Opinons...what's The Optimal Shop Humidity?

coolidge

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Stepped out into the shop this evening and the humidity level was 80%. I thought before I go buy a dehumidifier I'd check opinions on what the optimal shop humidity level should be. I don't live in the desert I live in the wet Pacific NW, shop is in my garage. I'm thinking less than 80%. I left the door to the house open for a couple hours and it dropped to 70%. Its cool and its been raining outside most of the day.
 
Don't know about the NW but I do live in the South and humidity is a problem here. I have to deal with it as awood flooring contractor at least 9 months a year . I try to keep my shop in the 45 - 60% range, 50% being about right. Still though dew point is more of an issue. A matter of temperature and humidity. Just my thoughts.
 
In southern Wisconsin, humidity can be a problem. I run a dehumidifier in the basement shop from June into November. With the central air, the relative humidity stays around 50% and I do not have a rusting problem or mold/mildew problem. We do not humidify the air in the winter and the humidity van drop considerably lower then. If we get a lasting cold snap, the r.h. can drop into the teens.

Before running the dehumidifier, rusting was a constant problem. During the summer, I will pull about 2 gallons of water out of the air each day plus whatever the central air takes out. I should point out that the house is over a hundred years old and the is no vapor barrier in the walls and the foundation is sandstone/limestone with lime mortar so in in the past the walls would wick moisture in from the surrounding soil. The shop is maintained at a fairly constant temperature year around; aqout 65 - 70 degrees F.

IMO, as far as metalworking machinery is concerned, the less humidity the better.

Bbo
 
I'm in central Indiana where the humidity is always high, I have an external humidistat that comes on at 50% and off at 40%. Also if the outside humidity is above 85% I never open the outside doors as sweating can cause a problem here. The real problem today is finding a good dehumidifier, since the powers to be outlawed R12, the dehumidifiers today put out more heat than water removed, also most today run the fan continually rather than cycling on and off with the compressor which drives me nuts so I installed an external switch to turn the entire dehumidifier on and off. Whirlpool no longer makes one and the ones being sold today only last 2 years and you need a new one, the old whirlpools I had lasted 22-25 years, what has happened to American PRIDE and QUALITY.
 
Down here in the desert 30% is pretty common. No rust issue but it can cause problems due to static electricity and electronics. They add humidity in our computer room to get it to 60%. I think if you can get it between 50 and 60 you'll be in good shape.
Dave
 
Living in the desert, I'd have to say 4-5% relative humidity is best. :big grin: Seriously though, I never gave humidity levels much thought. As Dave said above, the QC departments are always controlled but I've no idea to what level the humidity is maintained.
 
Lower is always better but I think at any given humidity level its wide temperature swings that cause the most trouble. Eg condensation.
 
28 years of living in wet PNW I have found to keep rust at bay when humidity is high, run a fan to keep air moving and keep dust off little used tools so it does not trap moisture. Wild temperature swings are more dangerous than the humidity in my opinion.

cheers
michael
 
I'm planning on building a 15' x 30' room in my 30' x 50' shop bldg. to house my lathes and Bridgeport. Until I read this thread, I was planning on buying a good quality dehumidifier to go along with my A/C. I plan to use vapor barriers in the walls and ceiling and I am going to seal the concrete floor with an epoxy paint. Anything else I can do to minimize humidity in my "clean room"?

Do I understand correctly, that no one builds a quality dehumidifier now?
 
I purchased a de-humidifier this evening. Fact is I had issues with surface rust on my lathe last winter. My 3 car garage gets almost no sun, a couple hours late in the afternoon at most. I already have moss issues on the garage roof and its only 3 years old. That's also the wet side of the property. The mill was $6k plus so I'm going to do what I can to protect that investment. This should also help with my shop air moisture issue. The question is once I get the moisture level down how long will it last before the unit has to turn back on. The garage is sealed pretty well for a garage I guess, and its insulated.
 
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