Good point about attic hatches—those things are sneaky. Another spot people often overlook is bathroom exhaust fans. I've seen a lot of cases where the ducting isn't insulated or properly sealed, and warm, humid air ends up leaking into the attic space. Over time, that moisture builds up and finds its way back down, causing windows to sweat or even mold issues.
If you haven't already checked, take a quick look at your bathroom fan ducts. Make sure they're vented directly outside (not just into the attic), sealed tight at all connections, and insulated well. Also, sometimes the fan itself isn't strong enough or gets clogged with dust, reducing airflow. Cleaning it out or upgrading to a higher CFM model can make a noticeable difference.
Have you noticed if the condensation is worse after showers or baths? That might help narrow things down a bit...
Bathroom fans can definitely be culprits, but honestly, I've seen plenty of cases where the windows themselves were the main issue. A few years back, I chased condensation problems all winter—sealed ducts, insulated attic, upgraded fans... nothing helped. Turned out my double-pane windows had lost their seal and weren't insulating properly anymore. Swapped them out and problem solved. Might be worth checking your window seals before diving too deep into ductwork.
That's a good point about window seals—I hadn't really thought of that. We had a similar issue last winter, but it turned out to be mostly humidity levels inside the house. Got a cheap hygrometer and realized our indoor humidity was way higher than recommended. Tweaked the humidifier settings and it made a huge difference. Have you checked your indoor humidity levels yet? Might be another angle worth exploring before replacing windows or messing with ducts...
"Got a cheap hygrometer and realized our indoor humidity was way higher than recommended."
That's a solid suggestion. I've found that even cooking or showering without proper ventilation can spike humidity levels surprisingly fast. Have you noticed if the condensation is worse in certain rooms or at specific times of day? Sometimes pinpointing those patterns can help narrow down whether it's purely humidity-related or if there's another factor at play, like insulation or airflow issues...
Totally agree about cooking and showers—those are big culprits. But honestly, even breathing can add a surprising amount of moisture to the air, especially if you've got a full house. I used to think condensation was just a humidity thing too, until I noticed it was way worse in rooms with older windows. Turns out, poor insulation and drafty windows can make the glass surface colder, causing moisture to condense more easily.
If your hygrometer is showing consistently high humidity, definitely tackle ventilation first (bathroom fans, kitchen exhausts). But don't overlook insulation or sealing gaps around windows either. I was skeptical at first, but after sealing up some drafts and adding weatherstripping, the condensation dropped noticeably—even without running a dehumidifier constantly. It's worth checking out before you spend money on bigger fixes...
You're spot on about the impact of insulation and drafts. Another thing people often overlook is window coverings—heavy curtains or blinds can sometimes trap cold air against the glass, making condensation worse. I've noticed in my own place that leaving curtains slightly open overnight helps air circulate and reduces moisture buildup. Also, double-glazed or low-E windows really make a noticeable difference if you're ever considering an upgrade down the line... pricey, sure, but worth it for comfort and energy savings in the long run.
"I've noticed in my own place that leaving curtains slightly open overnight helps air circulate and reduces moisture buildup."
Interesting point... I've actually tried that too, and it definitely helps. One thing I'm still wondering though—has anyone experimented with those window insulation film kits? Curious if they're effective against condensation or just drafts.
I've installed quite a few of those window insulation film kits for clients, and honestly, they're pretty good at cutting down drafts and improving thermal efficiency. But condensation? Not so much. The thing is, condensation happens when warm, moist air hits a cold surface—usually the glass itself. The film creates an insulating barrier, but it doesn't necessarily stop moisture from forming if humidity levels are high inside.
One thing I've noticed helps more consistently is improving ventilation or using a dehumidifier. I had a client once who swore by those little moisture absorbers you can buy at hardware stores—she'd tuck them behind curtains and near windowsills, and they seemed to help quite a bit. Might be worth trying if you're still seeing a lot of moisture buildup.
Also, just a heads-up: if your windows are older single-pane types, the film kits can make a noticeable difference in comfort levels, but don't expect miracles with condensation. Sometimes the best solution is upgrading to double-glazed windows...though I know that's not exactly cheap or easy!
I've seen this a lot too, and you're spot-on about the humidity issue. Those film kits do wonders for drafts, but condensation is tricky because you're dealing with moisture in the air itself.
"One thing I've noticed helps more consistently is improving ventilation or using a dehumidifier."
Couldn't agree more here—ventilation is key. Had a client with a similar problem who was cooking a lot without running the exhaust fan, and it turned out that was contributing majorly to the window sweat. Once they started using the fan regularly and cracked open windows briefly after showers, things improved dramatically.
Also, if you have curtains or blinds, try opening them during the day to let air circulate around the window area. It sounds minor, but it can help reduce moisture buildup quite a bit. And yeah, double-glazing is ideal...but until that's an option, small changes in daily habits can make a noticeable difference.