Foggy Window? Defog, Swap the Glass, or Replace the Window — 2026 Costs and What the Warranty PDFs Actually Cover

Last reviewed: 2026-09-27

Researched and written by one person, not an editorial team. I am an independent researcher, not a licensed contractor, and I do not install windows — see the About page for exactly what I do and don't do. This page carries a lead-capture form at the foot; if you submit it, your contact information is routed to a disclosed set of window-installation companies and/or lead networks, and I am paid for that referral. That disclosure, and the current list of who sees your information, is shown next to the form itself, not buried here.

A foggy window is a broken seal, not a dirty window

If there's haze, water film, or mineral streaking between the panes of a double- or triple-pane window — not on the inside or outside surface, where a rag fixes it — the sealed insulating glass unit (IGU) has failed. The gas-filled cavity between the panes is sealed at the factory; once that seal breaks, humid room air gets in, condenses against the cooler outer pane, and it never fully clears again on its own. That's the whole mechanical story, and it's why the fix isn't "clean it" — it's one of three different jobs at three different price points: defog the existing sealed unit cosmetically, swap the glass unit for a new factory-sealed one inside the existing frame, or replace the whole window, frame and all.

Those three options aren't graduated versions of the same repair. They fix different amounts of the problem, they carry different warranties, and — as the sources below show — the businesses selling each one have a financial reason to tell you it's the right call. This page compares what each option actually does, what it costs in 2026, and what four manufacturers' actual warranty documents say about how long a seal is covered, whether labor is included, and whether that coverage survives a home sale.

The three options, compared

Option	Typical 2026 cost	What it actually does	What it does not do
Defog ("drill and dry")	$60–$200 per window	A technician drills a small hole in the glass, injects a drying/cleaning agent, dries the cavity, and reseals the hole — clearing the visible haze	Does not rebuild the broken seal or replace the argon fill; the unit still performs like a failed seal, and haze commonly returns
IGU (glass-only) replacement	Roughly $100–$980+ per window installed, depending on size and brand	Removes the failed sealed glass unit from the existing sash and slides in a new, factory-sealed IGU with its own gas fill and coatings	Does not address a rotted sill, a warped or air-leaking frame, failed hardware, or a window that's structurally at end-of-life
Full window replacement	Roughly $300–$1,823+ per window installed (material- and scope-dependent — see this site's window replacement cost page for the full breakdown)	Replaces frame, sash, hardware, and glass — the entire unit	Costs more than necessary if the frame is sound and the seal is the only failure

Sources for the cost ranges: Installix, "Foggy Window Repair Cost: What You'll Pay (and When It's Warranty)" (page dated 2026-07-21) · FixUpFirst, "Window Repair Cost 2026: $75–$400 by Problem Type" (published 2026-05-14, updated 2026-05-18) · Carolina Glass Replacement, "Repair vs Replace Foggy Windows – Honest Cost Guide" (August 2026) · Bob Vila, "Broken Window Seals? Here's How to Identify and Repair Them" · Window Gurus, "Window Seal Failure: 5 Key Signs and Prevention Hacks 2025" (published 2025-11-29, updated 2026-05-04). All retrieved 2026-09-27.

The spread inside each row is real, not sloppy sourcing. Bob Vila's IGU figure ($100–$600 for the unit, plus $150–$500 labor) is priced as separate glass-and-labor line items; Carolina Glass Replacement prices a named-brand distinction directly — "$365 - $825" per window for a standard brand and "$395 - $980" for Pella or Andersen units — because a name-brand sash holds a proprietary glass pack that a generic glazier can't always source generically. Installix's spread by size runs from "$300 to $450" for a small window up to "$900 to $1,500+" for an oversized or specialty unit — but Installix prices the Greater Toronto Area market specifically, so treat that spread as directional for shape (small vs. oversized) rather than as a U.S. dollar figure directly comparable to the other sources on this page. None of these disagree with each other; they're pricing different sizes and brands under the same two-word search term, the same pattern this site has found on every other cost page.

Defogging: what it clears, and what it doesn't

Defogging (also sold as "drill and dry" or "window restoration") is the cheapest option and the one most likely to disappoint. Installix describes the mechanism plainly: "A technician drills a small hole, injects a cleaner, dries the cavity, and reseals it." The same source is direct about the limits of what that accomplishes: "it does not rebuild the broken seal or put the argon back, so the window still performs like a single pane and the fog often returns," and again, "Defogging costs $75 to $200 and clears the view for a while, but it does not restore the seal or the argon gas. You are paying to hide the problem, not fix it."

