Secondary Glazing for Listed Buildings & Conservation Areas
Secondary Glazing is ideally suited for Listed Buildings and Conservation Areas - where it may be inappropriate, prohibitively expensive - or where permission has been or may be refused to replace the original windows.
Listed Building and Conservation Area Planning Officers generally welcome the idea of Secondary Glazing and for most instances Planning Permission is not required.
Conservation Double Glazing for Heritage Windows
What is a historic or traditional building with Heritage Windows? English Heritage give the following definitions:

- solid wall construction
- bay windows
- sash windows
- single glazing
- built without a damp proof course (DPC)
- likely to have been built before 1919
In other words, the earlier traditional homes that form so much of our heritage - many of which are now Listed Buildings and/or in Conservation Areas - with original period single glazing of all types, including:
- Georgian casement and sash windows
- Victorian casement and sash windows
- Edwardian windows and doors
- Crittall type steel windows and doors
Secondary Glazing Listed Properties

The installation of discreet internal secondary double glazing for Listed Buildings, Conservation Areas & all types of Historic & Heritage Windows is considered the best - and in fact, usually the only - acceptable treatment:
- for creating comfortable living conditions:
- that are draught free & warm
- and provide maximum noise reduction
- whilst reducing energy usage
- and cutting co² emissions
Secondary glazing achieves all of the above whilst also tackling any condensation problems as well as providing added security
Listed Building & Conservation Double Glazing

During the last few decades of the Twentieth Century, modern replacement windows spoiled the appearance of thousands of older houses, flats and commercial properties, destroying their special appearance and charm.
Additionally, poorly designed replacement windows have actually damaged many older properties, which were not designed to be completely sealed up, by:
- reducing ventilation
- trapping humidity
- creating condensation traps
Apart from the strict regulatory controls on upgrading & improving Conservation Area & Listed Building Windows, practical common sense also makes secondary glazing Listed Properties and Conservation Areas the product of choice.
Ventilation of Listed, Conservation & Heritage Windows

All buildings need regular changes of the internal air to avoid:
- damp
- condensation on windows & other surfaces
- mould infestation
This is particularly relevant for buildings containing Listed Windows as these older properties need more frequent air changes than modern ones.
Modern double glazed windows do not enable an old property to “breathe” sufficiently in order to avoid problems and continue in a good, sound condition. Listed double glazing needs to take that into account.

As a rule of thumb, a traditional building needs to be ventilated at a rate of:
- 0.8 to 1.0 complete air changes per hour
- Which is twice that for a modern building
Since natural ventilation rates in many older buildings actually exceed this value, secondary glazing listed properties is very beneficial in reducing the rate and creating listed double glazing that improves the thermal insulation without damaging the fabric of the property.
Secondary Glazing for Listed Buildings - The Reasoning
The reasons for secondary glazing Listed Building Windows rather than replacing them can be summarized as follows:

- regulatory control - generally specified by Planning & Conservation Officers
- aesthetics - secondary glazing does not spoil the appearance of an older property
- protection of the fabric of the building
- protection of the value of the property
- costs of secondary glazing Listed Buildings will be considerably less than replacements
- environmental costs of secondary glazing are far lower than replacements, in terms of:
- the manufacturing energy usage
- the disposal of the original windows
- most old windows can actually be repaired when necessary, frequently they have been needlessly replaced
- good quality secondary double glazing for Listed Buildings will be virtually invisible externally and extremely discrete internally
- conservation - to survive both structurally and financially, old buildings need to remain in use but with improved thermal and noise insulation and better security
- the value for money will be greatly increased by installing secondary glazing to Listed Buildings in London and the surrounds, due to:
- the reduced costs of upgrading
- well maintained and insulated period properties are increasingly sought after
- reduced energy costs quickly return capital investment
London Secondary Glazing for Listed & Conservation Double Glazing

We have designed our Legacy Range™ specifically for older, traditional properties - it is unobtrusive but very effective, providing:
- exceptional heat insulation
- effective soundproofing
- condensation control
- improved security
Fixing methods are concealed and a sympathetic range of finishing trims and mouldings assists in blending the secondary glazing into traditional surroundings.
Frames can be manufactured out of square, arched, radiused or curved, to achieve the best possible end result.
The full RAL colour range is available for colour matching so that each secondary window can be matched to either the existing or proposed décor.
London Secondary Glazing Installations:


Our secondary glazing has been installed in houses, flats and commercial properties across London and the Home Counties - everything from cottages, houses, mansion blocks, Art Nouveau buildings and thousands of other period properties.
We have worked in Listed Buildings and Conservation Areas for over 30 years and we can therefore give an expert service from initial contact and advice - through to the finished job - all supported by our unique knowledge base, depth of experience and most of all - by our expert personnel:
Planning (Listed Buildings and Conservation Areas) Act 1990
Listed Buildings
Alteration of any type to the windows and doors requires Listed Building Consent - including the installation of secondary double glazing
Conservation Areas
Installing secondary glazing to a building in a Conservation Area does not require consent - unless the building is also Listed
Planning
If you are in any doubt or just want confirmation - consult the Planning Portal here
Further information:
- Listed Building Case Study
- Our Unique Survey & Installation System for Listed & Conservation work
- Legacy Range™ for Traditional Sash Windows
Download our Secondary Glazing Brochure