Double and triple glazing#
If you’re thinking of changing your glazing, think first about what the problem is. It makes a big difference to move from single glazing to double, but we’re less sure about replacing old double glazing with new. If you’re considering this, you want to be sure the glazing and frames will let less heat through. Often the problem with old windows is just that they’re draughty.
If you have double glazing and your walls are uninsulated, we’re told triple glazing won’t be worth the added cost.
If you have single glazed sash and case windows in a listed building, many local authorities will allow you to install slim-line double glazing. Visually, it’s hard to tell the difference. If the sash-and-case windows are in good condition, consider keeping the window and just replacing the glass. If the window frame is thick enough, a good company can just cut a wider channel for the double glazing. Victorian wood is hard because it was grown slowly. Victorian windows could have as much life left in them, 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 to make providing ventilation more efficient and more comfortable.
U-value calculations - table shows many glazing options (technical)
Retrofitting sash and case windows - for homeowners, but very useful for some community buildings
Sometimes venues with very mediocre stained glass of no significance change it for clear double glazing. There are also new methods for improving the thermal efficiency of historic glass, including a technique for double glazing stained glass windows. Historic England has enough confidence to be putting this in some high profile buildings.