A glass wine wall that fogs isn't dirty and isn't badly cleaned. It's physics, and it was decided before the glass went in.
This matters more in Atlanta than in most places, because the outside of that glass spends half the year in warm, humid air.
What is actually happening
Air holds a certain amount of moisture depending on its temperature. Cool it enough and that moisture has to go somewhere — it condenses on the nearest cold surface. That temperature is the dew point.
A conditioned cellar is held well below room temperature. A single sheet of glass between the two conducts that cold straight through, so the room-side face of the glass sits cold. When humid living-room air touches it, you get condensation — on the outside, where you can see it and can't wipe it away for long.
Why an insulated unit fixes it
An insulated glass unit is two panes with a sealed airspace between them. That airspace is a poor conductor, which is the whole point: the cold side stays cold, and the room side stays close to room temperature. Above the dew point, nothing condenses.
A low-emissivity coating on one of the internal surfaces reduces radiant heat transfer as well. That helps twice: less condensation risk, and less work for the cooling unit, which is the difference between equipment that cycles and equipment that runs constantly.
The door is usually the weak point
Most disappointing cellars we hear about don't fail as glass, they fail as an envelope — and the door is where envelopes leak. An unsealed perimeter or a gap at the floor bleeds conditioned air continuously. The cooling unit never catches up, the room never holds its setpoint, and the glass sweats near the leak.
A cellar door needs a proper seal at the jambs and at the threshold. It's an unglamorous detail that decides whether the whole installation works.
Why low-iron matters here most
Two panes of ordinary glass stack two green casts on top of each other. Looking through that at your labels, everything shifts warm-green. Since displaying the bottles is the entire purpose of the wall, low-iron is less of an upgrade here than a requirement.
What to settle before anyone orders glass
Who is specifying the cooling equipment, and has the glass been sized into their load calculation? Is the space insulated and sealed on all six surfaces, including the ceiling and the slab? Where does the cooling unit exhaust its heat? Glass is one part of a conditioned envelope — designed in isolation, it disappoints no matter how good it is.
Common questions
Can an existing single-pane cellar wall be fixed?
Usually the glass has to be replaced with an insulated unit — you can't add an airspace to glass that's already installed. Before doing that, it's worth checking the seals and the cooling capacity, because sometimes the fogging is a leak rather than the glazing.
Does the glass protect the wine from light?
Coatings and laminated interlayers cut UV transmission substantially, which helps. It isn't a substitute for keeping direct sunlight off the bottles — position the cellar and choose its lighting with that in mind.
Can a closet or under-stair space become a cellar?
Those are two of the most common locations in a house that wasn't built with one. It comes down to whether the space can be insulated and sealed, and whether the cooling unit can vent its heat somewhere sensible. That's assessed on site, with whoever is doing the cooling.