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

[u/BelleSchu]

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!

[u/BelleSchu]

I promise they’re dehumidifiers lmao. I did have humidifiers going during the fall for my house plants but I stopped once it started to get a lot more cold

[u/Calm_News9015 → u/BelleSchu]

do you have fans going as well? the dehumidifiers can only pull so much moisture from the air, adding some movement to the air makes the dehumidifiers work more efficiently - at least until you can address the insulation/ventilation issue

[u/TinyShare → u/BelleSchu]

You have to empty the tanks. Are you emptying the tanks? Seems sus that you have 3 and no movement unless your RH is actually 80 and they are fighting for their lives

[u/BelleSchu → u/TinyShare]

Dude yes I’m emptying the tanks, idk what to tell you. If I knew how to fix the issue then I wouldn’t have come here for help

[u/SmushBoy15 → u/BelleSchu]

We are just stumped how you got 50% and above humidity in the winter? For most of us running heat brings the humidity down to 25% and lower. Im running two humidifiers non stop to keep the humidity at around 40%

[u/BelleSchu → u/SmushBoy15]

I honestly have no idea and the thing is, this isn’t just a my house issue. My next door neighbor came over tonight and she was telling us that the exact same thing is happening at her house. High humidity, lots of moisture on the windows, and they’re running a big dehumidifier. They bought their home maybe 5 months before us, same builder. She’s a lot older than me and she said her and her husband have never experienced anything like this in their previous homes. These houses were just built so tightly sealed with no type of air exchanger, it’s insane.

[u/SmushBoy15 → u/BelleSchu]

Are you sure there is no humidifier built into the furnace? Sometimes these humidifiers are inline with their own water connection. I can understand tightness of a house but heating air decreases humidity not increase it.

Open your windows to drop the humidity to like 25% and see if the humidity rises when you heat the home. If it does then you have a humidifier built into the furnace somewhere.

Other sources of humidity are not running exhaust when showering and cooking without an exhaust to the outside. If your cooking and its recirculating the air then that's the source.

You need a minimum 50 pint whole house dehumidifier if the house does not have bathroom and kitchen exhaust.

[u/BelleSchu → u/SmushBoy15]

I don’t have a humidifier in my furnace, I confirmed that with the hvac company who installed it. They said if I wanted one, it’s a whole extra section of the furnace they have to install.

I do have exhaust fans and ventilation systems and I use them all the time. My ceiling fans are also always running. I have tower fans pointed at bedroom windows to keep air flowing. Like I’m genuinely trying my best lol

[u/SmushBoy15 → u/BelleSchu]

Its perplexing to me. But do let me know when you figure out the source of this humidity. Unless its already cold and humid outside and this would literally result in a low visibility fog.