Metal building condensation (help please)!

[lilranch2001]

I have built three steel sided buildings with and without insulation. My friend built two. FWIW the first year there seemed to be moisture inside then after that no problem. Not sure we had anything of the scale you are describing. Anyhow maybe it will lighten up.

moisture will work its way out of concrete for a year or two, but the first 3-6 months is the worst
How long has the building been up?

 

[slowzuki]

Some bad advice in the thread. Venting completely defeats the purpose of insulation and will not solve condensation on things like the slab and large metal objects like table saws or milling machines, tractors etc, and it can make it worse. Venting only helps when you have source of moisture inside the building (most shops don't have significant sources inside)

You need to heat it without introducing more moisture, just above the dew point (doesn't take much, 5 f above the outside air temp will work), or you need to dehumidify it to below the dew point. Fans, not outside venting, will help objects in the building stay closer to the air temperature so you don't need to heat or dehumidify as much.

 

[Bama67]

My shop is fully insulated, it is up against the metal, between the purlins and sheet metal. It is the foil faced, bout an 1" of some fill, then the thick white vapor barrier.

Rain is not the problem. No leaks in the rain.

The barn has been done 2 months, so alot could be coming out of the slab.

I got the building from Alabama Steel in Montgomery, they were very good to work with. My father in law, here in Elba (hays concrete) did the slab.

No heaters in there of any sort, except what heat the 12 8ft flouros and two 400w low bays put off. Which isn't much.

So, do you think a couple large fans circulating air inside would help?

 

[EddieWalker]

Some bad advice in the thread. Venting completely defeats the purpose of insulation and will not solve condensation on things like the slab and large metal objects like table saws or milling machines, tractors etc, and it can make it worse. Venting only helps when you have source of moisture inside the building (most shops don't have significant sources inside)

You need to heat it without introducing more moisture, just above the dew point (doesn't take much, 5 f above the outside air temp will work), or you need to dehumidify it to below the dew point. Fans, not outside venting, will help objects in the building stay closer to the air temperature so you don't need to heat or dehumidify as much.

I don't understand anything that you just said.

Are you saying that air flow on the underside of the metal roof will not stop the condensation?

What does a table saw have to do with condensation?

What does the concrete slab have to do with how much moisture the air can hold?

Eddie

 

[yelbike]

Some bad advice in the thread. Venting completely defeats the purpose of insulation and will not solve condensation on things like the slab and large metal objects like table saws or milling machines, tractors etc, and it can make it worse. Venting only helps when you have source of moisture inside the building (most shops don't have significant sources inside)

You need to heat it without introducing more moisture, just above the dew point (doesn't take much, 5 f above the outside air temp will work), or you need to dehumidify it to below the dew point. Fans, not outside venting, will help objects in the building stay closer to the air temperature so you don't need to heat or dehumidify as much.

Agreed. Good intentions but still bad advise.

The concrete will dry eventually. I don't know where you live but you need to insulate(R10 isn't much around here), create a vapour barrier. The spray foam works well for this but not cheap. You get what you pay for. Most of your moisture is likely coming from the outside, so don't bring in more air. It is counter productive.

Heating even only a few degrees will help. You could use an HRV but you'll need to add additional heat on the intake. I don't like this approach as I don't think you get enough of a return on the install(Not very efficient).

Once your properly insulated and sealed, then you can buy a good pump out dehumidifier. It will save your tools, cars and building.
Good dehumidifiers aren't cheap but they work very well and they last.

- LGR 3500i

 

[slowzuki]

-His roof is insulated, and yes, airflow from providing vents won't stop condensation.
-Table saw is representative of metal object in shop, could be wrenches, etc, the larger the mass the better "dehumidifer" it becomes when you let wet air into the shop.
-The concrete slab is mentioned because it is one of the huge things that get soaking wet when you start pumping outside wet air into a cold shop. Today after a cold spell it warmed up and rained today, the undercut below by shop door has standing water from the wet air blowing over the cold slab. It forms a condensing surface.

If I opened my shop doors up the entire shop would be soaked. Running a fan helps heat the slab up faster, but it can't change in temp fast enough to prevent condensation from forming on it.

Eddie, what is the climate like where you're at? Humid, dry, warm, cold? I'm talking about a wet climate with heating, not air conditioning.

I don't understand anything that you just said.

Are you saying that air flow on the underside of the metal roof will not stop the condensation?

What does a table saw have to do with condensation?

What does the concrete slab have to do with how much moisture the air can hold?

Eddie

 

[Rustyiron]

Ventilation? I have two 3 sided (3 closed sides) machinery sheds, one is 70'x24' deep, and another one that is a "lean to" shed attached to the side of a bigger bldg., it is also 3 sided, 64'x22 deep. They both will drip from the roof metal when conditions are right. I would cut in some gable end vents (each end) and call it done. This is an easy and cheap DIY job. After that you may need to look into the closed cell spray foam directly on the under side of the metal.
As I was writing this I thought about this, there might be another solution, heavy on the labor side but light on the material expense.... pull off the metal roof, add 1/2" osb and tar paper it. Add new roof purlins and put the steel back on. This is called a "cold roof" and should deffinetly fix it. A synthetic "shark bite" type felt substitute would be prefered. Hows that for a crazy answer!

