Condensation is visible during some days in my BiltBest windows - what causes this?

Insulated glass consists of two or more pieces of glass which are bonded to, yet separated from, one another by a spacer bar. The space between the glass panes is an insulator by virtue of "dead air space”. This fabricated glass sandwich is glued together with sealants designed to keep the glass together and moisture out. The spacer contains a dessicant that removes moisture which might be residual from actual manufacture. Insulated glass seal failure occurs when moisture penetrates the edge seals and wets, or condensates within the air space. Condensation between glass panes is a real "eye-sore" for homeowners.
KEYWORD RELATED PHRASES - About windows & glass, Construction defects in glass, fogged glass, fogging glass, foggy windows, window glass condensation, window glass failure, insulated glass, insulating glass seal failure, IG seal failure, thermo-pane, water between the panes, BiltBest window condensation issues, Dew Point - Frost Point - Glass - Insulating Glass - Phase Transition Temperature.
A serious seal / glass failure will involve the permanent presence of moisture in the airspace.  The worst IG seal failures usually involve degradation of the spacer. Sometimes the spacer corrodes or even rusts. Sometimes the dessicant becomes so saturated that it turns to mush and becomes visible on the spacer. We often see failures in which, upon deglazing, one lite of glass completely separates from the spacer bar.