ACE Glass, a glass-repair company that pointedly does not offer defogging, makes the same case from the seller's side: "Defogging is an optical illusion. It might remove the visible water droplets, but the window's seal is still completely broken," and the company says it won't perform the service because "we cannot stand behind a service that leaves your home less energy-efficient than it should be" (source: ACE Glass, "Can You Repair a Foggy Double-Pane Window? The Honest Truth", retrieved 2026-09-27). The same page states, in the context of drilling into the glass, that "Modifying the glass by drilling holes into it instantly voids any remaining manufacturer warranties you might have." I want to flag that specific claim rather than just repeat it: I read four manufacturers' current warranty documents directly for this page (below), and none of the four names "drilling" or "defogging" as a listed exclusion in so many words — the closer, verifiable fact in those documents is that all four exclude non-factory glass work and field modifications generally (Andersen: glass warranty "does not apply to... glass that is not factory installed by Andersen"; Marvin: glass warranties apply only to "factory-installed glass or Marvin-supplied glass installed by Marvin-authorized service personnel"). A third-party drill-and-dry service is exactly the kind of non-factory glass work those clauses describe, which is consistent with ACE Glass's warning even though I couldn't find the word "defog" printed in any of the four PDFs themselves. Treat the warranty risk as real but inferred, not a clause you can point to by name.

Defogging is a reasonable choice only as a stopgap — a rental you're about to sell, a budget crunch before a planned full replacement, a window you know is getting torn out next year anyway. As a permanent fix for a window you intend to keep, every source above agrees it isn't one.

IGU replacement: the middle option, and when it's the right one

Swapping just the glass unit keeps the existing frame, sash, hardware, and trim, and puts a new factory-sealed IGU — with its own gas fill, Low-E coating, and warranty — into the opening. ACE Glass's description of the physical process: technicians "remove the protective stops around the glass, carefully lift out the failed, foggy glass unit, and slide a brand-new, factory-sealed IGU right into your existing window frame."

The decision criteria that the sources converge on, independent of price, are about the frame, not the glass:

Choose the glass-only swap when, per Carolina Glass Replacement, "the frame is in good condition and the only problem is the glass itself," the frame shows no rot, warping, or structural damage, "the window opens and closes smoothly," the hardware still works, and there's no draft around the frame perimeter. Tri-City Windows and Doors' framing of the same question is nearly identical: glass-only replacement makes sense when "the window frame is still in good condition," "the window opens and closes properly," and "there are no significant drafts around the frame" (source: Tri-City Windows and Doors, "Foggy Windows: Replace the Glass or the Whole Window?", retrieved 2026-09-27; the article's own date stamp reads "August 13, updated September 10" without a printed year, so I'm not dating it more precisely than that).

Choose full replacement instead when the frame is rotted or structurally compromised, significantly warped, has hardware that's broken with parts no longer available, shows water damage reaching the surrounding wall, or — separately from condition — you want a different window style or operating type than what's there (Carolina Glass Replacement, same source as above). Window Gurus states the same threshold from the other direction: full replacement is the better call given "persistent drafts, severe frame rot, or moisture penetration that repeatedly returns," while smaller issues "often make sense to fix as long as the main structure remains stable" (source: Window Gurus, "Window Repair Costs in 2026 – Prices & Services", published 2025-02-17, updated 2026-06-17, retrieved 2026-09-27).

Carolina Glass Replacement states that roughly "85%" of foggy-window cases are correctly solved by glass-only replacement, with the remaining "15%" needing full replacement for a secondary frame or hardware problem. I want to be precise about how much weight that number can carry: I went back to check whether Window Gurus's similarly-framed pages stated the same split, since near-identical percentages across cost-guide sites is often a sign of templated or syndicated content (the same pattern the ENERGY STAR page and the patio-door cost page on this site have both had to call out). Neither Window Gurus page I cite on this page actually contains an 85/15 figure — so this is one source's number, not two converging on the same one, and I'm treating it accordingly. The underlying decision criteria (frame condition, drafts, hardware) are corroborated independently by Tri-City and by Bob Vila below, which is why I'm using those criteria; the specific 85/15 split is not something I'd repeat as a hard number.

Also worth naming plainly: the two companies with the clearest opinions on this question both sell exactly what they recommend. ACE Glass sells glass-only IGU swaps and argues you almost never need a new frame. GetKenco sells full replacement windows starting, per its own page, at "around $599," and argues repair is usually a false economy: "a non-warranty seal repair (replacing the insulated glass unit) typically runs $300–$500 in parts and labor," which the company frames as inefficient relative to a new window (source: GetKenco, "Window Repair vs Replacement: 2026's When to Fix or Replace Guide", retrieved 2026-09-27). Both numbers are consistent with the ranges cited elsewhere on this page; it's the conclusion each draws from its own number that reflects what each business sells. Use the frame-condition criteria above, which every source — including the two with something to sell — agrees on, rather than either seller's bottom line.

