Haze between the panes. A milky patch in one corner that comes and goes with the sun. Streaks you cannot wipe off because they are on the inside of the glass sandwich.
That is a failed sealed unit, and there is one thing about it almost nobody tells buyers: you can find out exactly how old that glass is, in about five seconds, without asking the seller anything.
What fogging actually means
A modern window is not a pane of glass. It is an insulating glass unit — two or three panes separated by a spacer bar, sealed at the edge, with the cavity between them filled with dry air or an inert gas.
When that edge seal fails, humid air gets into the cavity and cannot get out. It condenses on the inside surfaces when the temperature drops, and over time it leaves mineral deposits behind. Natural Resources Canada is brief about the remedy: condensation forms between the glass panes “if the seal is broken”, and the fix is to replace the insulating glass unit.
Two things follow from that, and both are good news relative to what people fear.
First, it is a glass problem, not usually a window problem. The frame, the hardware and the installation are often perfectly fine. Second, a failed unit is not a structural or a safety issue — it is a performance and appearance issue. What it costs you is the insulating value you paid for, and the view.
★ How to find the exact age of the glass
This is the part worth knowing.
Insulating glass units made in Canada are commonly certified under the IGMAC programme — the Insulating Glass Manufacturers Association of Canada standard, now administered by FGIA and tested to the National Standard of Canada CAN/CGSB-12.8. That certification comes with a labelling requirement.
Under the IGMAC Certification Program Manual, the minimum identification on a certified unit is:
(a) IGMAC® Trademark (b) Company name (or abbreviation as approved by the IGMAC Program Administrator) (c) Location of production facility (city, town, etc.) … (d) Year of manufacture.
IGMAC Certification Program Manual — Section D.1, minimum identification of certified products
And critically: the marking must be permanently applied and remain visible after installation.
So go and look. Put your face close to the glass and look at the metal spacer bar around the edge of the pane, usually along the bottom. On a certified unit you will find the IGMAC mark, a company name, a place, and a year. Sometimes a month and year.
That is the true age of the glass in that opening, stamped by the people who made it, and it does not care what anybody says in a listing.
Why that beats the seller’s description
“Newer windows” is one of the most elastic phrases in real estate. It can mean last year. It can mean 2007. It can mean the previous owner replaced four of fourteen and the rest are original.
The spacer bar settles it, opening by opening. I check a few around the house rather than one, because mixed dates are extremely common — people replace windows as they fail, or as budget allows, and a house can easily carry three different vintages of glass.
If the label says 2006 and the listing says the windows are newer, that is not necessarily dishonesty. It is usually somebody repeating what they were told when they bought. But it is your money, and now you can check.
What I see around Fredericton
An honest account of my own experience, offered as exactly that rather than as a study.
I come across failed sealed units constantly in this market, and the concentration I notice most is in homes built roughly between 2005 and 2015. In houses of that period it is common to find several units gone rather than one, and to find hazing or a patchy, filmy appearance in the cavity as well as straightforward fogging.
I am not going to tell you why, because I do not know and neither does anybody else publicly. I have looked for a documented defect, a recall or a published notice affecting glass of that era in this region and I have not found one. There may be a common cause. There may just be a cohort of houses that all hit the same age at the same time. What I can tell you is what I see, and that in that vintage of house I check every window rather than spot-checking.
If you find the same company name and the same few years across a run of failed units in your own house, that is worth raising directly with the fabricator named on the spacer bar. Warranty terms differ, and some of them are longer than people assume.
What it costs
Because the fix is the glass rather than the window, the cost is a great deal lower than replacing the whole unit, frame and all. Sealed units are made to size and swapped into the existing frame, and a glazier can usually do several in a visit.
I am not going to publish a per-unit figure, because it moves with size, glass type, whether it is coated, whether it is a fixed pane or an operating sash, and how many you are doing at once. Get a written quote from a local glazier with the sizes in hand. What I will say is that a house with six or eight fogged units is a real number and belongs in your negotiation, and that it is nothing like the cost of new windows throughout.
Warranties, and why they often do not help
Sealed units are usually sold with a warranty against seal failure. Two things tend to get in the way:
- Transferability. Many warranties run to the original purchaser and do not follow the house. If you are buying, assume it does not transfer unless somebody shows you that it does.
- Proof. A claim generally needs the original invoice, and by the time a unit fogs, two owners have come and gone and the paperwork is long gone.
Worth five minutes anyway. The date on the spacer bar tells you whether it is even plausibly in period, and the company name tells you who to call.
What I check on a walkthrough
- Every window, not a sample — and on a bright day, from both inside and outside, because fogging hides at some angles
- The spacer bar labels, in several openings, for the years and whether they match
- Whether failed units are grouped on one elevation, which sometimes points at sun exposure
- Condensation on the room-side surface, which is a different problem — that is indoor humidity, not a failed seal
- The condition of the exterior caulking and the sills below the glass
What this means for your offer
Fogged units are one of the more negotiable defects in a house, because they are countable and quotable. Count them, get a number, and put it in the conversation. They are also one of the least alarming — nothing is rotting and nobody is unsafe.
The one thing not to do is accept “newer windows” without looking. Five seconds at the spacer bar is the cheapest piece of due diligence in the whole house.
Where to go from here
Older and mid-age Fredericton houses tend to arrive with a few of these at once — aluminum wiring, oil tanks and insurance, and wet basements and radon are the others I check for. The buying guide covers what the rest of the purchase costs here.
Or call or text me at (506) 261-7373. I answer my own phone.
Sources
- IGMAC Certification Program Manual, Section D.1 — minimum identification of certified products. Programme administered by FGIA, tested to the National Standard of Canada CAN/CGSB-12.8.
- Natural Resources Canada — Condensation, product energy ratings
This page is general information from a REALTOR®. Sealed unit replacement should be measured and quoted by a qualified glazier. Nothing here identifies any manufacturer or product as defective.
