[Zeke]

Well, MRM may know more about windows than anyone, but I have personally installed around 5000 windows with my own two arms, hence the shoulder replacement.

Here in CA we hardly ever see temp differential of more than 40º F. In Canada, I can see the usefulness of argon whereas here not so much.

Here's the deal: some window manufacturers will leave a small equalizer tube in between the glass panels. The reason is, if the windows are built and sealed at 1000' elevation and shipped to Vail, they can explode. At least they will be distorted like a football.

Therefore, as the temps go up and down daily, the little tube acts as a pump and the argon is removed over time. There is no practical way of replacing the gas.

As mentioned, and condensation inside is proof that the seal is compromised if only the tube. I've never experienced it, but I've been told that on some windows the tubes can be accessed and pinched off once the windows have become acclimated, which should be rather quick once they reach their destination and altitude.

It isn't out of the question to replace the glazing but you want to answer the following questions first: is there any draft or convection in and around the windows, or indeed, the house itself? And the surround of the installation, once again covered above in other posts. Last in the convection category is weather-stripping. Must be intact and in good order.

Is there unnecessary conduction, or heat loss? This would be weak glazing, too close of a gap, loss of gas and even not enough window covering (inside or outside).

The third energy factor is radiation and heat can radiate both ways (in and out). The LowE coatings are designed to reflect infrared rays. Here in SoCal, we just reflect the incoming, but dual LowE (both ways) is available.

A quick and inexpensive fix is fitted storm windows. Your R rating will be increased by the addition of a 3rd pane, even if it is not sealed to the dual pane unit. But it must be fitted with some W/S or you won't gain the potential.

I'll leave the subject of heat gain (summer) for another discussion, but it will be similar in nature.