Humidifiers vs. mildew

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Where I live, the weather forecast for this weekend calls for outside temps to fall below zero degrees Fahrenheit. And I find that with the heated indoor air being so dry, during sleep my throat gets parched at night and my skin dries out too.
I've got a humidifier that I bought a long time ago but never used. I'm thinking of using it. But the last time I used one of those, I got condensation everywhere--the windows and window shades and even the toilet bowl--and mold and mildew began to grow on those things.
Do folks here use humidifiers and just cope with the inevitable condensation and mold and mildew? Or do they just live with the dry heated air during winter?
-- Steven L.
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You need to size or adjust your humidifier to get the right humidity.
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Adjust the humidity to where condensation does not occur, you had it way to high. I can only raise mine 10-15% or I get consensation, so at below zero its going to be low, maybe 25% for me.
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what RH you end up with not only depends on how cold it is outside but how well insulated your house is, and more importantly, how well insulated your windows are (windows are likely where condensation will show up first.)
So basically you have to tinker with the humidistat until you find a happy setting... keep bumping it up until you start to see condensation then dial it back a little bit.
nate
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I've been posting a lot on here lately about my humidity obsession. I've finally been able to maintain it in the 35-40% range over the last few days. This morning it was -20F outside and I had some condensation - not much, just a little on the first inch of the low end of each window. It's been in the low single digits all week and it's the first time I've seen condensation (so yes, the quality of windows etc definitely plays a big part).
I am holding RH at a high level because I'm installing hardwood floors, but without that need I would probably aim for 30-35. I found that before I started cranking it up (when I realized it was only 22%), the family were having skin problems and my 3 year old suffered a lot of nosebleeds (took me a while to realize dry air was a factor). Buddy of mine is going through the same thing, except that his is just 13%(!). Apparently his dog is constantly scratching and his stairs all squeak.
First advice I would give you is to get a hygrometer if you don't already have one (I like the electronic ones - not expensive). And then, if necessary, fire up the humidifier. You will have to make your own mind up about what the right balance is between moist enough to be comfortable and dry enough to limit condensation. Personally, I would not allow it to get down below high 20's, and if you have significant condensation at that level, you need to do something about your windows.
Good luck.
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In northern N.American winters, if the furnace has no humidifier function, a room humidifier helps people feel more comfortable. Condensation on window glass varies with local indoor and outdoor temperature and the thermal efficiency of the window (e.g. 1, 2 or 3 panes.) Interior condensation should be mopped up once a day. This prevents the development of mildew on these surfaces. (The medical and structural danger of mildew on surfaces we cannot see, e.g. within walls, is a separate and more important topic.)
--
Don Phillipson
Carlsbad Springs
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Which is why I don't see the point to mopping up condensation once a day. If you have siginifacnt condensation, you should be lowering the humidity immediately, not letting it get to the point it needs to be mopped up once a day. The water that you can't see or get to can be causing substantial damage over time
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On Fri, 21 Jan 2011 14:45:00 +0000, "Steven L."

What kind was it? Did you have to fill it with water or did it have a water connection?
If it had a connection, did it have a method for varying how much humidity it put out? I'm sure it did. What did you set it at?

I don't think either mold, mildew, or condensation is inevitable.
When I used a humidifer for 15 or 20 winters, I never had any of them. Houses and climates and weather and humidifiers vary, but I'm sure you can find the right humidity for your house. Didn't someone here say that was about 50%? Certainly more than 29%.
Did you have a hygrometer, a humidity meter? What did it say the humidity was? How humid was it when the condensation began? 70 or 80%? Did you stop adding water before that point?
Hygrometers used to be very unreliable. Many just used a string whose length changed when it was humid. I don't know if current ones work differently or are any better. Does anyone know?

Only since my the copper screen in the water supply line in my humidifier got clogged. As soon as I can, I'm fixing that.

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wrote:

It's one of those you fill with water and it has a wick filter.

Well....
According to my calculations, when the temperature is 70 degrees Fahrenheit and the outdoor dew point is zero degrees Fahrenheit, the relative humidity is only 6% (!!!).
So even raising indoor humidity to 25% is quite a lot of additional moisture--enough to cause condensation on any surfaces (like windows) that are cooled by outside temp.

