Even in climates that aren't considered extreme, it's
common to find double-paned, sealed windows. Sealed windows have an air vacuum between the panes--or a low conductivity, inert
gas like argon. It's a combination of the double-paning (or even triple-paning) of the windows and the gas within which
keep the cold away. If the seals between the thermal panes fail (seal failure), the glass becomes saturated with moisture. This will cause the glass to stain between the panes. The performance
value of the glass has been rendered all but worthless.