Double and triple glazing#
Slim-line double glazing is almost imperceivable from the outside and acceptable in many listed buildings. If sash-and-case windows are in good condition, it may be possible to retain most or all of the original window, cut slightly wider channels, and replace the glass. Victorian wood was grown slowly so the original wood could have as much life left in it, or more, than modern replacements. Think about how well the windows fit and whether any draughtproofing or professional refurbishment is needed at the same time. Also think about how ventilation will work for your users - modern windows tend to have trickle vents for better and more comfortable control of airflow in cold weather.
For triple glazing to give you any benefit over double glazing, the walls have to be well-insulated.