Full replacement: when the seal is the smaller problem

Full window replacement is the right call less often for a single foggy pane than cost guides on this topic sometimes suggest, but it's clearly right in specific, checkable situations: multiple windows throughout the house failing at once (a sign the whole batch is at the end of its manufactured seal life, not that one unit had a defect), a frame that's rotted, warped, or water-damaged into the surrounding wall, hardware that no longer functions and can't be sourced, or a window that's already 15–20+ years old, per GetKenco's age framing: "Wooden and new construction windows 15-20+ years old are at the end of their useful life" (same source as above). Bob Vila's installed full-window range — "A replacement window runs $175 to $650, or much more, depending on quality. Labor costs to install a replacement window typically run $200 to $400 per window" — sits at the low end of what this site's own window replacement cost page found for national aggregator figures generally, which is consistent: the same scope and material variables (insert vs. full-frame, vinyl vs. wood, national database vs. regional installed quote) that drive a 3–6x spread on that page apply here too. If you're comparing a full-replacement quote against an IGU-swap quote, get both itemized the same way — glass, labor, and any frame/trim work — before deciding the frame is (or isn't) part of the job.

A region-specific fact: climate cycles the seal, not just time

Seal failure isn't purely a clock running out — it's driven by how hard the glass and spacer expand and contract, which is a climate variable, not just an age variable. Window Gurus, discussing seal failure in Ohio specifically, states that "Ohio's -10°F winters to 90°F summers" create thermal stress that "ruptures seals in 30% of diagnoses," and that this cycling "reduces this to 12-15 years" of expected seal life, against a 10–20 year national baseline the same article gives elsewhere. The same source adds that "south/west exposures fail first" due to UV and heat load, and recommends shading "extreme south/west exposures with awnings" (source: Window Gurus, "Window Seal Failure," cited above). That's a single regional data point from one source, not a nationwide climate model, so I'm citing it as exactly that — a named place with a named freeze-thaw swing, not a claim that every cold-to-hot climate behaves identically. If you're in a climate with wide seasonal swings (the upper Midwest, the Mountain West, the desert Southwest) and your windows are in the 12–15-year range rather than the fuller 20-year mark, seal failure showing up earlier than the warranty term would suggest is consistent with what this source describes, not necessarily a manufacturing defect.

What the manufacturer warranty PDFs actually say

Every one of these companies' marketing pages says some version of "long seal warranty." I opened four current warranty PDFs directly — Andersen, Marvin, Simonton, and Milgard — to see what the operative documents actually say about seal-failure length, labor, and transferability. The short version: all four cover the glass a long time; all but one explicitly exclude labor; and transferability varies by manufacturer and, for Milgard, by whether you paid for an upgrade.

Manufacturer / document	Glass seal-failure coverage	Labor included?	Transferable to a new owner?
Andersen 400 Series/200 Series Windows & Doors Limited Warranty (rev. 12/16/14, effective Feb. 2015)	20 years	No	Yes
Marvin Signature/Elevate/Essential Window and Door Limited Warranty (effective 2/26/2024)	20 years (≤60 sq ft w/ stainless-steel spacers) / 10 years (>60 sq ft)	No	Yes
Simonton Limited Lifetime Warranty — Brickmould 300/600, Pro Finish Builder, Contractor Series (effective 10/1/2022)	15 years (10 years for "Specialty Goods" — laminated, obscure/decorative glass, bay/bow, garden windows)	No	No
Milgard Full Lifetime Warranty Upgrade (effective 1/1/2026 — a purchased add-on, not the standard warranty)	Lifetime, for as long as the original owner owns and resides in the home	Yes	No — lapses on sale

Andersen (primary-document extraction)

Andersen's document is titled, unambiguously, "Transferable Limited Warranty on Glass" and states the glass "is also warranted not to develop, under normal conditions, any material obstruction of vision resulting from manufacturing defects or as a result of premature failure of the glass or organic seal for twenty (20) years from the date of purchase from the retailer/dealer." But labor is carved out explicitly and twice: the remedy clause says Andersen will "provide the appropriate replacement glass product to the Andersen retailer/dealer you specify — labor is not included," and the exclusions list separately names "Labor to replace sash or door panels, glass or other components" and "Labor and other costs related to the removal and disposal of defective product." Condensation itself is a listed exclusion too — expected, since condensation on the outside surfaces is a humidity effect, not a seal failure; the seal-failure clause above is specifically about obstruction within the sealed cavity. Source: Andersen, "400 Series/200 Series Windows & Doors Limited Warranty" (PDF), retrieved 2026-09-27.

