Insulation, Radiant and Vapor Barriers - Insulating outbuilding

I want to add insulation to an outbuilding on my property, but it's a rickety old building. The siding is attached directly to the corner posts like a barn, and there are small gaps that let light through. I don't need to make this the Taj Mahal, but I'd like to foam the holes and install water-resistant insulation to make a slight difference when I need to be in there for an hour or more. Is there any kind of insulation that can hold up to a high level of moisture?

I'd attach a rainscreen to the inside of the siding, between the studs. Like tyvek, or building paper. Something to maintain an air gap behind the siding (to help the wood dry).

Then on this inside you can blow in closed-cell (water resistant) foam insulation. Or, if rainscreen is really well sealed, open cell (more flexible, to survive colder climates).

That sounds like a great idea. Thanks.

:confused: Will spray on foam cause an out building like a ( pole barn ) with metal walls to rust out if sprayed right on the metal interior surface? This is my fear. I been told by a friend that he knows someone who did this and in 5 years he had to screw new metal on the building and he blamed the foam. :confused: I see online where some co are spraying right on the bare metal.

Thanks
Rich

Foam on metal is climate specific. And yeah, if you don't do it right, 5 years could be all you get.

In warm climates, it'll work pretty easily.

In cold climates, the rigid foams can crack from the metal contracting, and these air leaks, if allowed to accumulate, allow moisture to condense on the metal. Flexible, softer foams won't crack, but need to be coated by a special vapor retarder coating in order to prevent moisture from accumulating inside the material.

The cut off is around 7200 HDD.