Replacement Windows
Adding a window to a current windows? Is it useful?
In a window replacement, secondary glazing is often viewed as low cost option. Generally it involves attaching an aluminium framed secondary sheet of glass to a single-glazed window.
It is advisable to ensure that the primary double glazing window is relatively draft free and to leave a gap between the two panes of 5 to 10cm. Although secondary glazing does improve acoustic and thermal insulation, its insulation properties are less efficient than double glazing window and it will not obtain a high Window Energy Rating like in a real window replacement.
As there is no air-tight seal with secondary glazing, dirt and condensation can build up and the panes will need to be dismantled for cleaning. Secondary glazing is sometimes used in historic buildings where a true window replacement is not possible due to planning permission requirements.