Marvin (primary-document extraction)

Marvin's current warranty (effective February 26, 2024, Part #19980996) splits coverage by unit size: "Standard insulating glass with stainless steel spacers is warranted against seal failure caused by manufacturing defects and resulting in visible obstruction through the glass for twenty (20) years in sizes up to sixty (60) square feet, and for ten (10) years in sizes sixty (60) square feet and larger." A 60-square-foot IGU is a genuinely large window — most residential units are nowhere near that — so in practice most homeowners land in the 20-year tier, but a large picture window or a big patio-door sidelite could land in the shorter 10-year tier without the buyer necessarily being told which one applies. Coverage is explicitly "fully transferable" to a subsequent owner of the same structure. Labor is excluded the same way Andersen excludes it: "Removal, installation, finishing, refinishing, and disposal costs and services are not included." Marvin also disclaims argon specifically, in language functionally identical to what this site found in Marvin's coastal cladding warranty on the vinyl vs. fiberglass vs. wood windows page: "Marvin does not warrant the amount or percentage of argon or other inert gas present in insulating glass at any time after manufacture." Source: Marvin, "Window and Door Limited Warranty" (PDF), retrieved 2026-09-27.

Simonton (primary-document extraction)

This document covers Simonton's builder/contractor-grade lines (Brickmould 300/600, Pro Finish Builder, Contractor Series) rather than its premium retail lines, and it reads more restrictively than either Andersen's or Marvin's on two of the three axes this page is comparing. Coverage: "The installed, sealed insulating glass unit is warranted to be free from material obstruction of vision on the internal surfaces of the insulating glass unit, for up to 15 years from Purchase Date. The coverage for Specialty Goods is limited to 10 years from Purchase Date." Transferability is stated as a hard limit, not a carve-out for specific cases: "'Customer' used hereinafter shall only include the initial Customer for Simonton Goods and the first consumer user of such Goods. The Warranty is not transferrable beyond the first consumer user." Labor is excluded via the general remedies clause — "Simonton is not responsible for any costs incurred in the removal, replacement, installation, re-installation or repair of product or adjacent materials" — with no initial labor-inclusion window of any length, the same structure this site found in Andersen's and Pella's patio-door warranties on the patio door cost page. Source: Simonton, "Limited Lifetime Warranty" (PDF), effective for purchases on or after 10/1/2022, retrieved 2026-09-27.

Milgard (primary-document extraction) — and a distinction worth being careful about

The Milgard document I read is titled "Full Lifetime Warranty Upgrade" and it says explicitly that it is an add-on, not the baseline coverage: "This Warranty is an optional warranty upgrade for certain lines of Milgard Manufacturing LLC... products... The upgrade must be purchased at the time of the original product sale and be reflected in Milgard's order documents for this Warranty to apply. Where unavailable or not selected at the time of sale, Milgard's standard warranty for new construction or replacement product will apply." I read this document only — I did not separately fetch Milgard's baseline "New Construction Limited Warranty" or "Replacement Product Limited Warranty" that applies when the upgrade isn't purchased, so everything below describes the paid upgrade specifically, not what a Milgard buyer gets by default (see "What we could not verify" below).

Under the upgrade, IGU coverage is open-ended by time and unusually broad by cause: "Milgard will offer a Remedy to address a material obstruction of vision through the glass due to accumulation of dust, moisture or chemical outgassing on an internal surface of the IGU (standard, laminated or impact glass) throughout their ownership" — i.e., for as long as the original buyer owns and lives in the home, not a fixed year count. Labor is the one place this document beats the other three outright: "Milgard will provide all labor necessary to complete the Remedy and pay shipping costs during the coverage period." But transferability is the trade-off, stated as flatly as Simonton's: "The coverages in this Warranty cannot be assigned or transferred. If the original consumer sells the dwelling, uses the dwelling for rental or commercial purposes, or ceases to reside in the dwelling, this Full Lifetime Warranty coverage shall lapse." A homeowner planning to sell within the seal's likely failure window gets less real protection from this coverage than the "lifetime" name on the document suggests. Source: Milgard, "Full Lifetime Warranty Upgrade" (PDF), effective January 1, 2026, retrieved 2026-09-27.

