# Reducing Garage / Workshop Humidity



## apehl (Jul 18, 2016)

I have an older 16×24 detached garage for a shop. For now we still park a car in it year round and we live in Iowa so our summers are very humid. The high humidity is an issue for my tools and general working comfort.

The garage is open span so their is no attic. There is no insulation in between the gables and intermittent insulation in the walls. Lastly there isn't any vents in the soffit.

I have been thinking about adding a whirlybird turbine and additional vents for added airflow to support the fan. What kind of vents would you recommend and where should I place these? Is there a better option that won't break the back? Where should I position the whirlybird?

My goal is the eliminate as much humidity as possible while I'm not around so my tools won't rust as fast and i won't have to go out there regularly to vent it. Thanks!


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## apehl (Jul 18, 2016)




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## wapakfred (Jul 29, 2011)

The turbines I've seen and installed (my own) were generally centered along the ridge. Not sure what to suggest for vents, since I always had vented soffits. One piece os advice: be sure to buy a quality turbine with ball bearings. The is nothing more annoying than a wind turbine with a squeaky bushing bearing.


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## HokieKen (Apr 14, 2015)

I would think as far as humidity goes, you may be better off with a dehumidifier in your shop. Assuming it's fairly well sealed of course. Moving air makes it feel less humid to you because the air is convecting heat off of your skin. I'm not sure it actually relieves the relative humidity of the atmosphere in the shop though. Not saying it doesn't 'cause I don't know, just saying before I went to all that trouble, I'd make sure that providing air movement will actually lower humidity levels.

If you do decide to go that route, I'd think that louvered attic vent panels would be suitable and economical.


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## dhazelton (Feb 11, 2012)

Is it rising damp from the concrete floor? A vapor barrier, insulation and plywood floor may be in order.


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## ScottM (Jul 10, 2012)

What do you consider "very humid"?


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## apehl (Jul 18, 2016)

I thought about getting a louvered attic/gable vent along with a whirlybird but I wasn't sure if only venting the air above would circulate the air where I stand and work.

I have a free standing space air conditioner with a dehumidifier option, however I don't want to worry about turning it on all the time or paying a much higher electrical Bill. (Maybe a designated dehumidifier isn't that costly).

I just bought a temp/humidity Guage so I will let you know but it was only 60 or so degrees the other day and I walked in to a very stagnant garage that seemed 10-15 degrees warmer and 20% more humid. It gets to the point in the middle of the summer where I'm sweating in the first couple of minutes. At times yes the floor has condensation but that is rare.


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## r33tc0w (Jan 27, 2017)

Look in to a radiant barrier: www.atticfoil.com - make sure to get perforated. This will help keep the heat out of the garage in the summer and heat in the garage during the winter. I installed this during the crazy heat of a Louisiana summer and the difference it makes will blow your mind


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## ScottM (Jul 10, 2012)

Check it both inside and outside. Just check the weather channel for the humidity in your zip code. I'm just curious. I live on the coast in Alabama. In the summer time the outside humidity averages 90% to 95%.

I don't use any kind of dehumidifier or have any insulation in my garage but I do have attic space with soffit vents and ridge vent.


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## Firewood (Dec 4, 2013)

Condensation on the floor is most likely humid air condensing on the colder concrete floor.

Moisture will always condense on any surface colder then the surrounding air (windows, floor, cast iron saw tool


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## WhyMe (Feb 15, 2014)

If trying to reduce condensation on your tools from humid air you need to keep the air circulating from inside to outside to maintain an equal temperature and humity between the inside and outside. If it gets cool in the garage over night and warms up outside in the morning and you open up the doors that warmer air hits the cool tools and condenses. The other solution is to keep the garage closed up and use a dehumidifier. I live in Virginia and go through the same thing.


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## wapakfred (Jul 29, 2011)

> What do you consider "very humid"?
> 
> - ScottM


Iowa is known for being a lot more humid than surrounding areas…mostly due to the corn crop. The massive fields of corn distribute so much water vapor to the atmosphere you can actually see it on those humidity maps that some weather broadcasts show.


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## JBrow (Nov 18, 2015)

Apehl,

It seems to me that by lowering the summertime temperature in the garage should be the overall goal, since warm air can hold more moisture than cooler air. This goal could be achieved by properly venting the attic and adding insulation in the walls and ceiling of the garage.

