Frequently asked questions

Frequently asked questions 

Q. My wooden windows have a lot of rot in the frames: should I replace them?

A. The first course of action for windows in poor condition should be repair by an experienced joiner. Repair will not only improve the appearance of the window, it will extend its life and improve its thermal performance. Another option is to consider one of the two-part epoxy resin repair systems that can extend the life of historic windows.

If the window is beyond economic repair then replacement must be considered. In this case reproductions of historic windows can be made that are identical in appearance to those being replaced. Historic glass from the old windows can be reused in the new frames.

Q. Some of the old windows in my house were replaced about 20 years ago with plastic units. Should I take the opportunity to install new wooden replicas of the originals but with double-glazed panes?

A. Be very cautious. Modern double-glazed replacement sash windows cannot replicate the fine detailing and proportions of many traditional windows, as the window frames and glazing bars have to be thicker to house the glass. This may not be important if the windows being replaced are on a separate elevation, but if they are mixed in with originals they could be obvious and visually glaring.

Q. Should I replace the old panes in my windows with thicker glass or slim double-glazing units?

A. Old glass is of interest and is becoming increasingly rare. It is of value not just for its age, but because it has more richness and sparkle than today’s flat sheets with their uniform reflections. Where it survives, it should be retained and alternative means of thermal improvement considered. Thicker glass will not make much difference to heat loss. Slim double-glazing units are much heavier than old panes and this extra weight could distort the old frames.

Q. I know that ventilation is important in old buildings – isn’t draught-proofing dangerous?

A. Ventilation is essential to the sound working of historic and traditional buildings. Their fabric often needs to ‘breathe’ – releasing and absorbing moisture. Moisture from rising damp, driving rain, defects and condensation can move through traditional permeable building materials until it eventually evaporates both internally and externally through traditional surface finishes. Ventilation is critical to this mechanism.

While draught-proofing reduces the infiltration air most old buildings will still have adequate ventilation for the fabric to continue to breathe satisfactorily. Draught-proofing will not totally exclude all ventilation.

Q. Are there any windows that should not be draught-proofed?

A. Generally it is not advised to draught-proof windows in bathrooms, kitchens, and utility rooms where lots of water vapour is produced and high levels of ventilation are required. It is wasteful to draught-strip a window and then leave it open!

Q. Will secondary glazing prevent me from closing my shutters?

A. Not usually. New secondary glazing systems are available with very thin profiles.

Q. Should I draught-strip and secondary glaze for extra benefit?

A. No, good quality secondary glazing will be tight fitting and stop draughts, so draught-proofing the original window will have little additional benefit. It is also good practice to have a little ventilation of the space between the original and secondary windows.

Q. I am fitting new windows to my house to replace some inappropriate plastic double glazed units. Do the Building Regulations mean that I have to use double- glazed units?

A. Not if your house is listed or in a conservation area.  The Building Regulations allow single-glazing to be used in those circumstances if double-glazing would harm the appearance or character of the building or area.

Q. I’m building an extension to my house: can I have single glazing to match the windows to the original house?

A. Quite possibly if your house is listed or in a conservation area. You may need to discuss this with the local authority’s conservation officer and building control officer.  The key issue is whether well-made new double- glazed units would detract from the appearance or character of the building or area. Sometimes this is the case on a formal front façade, but may not be a problem if the extension is of an obviously modern design.

Q. Is double glazing allowed in listed buildings?

A. It is very rare for a local planning authority to give listed building consent for the replacement of original windows if they are beyond economic repair with copies that do not exactly match the originals. The Secretary of State has dismissed over 90 per cent of appeals against the refusal of listed building consent for replacing traditional single-glazed sash windows with double- glazed plastic (PVCu) windows because of the loss of important features and the fact that the replacements proposed would detrimentally affect the special character and appearance of the building.

Q. I live in a conservation area; do I need permission to change my windows?

A. Check with your local planning authority’s conservation officer as rules vary from area to area. You will need Building Regulations approval.

Q. What is wrong with plastic windows?

 A. They seldom look the same as the original windows and may look totally different. Indeed they can mar the appearance of a whole street. they will need maintenance and unlike timber windows they are very difficult to repair.

Q. Plastic windows are more energy-efficient aren't they?

A. No, a lot of energy is used in their production and they are no more efficient than timber windows which have been improved by either closing shutters, using insulated blinds or secondary glazing.

Q. Why are timber windows better for the environment?

 A.  Old timber windows last much longer.......... many have lasted two hundred years plus and are capable of being repaired. Plastic windows are only expected to last for around 20 years and at present most go to land-fill. Incineration can lead to the production of harmful pollutants and only small amounts of plastic are currently re-cycled.

Q. What is wrong with wooden double glazed sash windows of the same pattern as the originals?

A. It is virtually impossible to replicate wooden windows in double glazing. This is because two panes of glass set 12mm apart need much thicker timber supports to deal with the heavier weight. Details such as glazing bars are correspondingly bigger. Some of the new slim line double glazing gets much closer in design to the originals but it is quite obvious because of the double reflection caused by two panes of glass close together.

Q. Won't I enhance the value of my house by putting in plastic windows?

A. Evidence shows the reverse is often the case. Estate agents generally make a great play of advertising original features and most confirm that these sell homes much more quickly.

Q. What difference does living in conservation area make to what I can do and cannot do with my windows?

 A. Some local authorities may have greater powers over controlling changes to important features like windows. If so, planning permission is then needed to change them. All local authorities and many residents try to encourage their neighbours to keep features like original windows which are so important to the appearance of conservation araes and which make them special.



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