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 or have the work carried out by a certified member of FENSA (FENestration Industry Self Assessment scheme). 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.
In summary we have to ensure that:
- 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.
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, W.C.s or shower rooms) at floors above ground level are required to be suitable for escape in the event of a 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 at 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.
Requirement F1 – means of ventilation
See table 1 below for current requirements. If the 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 ventilations 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) | 4000mm2 |
| Bathroom/Shower rooms | Opening window (No minimum size) | 4000mm2 |
| Sanitary accommodation | /20th of the floor area of the room served | 4000mm2 |
Requirement 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 there is 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 manufacturer’s advice should be followed with regard to proximity of opening windows and doors.
Requirement 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.
Requirement L1- conservation of fuel and power
All UPVC and wood replacement windows should attain a minimum U value of 2.0W/m2K.
Kömmerling’s Connoisseur system achieves an average of 1.8W/m2K while our Double glazed units achieve 1.4W/m2K
Requirement 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.
Requirement N1- glazing protection against impact
Glazing should either:
- Break safely (TSG) as defined in BS 6206:1981 Specification for impact performance requirements for flat safety glass and safety plastics for use in buildings, clause 5.3
- Be inherently robust, i.e. annealed glass, glass blocks, polycarbonate or glass that gains strength through thickness (laminate etc).
- Be in small panes (a maximum area of 0.5m2 with a maximum width of 250mm is acceptable). Annealed glass should be not less than 6mm thick, except where it is in traditional leaded- or copper- lights in which 4mm glass is considered acceptable when fire resistance is not a factor.
- Be permanently protected by a suitable screen which has a minimum height of 800mm and which incorporates a gap no greater than 75mm.
Diagram 1. Glazing in window, partitions glazing in doors and side panels and walls
Diagram 1 gives examples of glazing in windows, partitions, walls, doors and side panels. ‘Critical locations’ are shaded grey. Any glazing within a shaded area must comply with BS 6206.
In Diagram 1, glazing unit No. 10 falls wholly within a ‘critical location’ and so the glazing must
comply with BS 6206.
Where only part of a glazing unit falls within a ‘critical location’ the whole of that unit must comply with BS 6206. In Diagram 1 this applies to units Nos. 2, 3, 5, 6, 7, 9, 11 and 12.
In Diagram 1 only glazing units Nos. 1, 4 and 8 fall wholly outside the ‘critical location’ and need not comply with BS 6206.
Replacing Vertical Sliding Sashes
FENSA Guidance Notes 2
When replacing vertical sliding windows it is important that the compliance to Approved Documents F (Ventilation), N (Safety) and B (Fire Egress) is either maintained, or that the replacement windows are not worse than those being removed.
Example
The surveyor is called to a house fitted with a wooden vertical sliding sash window in a room measuring 4m by 4m.
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Diagram 1The customer requires the external appearance of the window to be fundamentally the same and requests a PVC-U top hung vent over a fixed light. |
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Diagram 2This solution will fail (Fire Egress) |
Approved Document F – Ventilation
1. Rapid Ventilation
The original window provided 0.45m2 of rapid ventilation (less than required for new build regulations 4m x 4m x 1/120 = 0.8m2) however a portion of the opening sash set out in Diagram 2 is 1750mm above floor level and therefore, does not make the situation worse and is acceptable in this respect.
2. Background Ventilation
As the original window did not contain trickle vents, nor was it capable of being locked in the open position, it did not provide background ventilation. The design of the window in Diagram 2 is acceptable in this respect. If a background ventilation facility was available, then the replacement window would need to be fitted with either trickle vents or a lockable night vent, so compliance would be maintained.
Approved Document N – Safety Glazing
The replacement window is less than 800mm from floor level and therefore the lower sash needs to
be fitted with safety glass to BS 6206.
| Diagram 3 – window on a staircase |  |
Note: Diagram 3 shows how the distance from a staircase to the bottom of the window is to be measured.
Approved Document B – Fire Egress
1. Fire Egress
The original window provided a clear opening 600mm high and 750mm wide at height of 600mm from the floor. This more than satisfied the size requirement for a fire egress window in a new build situation (i.e. 0.33m2 with a minimum dimension of 450mm). The replacement window (Diagram 2) can, dependent upon the type of hinge used, maintain the size of opening required for egress (taking into account an external stone cill if in place). However because symmetry is required the transom height will be above the 1100mm level. (This height is the maximum required for a fire egress window to comply with the legislation.) Therefore the window in Diagram 2 fails fire egress compliance (it makes matters worse).
Options available:
- Revert to vertical sash design.
- Lower the height of the middle transom to below 1100mm (top opener becomes a fire egress window).
- Redesign the window to be two top opening vents, one above the other. (Diagram 4).
- Redesign the window to be one single top hung opening, measuring 1200mm x 750mm, if suitable hinges are available.
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Diagram 4 |
Our Thanks to FENSA for permission to reproduce these notes here:
http://www.fensa.org.uk FENSA Limited is the Fenestration Self-Assessment Scheme for companies
that install windows and doors in dwellings.
Special Note: These are the interpretations being used by “FENSA registered companies”. This is important because some of the local authorities may interpret some of the building regulations slightly differently. If you are not using a FENSA member and are going to apply to the local authority for permission rather than use a FENSA company you would be well advised to seek clarification before an installation commences. Also worth reading are the FENSA Technical FAQ’s at http://www.fensa.org.uk/faqtech.phtml
Downloadable documents