Replacement Windows
For many years, it had not been necessary to apply for building
regulation consent when replacing windows in existing dwellings
unless a structural alteration was involved. From 2002
however, all owners replacing windows need to make an
application, and the new windows themselves will have to meet the
requirements of the building regulations. So even if you are
replacing only one window with one bought from a local DIY centre
you still need to follow the guidance below.
You have a choice, you can either:
- Use a contractor registered under the FENSA or CERTASS scheme
or,
- Use Ashford Borough Council and submit a building regulations
application. In most cases the simplest way of doing this will be
to submit a Building Notice. With this procedure, the application
form must be fully completed, and returned to us together with the
appropriate charge (refer to fees guide) and a site location plan
at least two working days before removing the old window(s).
Once we receive the Building Notice, a Building Control Surveyor
will normally visit your property twice - once before and once
after the replacement windows are installed. If all is found to be
satisfactory, a completion certificate then will be issued to
confirm this. You may well be asked by your solicitor to produce
this certificate if you sell your property. If your windows are
being replaced by a specialist window firm, they may well make the
application on your behalf, but be careful to check this with them
in advance to make sure.
What regulations do the windows have to comply with?
Thermal Insulation
The replacement windows (including replacement roof windows and
rooflights) will need to meet the new thermal insulation
requirements of the regulations. If the replacement windows have
wooden or plastic frames, then the glazing needs to achieve a
U-value no worse than 1.6W/m2K.
If this cannot be achieved because of a
planning/conservation requirement to maintain the
external appearance of the facade or the character of the building,
replacement windows should meet a centre pane U-value of
1.2W/m2K, or single glazing should be supplemented with
low-e secondary glazing. In this latter case, the weather stripping
should be on the secondary glazing to minimise condensation risk
between the primary and secondary glazing.
Take great care when ordering new windows that your supplier can
prove the glazing units used will satisfy this requirement, as the
Building Control Surveyor will need to see this proof before
issuing a completion certificate. We would particularly recommend
that you leave any labels on the glazing in place until after a
satisfactory inspection has been carried out by the Building
Control Surveyor.
Please note that external doors where over 50% of the internal
face is glazed should achieve U-value of
1.8W/m2K.
In some cases it may be permissible to use glazing units which do
not meet the above specifications, but to do so you (or your
supplier) 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.
The benefits gained by installing this extra insulation can be
used to offset the higher losses through the glazing, but this
should not to be undertaken lightly. We would strongly advise you
get any such calculations checked by the Building Control Surveyor
well before the replacement windows are installed, so that
expensive mistakes can be avoided.
Safety Glazing
Low level glazing (glazed areas within 800mm of floor level) and
glazing in doors within 1500mm of floor level should generally be
of a type so that if broken, it will break safely. In practice this
means such glazing should be either laminated or toughened.
Ordinary glazing can still be used in small pane sizes however,
provided the glass is sufficiently strong to resist breakage. The
approved document to Part N of the building regulations gives
maximum sizes according to the thickness of glass - for example, in
a single pane less than 1.1m square - 8mm glass would be
satisfactory.
Means of Escape
All first floor windows in
dwellings should ideally have opening lights large enough to allow
you to escape through them if you were trapped in the room by a
fire. This also applies to rooms in bungalow that open into to a
hall (unless the hall itself has an external door through which you
could escape).
To meet this requirement all such windows should have an
unobstructed openable area of at least 0.33 square metres and
be not less than 450mm high and 450mm wide (the route through the
window may be at an angle rather than straight through). The bottom
of the openable area should be less than 1100mm above the
floor.
If your existing windows do not have opening lights which meet the
above requirements, we would strongly recommend (for your own
safety), that you take the opportunity to provide them in the
replacement windows. This is not however a requirement of the
regulations provided the replacement windows are no worse than the
ones replaced in this respect. Where the existing windows already
have opening lights which are larger than the above requirements,
those in the new windows can be reduced in size provided they are
not reduced to less than the dimensions above.
Ventilation
The Building Regulations require that adequate ventilation is
provided for people in the building and this should be considered
when deciding on the size of opening lights in the replacement
windows. For most rooms, one or more opening windows totalling 5%
of the floor area, with background "trickle" vents totalling 8000
square mm will be adequate.
For kitchens, utility rooms and bathrooms an extract fan is also
normally required. In some cases the existing windows may contain a
permanent vent to supply combustion air to a heating appliance,
although this is now rare. If this is the case however you should
ensure that either the replacement window contains a similar
permanent vent, or that some other means of providing the required
ventilation is installed at the same time.
Structural Safety
If the replacement windows are wider than those they replace, or
involve the replacement of bay windows, then the Building Control
Surveyor will need to be satisfied that proper structural support
is provided above the window. In older buildings, the timber frame
of the window was often sufficiently strong to carry the load of a
wall or roof above it without a lintel. Obviously in these cases
either a lintel needs to be installed when the window is replaced,
or the new frame carefully reinforced to carry the load.
This webpage was updated on
1/31/2012