At around 68F air supports about 17 grams of water per cubic meter of air to reach 100%.
My bedroom is about 40 cubic meters, give or take. That works out to about 680 grams of water, which is 680ml to totally saturate the air starting from zero.
So why is a gallon vaporizer running all night not increasing the humidity? I have a device to read the humidity, but it almost always reads about 25% or so despite the fact that it is on a table about a foot from the vaporizer. If I hold it right over the vaporizer in its steam, it will rapidly climb so I don’t know if the hygrometer is broken. I tried holding it over the vaporizer and it quickly climbed to 80% before I took it away. It eventually went back down to 25% again after I moved it to a different part of the room.
I do notice the window will develop condensation. But the hygrometer still says the humidity is a constant 25-35% or so.
Just as a temperature differential between your room and the environments on the other side of your 4 walls will create a heat transfer, a humidity differential will create a humidity transfer to the outside environment. (I assume 1 or 2 of those walls is an outside wall)
So…either:
Your hygrometer is inaccurate.
or…
Humidity is being transferred to the outside environments at a rate that is as great as your vaporizer can produce/ replace it.
So…assuming your hygrometer is good…either your vaporizer is too small to maintain the humidity you wish, or your wall insulation/ vapor barrier sucks. (which means that, unless you improve the walls, the unit is too small)
As an example, assume your home needs an 80K Btu furnace, but you get a great deal on a 60K Btu model. In cold weather the furnace won’t keep up. (and you’ll suspect a bad thermostat or thermometer)
Have you done the math to see if the unit you have is of sufficient size to maintain the humidity you wish?
(And keep in mind, that is a moving target. The colder it is, the more humidity you need, generally)
In cold weather the air is dense and cold and the room, while warm, won’t accept the water vapor without condensation whenever it nears a surface below the dew point.
People with humidifiers that are on central systems will see a chart on the humidstat that states they should progressively lower their humidity setting as it gets colder.
It’s right on the humidistat, and it’s very common.
At 30° the chart dictates a 30-35% RH setting. As it gets colder the allowable setting is reduced. At 0° the setting is 15%.
You might like 35% humidity, but the air won’t accept it if it’s really cold outside, and the condensation you see on the windows/ walls is water that a few minutes ago was water vapor. (humidity)
I noticed at the end of your post you mentioned that you’re seeing condensation on the windows.
IME, that means you’ve eclipsed the maximum amount of water vapor that room will accept, and the excess is condensing on the windows.
In HVAC parlance, the room has reached ‘saturation.’
(and the unit probably isn’t too small, and your hygrometer is probably OK. That’s my internet guess.)
If you haven’t guessed already, the presence of condensation on the windows suggests to me that this is the best you’re going to get.
Based on the outside temperature the room will top out, and since the vaporizer doesn’t have a humidistat to tell it stop, it keeps humidifying and the excess water vapor simply condenses.
It would help if you chart and post the hygrometer readings and the outside ambient temperature. (and humidity too as that’s sometimes helpful)
That would be the case if the windows were the same temperature as everything else in the room. But since they are likely much colder, condensation takes place at the window surface way before moisture saturation of the room.
My theory for the lack of increase in humidity is not only the absorption of moisture of so much dried out stuff in the room, but also in leakage. After all, I doubt the room is air tight, otherwise the occupant would die for lack of oxygen. The question is how much leakage of air is there? If the heat is running constantly, then that’s a good sign that the room is quite porous.
I would disagree. The windows are indeed cooler, and that’s where the condensation is taking place. The room is saturated. It cannot accept any more water vapor.
The OP asked, “Why isn’t a vaporizer affecting the humidity in my room” and the fact is, it is. Quite a bit actually. In fact, I’d bet that although the OP finds the 25% RH unacceptable, it is almost certainly higher than the outside ambient RH. Much higher.
And, if migration of humidity through the 4 walls was the issue, the windows wouldn’t sweat. The vaporizer would run non-stop, but the windows wouldn’t sweat.
Sweating windows is a tell tale sign that there is too much humidity in the room, not, not enough. (via migration)
That is not how condensation at saturation takes place. If the room was so saturated that condensation was taking place on the window, and the temperature of the window was not a factor, then everything in the room would be covered by condensation. That’s a fact. Well, maybe not everything since different materials would respond to supersaturation in different ways with fabrics becoming damp. But, if the glass of the TV isn’t covered with condensation, but the glass of the windows is, then that is because of the colder temperature of the windows. And thus, it is not a sign of 100% RH.
It is not. At least, not according to the OP’s hygrometer, which could possibly be not working correctly. If it is working correctly, then the humidifier is having a neglible to no effect.
And here I’m going to stop you. You don’t know what you’re talking about. Here in NJ with temperatures going below and above freezing point, the average RH here is about 55% outside (which is about 20% inside [and the comfort range for humans is the 45-55% range]). So, unless you know the OP is living in a dessert, your WAG is pretty wild.
It seems moriah is taking the phrase “saturation” to mean the air in the room is at saturation (100% relative humidity), while raindog is using the term to mean “high enough humidity to cause condensation somewhere in the room”.
Correct. But when the term is used in the HVAC industry it means loosely, “conditions existing when a substance contains all of another substance it can hold for that temperature and pressure.”
In the case of humidity, this room cannot hold anymore water vapor without a resulting change of state; condensation.
In this context, the room cannot hold any more water vapor; it’s saturated.
You do know that when at a certain temperature and pressure, when there is enough water vapor that it “contains all… it can hold”, then that is the very definition of 100% Relative Humidity, right? (If one can use the phrase ‘hold water’ which is technically not what’s happening with water vapor in the air.)
If the OP’s room couldn’t ‘hold’ any more water vapor, the OP’s hygrometer would have read 100%.
If the OP’s room was at 100% RH, or, that very loose definition of “can’t hold any more” then when the OP’s humidifier throws a gallon more water into the air… where is it going? Is there a full gallon’s worth of condensation on the windows? That’s going to rot the windowsill for sure.
At rather low levels of relative humidity you can get condensation ‘somewhere in the room’ if that somewhere is locally cold enough. Just like your cold drink ‘sweats’ even in low relative humidity. A sweating cold drink does in no way imply that the air in the rest of the room can’t take on more water vapor. It is not saturated by any definition of the word.