Authors note

[UPDATED 15 June 2022]

It's always best to check with the certifying body (Building Control, Certass, Fensa) to make sure that you are compliant. Also, local councils have their own specifications which need to be adhered to, if the work is going to be signed off by building control.

Important note

Part L – Conservation of Fuel and Power, Introduction 1.11 states the responsibility for compliance as;

“It is important to remember that if you are the person (e.g. designer, builder, installer) carrying out building work to which any requirement of building regulations applies you have a responsibility to ensure that the work complies with any such requirement. The building owner may also have a responsibility for ensuring compliance with building regulation requirements and could be served with an enforcement notice in cases of non-compliance”.

Consequently, every installation has to be certified by one of the following;

  • Building control (through the council in which the property resides)
  • Certass (
  • Fensa (
  • BM Trada

Subsequently, once the installation is complete and all parties have upheld their part of the contract you should receive and keep safe the following;

  1. Certificate from the certifying body,
  2. Installer invoice & guarantee,
  3. Insurance-backed guarantee.

The first item will be requested by the solicitor if you sell your home.

Most importantly building regulations changed in October 2010. They undergo regular amendments, the latest of which was Part F & L in 2022 (at time of writing).

One of the main points of the regulations is that new the window or door cannot be worse than the one they are replacing.


Minimum Opening

The clear area of the escape needs to be a minimum area of 0.33m². Also, it should have a width and height of no less than 450mm in either direction. This opening should not be higher than 1100mm from the floor of the room. However, this does not apply to habitable rooms on floors which are more than 2.5m from ground level.

Definition - Habitable Room

A habitable room is classed as – “a room used or intended to be used, for a dwelling house purpose (including for the purposes of Part B, a kitchen but not a bathroom).”
This is according to Part B of the building regulations. In other words, a habitable room is classed as a lounge, bedroom, kitchen or dining room.

Ground Floor

All habitable rooms above ground level have to have a means of escape. However, bungalows need to have either a door opening to a hallway leading to an exit or an escape window/door. To clarify, one of the openers in one of the windows in the room needs to have an escape hinge.

Upper Floors Below 4.5m

Where served by only one stair, all habitable rooms (excluding kitchens) should have either of the following;

  • An emergency escape window or external door
  • Direct access to a protected stairway

Two rooms may be served by a single window. A door between the rooms should provide access to the window without passing through the stair enclosure. Both rooms should have their own access to the internal stair.

Upper Floors Above 4.5m

Habitable rooms on floors above 4.5m do not need to have a window with a means of escape.


This is about ventilation that is either in the window/door or in the wall by means of an air brick. This can be fitted in a window or door either in the head of the frame, the sashes or as an over glass vent.

Replacing existing windows with background ventilators

They should be;

  • No smaller than the existing vents
  • Are either controllable automatically or by the occupant

Replacing existing windows without background ventilators

They should be;

  • Habitable rooms and kitchens - 8000 mm² equivalent area
  • Bathrooms (with or without a toilet) - 4000 mm² equivalent area

Addition of a habitable room (excluding conservatories)

  1. If the new room is connected to an existing habitable room that now has no windows opening externally then it needs either
  2. If it is connected to a room with a window that opens to the outside world then;
    1. If the existing habitable room windows have less than the equivalent area of 5000 mm² then;
    2. If the existing habitable room has a total background ventilator equivalent area of at least 5000 mm², both of the following should be provided.
      • Background ventilators of at least 12,000 mm² equivalent area between the two rooms.
      • Background ventilators of at least 12,000 mm² equivalent area between the additional
        room and the outside.

For new builds

Part F building regulation - table of requirements


Glazing in critical locations must comply with one of the following;

  • If the glazing breaks, it will break safely, e.g. toughened glass
  • Choose glazing that is one of the following;
    • Robust, i.e. the thickness of the glass is the right thickness for its size (please ask for details)
    • Are small panes
  • It's permanently protected by a screen which has a minimum height of 800mm

Critical locations are as follows;
Any doors

  • The glass line is less than 800mm from floor level
  • If the window is within 300mm of a door and 1500mm from floor level
  • The window is in a stairwell.

Most importantly, all toughened glass must be marked with an approved kitemark, this shows that it's been produced to the required standard.


Please note that on the 15th June 2022 the building regulations will be updated again after which the energy-efficiency requirements of windows and doors will be;

Extensions and New Builds

  • Windows; 1.2 uValue
  • Doors with >60% of internal face glazed; 1.2 uValue
  • Other doors; 1.0 uValue

UPDATE; within the Approved Document L document there is conflicting information about uValues (pages 12 and 24). We, therefore, recommend that you consult the architect's plans and proceed with what they have stipulated.

Replacement windows and doors

  • Windows; 1.4 uValue or B Rated
  • Doors with >60% of internal face glazed; 1.4 uValue or C Rated
  • Other doors; 1.4 uValue or B rated

Changes in the legal requirements

There's an exemption from the energy efficiency provisions for extensions consisting of a conservatory or porch. This amendment grants the exemption where any existing walls, windows or doors are retained, or replaced if they're removed. Also where the heating system of the building is not extended into the conservatory or porch.

