What would you do if your double-pane windows started fogging up?

- That makes sense, but does leaving the foggy panes in place ever cause long-term issues with the frames or sills?
- I get the cost factor, just wondering if waiting too long could end up making repairs pricier down the road.
- Anyone ever tried those defogging services, or is that just a temporary fix?

Yeah, I’ve wondered about that too. I left a couple foggy panes alone for a year or so, and it didn’t seem to mess with the frames much, but I live in a pretty dry area. If there’s moisture trapped in there all the time, though, I could see it eventually causing wood rot or even mold if the seals are really shot. As for those defogging services - tried one once. It cleared up the glass for maybe six months, then the haze crept back. Felt like putting a band-aid on a bigger problem, honestly. Still cheaper than full replacement upfront, but maybe not long-term?

That’s pretty much been my experience too. Defogging is a quick fix, but if the seal’s blown, the moisture finds its way back in sooner or later. In dry climates, you might get away with ignoring it for a while, but where I am - lots of rain - it’s not worth the risk. I’ve seen sills go soft and even a little black mold pop up under the trim after folks left foggy panes too long. If you’re handy, swapping just the glass unit (not the whole window) can be a decent middle ground. Costs less than full replacement and actually fixes the issue for good.

Funny timing - just had my first foggy window show up last month. At first, I thought it was just condensation, but nope… classic seal failure. I did some research and yeah, the defogging kits seemed tempting, but I kept reading that it’s usually just a band-aid. I’m in a pretty humid area too, so leaving it didn’t seem smart. Ended up ordering a replacement IGU (insulated glass unit) instead of a whole new window. Not cheap, but definitely cheaper than full replacement and no more mystery moisture creeping in. Kind of wild how fast the sill can get gross if you ignore it - lesson learned.

That’s the smart move, swapping just the IGU. I’ve run into a lot of homeowners who try those defogging kits and, like you said, it’s really just a temporary fix. In my experience, especially with humid climates, the moisture just keeps coming back. I’ve seen sills rot out surprisingly fast when folks ignore it -

Kind of wild how fast the sill can get gross if you ignore it - lesson learned.

Kind of wild how fast the sill can get gross if you ignore it - lesson learned.

I hear you on that. Years ago, I thought I could just let a foggy window ride until I had more time. Big mistake - by the time I got around to it, the wood under the window was practically mush. Ended up costing way more to fix the rot than just swapping out the glass in the first place.

I tried one of those defogging kits once too. Looked decent for a few months, but then the haze came back and brought a little mold with it. Not worth the hassle, at least in my book.

If I spot fog now, I just bite the bullet and order a new IGU. It’s not cheap, but neither is replacing trim or repainting every couple years. Especially here where humidity is a year-round problem... windows just don’t forgive neglect.

by the time I got around to it, the wood under the window was practically mush.

That’s exactly what happened in my old place. Figured I could just ignore the fog for a season... ended up with warped trim and a musty smell that wouldn’t quit. Never trusted those “miracle” kits either - just seemed like putting off the inevitable. Honestly, swapping the IGU is a pain, but it beats replacing half the window frame later.

Never trusted those “miracle” kits either - just seemed like putting off the inevitable.

Right there with you. Tried one of those kits once - just ended up with a weird patch job and the fog came back anyway. If you catch it early, swapping out the IGU isn’t too bad. Pry off the stops, pop out the old unit, slap in the new one... but you’re right, if you let it slide, you’re looking at swollen sills and maybe even mold. Way easier to deal with glass than rotted wood.

Way easier to deal with glass than rotted wood.

Yeah, totally agree - once the wood goes, you’re in for a much bigger headache. I swapped out two IGUs last winter when I noticed the fog, and honestly, it wasn’t as bad as I thought. The hardest part was tracking down the right size. Anyone else have issues with finding replacements that actually fit? Sometimes I wonder if it’s worth just replacing the whole window, but that gets pricey real quick.

- Ran into the same sizing headache last fall - seems like every window in my place is just a little off-standard.
- Measuring twice helped, but even then, one IGU was a hair too big and I had to trim the stops.
- Full window replacement makes sense if the frames are shot, but if your sashes are solid, swapping just the glass is way easier on the wallet.
- Only downside: matching the tint or low-e coating can be tricky if you care about that.

I hear you on the sizing weirdness - my last place was built in the 70s and not a single window matched anything in the catalogs. Ended up having to custom order a couple panes, which wasn’t cheap, but still beat full replacements. I’m with you: if the frames aren’t rotted and the sashes are still decent, just swapping out the IGUs is usually the way to go.

That said, I’ve had mixed luck with matching coatings. One room ended up with two windows that look slightly different in certain light. Not a big deal for me, but it’d probably bug someone pickier. Also, some of those “fix foggy glass in place” companies promise miracles but… let’s just say I wouldn’t waste my money there. If you’re already pulling stops and getting your hands dirty, might as well do it right.

Curious if anyone’s found a good source for odd-sized IGUs that doesn’t take months to deliver? That’s always been my biggest headache.

Curious if anyone’s found a good source for odd-sized IGUs that doesn’t take months to deliver? That’s always been my biggest headache.

Yeah, the custom size struggle is real. My house dates to the late 60s, and it’s like every window was measured by a different person with a different tape. I actually had a similar experience - ended up tracing cardboard templates and driving them to a local glass shop just to avoid the “wait 8 weeks and cross your fingers” routine. It wasn’t cheap (I think I paid about $230 per unit for two weirdly shaped IGUs), but at least I could talk to someone in person and make sure the low-E coating was on the right side.

