What is the Ideal Humidity Level for Your Shop or Garage?

[3macboys]

I have two dehumidifiers running in my shop - it is divided into two separate areas.  At the moment they are both at about 55 % and slowly dropping but I am wondering if there is a point where the air gets too dry in the shop.  Is there a range where the cars will be most happy while in storage?

 

Don

[Robert G. Smits]

Mine are set to turn on above 55% and turn off around 50%

[zepher]

The general rule of thumb for RH in a server room is from 40% to 60% so you should be good anywhere in that area.

 

The main purpose of controlling RH in that environment is to prevent corrosion from too high a RH to prevent static sparks from too low a RH.

 

If that RH level helps keep hundreds of thousands or even millions of dollars worth of server equipment safe it should be good for old cars.

[3macboys]

2 hours ago, zepher said:

The general rule of thumb for RH in a server room is from 40% to 60% so you should be good anywhere in that area.

 

The main purpose of controlling RH in that environment is to prevent corrosion from too high a RH to prevent static sparks from too low a RH.

 

If that RH level helps keep hundreds of thousands or even millions of dollars worth of server equipment safe it should be good for old cars.

Thank you very much - put in that perspective it makes perfect sense.  

[Hudsy Wudsy]

Here in Minnesota when the RH solidifies into crystal clear spear shaped things we turn the thermostat up a little, but not too much. We find that usually those spear shaped things go away on their own come the following May.

Edited September 17, 2021 by Hudsy Wudsy (see edit history)

[TAKerry]

I would think 50% would be ok, if not a bit high.  Of course in MD the de humidifiers work over time trying to keep up in summer. I wouldnt want more than 50% then again my shop isnt controlled and it gets to be very high in the summer. Im pretty sure most fine furniture museums run at about 50% which to me feels a bit 'damp'. Would be curious to see what car museums feel is the right amount.

[3macboys]

5 minutes ago, Hudsy Wudsy said:

Here in Minnesota when the RH solidifies into crystal clear spear shaped things we turn the thermostat up a little, but not too much. We find that usually those spear shaped things go away on their own come the following May.

Here in southern Ontario we hope that those spear shaped things don't show up until Dec 24th and go away on Jan 1st, unfortunately it's more like Dec 1st and April 1st - bit of a cruel joke by Mother Nature...

[BearsFan315]

Here in Coastal Virginia, we have HIGH humidity in the Summer !! avg around 65-70% with some mornings upwards of 80%

i keep mine at 50% and it has no problem keeping up. I also do not open the door unless i am going in or out. I also have mine plumbed through the wall, so it can run and not stop to dump the tank. also garage is insulated, and conditioned. 65 in winter, and 75 in summer. it is amazing how 75 feels with 50% humidity. 

[davenc]

Here in central Virginia, I'm doing the same as BearsFan.  The garage is insulated, and air conditioned.  65 in winter and 75 in summer.  Running a dehumidifier with the drain hose plumbed to the outside so there is no bucket to empty.  I'm keeping the RH at 45%.  50% just feels a little too moist to me.  I have found it's key to have a dehumidifier with large enough capacity that it doesn't have to run continuously.  It runs a lot in the summer but shuts itself down in the winter.  Once the space is dried down, which includes the concrete floor, it's a very comfortable space to work in.

[playswithbrass]

Too high here and a white powder mold forms on the leather. Too low and the wood spokes all go loose. 

[28 Chrysler]

I have had humidity up over 30% after spraying the floor down or after a big rain.  It goes back down to the 5 - 15% in an hour or so. We get 2 to 4 inches of rain a year and that keeps every thing fairly dry.

[Larry Schramm]

5 hours ago, playswithbrass said:

Too high here and a white powder mold forms on the leather. 

 

I just had that happen for the first time this year on our Corvette. Never happened before in the 40+ years we have owned the car.  Cleaned up with a little cleaner with bleach, but still not desirable.

[39BuickEight]

22 hours ago, BearsFan315 said:

Here in Coastal Virginia, we have HIGH humidity in the Summer !! avg around 65-70% with some mornings upwards of 80%

i keep mine at 50% and it has no problem keeping up. I also do not open the door unless i am going in or out. I also have mine plumbed through the wall, so it can run and not stop to dump the tank. also garage is insulated, and conditioned. 65 in winter, and 75 in summer. it is amazing how 75 feels with 50% humidity. 

I do it similar here in Kentucky— I keep it 55 in the winter and 85 in the summer, 50% humidity set.   I can always turn it up or down if desired when I’m out there all day. 😀  I keep the house at 78 in the summer and 68 in the winter to keep bills down.

