humidity in my shop

I recently moved to a bigger garage that fit all my father's and my cars. the problem is that it is not properly insulated.

My question is what is the best humidity level for my cars?

I have original cars, projects but also cars that are "ready"

I bought a moisture meter and at the moment it gives me 85%
So I think that is not good for cars. Most cars have a covvers, blanket or plastic to keep the dust off and maybe some moisture.

I hope that here are people who have more knowledge about this than me and can give me advice. I'm sure there are many people here with the same problem.

old shop: (with a good roof insulation)

 

The plastic covers will trap any moisture that gets under them, which will promote rust, mold, mildew and all the other bad stuff. Get some cloth tarps or covers to fit the cars. That way, they can "breath" and let out any moisture that gets under them.

As far as the humidity, it seems high; what is the outside humidity level? Roof vents or vents in the gable ends of the shop may help the excess humidity escape. If you have deep pockets, air conditioning (heating and cooling) may be the route to go. I hope this helps.

 

Do you know how many square feet your shop is? HRP

 

Until you can get that humidity under control, you should run a couple of fans just to keep the air moving in the shop. At least that will keep the moisture from condensing on the shop contents.

 

You need a dehumidifier,,you will soon have mold setting up on everything if the humidity is not kept in check.

You might read up on them. HRP

http://www.lowes.com/cd_Dehumidifer+Buying+Guide_174021230_

 

For the moment it is around freezing at night and during the day a few degrees above it. the shop is about 2500 square feet. heating is financially not an option (high roof and no instalation)

 

HRP is right on the money on this one. You definitely need a dehumidifier. That much humidity is going to cause nothing but problems.

 

I wish you were near my home in Michigan. I have 3 dehumidifiers, each of which have the ability to drain the condensation water via a hose so you can send it to a floor drain.... you don't have to be there to empty them because they won't fill up and shut off. I don't know what the stores have in stock near you but I bet you could find units like these on Amazon

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I could be wrong, but I didn't think dehumidifiers work at these temps?


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condensation happens when warm(er) moist air hits cold objects.

Circulating warm high relative humidity moist air over cool objects may just dump more water on them until the objects are warmed op to the "dew point" temperature.

Warm air holds a lot more moisture than cold air, and what is commonly called humidity is "relative" humidity. There is really not much moisture in 32F / 0 C air with 85% relative humidity. Just warming it up 20 or 30 degrees can double or triple the amount of water vapor it can hold, so the same air would be more like 40% relative humidity.

Haggerty seems to recommend < 60%.
http://www.hagerty.com/articles-videos/ask-hagerty/What-is-the-Ideal-Humidity-in-Storage

 

I had that problem in an old building. What I did to control it somewhat was to run 3 pedestal fans pretty much 24 7 on the oscillation mode. It helped a lot with the moisture in the air. Without the fans my aluminum would fog up and turn white with them that no longer occurred.

 

Fans tend to be the quick fix - particularly overhead fans that pull air upwards and circulates the envelope of space in warm climates. In cold climates reverse the direction of airflow downward to the floor.

The real fix is to insulate the space leaving an airgap surrounding with soffet vents that pull the air upwards in attic or peaked roofs to ventilate moisture etc. way from the insulated space.

Humidifiers help particularly when opening garage doors (outside warmer air condensing in cooler inside air and vice versa)...

But the ability to keep air circulating is a start and in cold environments - proper insulation and heating will "burn" the moisture to a great extent. - I know all this stuff is pretty profound haha.

 

I don't know all the tecticnal stuff but my Corvair has spent 15 out fo 20 years in a unheated garage in bare metal and it has hardly changed color . The garage has a full length ridge vent that aloud moisture to escape ,the only rust isues i have with the car is when people come in and put there sweaty hands on it, i would suggest you open the hoods to let the moisture out,i leaned that one the hard way

 

From experience (not good) you don't want plastic like Visqueen covering the cars or equipment and especially bare metal as it traps condensation under the plastic. We found that out with a table saw covered in plastic when I was a kid.

 

Hey Belgium, If this is an option the best way to help curb the problem is to put a barrier between the ceiling Truss' and the main part of the room ( kind of like a ceiling where your walls meet the roof.) Some insulation board or a vapor barrier even. the roof is heating and cooling like the outside and since the shop is like a box it cant fluctuate like the outside does. Also try a ridge vent or two to help.

 

Don't cover the cars in plastic. But do cover the concrete floor with plastic to prevent moisture from the floor. This is a common problem with cars stored on concrete here (Minnesota) in the spring. You will be amazed a the amount of moisture that can come up from a concrete floor. And yes , dehumidifiers will not work at the temps you are storing these cars in right now. Take a look at the underside of these cars, you will think its raining from the floor up.

