The thermal efficiency is just not as superior as that of a complete double or triple glazing alternative. It's because of the massive advance in sealed insulating that double and triple glazing units have, trapping gases in between the panes. Transferring in 2002 to a small-holding in South Wales, https://waylonncobs.blogofoto.com/65791633/the-smart-trick-of-secondary-glazing-that-nobody-is-discussing