[Greenbuilding] indoor humidity levels and how to lower them
nick at early.com
Fri Dec 30 13:28:00 PST 2011
Reuben Deumling <9watts at gmail.com> writes:
>... Are there other tricks for lowering humidity indoors?
Turn on a kitchen or bathroom exhaust fan when the house RH rises to 60%.
Andersen windowfolk say an average family of 4 evaporate 2 gallons of water
per day, ie 0.67 pounds per hour... 70 F house air at 50% RH has Pa = 0.374
"Hg and wa = 0.62198/(29.921/Pa-1) = 0.00787 pounds of water per pound of
dry air. If 60C0.075(0.00787-0.0025) = 0.67 (with outdoor humidity ratio
00025 in Phila in January), C = 28 cfm. ALMOST ALL US HOUSES NATURALLY LEAK
A LOT MORE AIR.
>I'm not sure where they'd get the makeup air.
Through cracks and crevices in the house envelope. For a lot less heat loss,
turn on a reversing fan in a house partition wall to draw air in through
half of the house envelope and exhaust from the other, then vice-versa,
turning all the cracks and crevices into extremely efficient bidirectional
air-air heat exchangers, if your house leaks less air than 1 in a million US
houses. Or use an exhaust fan and add enough solar siding to make up for the
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