We've bought a huge Georgian B&B in the UK. It has vast single-glazed windows. The house is not listed however we want to retain as much fabric as possible. Therefore we are looking at secondary glazing rather than double glazing for the windows.
Given the style of some windows I've some flexibility in how far I separate the original and secondary panes. Is there an optimum distance, or some algorithm for this?
Historically I recall that a wide separation can set up circulation within the gap, thus transferring the heat; however, current hearsay is that wide is better. They can't both be right.
For some windows we are employing a carpenter to remake the windows to take double-glazed units - so I do know that can be an option. However, with the expense it's one I'll use selectively.