According to this: Are engineering questions appropriate for this site?
When constructing a product for use in the world, there are many considerations that go into the decision-making process. The underlying physical principles are only a part of this. The physics community, while often tangentially knowledgeable in these areas, is not the place to seek guidance when ease-of-use, manufacturing costs, material availabilities, etc. are also primary considerations.
Ease of use, manufacturing costs, and material availability are not considerations in my question. I specifically said that it doesn't matter how impractical it is. The material is not a variable. I just want to know what the ideal gap is (and how to arrive at that information), which I suspect makes it a physics problem. A physics problem I still have no idea where to begin with.
All of the responsibility of engineering it: thermal expansion of glass vs. the frame, size of the glass, strength of the glass, whether the glass will bow or break under its own weight, whether the gap is too large or small for my limitations, fog between the panes of glass, etc. are all not in question. In order to make my sad rendition of a "good" balance of these factors, I need to know which direction "perfect" is, and I don't.
Please understand the answers I've found range from "basically as close possible without touching" and "wide enough to stick your finger in there".
Yes, I include a specific thickness of the glass, but how does that make it engineering? I suspect that things like how thick the glass is, whether it's glass, the temperature of the air, the fact that it's not argon (which is what manufacturers put between glass layers) are required information to get an answer that doesn't contain the words "not enough information".
I'm asking how to determine a single dimension under idealized circumstances. It's a five-layer sandwich of infinite planes of: hot air, glass, air gap, glass, cold air.
If that isn't physics, why isn't the question that my question links engineering also?