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[APD] Re: Excessive Humidity
> Unfortunately, I have had first hand experience with humidity and open-top
> aquariums in the home.
This is a very interesting situation. Fortunately you dealt with the
problem immediately to avoid further complications. Here in Texas, many
homes have mold problems similar to what you had, but they let it go on for
many years. It is estimated that 80% of the homes in Corpus Christi have
malfunctioning, or mismatched AC systems which can easily cause mold to
With 76degF 60% RH air the dew point is about 61 degF.
With 76degF 80% RH air the dew point is about 69 degF.
These dew points are a lot higher than I had anticipated. With the latter
if the wall surface is at 69degF, you get condensation. A concrete slab
floor could be even colder. At first I thought you might have an old house
with inadequate insulation, but this shows that the wall can be rather warm
and still condense moisture!
Since we are talking about a cold area, if heaters are used in the
tanks and the air in the room is kept to 68degF and 55%RH the dew point goes
down to about 51degF. (However, increased evaporation due to the temp
difference can increase the humidity!) This may be manageable in a house
good insulation. Also you didn't say if the room was small and had a closed
door. Opening up the room would spread the humidity out to the rest of the
house. I would keep that dehumidifier going.
We have a situation here in Texas where in bathrooms, even with expensive
exhaust fans, mold forms anyway. There are so many air leaks around the
ceiling light fixtures and around the actual exhaust fan and vent registers
that hot humid air from the attic travels downward, collects around the
ceiling, get cooled from the room air and condenses on the ceiling. Also
after a hot shower the humid air travels up to the attic here it hits an AC
duct just over the opening in the ceiling, condenses and causes mold on the
duct. This is similar to your situation in the attic where condensation
caused the icicles. Probably 40% of air conditioned air in most houses is
lost through leaks, most from unknown openings in the ceiling.
You really should try to patch those voids in the ceiling, and check to be
sure the vapor barrier and insulation is good in the attic.
I would suggest that anyone in this situation up north or in any cold area
get an inexpensive digital pocket thermometer/hygrometer to monitor the
Thanks Eric for your perspective.
I suppose there is an unlimited number of
> calculations you could perform based on tank size, temperature, relative
> humidity, home design, etc. to figure out what would work for your
> application but I found out the hard way. I had a 125 open-top setup and
> another ten tanks with lids on them in a home in a relative cold
> climate/environment. After finding mold growth along the bottom of the
> walls and on the carpet and walls in enclosed spaces like closets, I
> a $400 dehumidifier. I had to special order it because I live in Colorado.
> No one has a dehumidifier in Colorado. Its a very dry climate and every
> has humidifiers in their homes. In the summer most homes do not use air
> conditioning; they use evaporative cooling as its very effective in a dry
> environment and also provides a welcome relief from the extremely dry air.
> It basically pumps cool moist air into your home.
> Anyway, I got the dehumidifier going and that seemed to clear up the
> mold/mildew problem and increased the electric bill by a large amount as
> ran 24/7. I thought I had this humidity problem under control but during
> the winter I went up into the crawl space between the ceiling and the roof
> for some reason and found a real nightmare; large icicles hanging from the
> roof trusses. I estimate about 30 gallons of water in the form of ice
> covering the inside of the roof. This was a real problem. It took a week
> for the ice to slowly melt and evaporate by shutting the dehumidifier in
> the room that had the attic portal in it and running it full blast. It
> wouldn't fit into the attic. Of course I immediately put tight fitting
> on all the tanks to control the humidity/evaporation rate.
> I attribute the problem to having high humidity in a cold location
> the relative humidity of the atmosphere is usually very low, its quite
> inside the house and when the moist air contacts a cold surface it
> condenses. The house is located in Summit County, Colorado at an elevation
> of about 9000 feet. Its relatively cold all year long.
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