[Frank DuVal]

Must be nice to have HVAC garages. I'm still in the open the doors and let the breeze flow through camp in Virginia, where the humidity runs high.

 

Currently I can not get the basement below 62%. Currently running an April Air or such. Must be too small. Two Frigidare ones broke within a year, first was replaced under warranty.  I do have them drain into a daylight drain so I do not need to empty a bucket.

[TTR]

Due to climate of the location, inland Southern California, only humidity concern in my shop is to maintain +/-70% RH along with +/-70 degree temperature inside the cigar humidor. 😉

 

[Trulyvintage]

85 degrees Fahrenheit 

85% humidity

Typical Fall Day In Florida

 

 

Jim

[playswithbrass]

We wake up to 90% humidity, at 60 deg F. Not a level you want in your house or your shop. 

[Walt G]

Can be damp here on long island, dehumidifier in the finished basement . Garage is insulated but no dehumidifier - had one there once. It is heated thought which I turn on in the colder months . This is all making me think I need a dehumidifier in the garage again.

[3macboys]

As spring is quickly arriving and the humidity will be rising soon as well here's a quick update on the thoughts above.  We just took in a tour of the Louisville Slugger factory on a little road trip this week.  They keep the plant at no lower than 40% as any lower the wood tends to be too dry and cracks.  They actually have misters to ensure that it stays above that 40%.  Now considering that they use ash, maple and birch I would think that is a good benchmark for the low end of the range that you would want in your shop/garage.   

[30DodgePanel]

Any time from Feb - July 4th in the great southwest is a joy to work outside or in the shop. After July 4th the humidity and monsoon moisture start its slow stranglehold of death. Happens every year like clockwork right on the 4th, damnedest thing I've ever seen. 

 

I watch the dewpoint more than the temps or humidity that time of year. Once our dewpoint reaches 45-55 it becomes too unbearable and most of us become hermits for the summer from July to Sept (opposite of back east). 

 

Anything under 40% with a dewpoint of less than 20 degrees is fine with me. Anything above that can suck it (I hate humidity, there's a reason I live in the southwest). 

Edited March 20, 2022 by 30DodgePanel (see edit history)

[dictator27]

Current humidity here (Vancouver BC) 91%, likelyhood of precipitation 98%, temperature 3 C.  Still some time to go before we see ideal humidity range here.

[Gunsmoke]

Had a bit of a disaster with my 1931 Chrysler Roadster rebuild project summer 2021 up here in Nova Scotia, where proximity to the Atlantic Ocean means generally higher relative humidity year round. 3 years ago I had the frame and all running gear sandblasted, primed (ordinary grey primer), and then I brushed on black Rustoleum (Tremclad). Everything looked great and eventually I placed body on, engine in place etc. This past summer while renovating my main house and guest cottage I left the garage door open days on end for about 6 months (April thru October) as I was using a lot of woodworking gear and tools. Paid no attention to the Chrysler. Went into garage one bright day in early October and could not believe my eyes. About 50% of all the chassis was showing serious oxidation (faNCY WORD FOR RUST), and the previously "primed only" wire wheels had not a spec of primer left. Same for brake backing plates, shocks etc. The roadster body had been epoxy primed fortunately so did OK. So now I'm faced with lifting body back off and figuring how to redo the chassis, may use epoxy this time, but hate to think I have to sandblast again. And buying a good dehumidifier for the garage. 

[Frank DuVal]

Epoxy primer well worth the price! Real two part epoxy primer. Sticks like glue... Ha! 😆     Like the old DP40 from PPG, now a newer part number.

[John_S_in_Penna]

On 9/16/2021 at 8:28 PM, Hudsy Wudsy said:

Here in Minnesota when the RH solidifies into crystal clear spear shaped things we turn the thermostat up a little... 

 

Indirectly, you raise a good point.  What is the best

TEMPERATURE range for antique cars, too?

 

And in the wintertime, a true climate-controlled garage

probably should have a humidifier.  If the humidity is too

low, might wood shrink, and leather interiors get dry and crack?

[edinmass]

 

Our museum is designed to keep a constant 72-73 degrees, and 40-50 percent humidity for all the cars....( Coach built cars with wood frames)........in Florida in the summer we rarely take a car out as the cool surface will become wet from condensation in a matter of seconds.........so unless the day is unusual in the summer.....our cars stay inside. Our "Southern" version of New Englands winter.

 

Every year a cars leather is treated to keep the leather from drying out. Too much humidity change can cause nail head to pop through the finished paint. They weren't perfect when new.....and today's expectations are a bit over the top when you consider a early cars construction type..........wood is NOT a very stable material when you consider the quality of finish people expect today.

Edited March 21, 2022 by edinmass (see edit history)