Replacement windows building regulations
- Replacement windows must meet minimum insulation levels
- The lower the ‘U’ value, the better the insulation
- Proof of compliance required when you sell your home
Thanks to world-wide agreements to reduce energy consumption, there are now
strict regulations covering replacement windows.
All replacement window installations in England and Wales are subject to Document
L of Building Regulations which affect, in particular, the minimum levels of
insulation that replacement windows must have when fitted in the home.
These levels of insulation are measured as U values. The lower the U value,
the better the insulation level. In future what was in the past 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 is almost certain some sort of Low
E glass (typically Pilkington K in the UK – although there are other
brands) will have to be used. It may also be necessary for the sealed double-glazed
units to be gas-filled (probably Argon).
FENSA self-certification scheme
With so many replacement windows being installed it was agreed that the industry
could adopt a self-assessment method for administering the many thousands
of window installations that are now subject to building regulations. What
this means is that it is not always necessary for a building control officer
to inspect each installation or for companies to make separate Building
A contractor registered with the FENSA (Fenestration Self-Assessment) self-certification
scheme is 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.
If you are not using a FENSA registered contractor or if you are doing the
work yourself then you will need to arrange for building regulation approval.
This will mean that you must be able to confirm that you have met a number
of criteria. You will be responsible for paying for the building regulations
application and should check with your local council for costs. The time taken
to obtain approval will depend on the local authority concerned.
In addition to Building Regulation consent you must ascertain whether or not
planning permission or conservation area consent is required. Your local council
can advise you on this.
For further details see www.double-glazing-uk.co.uk/Englandwales.asp
Scotland’s Building Standard Part J requires an even higher performance level from windows
than that specified in England and Wales.
Replacement windows and doors in Scottish homes are expected to achieve U
values 10% lower than those in England and Wales, which means a difference
of 0.2 of a U value. Soft coat Low E glass with a 16mm cavity containing an
inert gas will be necessary in most cases.
This means that in most existing dwellings, replacement windows will need
to have a U value of not more than:
- 1.8 for windows made of plastic or wood
- 2.0 for windows with metal frames
Windows also need to comply with all other appropriate aspects
of the technical standards to the Scottish building regulations – eg
emergency escape, safe-cleaning, safety glass and ventilation.
More information is available at www.scotland.gov.uk/library5/development/brn103.pdf
Selling your home
When you sell your property, surveyors will ask for evidence that any replacement
glazing installed after April 2002 complies with the new Building Regulations.
There are two ways in which you can prove compliance:
- a certificate showing that the work has been done by an installer who
is registered under a FENSA, CERTASS Limited or the British Standards Institution
self-certification scheme, or
a certificate from the local authority saying that the installation has approval
under the Building Regulations.
If there is any doubt, a glass analysis gauge can be used to establish whether
or not the correct glass has been used.
Note that this only applies when windows have been replaced – original
windows are not subject to this scrutiny.