Is a metal ceiling going to be a problem with moisture in a heated barn?
Hi everyone,
I have a client which has asked us to complete his new pole barn project. The building has a truss roof, which has a metal roof (exposed on the back side), as well as the outside walls, which are exposed as well. His plans are to pour a concrete 5″ floor slab with radiant heat, over 4″ of XPS.
His plans are to spray 2″ of closed-cell foam on the inside against the back of the metal wall sheathing, then apply 3 1/2 more inches of fiberglass unfaced insulation. Drywall will then be applied finished and primed.
The previous contractor, which was hired only to build the shell, applied corrugated metal roofing to the underside flat portion of the roof trusses as to create a finish flat ceiling on the inside of the building. The plan is to blow 24″ of cellulose up on the back side of the metal ceiling.
My question with all of this is, does this metal ceiling present a moisture problem where water droplets will form on the interior face?
Thanks
Norm.
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Replies
Norman,
If the barn is heated, the metal ceiling will be warm. It shouldn't be cold enough to be a condensing surface.
I'm a little worried about a couple of things, though -- air barrier continuity and the fact that the spray foam is glued to the wall panels. Make sure that the air barrier is continuous, starting at the slab, up the walls, and over the ceiling. And if the wall panels ever rust, it's going to be very hard to replace them.
Is it a calving barn, or one that will house large animals, or many such as chickens or pigs? Will it be mucked out regularly, pressure washed? All things to consider when building an insulated barn. If you build a tight barn with a continuous air barrier make sure its adequately ventilated. Animals and organic matter will affect the humidity and air quality, making ventilation and make up air very important.
And I agree with Martin, about the continuity of the ceiling air barrier. Cellulose is an organic matter and will mold/break down over the long term if vapor is allowed to penetrate the seams/penetrations in the ceiling panels. Plus, cellulose is a good nesting material for rodents etc (even though it is usually treated, they will use it). Is spray foam an option for the ceiling panels? This would tie the wall and ceiling air barrier together, creating a tight envelope that would be resistant to moisture, pests and bacterial growth. But then you'd need to carefully ventilate.
I appreciate the feed back, Thank you. Just to answer the question on the use of the barn, which i apologize for not stating, It will be used for "Man toys",.... no live stock.
Norman,
As the old Vermont farmers say, "That's not a barn. It's an equipment shed."