Humidity

[Bill]

Heating with wood or not I always have to add moisture to the air. I understand that if your house is extremely tight, you can have stale air and high humidity. But right now it's -3* below zero and the outside humidity is 100%, so how come this incoming cold air does not humidify my house? As much hot air that leak's out of the house, must draw cold moist air to replace it. I must be missing something here and I know we have at least one Meteorologist on the forum, that could explain what's going on.

 

[pen]

with cold air, the air molecules are moving slower and have less "space" inbetween them to hold water molecules. Because of this, cold air will be filled to its max (100% relative humidity) and have less moisture in it than an equal amount of warm at at 100% relative humidity.

That's why it is relative.

So, as that cold air warms up upon entering your house, it's ability to hold water increases while the amount of water stays the same.

Because of this the Relative Humidity drops and you get a bloody nose.

To go the other direction, warm moist air at 100% humidity leaving your lungs will be supersaturated as it cools down in cold air and will create the moisture that you can see as the water vapor condenses back to water the liquid, making fog.

pen

 

[Bill]

Excellent explanation, thanks

 

[ikessky]

I love bloody nose season! :roll:

 

[stockdoct]

Very nice explanation, thank you!

So, if wood is sitting outdoors (or indoors in my ice-cold garage) and the wood is 30-40% water ..... and the relative humidity outdoors at 3 degrees F is 80% ..... and the wood is also 3 degrees F because its been out there for weeks ....


..... then my wood really isn't drying out at all?


I'm confused, since I always thought wood would dry, or season, in the "dry winter air"


Has anyone with a moisture meter checked a single piece of outdoor wood monthly during the winter to see if moisture is added, or taken away, or stays the same? That'd be a very cool thing to know.....

 

[LLigetfa]

Of course there will be regional differences but the wild temperature swings outdoors will drive moisture out of the air. The RH may be high as the temp is falling but when it warms, it will be dehumidified.