Another pole barn/insulation scenario

[katman]

I've got a 30x40x12 pole barn with t-111 exterior walls and asphalt shingles. The T-111 is nailed directly to the 2x4 horizontal stringers (no vapor barrier).

I've decided to insulate and I'm a little concerned about moisture entering through the lap seams of the t-111 and getting the insulation wet. Eventually I might put siding on the outside to match the house, but for now it will stay t-111. So, I've been thinking of putting a barrier up first, on the inside by stapling housewrap to the inside of the 2x4 stringers. Then I'll stud vertically, put fiberglass (kraft faced) between the 2x4 studs (on top of the barrier), and finnish the inside with OSB.

for the ceiling I'm probably going to foil the underside of the trusses and put up some furring strips on top of the foil. then I'll lay fiberglass down in the attic.

Sound like a workable approach?

 

[aerobb]

I sure hope it's workable, because that's exactly my plan.

 

[anojones]

This seems like a reasonable way to go, ideally the housewrap would be put on over the stringers and the t-111 on top, but so it goes. The housewrap if placed carefully will allow moisture from outside a place to go without getting to the insulation. It also has the added benefit of an air barrier to limit air movement and better insulate the shop. One thing I'd think about is where is the moisture going to go that gets in there? Having a pathway to the ground on the outside of the sill plate between the t-111 and housewrap would work or you may have enough air movement between the two for the moisture to dissipate. I actually did this under the windows in my pole barn where I get wind driven rain during heavy storms, it allows any moisture out without getting to the insulation or drywall.

 

[katman]

I am a little concerned about the moisture between the housewrap and T-111, but there will be a horizontal air "channel" created between the 2x4 stringers (they are about 24 inches apart) and the housewrap. Not sure how much the T-111 breathes, but the lap between sheets and the corners aren't air tight so hopefully that will work for venting.

Sure wish I had thought about this before the T-111 was put on!

BTW, heat for this is going to be anthracite coal. I recently switched out the wood stove and put an old stoker stove in and with no insulation I can maintain close to 60 on a cold day. Should get real nice once the insulation is in.

 

[Franz©]

So how do you plan to handle the water wicking up intothe insulation from the bottom?

T111 was made to be a siding material, with waterproof glue, and IF it was installed properly the seams self seal against water intrusion. If your seams aresufficiently open to present water intrusion problems, hang 6 mil poly between the outside wall and the insulation. The small amount of water that penetrates the seams won't pass the poly.

Upi need a poly boot at the bottom of bat insulation unless it's enveloped insulation.

 

[katman]

The slab was poured after the barn was up and is about 8 inches above grade. When I stud inside I'm putting a pressure treated 2x4 on the slab between the 4x6 poles. Regular 2x4 goes on top of this and is the base of my interior stud wall so the bottom of the insulation will be approx. 11 inches above grade. Never had a moisture problem on the slab. However, might not be a bad idea to let my housewrap sort of envelope the bottom!

 

[graphictree]

Ok....excuse my terminology if wrong.

I also have T111 nailed directly to the studs. This is new construction where it meets code, but not my code. The T111 has been sealed/caulked and stained.

I'm also worried about moisture problems. I already bought the standard insulation, paper back that comes in roles.

Now - can I cut 24" width pieces of tyvek and place them in between the studs? I guess I could attached them with a couple staples and then caulk the heck out of everything.

Just looking to avoid moisture traveling through the T111 and touching the insulation, but also knowing that the moisture inside needs to travel out. I have a vented propane heater, so the heat moisture goes outside. So interior moisture exiting is not the concern, it is the moisture from outside entering that I'm worried about.

any thoughts?

Thanks,

 

[Steve in Mi]

House wrap, Tyvek, and Poly serve different purposes - don't confuse them. Also DO NOT double a moisture barrier (poly) - use it on the warm side of the wall only.

The moisture you need to keep out of the insulation will enter the wall from the inside of the space.

 

[katman]

I thought the specs for the Tyvek-style housewrap said it permits moisture to travel through in one direction. That's why installation is supposed to be with the printed side facing outside. Is that wrong?

 

[anojones]

That sounds right- a vapor barrier over the insulation on the inside of the building (kraft faced insulation or poly) will limit the amount of moisture that travels from the inside heated area through the insulation as vapor. There will always be some moisture getting through, and it should be able to pass through the tyvek as vapor and then through the siding and outside. Moisture that gets in through the siding on the outside as water (windblown rain etc) will not be able to penetrate the tyvek, although I'm sure some vapor gets through. The tyvek acts as an air infiltration block improving insulation and protects the sheathing (or in your case the insulation) from water inflitration. Tyvek is a air barrier and water droplet barrier, but not a water vapor barrier and as such is used on the outside of the structure under the siding.

 

[katman]

Thanks. That is my understanding of how the product works,