shop relative humidity

[Frank Ketchum]

I have had some problems with rust on my tools (tablesaur, jointer) in my shop in the last couple of springs during the rainy damp season. So this year, I picked up a used dehumidifier for $20 (it even works!) Today I bought a digital temp/hygrometer from the hardware store and it said my rh was around 77%. I let the dehumidifier run for a few hours and it is down to about 60%.

So the question is, what do you try to keep your shop at? In the latest issue of FWW, there is an article on wood (go figure) and a graph comparing moisture content to relative humidity. It looks like a rh of around 50% will keep lumber at around 8-9% or so. I was thinking this would be a good benchmark to shoot for.

So, what do you all do? I know some of you live in climates much more humid than Michigan.

Frank

[Edwin Pawlowski]

I do nothing. My shop is in a detached garage. In the warmer weather, I work with the side door and the overhead door open so whatever the RH is outside, it is the same in the shop. In the winter, the only time it is heated is when I'm going to be out there.

I'm sure it is not the best way to keep wood, but it would be costly to try to control the environment all the time. Ed [e-mail]

[George]

Yep 45% RH is preferred for wood storage.

Remember that it's _relative_ humidity that counts. You can beat the curve by warming the air or lowering the absolute. I strongly suspect that efficiency favors the first approach. Makes the occupant more comfortable, too.

Oh yes, make sure that your dehumidifier is the kind that defrosts itself, or it could run and run and run ....

There is no more humid climate than Michigan - near the lakes.

[Larry Kraus]

Here in central Ohio, a 50% setting seems to make the dehumidifier run nearly constantly. I've set mine at 55%, which has eliminated the problems I was having with light surface rust and wintertime window condensation. A very nice bonus is the increased comfort level in the summer. Since I no longer feel like I'm wading through a swamp, I have given up the idea of putting in a window air conditioner. The standard August cliche around here is "It's not the heat, it's the humidity". My shop is nearly airtight, so I doubt a dehumidifier would work very well those with more open shops or garages. I know simply opening the door for a couple minutes can raise the RH to 75-80%.

A cautionary note to those that may be shopping for a dehumidifier: some of the electronic control models will not restart themselves after a power outage. I bought an electronic Maytag because it advertised working in low temps (I keep the shop around 50 degrees in the winter). We have power "flickers" in our area every 2-3 weeks which shuts down the dehumidifier until I get back out to the shop.

"Frank Ketchum" wrote:

[Mike G]

I like to keep it simple and so far it has worked out just fine.

When I have a job going I keep my shop comfortable to work in. No more heat then necessary in the winter and no more air conditioning then necessary in the summer.

For the most part that is the circumstances the pieces are going to have to live in.

I don't know for sure but I'd feel safe in giving good odds that 0% of the people receiving my output check the conditions in their house with a digital temp/hygrometer and most strive to just feel comfortable.

[Leon]

I live in Houston and the relative humidity often reaches 100% and is normally above 80%. I do nothing to try to reduce the humidity. I do use TopCote with great results. I think good air circulation and slow temperature change may be the answer.

[JohnT.]

I use a Santa Fe brand basement dehumidifer, one designed for larger areas (like a basement!) than your typical home dehumidifier. It cost about $1500.

Mind you, I have thick stone walls for a basement, not the "typical"

8-10" thick concrete walls. Mines about 18" thick. It really traps the humidity in the summer, and even though its cool, the humidity would have you sweating as if you were outside in the sun. Rust was a constant problem also. I tried in the past to use regular dehumidifiers, they either filled up too fast, or put out so much heat, that they were worthless.

Now, with this dehumidifier, I keep the RH about 50%, its dry and cool, the water the dehumidifer pulls goes down the laundry drain (has a pump).

BTW guys, simply increasing ventiliation to your workshop isn't going to reduce humidity. It will be the same as your outside humidity.

John

[Leon]

The out side humidity is not the problem if you are circulating it in your shop and allowing it to keep the temperature in the shop about the same as it is outside. It is when there is a drastic change in temperature that the humidity condenses on the tool surfaces.

[Roy Smith]

I've got a regular consumer model I got at Sears. Yes, it does put out a lot of heat, but it's hard to avoid that; that's how dehumidifiers work. Mine runs about 6 months a year (in my basement). Once the ambient temperature in the shop gets below about 60 degrees, you can't run the dehumidifier any more because it just freezes up. But you don't need it much in the winter, so that works out OK.

As for the emptying problem, that's easy. I've got mine mounted up high enough that a short length of garden hose leads from the collection container into a sink.