I have two panes of glass, about a 3/8" thick (.95 cm). Space efficiency and aesthetics ignored, how far apart should they be spaced to maximize heat insulation, assuming the gap contains regular air (and not Argon). I read that it's a balancing act between convection and conduction, and that store bought double panes windows are usually in the 1/4" - 1/2" range (0.635 cm - 1.27 cm). Other sources suggest a gap up to 2" (5 cm) is ideal, with the reasoning that a larger gap is always better up until it's wide enough to allow convection. Assuming it's exactly freezing outside and room temperature inside, how to I figure out what gap is best?