that’s where it’s most likely to be lowest. However, what you should be looking at is the overall U-value.

The current U-value regulation in the UK is set by the Government and is at 1.8W/(m2K). Meaning every building material shouldn’t exceed that threshold.

There are three different measurements you should be aware of:

  • Uf – thermal transmittance of the frame
  • Ug – thermal transmittance of the glazing
  • Uw – thermal transmittance of the whole window (incl. glazing and frame)

How energy efficient are bi-folding doors?

The British Fenestration Ratings Council (BFRC) scheme, the UK’s systems for measuring energy efficiency of windows and doors, applies to bi-folds, so consumers can better understand what they’re buying and what to expect.

The rating goes from A to G and is very similar to the ratings you’d find on household items, such as fridges or washing machines – with A rating being the highest.

Aluminium bi-folding doors are highly energy efficient:

  • They have thermal breaks which stop heat from being transferred in and out of your home
  • They can be fitted with high performance glass, usually 24, 28 and 32mm in sizes
  • You can opt for argon gas filled glazed units
  • They’re tested on the basis of wind and water tightness

Our aluminium doors with triple glazed units can achieve U-values of as low as 1.32 W/(m2K) which is a lot lower than the Government standard. This way you know the bi-folding doors you’re buying provide an optimum temperature regardless of weather conditions.

The Window Energy Rating (WER) is also something consider, it’s an accreditation given by the BFRC. It rates the energy efficiency of the glazing using the same A to G rating. It measures how weatherproof windows are – heat and sound insulation and how well it manages condensation.