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What is Approved Document L?

Approved Document L1B gives guidance for compliance for building work carried out in England, focussing on the conservation of fuel and power in existing dwellings.

What are the energy performance standards for windows according to Approved Document L1B?

Windows, roof windows or roof lights should achieve a U value of 1.6 W/m2k and have an energy rating of C or better.

Do Origin Windows qualify for Approved Document L1B?

Yes. Origin Windows achieve 0.9W/m2k with aerogel, 1.1w/m2k with triple glazing, 1.5W/m2k with double glazing. Origin Windows have an energy rating of A++. Therefore, Origin Windows exceed current building regulations by 0.1W/m2k with double glazing. To view Origin Window thermal certificates, click here.

What are the energy performance standards for doors according to Approved Document L1B?

According to the current building standards, doors should achieve a minimum U value of 1.8W/m2k and an energy rating of E or better.

Do Origin Bi-fold Doors qualify for Approved Document L1B?


  • Origin Bi-fold Door double glazed 1.6W/m2k
  • Origin Bi-fold Door triple glazed (with krypton) 1.3W/m2k
  • Origin Bi-fold Door triple glazed (with argon) 1.5W/m2k
  • Origin Bi-folds achieve an energy rating of D, exceeding current building regulations.

Read more about Origin Bi-fold Door thermal performance.

Building regulations for trickle vents

Building regulations require 800mm2 of trickle ventilation into a habitable room. Therefore, if installing bi-fold doors will remove or compromise your existing ventilation system then you may need to install trickle vents.

Do I need to do anything after my bi-fold door installation?

Yes. It’s essential that the install is checked and certified by a building control inspector. You’ll receive a certificate that will confirm the work complies with current building regulations. It’s important that you receive this certificate as you could have trouble selling the property without one. Your builder, installer or local authority will be able to provide you with more information.

I want to increase the size of my existing opening for replacement doors - do I need to do anything?

Yes. You will need to contact your local council and submit a building notice. Increasing the size of your opening may require you to make a structural alteration and therefore you may require the services of a structural engineer. Your local council will be able to guide you to ensure you comply with building regulations.

If the work has been done by an installer who is registered under the FENSA scheme, then you may also wish to obtain a certificate from them to show that the work has been done to high standards.

What are the building regulations for escape/egress windows?

Regulations state that all habitable rooms in buildings of one or two storeys must have an escape window in case of a fire. An escape window must:

  • Open sideways of upwards to at least 450mm
  • Measure at least 0.33m2
  • Measure at least 450mm x 750mm (or 750mm by 450mm)
  • Have a sill height of between 800mm and 1100mm from the floor (or 600mm and 1100mm for roof escape windows).
  • Stay open without being held
  • Be unobstructed
  • Lead to a place of safety
  • Be accessible by ladder
  • Stay open without being held
  • If the window is too low, then you can always use a step on the floor. Similarly, if the window is too high then you can use guarding, restrictors or safety glazing.

Can the Origin Casement Window be used as an escape window?

Yes. Side or top hung Origin Casement Windows that meet the minimum height and width requirements according to current building regulations can be used as an escape window. Origin French Windows are also able to meet emergency exit requirements.

Are building regulations different for listed properties or properties in conservation areas?

Yes, absolutely. Doors and windows provide character as well as function, therefore, you will need to speak with your local planning authority before carrying out any changes. With listed buildings and conservation areas, the council tends to favour repairing windows and doors rather than replacing them.

You will need to complete an application form and then wait up to eight weeks before hearing back with a decision. Carrying out unauthorised changes to a listed building is considered a criminal offense and it is the homeowner’s responsibility to comply with the approval process.