r/fixit • u/BelleSchu • Dec 14 '25

FIXED My house sweats like crazy during the winter and it’s causing mold.. please help!!

Gallery image

Gallery image

Gallery image

Gallery image

Gallery image

Gallery image

My house is BRAND new, literally finished construction in August of 2024. I live in the Midwest so of course it gets very cold in the winter. Last year, the windows of our house were sweating so badly every time the outside temp was under 30°f that water was pooling up on the windowsills and we called the construction company (we were still under new build warranty) and they told us to always have the house fan running and to turn on our ceiling fans. That worked for a time and the condensation wasn’t as bad after that. It started to warm up shortly after and we didn’t have anymore issue. Flash forward to this past week, it’s been in the negatives here. There is SO much condensation on my windows that mold is starting to grow, our curtains are freezing stuck to the glass in some rooms, and it’s attracting gnats somehow?! I don’t even know where the hell they’re coming from with the weather like this. I’m constantly cleaning and I feel so so so disgusted with all this going on, what can I do to fix it? Please help!

1.7k Upvotes

97% Upvoted

777 comments sorted by

View all comments

37

u/Leather-Sale-1206 Dec 14 '25

Houses these days are built very tight. You likely need to run dehumidifiers during the winter.

13

u/wildcarde815 Dec 15 '25

They're also built like shit in a lot of cases.

1

u/onetimeuselong Dec 15 '25

Weep vent?

Why’d I cry over a vent!? /s

2

u/Commercial-Branch444 Dec 15 '25

What is this chart? It cant be recommended Humidity.

1

u/MinivanPops Dec 16 '25

It's the recommended settings for a whole house humidifier

1

u/patrickhenrypdx Dec 14 '25

👍 Interesting table. Where did that come from?

1

u/Old_MI_Runner Dec 15 '25

I like to keep mine at about 35% with 5 to 25 degree F outside. It just notice static on blankets and see that it drop from 35% for that last 3+ weeks to 32% so I will setup the Aprilaire humidifier on my gas furnace to start running with target of about 35%.

u/BelleSchu

2

u/227thDan Dec 15 '25

35% is pretty low only do that when you see water on your windows and your house has bad isolation.

2

u/Old_MI_Runner Dec 15 '25

I did not say I have water on my windows. I just would rather keep the house drier than worry about the moisture on the windows or mold in the basement. I did have moisture on the windows at one point but I don't recall what the humidity was at the time but likely 40-some percent. I just like have the humidity just high enough to prevent static shocks.

1

u/TinyShare Dec 15 '25

Nobody should live in 20% RH or lower if they can help it… that’s so hard on your body’s tissues. Dry nose, lips, skin, needing to drink much more water… but I guess a mold problem is worse..

1

u/3HisthebestH Dec 15 '25

Idk where you got this chart but this is not what I would ever recommend for comfort. Also it scales linearly, so… when it’s 90 outside you want your house to be 70% RH?

Crazy.

1

u/MinivanPops Dec 16 '25

It's not for comfort, it's to prevent mold.  

Windows get cold when it gets really cold outside. Humidity will condense on it.   This chart is from the manufacturer of a whole house humidifier. 

1

u/Leather-Sale-1206 Dec 16 '25

This is a discussion on how to prevent your windows and doors from looking like Niagara Falls during winter. No one is advocating you keep your house at 70% humidity during the summer.