Changes in technical guidance

Amendments have been made for historic and traditional buildings which may have an exemption from the energy efficiency requirements or where special considerations apply. They've also amended the guidance where an extension is a conservatory or porch that's not exempt from energy efficiency requirements.

Energy Efficiency exemptions

There are two exemptions from energy efficiency requirements that apply to building work or extensions to existing dwellings:

a) Buildings which are:

  • Listed in accordance with section 1 of the planning (Listed Buildings and Conservation Areas) Act 1990
  • In a conservation area designated in accordance with section 69 of that act
  • Included in the schedule of monuments maintained under section 1 of the Ancient Monuments and Archaeological Areas Act 1979

For these buildings, the exemption applies only to the extent that compliance with the energy efficiency requirements would unacceptably alter the character or appearance of such existing dwellings.

b) Carports, covered yards, covered ways and some conservatories or porches attached to existing dwellings.

Conservatories and porches

Regulation 9 of the Building Regulations exempts some conservatory and porch extensions from the energy efficiency requirements. The exemption applies only for conservatories or porches:

  • Which are at ground level
  • Where the floor area is less than 30m²
  • When the glazing complies with Part K 4 of Schedule 1
  • Where the existing walls, doors and windows in the part of the dwelling which separates the conservatory are retained or, if removed, replaced by walls, windows and doors which meet the energy efficiency requirements
  • The heating system of the dwelling is not extended into the conservatory or the porch.

This means that if the conservatory or the porch does not meet the above they must comply with the appropriate energy efficiency requirements.

Conservatories and porches not exempt from energy efficiency requirements

Reasonable provision would be to provide:

a) Effective thermal separation between the heated area in the existing dwelling (i.e. the walls, doors and windows) and the extension, should be insulated and draught proofed to at least the same extent as in the existing dwelling.
b) Independent temperature and on/off controls to any heating system installed within the extension.
c) Glazed elements should meet current standards.

This means that removing and not replacing any or all of the thermal separation between the dwelling and extension, or extending the dwellings heating system into the extension means that the extension ceases to be exempt.


This aspect of the building regulations only applies to new builds and extensions. It outlines the necessary provisions that need to be made to provide for people with disabilities.

Over the last few years these have been updated and have now been separated into 3 different categories;

  • M4(1) – Visitable dwellings
  • M4(2) – Accessible and adaptable dwellings
  • M4(3) – Wheelchair user dwellings

M4 (1) – Visitable dwelling

This is as the regulations were before. The principal entrance must have a clear opening of 775mm wide and a Part M threshold.

M4 (2) – Accessible and adaptable dwellings

Here the principal entrance needs to have a clear opening of 800mm wide with a Part M threshold. The other necessary points to adhere to are;

  • On the inside, there needs to be a minimum distance of 300mm from the inside edge of the door frame to the wall which needs to remain that way for at least 1200mm into the room
  • The minimum distance on the outside has to be 200mm
  • On the inside of the property, the reveal should be a maximum of 200mm to the inside face of the frame

M4 (3) – Wheelchair user dwellings

The principal entrance for these needs to adhere to the same outline as above with one difference; the principal entrance needs to have a clear opening of 850mm

Part M threshold

The threshold of the door should have a maximum slope of 15° where it is necessary to drain rainwater, the gradient of the slope should not exceed 1:40. Thresholds may have a graduated upstand of 15mm.



These regulations apply to all doors which are easily accessible and allow access into the dwelling. If a garage provides access to a dwelling through an interconnecting door then the garage door or the connecting door needs to conform to these regulations. Where the garage does not provide access into the dwelling then these regulations do not apply.

All doors need to be manufactured to;

  • PAS 24:2012

OR whose performance satisfies or exceeds the following standards;

  • STS 201 Issue 5:2013
  • LPS 1175 Issue 7:2010 security rating 2
  • STS 202 Issue 3:2011 burglary rating 2
  • LPS 2081 Issue 1:2015 security rating B

OR carry the Secure By Design label.

Other provisions which need to be made are;

  • Doors which contain a sealed unit should include at least one sheet of laminated glass
  • Letterboxes should;
    • Have a maximum opening of 260mm x 40mm
    • Be located and/or designed in a manner to hinder anyone attempting to remove keys, for example, should incorporate a feature to restrict access such as a flap
  • The main door to enter the building should;
    • Have a spy hole/viewer or other means to view the caller, for example a window
    • The door should have a door chain or other means to limit the opening

NB: there are situations where a door limiter is not suitable for example warden assisted housing where the warden would need to gain access.


These regulations apply to windows which are within 2m of an accessible surface e.g. any ground floor, basement or other windows which are accessible from a flat surface, e.g. a balcony or roof with a pitch of less than 45° which is within 3.5m of ground level.

All windows need to be manufactured to;

  • PAS 24:2012

OR whose performance satisfies or exceeds the following standards;

  • STS 204 Issue 3:2012
  • LPS 1175 Issue 7:2010 security rating 1
  • LPS 2081 Issue 1:2015 security rating A

OR carry the Secure By Design label.

Windows in an accessible area (as explained above) where they are glazed with a sealed unit and have non-locking hardware each sealed unit should include one sheet of laminated glass.

The information supplied is for guidance only as requirements can vary between councils. Window Designs Ltd is not responsible for any action carried out based on the contents of this webpage. Please contact your local council building control for further advice.