Perhaps the misperception is yours, Loren. What I wrote was that you would be
less likely to need a humidifier in Virginia than in NH because of higher
*absolute* humidity in the outdoor air. Absolute humidity is the mass of
moisture per mass of dry air - it is different than relative humidity, which
can be 75% indoors at 70F, or 75% outdoors at 20F. These two cases have very
different absolute humidities, because relative humidity describes how much
moisture is in the air compared to how much moisture the air could hold at that
temperature.
So I stand by my earlier comment. Because Virginia is substantially warmer
than NH, the outdoor air holds more moisture as it leaks into the home.
Burlington VT and Richmond VA have the same average relative humidity in
January - 68%. But Burlington average January temperature is 16F, Richmond is
36F. So absolute humidity in Virginia is 21.1 grains/pound, in Vermont 8.3
grains/pound. Indoor air at 70F and 35% relative humidity is 38.1
grains/pound. So for a home of a given leakage rate, the air is almost twice
as "drying" in VT than it is in VA (drying potential being determined by the
difference in indoor air moisture content and outdoor air moisture content.)
N'est-ce pas?
Marc Rosenbaum
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