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I Want to Alter My Windows

Windows do more than keep the weather out. They are eye-catching features that give your house character through their design, materials and workmanship and help tell its story. They could be original, or they may have been altered or replaced in response to decay or changing fashions.

If your house is listed you should seek advice before making changes as listed building consent may be required. If your house is in a conservation area restrictions may also apply, so again speak to your local planning authority before carrying out changes. See What Permission Might I Need? and Who Do I Contact? for further information.

Why retain historic windows?

It’s important to know your windows before deciding on work on them. For instance, they might still be glazed with historic glass which is now very rare. Window glass was an expensive, hand-made product until the mid-1800s, when new processes made larger sheets possible. The thinness and imperfections of old glass make it attractive, but also fragile. Much has been broken and replaced over the centuries, and surviving panes are rare and valued.

Detailing around window frames has changed over time. This can help to date the window and the house. Frames can contribute to a building’s overall appearance either as part of the original design or as deliberate later changes. Historic windows were hand-made by craftsmen, often from more durable timber than we have today. Thinner, lighter glass meant that frames and glazing bars could be slender. As larger sheets of glass became technically possible and fashionable, stronger frames were required. Consequently sash windows were often made with ‘horns’  - where the side rails of the frame stick out a little way below the bottom rail - to make a firmer joint.

The importance of historic windows, with their wide range of styles and ages, can vary. But evidence of craftsmanship, the survival of old and rare material and detailed design are all of value, and can make them of special interest.

Repair is better than replacement

Historic windows of interest should be retained wherever possible using careful matching repair. Their complete replacement should be a last resort and is rarely necessary. If repair is beyond the skills of a good joiner or metal worker, an accurate copy should be made.

If your house is listed or in a conservation area with an Article 4 Direction (which restricts work you can normally do without planning permission) you are likely to require consent to replace or make any alterations to windows, whereas like-for-like repairs do not usually require any consent. If in doubt, consult your local planning authority or conservation officer.

For further information, see our page on Repairing Windows.

Can I replace non-historic windows?

Some windows, if they are later replacements which do not follow the historic pattern, may not contribute to the historic interest of your house and even spoil its appearance. You could consider replacing them with ones that match the historic pattern of your property to enhance it. Old photographs, or similar houses nearby, may have examples of the historic pattern. An exception to this may be where the replacement windows related to an important later phase of construction which did not follow the historic pattern.

We will support the removal of non-historic windows provided it is clear that they are not of interest and that the new windows are of an appropriate style which enhances the building. It is usually possible to fit new windows with integral slim-profile double glazing, subject to their detailed design. Multi-pane windows can be a problem as often the fine glazing bars are not able to accommodate the increased thickness of the glass.

New windows need to comply with minimum energy efficiency requirements as part of the Building Regulations (Part L). This can be achieved either with double glazing or secondary glazing. For listed buildings and buildings in conservation areas a case can be made for exemption where complying with required standards would unacceptably alter the character and appearance of the window.

More detail on windows and Building Regulations can be found in our guidance: Energy Efficiency and Historic Buildings: Application of Part L.

When repairing or replacing windows it is best to consult a joiner or metal worker with previous experience of historic buildings; see Finding Professional Help. For Building Regulations as they relate to windows, please see Planning Portal: Doors and Windows.

Keeping the cold out

There is no reason why older windows should not be as energy efficient as new ones. Making sure they fit well will help reduce draughts and heat loss, as will adding draught-stripping. If you have window shutters, it’s worth making sure they work and closing them at night. If your shutters are missing, consider having new ones made. 

We have researched different ways of insulating windows and found that you can significantly reduce heat loss by using window shutters, insulated blinds or thick curtains. To further reduce energy losses through windows and match the performance of new windows, you may consider secondary glazing. This retains your existing historic windows and, if designed carefully, will preserve the outside appearance of the house. It is important to make sure the design of the secondary glazing is compatible with any existing window shutters, panelling or mouldings.

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