I suspect that there is more to attic venting than simply cutting in some soffit and roof vents. Therefore in order to get optimum results in your situation some research may be in order. The link below is a list of search results from which helpful roof venting information can be found. Another resource may be your local building department.

https://www.google.com/search?q=spacing+of+roof+vents&ie=utf-8&oe=utf-8#q=how+to+vent+my+attic

Once the attic is vented, adding wall insulation with a vapor barrier and plenty of ceiling insulation would help reduce the temperature garage temperature and make mechanical conditioning of the space more affordable. A last step suggested by dhazelton (apply a vapor barrier to the concrete floor protected by some plywood), could reduce moisture from being wicked into the garage through the concrete slab. I would also think an epoxy floor coating could also act as a vapor barrier to the concrete floor, but I am not sure.


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## BurlyBob (Mar 13, 2012)

I put an epoxy floor coating on my concrete garage floor. Prior to doing so I could notice the humidity in my garage/shop. After putting the epoxy on the difference was quite dramatic. It was expensive but well worth to my way of thinking. I chose a bright yellow color which also improved the lighting situation. I was really surprised by the difference. The only thing I would change is to buy more and give it a 2nd coat.


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## MrRon (Jul 9, 2009)

You need good air circulation to keep the humidity down. The alternative is a well sealed garage and insulation which is expensive.


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## yvrdennis (Jun 14, 2015)

Is the air in the shop more humid than the outdoor air? If it is, then circulating more outdoor air will help. If it isn't then you need a dehumidifier. I'd invest in a tool to measure the humidity so you can check this.

If the air in the shop is more humid than outdoors, then you may have moisture coming through your slab. An easy way to check for this is to tape a piece of clear plastic down on the slab. When the shop is relatively cool in the morning you may see condensation on the underside of the plastic, which would suggest that there is moisture coming through the slab. If that's the case then sealing the slab somehow should help.


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## RobertsPlace (Aug 19, 2012)

Air seal the structure of the garage to prevent infiltration of warm humid air in the summer.

Insulate walls and ceiling. Vent behind the ceiling insulation.

If you concrete slab has a vapor barrier under the it, then your floor might be a good candidate for an epoxy floor finish. Or you could apply a vapor permeable floor sealer, which would help to reduce vapor transmission from moisture in the slab into the interior space of the garage, but without the risk of the coating peeling up as can happen with non-permeable coatings, such as epoxy.

Use an air conditioning unit or dehumidifier to help control the remaining climate issues.


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## RobertsPlace (Aug 19, 2012)

My shop/garage is under my house. The concrete in the shop was very uneven and pitted, so I busted it out and dug out 8" of the clay from under it. Then I placed and compacted stone and then poured concrete. Even though this floor is technically in my basement, the floor is actually 12 inches higher than the street in front of my house, because my house is in the side of a hill.

Prior to the new floor, my shop felt damp. But by putting a stone base between the slab and the clay ground, my floor is very dry, resulting in a dry shop. I plan to do the remainder of the basement this way.


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## hokieman (Feb 14, 2008)

The only thing that will reduce humidity is air conditioning or a dehumidifier. Increasing air movement will not do a thing for humidity as you will just be circulating humid air. The moisture in the air has to be removed through condensation then returned back to the room. You need to seal up your shop and then dehumidify the air inside. I put a ductless air system in my shop and it works great for both heat and AC. It was a little pricey, though. About 3 K for a 16 X 22 shop but it makes the shop very comfortable.


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## NewShop (Jan 19, 2019)

Hi, I live North of Boston and have a 16×12 gambrel style storage sitting on cinder blocks that needs a new roof so I am taking the opportunity to finally make myself a workshop. I plan on adding a 12×6 lean to the back of the 16' side. Using a 6' x 6' section for storage the other half will add to my floor space for my shop. It will be unheated and have no A/C. My original thoughts were to add a row of small windows to each side for natural light. Researching what I can do to prevent rust besides Boeshield and wax I am starting to think that I should skip adding the extra windows and cover the 2 windows I have now with shades and only open when I am in there. I read somewhere that after the cold of the night that the rise in temp in the mornings plus the additional rapid heat from the sun thru the windows creates most of the moisture and turns everything in the shop into a rust factory.

Would love some help to let me know if this makes any sense or should I go with the extra windows and buy myself a case of Boeshield?

Thanks for taking the time to read this,

John


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