Fensa Reg company no 16981

All replacement window installations in England & Wales are subject to BUILDING REGULATIONS. This regulation in particular affects the minimum levels of insulation that replacement windows must have when fitted in your home. Levels of insulation are measured as U values. The lower the U value, the better the insulation level. In future what we may have in the past have referred to as “normal” double-glazing – i.e. two pieces of glass separated by a spacer bar is very unlikely to conform to building regulations. To get the required level of insulation it’s almost certain some sort of LOW E glass Pilkington K or similar will have to be used. It may also be necessary for the sealed double glazed units to be Gas Filled (probably Argon) alternatively thermally broken spacer bar can be used with insulating glass to provide a lower U value.

FENSA self-certification scheme

There are two ways that you can ensure compliance with relevant regulations, firstly you may employ a contractor or installer who is registered under the FENSA self-certification scheme. This contractor will be approved to carry out the work in accordance with relevant regulations without inspection by the council and will inform FENSA when installation has been completed. Random inspections of completed work are carried out.

In addition to Building Regulation consent you must ascertain whether or not planning permission or conservation area consent is required. The Development Control section of the council can advise you on this.

If you are not using a FENSA registered contractor or if you’re doing the work yourself then you will need to arrange building regulation approval yourself.
Certain Exceptions may apply
Conservatories will not be included when the standard commences provided they are separated from the rest of the building (for example by doors) or they are unheated.
Historic buildings are expected to “achieve the best they can”.
Also when replacing a broken sealed unit, it can be replaced “like for like”. The regulations apply to the entire window replacement

In short this means you need to be able to confirm the following:

  • The replacement will achieve a U-value of 2.0 W/m2k for PVC or timber frames, or 2.2 W/m2k for metal frames.
  • Glazing within critical locations will be replaced with safety glass.
  • Existing measures for background and natural ventilation will be retained.
  • Existing measures for means of escape from relevant rooms will be retained. (If the window pattern is to be changed this may affect means of escape).
  • Open flue appliances affected by the window/door replacement will be checked for adequacy of combustion air supply by a suitably qualified person.
  • If necessary, a suitable means of support will be provided above the replacement window/door.
  • Where the dwelling was required to be constructed to provide an easily accessible threshold at entrance doors this will be retained.

Replacement Windows and Doors

As from 1 April 2002, Building Regulations request that building owners installing replacement windows or doors must obtain Building Regulations consent and have the installation inspected to ensure compliance with relevant regulations. The relevant regulations are:

L1 Conservation of fuel and power
N1 Glazing protection against impact

In addition, you must also ensure that replacement windows and doors are no less suitable than the existing windows and doors in relation to the following regulations:

A1 Structure
B1 Means of escape in fire
F1 Means of ventilation
J2 Combustion appliances and fuel storage systems
K2 Protection from falling
M2 Access and facilities for disabled people

Repair work, such as replacement glazing or repair of rotten or damaged frame members is not subject to Building Regulation approval.

Guidance on how to satisfy the requirements

Requirement A1-structure.

When installing new windows or doors an assessment should be undertaken by the contractor as to the suitability of the support of lintel above the replacement window or door.

Requirement B1- means of escape in fire

All windows to habitable rooms (but not kitchens, utility rooms, dressing rooms, bathrooms, wc’s or shower rooms) at floors above ground level are required to be3 suitable for escape in fire. In addition, rooms at ground floor level whose only escape route is via another room must be provided with suitable escape windows.
A suitable escape window is defined as ‘a window whose unobstructed openable area is alt least 0.33m2 and at least 450mm high and 450mm wide (a 450mm wide opening will need to be 735mm high). The bottom of the openable area should be no more than 1100mm above the floor. Any key required to open the window should be readily available.

F1-means of ventilation

See table 1 below for current requirements. If your original windows have trickle ventilators any replacement frames should also be provided with such. The area of opening windows should not be less than that which was originally provided.
As and alternative approach to the ventilation provisions listed in table 1 below, the overall provisions for background ventilation’s for the dwelling should be equivalent to an average of 6000mm2 per room for the rooms listed, with a minimum provision of 4000mm2 in each room.

Table 1 Ventilation: current requirements for various rooms

Room Rapid ventilation Background ventilation
Habitable room 1/20th of the floor area of the room served 8000mm2
Kitchen and utility Opening window
(No minimum size)
Bathroom/Shower rooms Opening window
(No minimum size)
Sanitary accommodation 1/20th of the floor area of the room served 4000mm2

J2 Combustion appliances and fuel storage systems

Certain fires and heating appliances relay on air infiltration for them to function correctly. They may require purpose made ventilators, or may have relied on air infiltration through existing ill-fitting windows and doors, If you have an open flued appliance in the house that does not have separate provision of combustion air, a check should be made by a suitably qualified person (CORGI, HETAS, NACE, NACS, etc) to ensure that adequate permanent combustion ventilation is provided.

The boiler or fire manufacturers manufacturer’s advice should be followed with regard to proximity of opening windows and doors.

K2 – protection for falling

Where a first floor window cill height is less than 800 mm above the floor level suitable guarding should be provided to prevent a person falling through an open window.
This requirement may conflict with Regulation B1 and provision of escape windows. One way of achieving the requirement may be to provide a restricted opening device that can be easily overridden in the event of an emergency.

L1- conservation of fuel and power

All UPVC and wood replacement windows should attain a U value of 2.0W/m2K.
One way of achieving this requirement is by providing a UPVC or timber double glazed window system incorporating a 16m air gap between panes and an approved low emissivity coating such as Pilkington K. This is not the only option, but if another system is used, substantiation may be required to prove that a U value of 2.0W/m2 is attained.

M2 – access and facilities for disabled people

Where the property was subject to the Disabled Regulations, any new principal entrance door should have a minimum 775mm clear opening with a low threshold.

Fensa update