Summary: Summary: Replace windows when you see persistent drafts, condensation between glass panes, rotting or damaged frames, difficulty operating, rising energy bills, outside noise intrusion, or single-pane glass in an older home. Repair is enough for failed weatherstripping, broken hardware, or a single cracked pane in an otherwise sound window. If most windows show multiple symptoms and the frames are 20-plus years old, replacement beats piecemeal repair.
Hold a lit candle or incense stick near the window edges on a windy day: flickering reveals air leaks that weatherstripping cannot fix when the frame itself has warped or the seals have failed. Some draft is normal in old windows, but if you can feel air movement a foot from the window, the window is costing you real money every heating and cooling season.
Condensation between the glass panes means the insulated glass unit's seal has failed: the argon gas is gone, moisture is in, and the window's insulating value has collapsed. This cannot be repaired economically; the glass unit must be replaced. If several windows show this simultaneously, the whole set is reaching end of life together, which is normal: they were installed together and they age together.
Probe wood frames and sills with a screwdriver: soft, punky wood is rot, and rot spreads. Surface rot in one spot can be patched with epoxy; widespread softness means the frame is done. On vinyl and aluminum, look for warping, cracks, and failed corner welds. Water staining on the wall below the window signals flashing or frame failure that is already damaging the structure.
Windows should open, close, and lock with one hand. If sashes stick, balances have failed, or locks no longer engage, the window is a security and egress problem, not just an annoyance. Failed balances and hardware are repairable individually, but when most windows in the house operate badly, the mechanisms are aging out as a set and replacement is the rational call.
Rising energy bills with no rate increase and no lifestyle change point at the building envelope, and windows are the weakest part of it. Compare winter bills year over year: a steady climb as windows age is the signature of failing seals and growing air leakage. An energy audit with a blower-door test quantifies exactly how much air your windows leak.
Increasing outside noise means the seals and glass are no longer doing their job: new windows, especially laminated or triple-pane, transform a noisy street-facing room. And single-pane glass in an older home is itself the sign: even perfect single-pane windows insulate roughly half as well as basic double-pane, so replacement is an upgrade with immediate comfort returns, not just a repair.
Repair when the problem is isolated and the window is otherwise sound. Failed weatherstripping: $50 to $150 per window to replace, and it fixes a surprising number of draft complaints. Broken sash locks, cranks, or balances: $75 to $250 per window for parts and labor. A single cracked pane in a sound frame: glass-only replacement at $150 to $400.
Caulking failures around the exterior trim are a $20 DIY fix that mimics window failure convincingly: always re-caulk before diagnosing the window. The repair rule of thumb: if the fix costs less than 30 percent of replacement and the window has a decade of life left, repair it. Past that, put the money toward the new window.
Score your windows honestly: count how many show two or more of the seven signs. If it is most of them and the set is 20-plus years old, get whole-house quotes: the per-window economics and the uniform result beat piecemeal replacement. If it is two or three windows, replace those and monitor the rest annually.
Get the assessment from a window professional, not a salesperson: an independent home inspector ($300 to $500) will tell you straight which windows are done and which have years left. Then get three installer quotes on the same scope. The windows decision rewards the same discipline as every big home project: diagnose first, price second, and never let urgency substitute for comparison.
Data current as of October 2026. Sources: Pella, Fixr, and contractor pricing data. Estimates only, not a quote. Always get multiple written quotes from licensed local window installers.