I live in England where radiators are commonplace to heat the house. And after I turned mine off inside my room I noticed excessive condensation on the windows. I thought the reason for condensation was a temperature differential. So why is making my room colder (closer to the outside temperature) causing more condensation on my windows?
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Cooler air can hold less water vapor, so as your room cools the vapor will be driven out of the cooling air. It will condense on the even colder areas that are your windows.
Water vapor and humidity. I’m sure you’ve heard the whole cold glass and hot day analogy? Do you realize that you also contribute to water vapor and humidity in the room? The water vapor that is turning into liquid form only has so many places to go. The window is an obvious place. Look at your radiator; there may be condensation there as well. Why there is more condensation when it’s colder in the room? The water vapor is hitting the point where it needs to turn into a liquid. If it’s colder in the room, the window is still the sweet spot.
Cold air is worse at holding moisture. It’s why heater make dry air. When you heat up air, you increase its capacity to hold water, so, if you don’t add water, you decrease the percentage full that the air is. It’s like how if you pour a full cup into a cup that’s twice as big, the cup is now half empty.
The same is true in reverse. If you let warm humid air cool down, the cooler air wants to get rid of all that water. The cold window is where the air in your house is coldest, so the water that leaves the air the fastest does so where jts touching the coldest objects.
As long as the object on which condensation forms is colder than the air touching it, condemnation CAN form. How much condensation forms depends on
1. How (relatively) cold the object is
2. How much excess water is in the air
The warm air that was in your house has lots of water in it. It cools down, and now all that water is excess water. It has to go somewhere. The result is that even objects with only slight temperature differences can form condesnation.
Interesting fact. Water vapor (not steam) is actually condensation. Hot water, like a cup of tea, heats up the air touching it. That airs sucks up more water cause now it’s hot and there’s water under it to suck up. That hot air rises, mixing with cooler air farther away from the tea. The result, is that the excess humidity from the tea condenses in midair forming tiny droplets of water that are so small that they float on the warm air currents several inches above your tea.
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