Metal building condensation (help please)!

Bama67 · Jan 22, 2012

Hello all,

A couple months ago I finally built (or had built) my dream shop, 40'x60' 16' eave steel building. My problem is, if is rains for a day or two, the condensation inside is TERRIBLE. Normal weather, it is fine. I have insulation, the thin-foil backed stuff R-10 value. So the metal is not exposed on the inside.

I am talking about bad, it looks like it is raining in there. Not just the water pouring off the purlins and beams. But anything that isn't cloth or wood is basically dripping with the stuff. Metal, plastic, etc.

My polaris ranger and fourwheelers are dripping so much water in the floor they look like I just washed them. My gun safe is pouring it off, my tools are rusted

This is an engineered steel building, and I think it is ridge vented.

I am thinking some serious ventilation would help this alot. But will it get rid of all of it? And I can't imagine how much a de-humidifier for this 2400 sq building would be.

I was think a pretty cupola would look nice, and I could put a big fan in there and I guess I would need some louvers on the wall? Or would I be better off with fans in the wall? How much air CFM/fan size do I need for this large building?

Thanks guys, I have been overseas basically since I built it, and will be home in a few days. My wife said it has been bad, and that alot of our clothes and stuff stored in there have mildewed while I was gone.

Pete Judd · Jan 23, 2012

In addition to adding vents, you need to warm the inside air to a temp just "at least" a little above the out side temp. The warmer the air, the more moisture it can hold. The science of it is that as the out side air as it enters the building warms, it's relative humidty will decrease and it's ability to more water will increase, then you move that wetter air outside.

On my sail boat, 46 ft. I just keep a 60 watt heater running all the time. 4 non powered vents, keep air moving through the boat and just the slight temp increase keeps everything dry and mold free. And this is in the wet PNW.

Hollow · Jan 23, 2012

Keeping it the same temp inside as it is outside is the key. A vent at each end should take care of it. Is the roof not insulated? Insulation will usually absorb light condensation and slowly evaporate it off.

Bama67 · Jan 23, 2012

Thanks for the quick replies.

The entire building is insulated. It has that this stuff that has the radiant barrier on the outside, then like 1/2" fiberglass, then the white inside. R-10 value.

Sucks I have to keep it the same temp when it is cold outside. But I would rather work in the cold than all my stuff ruining.

TonyF · Jan 23, 2012

Bama67 said:
Hello all,

A couple months ago I finally built (or had built) my dream shop, 40'x60' 16' eave steel building. My problem is, if is rains for a day or two, the condensation inside is TERRIBLE. Normal weather, it is fine. I have insulation, the thin-foil backed stuff R-10 value. So the metal is not exposed on the inside.

I am talking about bad, it looks like it is raining in there. Not just the water pouring off the purlins and beams. But anything that isn't cloth or wood is basically dripping with the stuff. Metal, plastic, etc.

My polaris ranger and fourwheelers are dripping so much water in the floor they look like I just washed them. My gun safe is pouring it off, my tools are rusted....:

I occasionally have the same problem, but in a wood framed shop, tools, machines, cars all have moisture on them, I bought a free standing dehumidifier, ran a hose to a drain so it would not shut off when full, and let it run pretty much constantly, seems to keep most of the moisture at bay.
I also try to keep tools and machines coated with oil.

Tony

slowzuki · Jan 23, 2012

Dehumidify or heat the building during seasons with temp swings. After a cold snap, when a warm humid spell starts, it looks like someone turned on the hose inside. The areas where I insulated the slab aren't as bad but still get wet.

Western · Jan 23, 2012

I would say get the air moving, might test a couple of fans until you figure out what you need. You may end up with an intake fan or 2. I had a neighbor that had that problem and he put in 4 cheap ceiling fans (home type) and it made a huge difference only 20x20 shop). It is hard for moving air to condensate

Either way I think you need ventilation as the other guys have said, that is even a standard recommendation for house attics, they can have the same problem without air movement, but usually to a lessor extent since they get some temp abatement from the home structure.

Hollow · Jan 23, 2012

Bama67 said:
Thanks for the quick replies.

The entire building is insulated. It has that this stuff that has the radiant barrier on the outside, then like 1/2" fiberglass, then the white inside. R-10 value.

Sucks I have to keep it the same temp when it is cold outside. But I would rather work in the cold than all my stuff ruining.

Condensation should only happen when its colder inside than it is outside, right?

slowzuki · Jan 23, 2012

Yup, anytime its colder than the outside dew point you get condensation. Thats why just putting in ventilation isn't the solution. My shop is the worst when the big doors are open when its warm out and is still cold inside.

The fans don't stop condensation but they help stuff in the shop stay the same temp as the air so stuff doesn't condense on it.

EddieWalker · Jan 23, 2012

At any given temperature, the air can hold so much water. When the temperature drops to the point of 100% humdity, you get condensation. With a metal building, you get an inside temp and and outside temp that is seperated by a thin layer of metal. That metal transfers the lower temp to the higher temp and raises the humidity of the air to the point of creating moisture.

More air flow will help, but it takes quite a bit to accomplish anything. All you eves need to be open and a full ridge vent. Not just a cupola. You have to move a lot of air, and since air rises when it's warm, it will flow under your roof and out your ridge vent. This movement will minimize condensation.

Or you could increase your insulation. Right now, your insulation isn't doing the job. More insulation will seperate the two different temperatures from the outside and the inside enough to stop this from happening.

Last choice in my view would be to maintain the same temp or keep it warmer on the inside then the outside. I don't like this because it means using energy that will cost you money every month.

Do you have any pictures? I'm really curious about the insulation that you have in there now and why it's not stopping this.

Eddie