I totally get what you mean about matching coatings. I swapped out two panes in my living room, and in certain afternoon light, one looks a touch more greenish than the other. Drives me a little nuts, but nobody else seems to notice. I guess that’s the tradeoff with piecemeal replacements - unless you’re doing the whole room at once, there’s always a chance of a mismatch. Not sure if there’s a perfect solution there, unless you’re way less picky than me.

About those “defogging” companies - I fell for one once, and it was basically a glorified cleaning job. The fog came back after a month, and I was out $120. Lesson learned: if the seal’s shot, there’s no shortcut.

For sources, I’ve had the best luck with small local shops rather than big box stores or online. The turnaround’s usually under 3 weeks, and they’re more forgiving if your measurements are a hair off. I tried ordering from an online supplier once (I think it was Glass Doctor or something similar), but the shipping cost nearly doubled the price, and the lead time was brutal.

If you’re handy and don’t mind some elbow grease, swapping IGUs is pretty satisfying - just be ready for a little trial and error. And keep a stash of glazing points and putty on hand... I always seem to run out right when I need them most.

- Totally relate to the “every window was measured by a different person” issue. My 1972 ranch is the same - nothing standard, everything a little off.
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“The fog came back after a month, and I was out $120. Lesson learned: if the seal’s shot, there’s no shortcut.”

Yeah, I’ve seen a lot of folks try those “defogging” services and honestly, I’m not convinced. Maybe they buy you a little time, but if the seal’s gone, the moisture’s just going to sneak back in. I’ve even seen some windows look worse after a quick fix - like, now you’ve got streaks and fog. Not great.

Custom sizes are kind of a rite of passage with older houses. I swear, it’s like every window in these places was made on a different day by a different person who just eyeballed it. Local glass shops usually know what’s up, though. The big chains look at you like you’re asking for a spaceship part.

You’re spot on about the coatings being tricky. Low-E, no Low-E, slight tint - sometimes you don’t notice until the sun hits just right and then it drives you nuts. I always tell people: if you’re swapping one pane in a set, be prepared for a subtle mismatch.

Putty and glazing points... yeah, nothing like realizing you’re out halfway through and making that emergency hardware run with dirty hands. Been there more times than I’d like to admit.

At this point, I just factor in the occasional IGU replacement as part of keeping an older place going. It’s annoying, but at least you know it’ll actually solve the problem.

That’s actually super helpful to hear, because I was seriously considering one of those “defogging” services for my place. The idea of just drilling a tiny hole and sucking out the fog sounded too good to be true... guess it kind of is. I’m not sure I’d want to risk making it look worse, either. Have you ever tried it yourself, or just seen the aftermath?

The custom window sizes thing cracks me up - my house is from the 1940s and literally nothing is standard. Tried to order a replacement sash last year and got the same blank stare at the big box store. Ended up at this local shop where the owner measured everything twice and still looked skeptical.

About the coatings - how do you even tell if you have Low-E? I’ve read about holding up a lighter or something, but I can’t tell if that’s legit or just internet nonsense. I’d hate to end up with that weird mismatched look when the sun hits just right.

And yeah, running out of putty mid-job... been there, done that, regretted every second.

Defogging services are such a weird gray area - I've seen them work okay for a year or two, but honestly, it's usually just a band-aid. A neighbor tried it and the fog came back within months, plus there was this odd little plug left in the corner of the glass. Not the look you want. I get the temptation though, especially with those non-standard window sizes. My place is mid-century, and every time I need a replacement, it's like a scavenger hunt for someone who can even make sense of the measurements.

For Low-E coatings, that lighter trick is actually legit - sort of. If you hold a flame up to the glass and see four reflections instead of two, one of them will have a slightly different tint if there's Low-E. It's subtle, though, and in old windows it gets tricky. I usually just look for any manufacturer stickers or etchings in the corners first.

Running out of putty halfway through is just... universal pain. I always think I've got enough, then end up scraping the bottom of the can with a screwdriver. At least you're not alone on that one.

For Low-E coatings, that lighter trick is actually legit - sort of. If you hold a flame up to the glass and see four reflections instead of two, one of them will have a slightly different tint if t...

That “odd little plug left in the corner of the glass” - I’ve seen that too, and it always bugs me. I get the appeal of defogging for weird window sizes, but like you said, it’s mostly a temporary fix. When you replaced a non-standard window, did you try sourcing glass locally or just bite the bullet and go custom? I’ve wondered if it’s worth hunting for salvaged panes from architectural salvage places, or if that’s just wishful thinking.

I know exactly what you mean about that little plug - drives me nuts, too. When I had to deal with a funky-sized window in my old bungalow, I tried calling around to local glass shops first. Most of them either couldn’t match the size or quoted prices almost as high as custom anyway. I did poke around at a salvage yard, but finding the right dimensions was basically a lost cause. In the end, I just bit the bullet and ordered a custom IGU. Not cheap, but at least it fits and looks right. Sometimes the hassle just isn’t worth the savings.

I ran into this last winter - noticed the fogging and tried the whole “drill a tiny hole and see if it clears out” trick I read online. Didn’t do much, just made me nervous about leaks. Ended up living with it until I could afford a replacement. Did you have to wait long for your custom IGU? I’m debating if I should just patch it for now or go all in and order a new one...

Drilling the hole never really worked for me either - just ended up with condensation and a drafty window. When I ordered a custom IGU last fall, it took about five weeks, which felt like forever in the cold. Have you checked if your window size is standard? Sometimes off-the-shelf units are cheaper and faster. If the fog’s not terrible and you can live with it, patching might buy you some time, but a full replacement is really the only way to fix it for good.