When undertaking a project it is important to ensure you comply with current building regulation requirements. To help you understand the current requirements relating to the installation of windows and doors we have detailed the information below. Whilst this information is here to help educate you, it is important that you are still liaising with your own local authority regarding building regulations.


Part L – Thermal Performance

In all cases where it is proposed to erect a new dwelling, building regulations require the person proposing to carry out the work to notify a Building Control Body in advance of any work starting. This notification would usually be by way of full plans (or possibly a building notice) given to a local authority, or an initial notice given jointly with the approved inspector.

This remains our clients’ responsibility and is not something undertaken by Fabco Sanctuary.

Dependent upon the type of property and nature of the work proposed, planning consent may also be required for works including the replacement of windows and doors.


 Energy Rating & U-Value requirements for existing dwellings

Replacement windows will need to meet the thermal insulation requirements of the regulations. These require minimum performance values of:


Replacement windows to be WER band C or higher                     1.6 W/m2K

Doors with 50% glazing or less                                                      1.8 W/m2K

All other doors                                                                                1.8 W/m2K


In some cases it may be permissible to use glazing units which do not meet the above specifications, to do so you would have to submit calculations to prove that the overall insulation requirements of the regulations would still be met. This may be possible if other insulation measures are undertaken at the same time as the window replacement - for example; installing cavity wall insulation or “topping up” loft insulation. We would strongly advise you get any such calculations checked by the building control officer well before the replacement windows are installed, so that expensive mistakes can be avoided.


U-Value requirements for new dwellings

Limiting fabric parameters (U Values for controlled fittings should not exceed):


Windows, roof windows, pedestrian doors                  2.0 W/m2K


No new dwellings are exempt from the energy efficiency requirements of the Building Regulations.

An architect may have the flexibility to install products that do not meet the above minimum requirements by use of area weighted averages for U values and DER or SAP calculations when designing the building. Details would need approval by a Building Control Body to ensure overall compliance with Building Regulations.


Part K - Protection from falling, collision and impact

The 2013 Approved Document K - ‘Protection from falling, collision and impact’, now incorporates the requirements of Approved Document N: Glazing – safety in relation to impact, opening and cleaning.


Part K identifies the following key areas:   


Requirement K2 Section 3 : Protection from falling


Guarding is to be provided where it is reasonably necessary for safety to guard the edges of any part of a floor (including the edge below an opening window), balcony or any other place to which people have access.


In the case of dwellings, guarding should be provided that is capable of preventing people from being injured by falling from a height of more than 600mm; i.e. the difference between internal and external levels (which can occur at ground floor locations). For buildings other than dwellings the height is reduced to 380mm.


Guarding can be described as any wall, parapet, balustrade or similar object which can include glazing. In the event that glazing acts as guarding, it must also provide containment in order to resist loads given in BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1.


Guarding in respect of glazing must be provided, as a minimum at the heights shown in Diagram 3.1 below.





•          Unguarded opening lights should be positioned no lower than 800mm from FFL.

•          A non-climbable barrier, no lower than 800mm, should be provided in the event that opening lights fall within 800mm of FFL.

•          Where fixed windows are located within 800mm of FFL, they must provide appropriate containment if no other barrier is present.

•          For single family dwellings, external balconies, including Juliette balconies, guarding must be no lower than 1100mm.


Requirement K4 Section 5 : Protection against impact with glazing


Part K identifies that impacts with glazing, particularly glazing in doors and side screens can result in cutting and piercing injuries, the risk being greatest between floor and shoulder level when near to the door handle or push plate.


Glazing, with which people are likely to come into contact whilst moving in or about the building shall:

  1. if broken on impact, break in a way which is unlikely to cause injury; or
  2. resist impact without breaking; or
  3. be shielded or protected from impact.

Part F - Ventilation

Part F states that there shall be adequate means of ventilation provided for people within the building. This applies to new buildings which can be ventilated by either manually controlled trickle ventilation within the window frames, directly through the fabric of the building or through an air management system.

Where replacement windows are provided to existing dwellings provisions should also be made to ensure appropriate ventilation is maintained and is made no worse as a result of a replacement glazing installation.


Part B – Means of Escape

In the event of fire or a need to vacate a building as an emergency, adequate means of escape should be provided throughout the entire building - including the ground floor. Windows or doors should enable the person escaping to reach a place free from danger and should be designed such that they will remain in the open position without needing to be held by a person making their escape.


Part Q – Security in Dwellings

Part Q is a mandatory requirement specifically relating to the security of a building and applies to all new buildings and building subject to change of use. It took effect on 1st October 2015. It does not apply to work started before 1st October 2015, or work subject to a building notice, full plans application or initial notice submitted before that date, provided the work is started on site before 1st October 2016.


Historic Buildings

Some buildings are subject to special considerations in deciding adequate provision for Building Regulations. Including:

  • Listed buildings.
  • Buildings in conservation areas.
  • Buildings which are of architectural and historical interest and which are referred to as a material consideration in a local authority’s development plan.
  • Buildings which are of architectural and historical interest within national parks, areas of outstanding natural beauty, registered historic parks and gardens, registered battlefields, the curtilages of scheduled ancient monuments, and world heritage sites.
  • Buildings of traditional construction with permeable fabric that both absorbs and readily allows the evaporation of moisture.


If your project falls into one of these categories, the aim should be to provide improved thermal performance and adequate ventilation as far as is reasonable and practically possible. The work should not prejudice the character of the host building or increase the risk of long-term deterioration of the building fabric or fittings.


Windows / Internal screens

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