 

Yesterday the frost came up through the concrete in my garage for the second time so far this winter. The floor was wet and left foot prints. I left a 20 inch box fan running all night blowing on the floor between the two cars. Today, all looked dry to me. I left some wrenches on a carpet square yesterday, when I picked them up, they were all wet.

 

I have heard from several different people who store cars long term in unheated areas that it is much better to park the cars on a gravel floor than concrete for the reason mentioned above. Concrete seems to draw moisture and apparently gravel does not. I have to admit though that I have never tried this myself.

 

I think you guys are on the right track about the concrete exuding moisture. That may in fact be the source of most of the humidity the op speaks about, not necessarily the relative humidity in the air. Concrete never really "cures" completely and will give off moisture for decades. I'm sure someone will dispute this, but think about it, some of the pours in Hoover Dam are still "curing" and they were poured in the 1930's. They were very dense pours, but the principal still applies to your garage floor.

 

Thanks for the advice, Never too old to learn.

the issue is certain that the roof is not insulated and the floor is concrete. So see what I can do there. also remove the plastic from the cars. so better plastic under than on the cars.

 

I don't think covering the floors with plastic is realistic. But I think sealing the floor, even with a simple paint would help keep the concrete from sweating.

I agree to only cover the cars with breathable covers, even cheap,ones from Walmart work well.

I would also put mothballs in mesh bags (because if you have a dog some actually will eat them) and place throughout the garage.

A humidifier is a good idea, so is a some ventilation. Either side vents or a roof vent. Even though heating is expensive, a simple baseboard heater running at a low temp kills a lot of moisture.

When you do want to insulate I would go with a spray foam which will act as a insulator and a vapour barrier.

Love to see some photos.

 

here is my roof, the structure is good but the what we call eternit plates have to go in the future. the plates do not isolate, summer is too hot and in the winter very cold in the shop.

 

a firm that do spray foam came to look but did not give a price up until now so do not know if it is doable.

 

I'm not sure my concrete floor sweat. it looks dry and is always dusty (which I hate)
I was thinking to place rubber tiles (fast, beautiful and movable)
like this


but I am not convinced about the density (water, oil, etc). and expensive.

also painting such a large surface area is expensive and a job for a professional because it must be thoroughly cleaned (oil, paint etc spots) and does not fill the cracks and holes.

 

..I would agree with sealing the floor with a good quality "sealer" not paint. It is a large area and you could do the sealing yourself economically enough and cut down on the dust. The mothballs do nothing to inhibit moisture. What you need are small bags of dessicant. Dessicant is what's in those little bags that come in the boxes when you buy a new TV, computer or other electronics. I always save those things and toss them in my toolboxes and under the car seats to absorb moisture from the air. And I think you meant a dehumidifier, not a humidifier.

 

If you go looking on the internet for sources for "Desiccants" note that I miss-spelled it in the above post.

 

I stopped my concrete guy just in time. he was about to poor the floor on my 48'X80' with no plastic under it. he said theyd on't normally do that with pole barns. I explained that I had collector cars and din't want moisture wicking up.

Like a glass of ice tea, anything cold from the night before will get wet when the surrounding air is warm and humid. I've had luck hanging a droplight in bare steel cars to prevent that.

I've had fine snow blow through ridge vents and dust cars in strong winds. No more ridge vents for me.

 

Fans, both on the ground and stationed to move it outside in a roof or wall vent .
In the 1800's ventilation was the answer for humidity problems. Cupola's and basement/crawl space vent openings were the norm. Cupolas act like a chimney.
Keep the air moving during the spring, summer and fall. Normally during the winter as stated the cold air doesn't hold that much moisture. If you floor isn't getting wet during temperature transition periods like spring and fall then you shouldn't have too much trouble controlling the moisture in that big building. Dehumidifiers are great in small enclosed areas but your space is too big for them to be effective.
The new exhaust fans now turn on at your desired temperature and humidity settings.

 

The weather was finally over freezing during the day a few weeks back in Massachusetts. I opened the southern facing garage doors to warm up the floor.
In short order All the iron and steel was damp and sweating.

When I bring my favorite HD radio into the house from the shop late in the fall I put it in a plastic bag and seal it while it is still cold. I don't take it out of the bag for a day or 2 when it has reached house temperature. I lost the first radio when I turned it on during a temperature change. I believe some of the cold boards got condensation on them that smoked something when power was applied. I was barely within the warrantee period.

Car electronics must have a conformal coating or something that makes them tolerant of moisture that surely condenses out during temperature swings.

A typical computer spec calls for a "non-condensing" atmosphere for use or even storage.

 

Interesting observations, Dan.