Reducing Garage / Workshop Humidity

  • Advertise with us

« back to Focus on the Workspace forum

Forum topic by apehl posted 04-27-2017 03:27 AM 7791 views 0 times favorited 19 replies Add to Favorites Watch
View apehl's profile


57 posts in 2140 days

04-27-2017 03:27 AM

Topic tags/keywords: garage humidity workshop exhaust ventilation whirly bird fan turbine

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!

19 replies so far

View apehl's profile


57 posts in 2140 days

#1 posted 04-27-2017 03:28 AM

View Fred Hargis's profile

Fred Hargis

7482 posts in 3956 days

#2 posted 04-27-2017 11:02 AM

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.

-- Our village hasn't lost it's idiot, he was elected to congress.

View HokieKen's profile


21746 posts in 2601 days

#3 posted 04-27-2017 11:09 AM

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.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View dhazelton's profile


2839 posts in 3759 days

#4 posted 04-27-2017 11:17 AM

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

View ScottM's profile


756 posts in 3609 days

#5 posted 04-27-2017 11:50 AM

What do you consider “very humid”?

View apehl's profile


57 posts in 2140 days

#6 posted 04-27-2017 12:00 PM

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.

View r33tc0w's profile


214 posts in 1947 days

#7 posted 04-27-2017 12:04 PM

Look in to a radiant barrier: – 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

-- Matthew 13:53-58

View ScottM's profile


756 posts in 3609 days

#8 posted 04-27-2017 12:08 PM

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.

View Firewood's profile


1727 posts in 3097 days

#9 posted 04-27-2017 12:24 PM

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

-- Mike - Ocala, FL

View WhyMe's profile


1450 posts in 3024 days

#10 posted 04-27-2017 12:42 PM

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.

View Fred Hargis's profile

Fred Hargis

7482 posts in 3956 days

#11 posted 04-27-2017 01:03 PM

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.

-- Our village hasn't lost it's idiot, he was elected to congress.

View JBrow's profile


1368 posts in 2383 days

#12 posted 04-27-2017 01:41 PM


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.

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.

View BurlyBob's profile


10528 posts in 3728 days

#13 posted 04-27-2017 06:00 PM

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.

View MrRon's profile


6323 posts in 4706 days

#14 posted 04-27-2017 10:08 PM

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

View yvrdennis's profile


50 posts in 2540 days

#15 posted 04-28-2017 04:15 PM

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.

showing 1 through 15 of 19 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics