Short answers, pulled from the story.
Insulated glazing uses two or more glass panes separated by a sealed gap filled with air or gas, reducing heat transfer through the window. A single pane of glass has an R-value of around 1; a standard double-paned insulated unit is roughly three times more effective, and high-performance versions reach R-24 or higher.
Thomas Stetson patented the basic concept in the United States in 1865. Commercial development followed in the 1930s, and the Libbey-Owens-Ford Glass Company announced the Thermopane product in 1944 under a trademark registered in 1941.
Argon's thermal conductivity is only 67 percent that of air. It is a monatomic gas that does not carry heat through rotational molecular modes, giving it a lower effective heat capacity. It also makes up nearly one percent of the atmosphere, keeping production costs reasonable compared to alternatives like krypton or xenon.
Most units last between 10 and 25 years, with manufacturer warranties typically covering 10 to 20 years. Windows facing the equator often last less than 12 years. Seal failure, which allows moisture to enter and condense between the panes, is the most common reason for replacement.
A low-E coating is a metallic layer, applied to the glass surface, that reflects infrared light and blocks portions of the ultraviolet and visible light spectra. It reduces solar heat gain and improves the unit's R-value. Hard coatings use tin oxide applied during glass production; soft coatings are vacuum-sputtered and offer higher performance but require protection from an inert gas fill.
Vacuum insulating glass removes nearly all air from the cavity between two panes, eliminating convective heat transfer. Early designs available from the 1990s reached R-4.7, equivalent to high-quality double glazing. Recent products claim up to R-14, surpassing standard triple-glazed units. Internal pillars spanning the vacuum space are required to resist atmospheric pressure.