At least I'm glad to hear that other folks rely on humidifiers in winter too.
I don't know about you, but 6% humidity (see above) makes my mouth and throat feel incredibly parched at night.
-- Steven L.
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-snip-
But that is indoors. My indoor RH is 33% - temp 64. Outside is 50% at a balmy 30degrees right now. This weekend it will go to 12below, my indoor humidity will probably drop to 28 or so-- and there won't be any condensation anywhere.
My windows are thermopane. Years ago when we had single pane, drafty windows, there would be some condensation.
If you're getting condensation at 25% RH, then fix the windows.
Jim
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Not an expert, but I don't think outside humidity comes into it. Nor outside temperature, directly. What matters is how cold the inside of your windows, frames etc get. If they get below the dewpoint for the RH, you get condensation. I believe some furnace/whole-house humidifiers have a sensor to measure outside temp solely so that they can dial down the RH when it's really cold, on the basis that otherwise you'll get condensation (don't know how they are calibrated though...as a few of us have said, the condensation point will vary based on the quality of windows etc).
6%! Man, after the problems we saw at 22%, I would jump into the bath before your skin peels off.
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cubby wrote:

normal rh in a lot of places is under 10% for a good deal of the year. my current local temp is 65 with a rh of 15% for today. summertime, it's frequently under 10% for weeks.
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Wow. I guess your body must adapt. Here in MN it's can get pretty humid in the summer and bone dry in the winter. Once the dry air hits you really notice it and it's not pleasant. Out of interest, where are you?
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cubby wrote:

Same here in Calgary, AB, Actualy in winter RH can read negative. When I moved from ON in 1970 on company x-fer I used to have nose bleed, too dry. Humidifier in this neck of wood is a must. Not maintaining proper humidity can increase heating cost. When too dry you feel colder. At present RH in the house is ~35%.
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wrote:

What! It can read negative but I doubt it is negative. How would that be possible? Wouldn't you need negative water or anti-water?

Oh yeah, that was a big reason I wanted the humidifier, to save money. Although evaporating the water does drain heat** from the air that is humidified, it is still cheaper if you turn the temp down, and most people will because it feels more comfortable at lower temp with moderate rather than low humidity.
When the furnace has been out of oil or broken on a couple occasions, I boiled water on the stove, or ran the shower into a stopped bathtub (don't let it overflow) and within 15 minutes it started to feel noticeably warmer. Within 30 minutes the whole house felt warmer.
**Not only does a humidifier take heat from the air (the furnace air in the case of a furnace-mounted humidifier) it takes a lot of heat.
The amount of heat needed to raise the temperature of a pint of water is so much, I don't remember. The amount of heat needed to evaporate that pint of water***, but still be at the same temperature that it was, is 5 or 10 times as much. But it's still well worth it.
***It's called the heat of condensation or the heat of evaporation, something like that.
Here it is http://en.wikipedia.org/wiki/Heat_of_condensation
"Water is also commonly expressed as 539.423 calories per gram".
From the page on calorie: * The small calorie or gram calorie (symbol: cal)[2] approximates the energy needed to increase the temperature of 1 gram of water by 1 C. This is about 4.2 joules. * The large calorie, kilogram calorie or food calorie (symbol: Cal)[2] approximates the energy needed to increase the temperature of 1 kilogram of water by 1 C. This is exactly 1000 small calories or about 4.2 kilojoules.
So iiuc, it takes 519 times as much heat to evaporate a gram of water as to raise its temp from 70^F to 71.8^F. Despite that, it's well worth it economically, if you turn the heat down too. You'll be more comfortable than at the higher temp.
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cubby wrote:

phoenix, az, where it's currently a brisk 70 and i had to put the top up on the car for the commute in this morning.
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Another factor in this discussion that no one has mentioned is a humidifier placed in one room versus a furnace mounted one. When using a room humidifier to try to increase humidity in the whole house, that one room is going to always have a much higher humidity than the rooms farthest away. Hence, you could have serious condensation in one room, while other areas are not a problem. With a furnace mounted one, the humidity is distributed evenly. If the room humdidifer is located near a window, that would make it even worse.
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Humidistats I see sold at box stores by Taylor will on the display rack be easily 20% off in their measurements.They do not come calibrated. Analog units must be calibrated every year, digital units are better but it probably isnt 6%, its probably higher, but maybe only 12%. Just add moisture until you get condensation then back off a bit. The % of humidity is not as important as is not making condensation.
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On Fri, 21 Jan 2011 18:35:14 +0000, "Steven L."

