Foggy Windows: Fix the Glass or Replace the Window?
If your IGU seal failed, you have two real options — and the difference is roughly $250 vs. $1,200 per window. Here's how to decide honestly based on frame condition, hardware, and overall window age.
Failed insulated-glass-unit (IGU) seals are one of the most common window problems we diagnose in NJ — typically appearing as cloudy/hazy glass that doesn't wipe clean. Most homeowners assume the only fix is full window replacement. That's usually wrong. If the frame and hardware are still in good shape, you can replace ONLY the glass unit for roughly 1/4 the cost.
This guide walks through how to diagnose the problem, when to repair vs. replace, and what each option costs in NJ in 2026. We do both — and we'll tell you honestly which is right for your situation.
8 symptoms of a failed IGU
- Cloudy / hazy view through the glass that doesn't wipe clean
- Visible water droplets BETWEEN the two panes (not on either surface)
- White mineral-deposit streaks on the glass interior surface
- Glass that fogs up on humid days and clears in dry weather (intermittent seal failure)
- Rainbow-colored film visible at certain angles (depleted argon gas)
- Frost or ice formation between the panes in winter
- Window feels colder to the touch than other windows in the same room
- Higher heating bill on the side of the house with the fogged windows
4 scenarios, 4 answers
Frame is sound, hardware works, sash opens/closes properly
$250–$500 per window→ Replace ONLY the glass (IGU)
If the frame and hardware are still in good condition and the failure is just the insulated-glass-unit seal (fogging between the panes), the cost-effective fix is to swap out just the IGU. Most major manufacturers (Andersen, Pella, Marvin, Provia) offer replacement IGUs that drop into existing frames. We measure the glass, order the matching IGU (typically 2–5 business days), and install in a single 30-minute appointment per window.
Frame is rotting, hardware is broken, sash is sticking
$650–$1,800 per window installed→ Replace the whole window
If the frame is compromised (rot, racking, water damage) or the hardware has failed beyond repair, glass-only replacement is throwing money at a window that's about to fail entirely. Full-window replacement (frame + sash + glass + hardware + new flashing) gives you a fresh 20-year service life and modern thermal performance.
Single fogged window out of many, all 25+ years old
$7,500–$18,000 whole-house→ Plan whole-house replacement
If one window in your house just failed and the rest are all the same age (25+ years), the others are statistically about to follow. A single fogged window today is often the first of a sequence over the next 5 years. Many homeowners do glass-only on the first failure to test our work, then come back for whole-house replacement when 2–3 more fog up. We honor pricing from the first quote on follow-up jobs.
Wood or cast-iron historic sash that's irreplaceable
$500–$900 per window→ Restore the existing sash + install new IGU
Pre-1940 wood sash, especially in historic districts (Cape May, Princeton, Montclair, Morristown, Hoboken brownstone, Asbury Park Victorian), is often worth restoring rather than replacing. Standard restoration scope: strip and re-glaze with linseed-oil putty, replace damaged muntins, install a modern IGU that drops into the original sash frame profile, replace sash cords + weatherstripping. Preserves historic look, often the only HPC-approvable path.
Common foggy-window questions
Can I really just replace the glass and keep the frame?
Yes — if the frame, hardware, and sash are sound, glass-only replacement is the right call. Most window manufacturers (Andersen, Pella, Marvin, Provia, Harvey, and others) make replacement IGUs that fit existing frames. We measure the existing IGU (overall dimensions + thickness), order the matching unit, and swap in 30 minutes per window. Cost runs $250–$500 per IGU depending on size and glass spec.
Why do IGU seals fail?
The seal between the two panes of glass is a polyisobutylene or silicone-based gasket that's not designed to last forever. Typical lifespan is 15–25 years depending on manufacturer quality, installation, and exposure. South and west-facing windows fail faster (more thermal cycling). Properties near salt air (Atlantic, Cape May, Monmouth, Ocean counties) see faster failure (8–12 years vs. 20+ inland). The actual failure mechanism: temperature cycling expands and contracts the glass + seal until microscopic cracks let humid air leak in.
Will glass-only replacement match my other windows?
Yes if the IGU is from the same manufacturer line. Modern manufacturer warranty lines (Andersen 100/200/400, Pella 250/350/450, Marvin Elevate/Essential/Ultimate) are designed to accept replacement IGUs that match the original spec exactly — same low-E coating, same grilles pattern, same color. If your existing window is from a defunct manufacturer or pre-1990 vintage, finding an exact match is harder; we'll tell you honestly if matching isn't possible.
How can I tell if it's a failed seal vs. just dirty glass?
Wipe both the interior and exterior surfaces with glass cleaner. If the haze is still there, the moisture is BETWEEN the panes (failed seal). If it wipes clean from one side, it was just dirt. The clearest test: drop a single ice cube on the glass on a humid summer day. If condensation forms on the OUTSIDE surface where the cube cooled the glass, the IGU is intact. If condensation forms between the panes (visible only at the right angle), the seal has failed.
What does whole-window replacement cost in NJ?
Per-window installed cost varies by frame material and size: vinyl double-hung $400–$800 installed per window; fiberglass $700–$1,200; aluminum-clad wood (Marvin Ultimate, Andersen Architectural, Pella Reserve) $1,200–$2,000. A whole-house package of 10–15 windows typically runs $7,500–$18,000. We line-item every quote so you see per-window cost + per-window install + flashing + trim + permits — never a bundled total.
Will insurance cover fogged windows?
Generally no — gradual IGU seal failure from age is NOT a covered insurance event. Sudden covered events ARE covered: storm-broken glass, tree-strike impact, vandalism, vehicle impact. If your IGU failed from age, financing or cash are the paths. If something hit the window and broke it (or stress-cracked it), that's a claim — call your carrier and we'll help with documentation.
Free on-site diagnostic — we'll tell you honestly
We assess the frame, hardware, and IGU condition free. If glass-only replacement is the right call, we'll tell you (and quote it). If whole-window replacement is the right call, we'll tell you that too. No upsell.