The ultimate difficulty is the fact secondary glazing won't ever provide the thermal overall performance of Principal glazing. The gap involving the panes will always be bigger than 12mm as it's mounted about the pre-present frames. Window panes are sometimes puzzled with window sashes. Panes are sheets of glass. https://arthurbjnqt.ssnblog.com/33657195/not-known-facts-about-acoustic-secondary-glazing