From the other replies, I might be wrong about the 50% and the 29%, which I read in another thread here.**

The Relative Humidity isn't nailed at 6%. And it takes more than those two numbers to know what the RH is.
I know the outdoor temp has something to do with what RH you want, but I don't think it is the number to be used when calculating RH. When people use a wetbulb hygrometer, the two thermometers are within an inch of each other, with one totally dry and the other having a wet wick or something around it. As the water in the wick evaporates, it cools the second thermometer. Then that temp is divided into the dry temp and they use other factors or addends to allow for the arbitrariness of the Fahrenheit scale and maybe other things that confuse things, and they calculate the Relative Humidity. Actually, there is a little chart on the device.
So my point is that whatever the outdoor temp has to do with what is the right RH to want, regarding condensation maybe, it doesn't determine the RH.
**Until this year, I've never even tried to get a hygrometer, so I don't know what my humidity has been. For a decade, I've been planning to get a furnace-duct-mounted humidifier, a good one with a humidistat, but now it seems that the new furnace will be the same shape and pretty much the same size as the old furnace which only provides about 3" clearance. All the fancy humidifiers need about 10" and I have only 3 inches. The only one that will fit in 3", (actually it only needs 1/2 inch except for a small part that needs 2") is the one I have now! By General Filter.
For that one, there is no humidistat possible. The only variable is the number of fiberglass T-plates that are put in it. EAch one increases how much water evaporates into the warm air from the furnace.

Then how about 20%?
BTW, a little condesnation won't hurt you. It will likely evaporate at some point. It's only bad if it runs down the window and makes the wooden window sills wet enough for long enough that they start to deteriorate. And even if they deteriorate after 5, 10, 15 years, they can be refurbished by painting them, perhaps filling any cracks with wood filler or paintable-caulk or something before painting. And if the aboslute worst happens, I think the molding around the windwo sill can be pried off and the sill removed and replaced.
I have storm windows, but they close separately, and there have been times when it gets cold before I close them, and they leak a little bit, so I've had condensation on many occasions. Usually it evaporates. The rest of the time, it runs down the window into the aluminum window channel, which I think is solid on the bottom but I've never looked inside.
There is even more condensation on the window frame, the part underneath the windows. That's because it is continuous to the outside, so it gets cold regardless of thermopane/no thermopane.
Newer ones would be vinyl clad I think, which iiuc prevent condensation. I even vaguley recall metal window frames that were in two parts, so a cold outside doesn't make the separate inside channel cold. If you ever get new windows, they probably only sell vinyl clad or other non-condensing window frames.
But like I say, this house is 31 years old and there has been a lot of condensation over time on the frames and some of it reaches the wooden window sills. The most it has done so far is raise the grain a little on part of the part of sill nearest the frame. AT this rate, I'll be 100 years old before there is substantial damage, which as I say can be repaired
If it is pouring down the window and creating big puddles, lower the humidity, but if it's a millimeter of water from the window an inch out, half the width of the window, some of the time, and dries other times, don't let it bother you.
I don't see condensation as a big issue.

Like I say, I've never measured the humidity here. Maryland is supposed to be humid, but I don't know if that means in the winter too. (Yes, the weather includes the humidity. It's 19^F and 40% RH out now at 10PM. I didn't know that.) I live right next to a stream, in a tiny valley, that is, only 10 or 20 feet deep, maybe 30 or more if you go 1/4 mile away, but I dion't know if that has any effect on my humidity.
I concluded the basement was very dry because water spilled on the basement floor dried up very quickly, but this year I noticed that heating oil dried up in only an hour! Well, I don't think heating oil evaporates much at all so I finally realized it, and the water, was soaking into the cement floor. I didn't know that was possible either -- is it? -- but it accounts for the quick drying, and says nothing about how humid the basement is.
Anyhow, my mouth and throat have never seemed dry. Maybe it's my general good health, and I'm almost never cold and since my 2 weeks in Panama, I'm almost never hot. My father said the same thing, that since his time in -- darn I forget and it's too late to ask him -- he was never hot again. So that doesn't say anything about humidity either.
Are the new humidity meters, including the ones in the humidistats, really any good?>
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They put humistats of dehumidifiers. No reason not to put them on humidifiers.
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