Need help with moisture problem in steel pole barn

[accobra66]

Hello, new to your forum. I was referred her from another user at ffcobra.com.

I have searched in some of the previous posts (did search on moisture problems) and found a host of posts/threads. After reading many of them I felt that it may be best to post the EXACT specifics of my garage design rather than trying to piece different threads together.

I moved to Marquette, Michigan back in August and purchased a home across from Lake Superior with a pole barn. I have found that I have a moisture problem that is causing rust on anything that is bare steel in the garage (tools, bolts, etc.). Being that I have a AC Cobra kit car that I built this is of great concern to me. The frame is powdercoated but there are still bolts etc. that seem to be rusting. I just finished sheeting the inside of the building with steel and installing a heater. I have not noticed yet if I still have this problem but I am sure that I will.

Exact construction details are as follows:

1. Cement slab foundation, no plastic under slab or any other type of insulating material.
2. 30' x 36' x 11' (ceiling) dimensions
3. 6" x 6" Post frame structure with steel siding (typical pole barn)
4. R-19 faced insulation on walls with newly installed steel sheeting (same as outside) on inside walls. (No plastic sheeting installed)
5. Ceiling is same steel sheeting with plastic stapled onto the bottom of the joists before the ceiling was drilled into place. I then blew in 16" to 20" of fibeglass insulation into the attic.
6. Ceiling fan is installed
   Roof is ridge vented on top as well as sofit vents and vents along the perimeter of the room all the way up.
7. Modine 100,000 btu vented propane heater (forced air).
8. Polyurethene insulated industrial grade garage doors.

What suggestions do you have on how I would go about fixing this problem? Leaving the fan on all of the time is not a problem. I am not sure if just circulating the same moist air will do anything or not. I really do not feel like peeling all of the steel off the walls and stapling up plastic. Is that what needs to be done? What about just painting the floor with an epoxy paint? I am at the point where I want to start mounting cabinets on the walls but in fears of having to take all of the steel down to staple up plastic I really do not want to mount them yet.

 

[comp]

having a fan moving air 24/7 helps here

 

[Willy Victor]

A little pricey but spray-on expanding foam should work.


Willy

 

[SteveU]

The reason it does that is because the parts inside are cold & the warm moist air from outside condenses on them. I try to keep mine shut up on days like today when it is warm & moist air compared to the temp in the barn. Another solution is to heat it to the point that the objects inside are warmer than the outside air so that whatever humidity comes in doesn't condense out. A while back there was a discussion about a rocksalt dehumidifier, I am going to look into doing something like that before spring when it is really a problem here. Welcome to the forum, always good to see another from MI.

 

[Red Green]

I run a Dehumidifier in my shop it helps alot

 

[daw53]

I agree with SteveU, it certainly sounds like a condensation problem. I have seen this in several buildings and at the plant that I used to work at. Adding heat, as you have already done, should hopefully take care of the issue.

 

[Franz©]

I read your specs, and the most concise description I can think of is youhave built a perfect condensation chamber.

Before you sealed everything up the moisture coming from the floor remained suspended in the air, and left via the vents. Now the moisture has no place to go, and will condense on any surface below the dewpoint of the ambient atmousphere in the room.

The question is how to get rid of the moisture laden air at greatest efficiency and least cost.
In a room that will be constantly heated, keeping the room above dewpoint will prevent condensation, but the atmousphere will be like a steambath.

If the room is only heated part time, the simplest thing is to powervent the room, making certain to have sufficient incoming dry air provided by Mother Nature. I've done this in a 20 x 20 x 8 room installing an 8" computer cooling fan into the opening of an unused chimney and providing a sufficient opening across the room for incoming dry air from outside.

Probably the most expensive way to remove humidity is a refridgerated dehumidifier as is found in half of America's basements. They cost more to run that the refridgerator and the efficiency *****.
A better way to remove humidity is a 4" diameter stainless stovepipe with a gutter pipe hung below it. Youcan circulate outside air thru the stovepipe with a computer fan and use Mother Nature's free refridgeration. Teh moisture in the room will condense on the cold stovepipe and drop into the gutter for collection and drainage. This will work as long as the outside air is below the dewpoint of the air in the room. Generally that will be most of the heating season.

 

[Steve in Mi]

"I really do not feel like peeling all of the steel off the walls and stapling up plastic. Is that what needs to be done?" The poly would have been a plus but there are some other things you can do that may make the problem more manageable. Actually R-19 faced insulation on walls plus the steel is a good moisture barrier.

"What about just painting the floor with an epoxy paint?" I wouldn't think epoxy would hold up well without poly under the floor. If you can live with the look of concrete perhaps a water based clear sealer would slow the migration of moisture up thru the floor into your shop. I say clear knowing that there are pigmented sealers but pigments don't go as deep into the concrete because their particle size is too large to get good penetration. Water based because water is what is already present and solvent based products are going to float on water - water based sealers will mix some with moisture already present and give better penetration into the floor. I'm not an expert on this but it seems reasonable to me so I offer it FWIW.


"I am at the point where I want to start mounting cabinets on the walls but in fears of having to take all of the steel down to staple up plastic I really do not want to mount them yet." I think it is a good idea to go slow at this point until you see if you can get the moisture under control. BTW, I do know from experience that the Rock Salt dryers work well and can pull a bunch of moisture out of the air. If you search "Rock Salt" you will find my eariler posts about them and the way I set my RS Dryers up.

Additionally, trenching all the way around your building and installing a gravel bed and weep tile will go a long ways to keeping surface water/moisture from entering under the slab and ultimately wicking up thru the cement floor. You will of course need to drain away any collected water from weep tile.

Also from Michigan with 4 years spent in the Soo and another 4 in Houghton, Mi (MTU)<!-- / message --><!-- edit note -->