The benefits of installing secondary glazing over replacing your existing windows are:
Usually fitted in a day
No huge openings while the replacements go in
No re-plastering or redecoration (unless frame painting is required)
No planning issues
Preserve the beauty and character inside and out
We rarely need to use power tools during installation
As well as all the benefits above, Extraglaze Secondary Glazing is nearly always supplied and fitted at considerably less expense than replacements.