condensation

[Awlknottedup]

This morning was a little colder than it has been in the last week after yesterdays rains. I went to the shop to continue work on the walls and I was greeted by rain, inside, sunny outside. Moisture was condensing on the underside of the tin roof, running down the metal to a purlin, then running down the purlin to drip on the floor. There was a row of drops under each purlin on the east side of the roof. No heat in the bbuilding yet and I had just entered.

It is typical pole barn construction for the Ozarks. 32' by 24', 5 by 5 poles on 8' centers, 4:12 trusses across the poles, 2X4 purlins on 24" centers, covered with tin, about 10 years old. I am insulating the building as a shop. I build a false wall between the poles of 2X4 studs on 24" centers. The stud bays are filled with R-13 insulation and the wall covered with 7/16 OSB. So far I have 6 of 13 sections between the poles completed and nothing on the ceiling yet. For the ceiling I plan to put 2X6s on 24" centers between the trusses, OSB or sheetrock on the inside then blow in insulation.

My question is how to deal with the condensation or will it stop when I complete the ceiling?

 

[willie in mn]

Your first sentence pretty much answered your question, high humidity with cold steel.
Ventilation now will get rid of the excess moisture.
You didn't mention it, but you need a sealed vapor barrior on the warm side of the insulation. Otherwise any high humidity will migrate to the cold steel surface, condense, & soak into insulation, making it worse than useless. If you don't have a vapor barrior now, remove all the OSB, add a sheet of plastic over the insulation. Fold over & tape all the seams to make it moisture tight, them put the OSB back on.
Key word is vapor barrior on WARM OR HEATED side of the insulation, keep insulation dry.
HTH
Willie

 

[S.Crum]

Are we safe to assume that you already have a concrete floor?

 

[Awlknottedup]

The floor is concrete, poured about 10 years ago. It is currently unheated, the outside temperature was heating up this morning and the interior temperature lagged a little.

 

[GordoSD]

I think you would really like a white tin ceiling with about 6 8 foot double HD cold weather florescent fixtures, one large industrial reversible ceiling fan. Then blow in the insul.

 

[WA-Hal]

I think you will continue to have condensation problems in your "attic" if you put a ceiling in the building. It might work to power ventilate the attic area really well. But what I would suggest doing is to remove the tin and add a thin insulation blanket/vapor barrier made specially for the purpose under the tin when you reinstall it. Even better would be to cover the purlins with OSB and tarpaper over that before reinstalling the tin.

The description of your building's construction would never hold up here. Once in a while we get lots of heavy snow loads, which I think would probably bring down a building like yours. Usually our pole buildings have 4 in 12 (or steeper) roofs to allow snow to slide off the metal exterior. 3 in 12 is a little too shallow for the snow to slide efficiently lots of times. I would also really worry about 2x4 purlins between trusses 8 feet apart being a little light, so we use 2x6's. But maybe the construction is fine for where you are.

I have built several pole buildings and will never build another one without either the insulation/vapor barrier blanket or full decking under the metal. The woodshed I built without either has condensation drips inside even though one whole side is open. Live and learn! Good luck.