When the seal on a double-pane window fails, fogging between the glass signals it's time for an insulated glass unit replacement. This involves removing the entire sash, carefully extracting the old sealed unit, and installing a new one with fresh desiccant and sealant. It's a precise job that restores your window's thermal efficiency and eliminates that cloudy look, often costing less than a full window replacement. insulated glass unit replacement 8