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From: msb@lsuc.UUCP (Mark Brader)
Newsgroups: net.consumers
Subject: Re: Furnace Humidifiers
Message-ID: <1131@lsuc.UUCP>
Date: Wed, 26-Feb-86 01:29:48 EST
Article-I.D.: lsuc.1131
Posted: Wed Feb 26 01:29:48 1986
Date-Received: Wed, 26-Feb-86 03:15:18 EST
References: <4@mit-prep.ARPA>
Reply-To: msb@lsuc.UUCP (Mark Brader)
Organization: Law Society of Upper Canada, Toronto
Lines: 38
Summary: 50% is too humid in winter, and other comments

Leonard H. Tower Jr. (tower@mit-prep.ARPA) writes:
> Our plumber recommended against this on the grounds that the ducts
> would rust out with time ...
> iron unprotected by the covering galvanization.

I would suspect that it would take a very long time before this was
significant.  After all, even a duct with a little rust in it will
carry warm air.  And a humidifier on the furnace gives you *central*
humidification, which is not to be sneezed at.

Leonard goes on to itemize the "homemade" humidification that he uses,
and concludes with:

> This is sufficient to keep the house above 50% relative humidity on
> the coldest, dryest days here in New England.

According to my references, Leonard is risking his *walls*.
This is a dangerously high humidity.  One source (the maker of our
humidistat) recommends the following settings:

Outside temperature (C)	  0	 -5	-10	-20	-25	-30
		(F)	 30	 20	 10	  0	-10	-20
Relative humidity	 40%	 35%	 30%	 25%	 20%	 15%

[I know the C/F conversions aren't exact.  Actually we were only given
 C, but the unequal intervals suggested that it was converted from the
 F line shown and then rounded to multiples of 5 degrees C.]

In any case, if there is condensation on the windows, it is too humid.

Our house is not at all "tight", and on a cold day our furnace humidifier
delivers only about 10% relative humidity anyway.  (Right now it's 8%
with a breezy -10C outside.)  This is almost enough for me anyway;
I personally like about 15% humidity.  But if you like more, and you
have a leaky house, a furnace humidifier won't have enough capacity
for you.

Mark Brader