Sash Window Glazing
While all sash window were traditionally single glazed, modern sash windows are now made to take sealed sash double glazing units. Single glazing may be a requirement when restoring/conserving listed buildings, restricted to the accurate representation of its original state.
The restoration and upkeep of sash windows are very important to preserving history and listed properties, the glass used within the windows are often overlooked. If anything, they could be considered even more valuable than the frames themselves, depending on the type of glass used within the sash windows. These can fall into old periods of ‘plate’ or ‘broad’ glass to ‘crown’ or ‘cylinder’. You’ll be able to identify the old glass in your sash windows by looking out for the imperfections, which is also known as ‘ream’. You should be able to tell quite easily by looking for any distortion when looking through the glass or viewing from the outside looking in. Out of all the glass mentioned, the only type which is still produced using traditional methods is cylinder. Meaning the remaining should be preserved and restored to the highest standard, and should be carefully observed before any major work is done to the sash window glazing.
But of course today we have the comforts of sash double glazing, more heat efficient and cost effective. However, many wish to keep sash windows in their original condition, and can be frowned upon. You may have to check the status and limitations of your home or property should it be listed, which is very likely should you have sash windows. Common practices of sash double glazing with sash windows involve mimicking the appearance using non-functional ‘glazing bars’. Which of course gives the appearance of individually separated panes of glass. However, this can be easily noticeable based upon the workmanship and materials. Ultimately, for the best aesthetic look using properly separated panes of glass with fully functioning glazing bars/muntins is the favourable option.