Secondary glazing

Replacing or double glazing old windows in the name of energy efficiency is expensive and hugely destructive to our heritage. There is another way: secondary glazing. Secondary glazing added to the inside of a window has little impact on the look of the building, does negligible damage and is reversible. Equally importantly, secondary glazing cuts draughts while improving the window’s overall thermal and acoustic performance.

A growing number of companies specialise in providing secondary glazing and they offer a range of options for different budgets and aesthetics. All comprise an extra layer of glass or high quality plastic that fits to the inside of the existing window. If well designed, this is unobtrusive with modern systems considerably more discreet than those of the past.

Where windows need to be opened, sliding secondary glazing is the answer. For windows that are never opened, or are permanently closed during the winter months, a single secondary glazing panel held in place by magnetic strips is a good option. These systems are easy to install. The magnetic strips are fitted around the edge of the glazing while a second magnetic or metal strip is stuck to the window frame so the panel simply drops into place. The strips fixed to the window frame may be painted the same colour as the woodwork so they’re inconspicuous when the panel is not in place.

Panels that are removed during the summer are best wrapped and stored under a bed. Even if the panels are not removed for storage, magnetic systems allow the secondary glazing to be easily lifted out for cleaning. Remember that the bigger the window, the heavier and more unwieldy it becomes, making lifting out more difficult; this is where plastic glazing has a definite advantage. When ordering secondary glazing bear in mind that careful measurements or a template are essential as old windows are often out of square.

Companies offering secondary glazing include: Clear view, CosyHome, DIY Plastics, Ecoease, MagneGlaze and Storm Windows. The Conservation Shutter Company has combined the idea of traditional solid wood shutters and secondary glazing by creating a glazed shutter system.