[R-390] Boatanchor Storage - Some questions???

[Bill Hawkins]

As far as I'm concerned, the biggest problem is mold. This
happens long before something gets rusty. When you are
sensitive to mold, you get to learn about dewpoint. This
is the temperature where moisture just begins to condense
from the air, like the moisture on the outside of a cold
drink in summertime. You can calculate dewpoint from %RH
(relative humidity) and vice versa if you know the air
temperature. Radio Shack and others sell $20 digital meters
for temperature and relative humidity. Weather stations, like
Oregon Scientific, will calculate dew point for you.

The trick is to store paper and easily rusted gear in an area
where the temperature never gets below the dewpoint. With no
condensed water, there is no mildew and no rust. If you have
other allergies, dust mites go dormant when the RH is below
50%. You need to know that dewpoint remains pretty much the
same in an area with air circulation, but that RH increases
in the vicinity of cold surfaces like concrete or glass that
has cold temperatures on the other side of it.

If water floods the floor, dewpoint will rise to at least the
temperature of the water. I don't have anything expensive less
than a foot off the floor.

Here in Minneapolis (dewpoint range -20 to 80) I finally got
the basement under control by installing heating air intakes
near floor level in the basement and blocking off the ones
upstairs. The circulating air fan is on all of the time. Those
with radiant heat would need to circulate air between basement
main floors.

I also installed an UltraAire dehumidifier developed for use in
dairy barns. It cost $3000, but it maintains 35% at 72 degrees
spring and fall. Two $300 standard dehumidifiers could not hold
60% some days. The basement never smells moldy, so it can be used
all year around. I think it was worth it. All of my good stuff
and >1000 books are in the basement. Nothing is in the vented
attic. Paper stuff in the garage is in sealed plastic containers.

In summer, the basement will not be a high temperature problem.
Forget the attic. The garage will also get hot, but military
gear can handle it. Wax capacitors and liquid electrolyte era
stuff is best kept in the basement (or living room :-).

With an older house, you should make an effort to seal major
outdoor air leaks, especially through the attic. When we bought
this house 20 years ago, the unfinished walkout basement had
neither insulation nor vapor barrier on the outside wooden wall.
The attic runs 50% RH when it is 10 degrees out, attic 23 deg.
BTW, dewpoint is never higher than air temperature. When it
tries to be, you get rain (or snow).

Regards,
Bill Hawkins