 

[Garybake]

My shop is fully insulated, it is up against the metal, between the purlins and sheet metal. It is the foil faced, bout an 1" of some fill, then the thick white vapor barrier.
Rain is not the problem. No leaks in the rain.

Your thick whit vapor barrier is not a good seal. Think reverse Tyvek on outside house for drafts. Eliminate air to metal with vapor barrier may save a lot of bucks. Wood firring runners to tyvek to so no metal contact on other side of barrier (transmition of cold).
Think of cold bathroom window and cheap but well sealed plastic over it. Tools will still get damp on humid warm day and inside is cold but it will stop rainning on you.
Gary

 

[slowzuki]

Awful lot of work to revapour barrier a building when it won't solve the problem of the wheelers and tools getting wet.

 

[Georgia Peach]

We had a pole barn built last year with 2" of insulation and a concrete floor. At first there was alot of condensation but after we sealed the concrete most of it went away. We put a piece of piece of plastic on the floor and the next day removed it and it was dry underneath. Before the sealer was put on it would be sopping wet. We also installed an agricultural fan and insulated the doors. Now the only thing we get is dust because the tractor brings in mud, the mud dries and we're left with dust.
Our place is in Westen Washington on a river and gets losts of drizzle and stays damp(outside) all the time except of the 10 days of summer we get.
If nothing else I think you will see a hugh difference after you seal the concrete. We sure did.

 

[Bama67]

i thought about sealing the concrete with epoxy. But figured I better let it dry out some more before I do it.

 

[Oldstuff]

Bama- I have an unheated 12 ft by 20 foot totally enclosed metal building. NO insulation of any type. It had some sweat and also in the warn weather a Mold or mildew or something started to form as a film or dusting on everything. I put in a 8 in by 16 in vent up high on each gable end to get some air moving thru it and it helped. I got to thinking about where can the air come from that is to be drawn in and then put in two 6 by 16 inch vents on opposite sides about 6 inches up from the rock floor and Eureka- no more sweat and mold or what ever it was. You must have air movement. Same principal in your attic- that is why they are vented.

Oldstuff

 

[earljr59]

I Wonder if your father in law put down a plastic barrier under your concrete slab? I am not sure about your area, around here plastic below and sealer on top of floor . As others have said ceiling fans moving some air will be an important addition. When you can afford to add even a little bit of heat later on somehow to help the fans,you will be just fine.One of my old buildings doesnt have a plastic vapor barrier under the floor,or sealer and the floor will sweat when conditions are just right. Good luck,we all hate it for you.

 

[Deere Dude]

If it were me, I would talk to the company that put your building up and see if I possibly could get in touch with others with the same type of building within a 30 mile radius. I'm sure they have the same humidity situation that you have, and went through all of this beforehand and compare notes.

I would also just drive around the countryside and ask others how their buildings are working out.
I sure would hate to rip anything apart or add something expensive without making sure it is correct beforehand. There is a lot of good advice on this forum but just picking out the correct one could be difficult.

 

[EE_Bota]

You don't by chance have a ventless gas heater in there do you?

Regardless of the answer, that is a very good question!

 

[slowzuki]

Not really, at least not in a cold climate, the attic is vented so the roof stays cold preventing the snow on top from melting and sliding down to the eaves and freezing forming ice dams.

You should not be dumping moisture into your attic, ie if you have a dry or shower fan that dumps there it should be dumped outside. Venting lets you get away with this for a while but it will mold eventually.

You must have air movement. Same principal in your attic- that is why they are vented.

Oldstuff

 

[Sutol]

I have a corugated metal roof on my garage at home and the building is prety well draught proofed with no vents.
The garage has been built for 26 years and I have a condensation problem.

the roof is about ten feet off the floor and if the sun gets on the roof after a cold night condensation drips from the metal roof quite badly.
This soon drys up if the weather is nice and is not realy a problem unless I have just painted something and left it overnight to dry.

Anyway the reason I am posting is because we have just put a corugated metal roof on a building at the farm and we are worried that it may have a condensation problem just like my garage.

The metal sheets are plastic coated but we haven't had a sunny morning yet so not sure how bad the condensation will be.

We were thinking of insulating the inside of the roof but not sure if that is nesessary , we have put vents in the gable end at the top and about two feet down so as the air will flow in and out just like the wasps will do

Any ideas ? I have read the full thread but its not quite the same problem.

 

[lilranch2001]

i thought about sealing the concrete with epoxy. But figured I better let it dry out some more before I do it.

you should not put epoxy on high moisture concrete, it will surely fail and delaminate

 

[forgeblast]

take a piece of plastic and tape it to the concrete, wait a day or two and peel off the tape, if there is condensation there you know its coming up from the floor too.

 

[EddieWalker]

take a piece of plastic and tape it to the concrete, wait a day or two and peel off the tape, if there is condensation there you know its coming up from the floor too.

New concrete takes several weeks to get to a dry point that it's dry and strong enough to work on. After a month, it's almost cured and about as dry as it's going to get.

The test you are describing has nothing to do with condensation. It is to see how much moisture is left in the concrete. They do this on TV all the time because it's a fun trick to show people watching the shows. It also shows that if you install flooring too quickly after a new pour, that there may be moisture issues.

It does not tell you if you will form condensation on your metal roof, nor is it related to what is happening on a metal roof.

Condensation - Wikipedia, the free encyclopedia

What causes condensation?

Eddie