On Fri, 21 Jan 2011 18:35:14 +0000, "Steven L."
wrote:


I don't think either mold, mildew, or condensation is inevitable.


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

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% (!!!).

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.

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.

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.

Or do they just live with the dry
heated air during winter?

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.

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.

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?