Double-pane windows last 15–20 years. The most common failure is insulated glass unit (IGU) seal failure — visible as permanent fogging between panes.
Double-pane (insulated glass unit) windows are the modern standard for residential windows and last 15–20 years per InterNACHI data. The frame material significantly affects longevity: vinyl frames 20–40 years; wood frames 20–30 years with maintenance; fiberglass frames 40+ years. The glass unit typically fails before the frame — the argon gas between panes slowly escapes over 15–20 years, and once the seal fails, moisture infiltrates and causes the permanent fogging that signals replacement is needed. Replacing just the IGU glass (without the frame) is often possible and costs significantly less than full window replacement.
Replace windows when the insulated glass unit is fogged (seal failure) and IGU replacement is not cost-effective due to age, when frames are rotted, or when windows are drafty despite weatherstripping replacement. Energy-efficient replacements (double-pane Low-E with argon) save 7–15% on heating and cooling bills in most climates.
Before replacing entire windows, check if just the glass unit (IGU) can be replaced. If the frame is in good condition, IGU replacement (the glass only, not the frame) typically costs $150–$400 per window vs. $500–$1,200 for full window replacement. Many glass shops and window companies offer this service and it restores full insulation value at a fraction of full replacement cost.
Permanent fogging between double-pane window panes indicates seal failure. The gas (typically argon) has escaped, and moisture has infiltrated the space between panes. Once fogged, the insulation value of the window drops significantly. The glass unit needs replacement — the frame may still be usable.
Enter your install date or last service, and IsItDue will tell you exactly when it's due — and how much to set aside each month.
Start tracking for free →