# Garage Shop Owners - Dehumidification



## dougswoodworks (Nov 6, 2014)

Hi Folks,

My shop is in a one car garage attached to the house. It's tight, but works. I have become a bit concerned about the humidity in the shop during damp weather. In the winter, the lower humidity and my heater take care of things well enough. However, rainy weather makes the shop too humid and I am growing concerned about the long term effect on my tools. Recently I found a ratcheting wrench frozen with rust - and I am meticulous about how I use and store them.

So, my question is for those who have garage shops:

How do you handle this? I am thinking about putting a dehumidifier in my shop. I would run it at a 40% humidity level - same as data centers, so it won't be bone dry with negative impact on my stored wood stock, but drier than the outside most of the time.

Does this make sense you you? Are there other ways to tackle this?

Thank you all in advance!

Doug


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## jamsomito (Mar 26, 2017)

I also have a garage shop and my heart broke a little the first time conditions were just right and there were pools of condensation on all my cast iron tops. I haven't had issues with rusting aside from that though - just general use and maintenance (lubrication) seems to keep everything in ok shape. I keep all my portable tools in their cases. It actually works *okay* for my wood stores too because my hardwood dealer has everything in unconditioned warehouses with the doors wide open all the time. When I get everything home it's still more or less in equilibrium in my shop. Moving things inside though… you have to expect some movement in the final pieces, but at least you can plan for that to some extent.

Other than regular maintenance, in general, I don't let anyone open the garage door when A) it's raining or damp/humid out, or B) if conditions are warming and humid (metal tools warm up slower than the air and usually cause condensation). That's about all I can do, and it seems to work out alright.

How is the state of the envelope on your garage? Insulation? Drafty windows? Seal around the garage door / access door if you have one? Any air changes to the outside is going to completely negate any dehumidification you do - especially if you're using an overhead door. And running that thing all the time will be fairly energy intensive. If you do run it, just try your best to keep the conditioned air in and unconditioned air out, unless conditions are favorable out, by sealing up fenestrations and making rules about window/door/overhead door use.


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## avsmusic1 (Jul 10, 2016)

I'll be following this one as well.

I work in an old detached garage that isn't insulated at all and it's always a challenge


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## jonah (May 15, 2009)

The air seal is going to be the key. If it's not well sealed, it'll cost you a fortune to run a dehumidifier all the time. Invest in good weatherstripping around the garage door and access door(s), insulate the walls, ceiling, and seal around any windows that happen to be in there.


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## Murdock (Aug 7, 2011)

Until last year my shop was in a separate garage stall that for reasons I don't totally understand stayed cooler and less humid than the outside all summer long.

However, in my new home the garage quickly became humid enough to cause issues. I did run a 70 pint humidifier out there for a while but didn't go all the way down to 40%, I kept it closer to 60% which seemed to be enough in my case. It did run a lot, but not constantly even with outside humidity above 90%.

As others have said opening the overhead door does let a large amount of humidity in, but I found if I just left it open long enough to pull the car in/out and closed it right away it wasn't to bad.

I do have good seals on my double overhead door, but the one on the single stall is a bit lacking. Something that needs to be resolved soon as I am also trying to heat the garage now.

My dream is to put in a mini split system, but that is at least a few years off.


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## dougswoodworks (Nov 6, 2014)

Right now I have insulation on two walls - and a garage door that is quasi sealed well. The biggest problem is that the attic has a small opening around the garage door opener. Built in 1955, so good by those standards.

In the spring, my adult sons and I are going to empty the shop, insulate, run new electric, epoxy seal the floor, put a side door in (opening the garage door just floods humidity on bad days, and finally close up the hole in the ceiling and re-seal the garage door. The final step will be adding heating from baseboard and radiators being torn out of my son's house in his renovation.  So, yes taking those steps to insure I am not trying to dehumidify the neighborhood.

I see no problems in winter with heat and good insulation. However, my neighbor across the street has done everything we are doing in the spring - and his is a problem from late spring to early fall.

So, apologies I did not add those plans to my original post.

Thank you all for answering!

Doug


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## jonah (May 15, 2009)

"Built in 1955" really means "not air sealed or insulated at all."

Houses in most of the US didn't have what I'd call adequate insulation until like the 1990s in the Northeast and upper Midwest. Some parts (the South) *still* don't put adequate insulation into their houses. In 2019.


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## EarlS (Dec 21, 2011)

I have a 2 car garage and use and air conditioner in the summer and a heater in the winter. The A/C cools things off and takes out the humidity in the hot humid summer days. The heater keeps it warm enough to prevent the metal surfaces from getting too cold and it also keeps the air temperature above the dew point. I'm careful to pull into the garage and get the door back down quickly. I also squeegee away any puddles from rain water or melting snow that drip off the truck when it is rainy.

In general, heat moves the air temperature above the dew point which works in winter. An air conditioner takes out humidity by cooling the air on cold surfaces in the A/C causing the moisture to condense on the A/C coils. The air leaving and A/C is at the dewpoint but it mixes with the warmer air in the room resulting in lower humidity. Additionally, for every 10 deg warmer, air can hold 2 times as much water (absolute). Your best bet is to remove the humidty and maintain a decent temperature. To do so, you can use either an A/C or a dehumidifier. Having a fan blow the air around also helps.


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## OSU55 (Dec 14, 2012)

While renovatng your shop figure out a way to add ac. Small 120v window unit would do it, or there are fancier ways as well, just depends on what you want to spend.


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## Planeman40 (Nov 3, 2010)

Some thoughts.

I doubt there is much you can do to alleviate the moisture problem without sealing up the entire garage and installing a dehumidifier or air conditioner.

Try sealing the cast iron tops of machines with a coat of clear lacquer or shellac after cleaning them thoroughly. If you are not happy with this solution, you can remove the finish with alcohol or acetone.

Spray all surfaces with AD-40, *let sit overnight*, then lightly wipe down the excess. WD-40 is made to seep into the pores of steel and cast iron, force out moisture, and seal the pores and surface.

Keep instruments and tools in moisture proof containers with a desiccant like silica gel (cheap and obtainable on the Internet). Note: silica gel absorbs the moisture in the air and holds it. Silica gel can be reused when saturated by placing in a oven at a temperature slightly over 212 degrees

That's about the limit of my 60 years of fighting this problem. Air conditioning and WD-40 keep my machines and tools rust free. This is the only thing that has really worked.


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## rwe2156 (May 7, 2014)

> The air seal is going to be the key.
> - jonah


I agree with this. Plus, climate control is also a key.

My shop is in a converted horse barn. When I remodelled I sealed things up quite a bit, although the barn door entry into shop is not sealed.

I keep a fan running at night. No climate control or dehumidifier. 98% improvement. Now about the only time I have to address rust is if I leave a water bottle on a table top.


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## BlueRidgeDog (Jan 2, 2019)

My last shop was a stand alone uninsulated building with an elevated floor. I solved the issue with a simple cheap window AC unit (the smallest they made) that also had a dehumidification setting. When hot I could cool things off, otherwise, I could just leave it in "dry" mode.


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