Realistically, the only effective control will be a dehumidifier. Buy an ENERGY STAR unit to save $$ on electricity use: energystar.gov. Now, the reason, if Dale will support my veering to the edge to help others protect their vintage bikes and tools:
1) Basement surfaces connected to the ground are cool relative to the house during summer, since the ground temperature varies less during the seasons than air temperature. Typical annual average ground temps run from the high 60s in the deep South to the upper 30s in the far North, if I recall correctly. 2) The ability of air to hold water vapor rises very quickly with increasing temperature. Conversely, humid 80F air doesn't have to be cooled much before it is supersaturated and begins to condense moisture. Just like the "dew" on the outside of your glass of favorite chilled beverage. Remember, the basement walls are cool relative to the air during the summer, just like the basement is usually cooler than the living area. 3) Dehumidifiers just pre-empt that by providing a very cold evaporator coil to condense the moisture by cooling the air a whole bunch. They then warm the air by blowing through the condenser, so they pull in relatively cool but very humid air, and exhaust warm, dry air. 4) So, where does that warm humid air come from that fills your basement? Outside. We call it "infiltration," and can easily be more than one air change (by volume) per hour. Oddly enough, on a warm summer day, you will increase the load on the dehumidifier by leaving the doors open to "fresh" (hot and humid) air. But, don't try to absolutely kill the air infiltration without thinking of possible risks, such as higher radon levels in some areas. 5) But, you say, I don't have a thermally conductive direct link from my hanging bike to the cold wall. Why does the bike get into trouble? Subtle it is: the bike and the wall/floor radiate infrared heat to each other. The bike is warmer, so it cools off to approach equilibrium with the wall or floor. 6) By the way, notice that I have not even addressed actual leakage from outside. My own basement is all but completely dry, but when I inadvertently insulated one wall with boxes of books hard against it, they got moldy. Seems to have been moist basement air cooling as it diffused toward the wall and cooled until it condensed, giving the fun guys (fungi) a bountiful harvest (Other hypotheses are tenable, but you get the point). 7) Bottom line: I hate wasting energy, both personally and professionally, but I consider the dehumidifier a necessary expense to protect health and my property of tools and bikes.
I'll try to respond to questions offline. I have no financial connection to any manufacturer of this or related HVAC equipment, but am an efficiency advocate, http://www.aceee.org, in my other life.
harvey sachs
mcLean va
(just inside the beltway, and just upwind from the CIA).
>
> Date: Thu, 29 Mar 2007 15:42:38 -0400
> From: "Jeff Dinsmore" <Jeff@BeSeennow.com>
> To: <classicrendezvous@bikelist.org>
> Subject: [CR]Humidity and steel bike storage
> Message-ID: <018001c7723a$68f19180$0900a8c0@Jeff>
> Content-Type: text/plain;charset="us-ascii"
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> Message: 1
>
> I am discovering that the basement in my new house is not as dry as I
> had
> hoped. The bikes are all hanging so I am not afraid of direct water
> contact,
> but will extended storage in high ambient humidity put the steel bikes
> in
> jeopardy? In that vein, how much humidity is too much humidity? I will
> need
> to get this taken care of anyway, but in the mean time I was wondering
> what
> my exposure was. Anyone else find themselves in a similar situation?
>
>
>
> Jeff Dinsmore
>
> Westmont, NJ