The pattern across all four

Long or lifetime glass coverage is close to universal in this product category — every document above puts seal-failure coverage at 15 years or longer. What actually varies, and what a "20-year glass warranty" headline hides, is labor (three of four provide none, ever) and transferability (one provider ties it to an optional paid upgrade that lapses on sale; one restricts it to the first buyer only). Ask for the specific document, not the marketing page, before assuming any of these terms apply to a specific quote — and if you're buying, ask directly whether labor is included and for how long, since three of the four documents above answer "never."

Getting quotes for either path

Whether you're getting bids for an IGU swap or a full replacement, the verification steps are the same ones this site covers for any window-installation job — checking a contractor's license, confirming insurance, and getting an itemized quote that separates material from labor. See how to vet a window installer for the license-lookup tools and certification comparison; it applies equally to a glass-only repair company and a full-replacement contractor.

What we could not verify

• Milgard's standard (non-upgrade) warranty terms. The document I read is explicitly the paid "Full Lifetime Warranty Upgrade." I did not fetch Milgard's baseline New Construction or Replacement Product Limited Warranty that applies when a buyer doesn't purchase the upgrade, so I can't state what seal-failure coverage, labor terms, or transferability a Milgard buyer gets by default.
• Whether "defogging" or "drilling into the glass" is named as a specific exclusion in any of the four manufacturer documents I read. ACE Glass's page states plainly that drilling "instantly voids any remaining manufacturer warranties." None of the four warranty PDFs I opened uses the word "defog" or "drill"; the closest verifiable language is each manufacturer's general exclusion of non-factory glass work. I'm treating ACE Glass's claim as directionally consistent with that general exclusion, not as a clause I can quote by name.
• Angi's foggy-window-repair page. Returned a 403 Forbidden error on direct fetch during this session; I used Installix, FixUpFirst, Window Gurus, Carolina Glass Replacement, GetKenco, Tri-City Windows and Doors, ACE Glass, and Bob Vila instead, all of which fetched successfully.
• Renewal by Andersen's own "Foggy Window Repair vs. Replacement" blog post. Returned a 429 (rate-limited) error on direct fetch during this session; I did not substitute an unverified claim from it.
• The exact publication year of the Tri-City Windows and Doors article. Its page carries a month/day stamp ("August 13, updated September 10") but no printed year; I've cited it without asserting a specific year.
• A single nationwide figure for how climate affects seal-failure timing. I found one region-specific source (Window Gurus, on Ohio) with a named freeze-thaw range and a stated seal-life reduction; I did not find a broader study covering multiple U.S. climate zones, so I'm not extending the Ohio figures to other regions.

Sources

All retrieved 2026-09-27. Sources marked (primary-document extraction) are facts pulled from a warranty PDF's actual text, not a marketing summary.

1. Installix, "Foggy Window Repair Cost: What You'll Pay (and When It's Warranty)" (page dated 2026-07-21)
2. FixUpFirst, "Window Repair Cost 2026: $75–$400 by Problem Type" (published 2026-05-14, updated 2026-05-18)
3. Window Gurus, "Window Repair Costs in 2026 – Prices & Services" (published 2025-02-17, updated 2026-06-17)
4. Window Gurus, "Window Seal Failure: 5 Key Signs and Prevention Hacks 2025" (published 2025-11-29, updated 2026-05-04)
5. Carolina Glass Replacement, "Repair vs Replace Foggy Windows – Honest Cost Guide" (August 2026)
6. GetKenco, "Window Repair vs Replacement: 2026's When to Fix or Replace Guide"
7. Tri-City Windows and Doors, "Foggy Windows: Replace the Glass or the Whole Window?"
8. ACE Glass LLC, "Can You Repair a Foggy Double-Pane Window? The Honest Truth"
9. Bob Vila, "Broken Window Seals? Here's How to Identify and Repair Them"
10. Andersen Corporation, "400 Series/200 Series Windows & Doors Limited Warranty" (PDF) (primary-document extraction; revised 12/16/14, effective Feb. 2015)
11. Marvin, "Window and Door Limited Warranty" (PDF) (primary-document extraction; effective 2/26/2024)
12. Simonton, "Limited Lifetime Warranty" (PDF) (primary-document extraction; effective for purchases on or after 10/1/2022)
13. Milgard, "Full Lifetime Warranty Upgrade" (PDF) (primary-document extraction; effective 1/1/2026)
14. This site, Window Replacement Cost in 2026 — cross-referenced for full-window installed cost ranges and the insert-vs-full-frame scope variable.
15. This site, How to Vet a Window, Door, and Siding Installer — cross-referenced for contractor verification steps applicable to either repair path.