Pole barn Vapor barrier or Not????

[Streetglide11]

I just completed a 40x60x15 pole barn with double bubble on the roof but no vapor burrier on the walls. I plan is to use R-19 faced batt insulation for the wall and finish with T11 or metal not sure yet. My question is can I use the faces batt against the metal or do I need a vapor burrier. I'm not concerned about being air tight I just don't want mold. Thank you

 

[Marctrees]

Street - Your location (climate) totally affects this answer day and night.

Add location to show under your name.

Marc

 

[Streetglide11]

I'm in Maryland we have mild winters with hot humid summers

 

[Streetglide11]

I also have 2 ridge vents and 12inch soffit all the way around

 

[Highbeam]

You're asking if you should use faced batts AND a second vapor barrier like plastic?

No. Double VBs are no bueno.

 

[Marctrees]

In all climates, all situations, multi layered w insulation between vapor barriers is not recommended.

One exception would be... Sometimes folks have Kraft faced fiberglass insul, and that face includes a hiding between paper layers a tar "vapor barrier"

In that case, depending on situation, it is recommended by authoritative sources to slash w a razor the Kraft all over, to allow vapor permeation. Marc

 

[Marctrees]

I just completed a 40x60x15 pole barn with double bubble on the roof but no vapor burrier on the walls. I plan is to use R-19 faced batt insulation for the wall and finish with T11 or metal not sure yet. My question is can I use the faces batt against the metal or do I need a vapor burrier. I'm not concerned about being air tight I just don't want mold. Thank you

Actually... YES, you can put the paper face against the steel.....BECAUSE... the steel is acting as a vapor barrier.

Sure, some water vapor can go through the overlapped un sealed seams, but it's minimal.

Don't listen to me, or "us" here, and definitely not Grandma... Google "Vapor Barrier" and read tech articles, NOT like idiotic **** from "Houzz" or something.

Go to "ORNL".... Oak Ridge National Laboratory....Learn who they are, what they do, THEN search "Building Envelope vapor barrier" to learn about this..... then make up your own mind. Marc

 

[Streetglide11]

Thanks I will be using face batt insulation and my concern is the metal will sweat causing the back of the insulation to get wet then I will have mold. I am going to be using OSB on the inside of the building so the faced back of the insulation will be on the metal side.

 

[bullnerd]

Doesn't the VB always face the heat source? In this case the inside? If you heat it.

You can see how I did mine in my sig. I'm no pro, but I did copy Morton, one of the biggest builders of pole barns.

Also, there is a space between the insulation and the metal. I don't want anything touching the metal anywhere if possible.

 

[theoldwizard1]

2" of spray foam will give you a vapor barrier and seal all air leaks. Then apply what ever additional insulation.

 

[Streetglide11]

Spray foam is not in the budget but thanks

 

[yeldogt]

I though that was why they used the fully encapsulated product on metal pole barns. It basically isolates the insulation form all moisture. The metal can't be a VB -- it's going to allow moisture to leak in -- but will trap moisture in the panel middle of something is tight against.

We don't have many pole buildings around me and the few we do are utility use -- typically with said incapsulated insulation and then wood boards for interior.

 

[Streetglide11]

I'm not really sure what your talking about

 

[lakeroadster]

Actually... YES, you can put the paper face against the steel.....BECAUSE... the steel is acting as a vapor barrier.

Sure, some water vapor can go through the overlapped un sealed seams, but it's minimal.

A lot of water vapor.. not just some. Especially if the building has wainscotting. Steel sheathing allows a lot of air flow through all the joints, and where there is air flow there is moisture.

Putting the paper face out is a bad idea.

The best plan would have been a building wrap before the steel was put on... At this point.. maybe do this..

Got to spend some time today working on sealing up the siding gaps. Basically the goal here is to seal the siding at the bottom and at the wainscot to keep insects and wind out.

I'm using some Sika 3/4 in. Closed Cell Backer Rod (Home Depot) to close up the large spaces, and will then use Great Stuff spray foam, the pest repellent type.
__________________
The Gaps

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The Backer Rod


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Should get around to spraying some foam tomorrow.

Great Stuff won't break down unless subjected to UV.. it, just like all spray foam, is supposed to be painted if it will be subjected to sunlight.

I'm not worried so much about rodents as I am insects.. and wind. But to your point, at least with it there, those vermin will have to eat their way through it.. as opposed to coming right in, unobstructed.

GREAT STUFF(TM) Insulating Foam Sealant PESTBLOCK is specifically made for insects and pests and the marketing data states it "contains a bitter ingredient". It's a light gray color.. looks different than the standard Great Stuff.

Speaking of which.. I used 3-1/2 cans of Great Stuff Pestblock today to seal up the lower closure to siding gaps, as well as the gaps at the wainscot.

 

[Marctrees]

I made a mistake with the quote below from my Post #7 ...

"Actually... YES, you can put the paper face against the steel"

If you would be in a clearly hot humid climate, then that MAY have been correct.

The way I understand the latest vapor barrier thinking is - Hot humid - vapor barrier to outside. Northern heating states like MN - vapor barrier to inside.

But in MD, you may be BETWEEN those two extremes.. SO- you might fall in the climate where NOW they are saying you may be best to not have ANY vapor barrier, but just an air infiltration barrier like Tyvek on the outside.

You need to study it as I suggested above. Marc

 

[theoldwizard1]

Spray foam is not in the budget but thanks

Only 2" ! Best vapor barrier you can get for metal siding. You can do it in 2 steps. Do the foam this year and the rest when funds arr available.

 

[Streetglide11]

I have spoken with a few spray foam guys in my area and they don't recommend it in pole barns and when they did do it they only sprayed 1in. It's also not in the budget and I don't want to go that route if it was in the budget. Spray foam is out of the question for me. Thanks

 

[lakeroadster]

You need to study it as I suggested above. Marc

More below..

Only 2" ! Best vapor barrier you can get for metal siding. You can do it in 2 steps. Do the foam this year and the rest when funds arr available.

That's a fire hazard..


Green Building Advisor, RE: Spray foam applied directly to steel siding

Q. "The contractor is planning to apply the open cell foam directly to the metal siding. Will this be a problem?"

A. The main problem with this technique has nothing to do with vapor diffusion. The main problem is that when some of the metal panels that you are using for siding begin to rust -- a phenomenon that usually starts at the bottom of the panels, which are subject to regular wetting due to splashback -- it will be very difficult to replace the rusting panels. The spray foam will glue everything together.

Q. "What will happen to the condensation?"

A. There shouldn't be any condensation. Because the metal panels won't absorb moisture, I doubt if you will have any problems. But the usual advice for buildings with wood sheathing, OSB sheathing, or plywood sheathing would be that you need an interior vapor retarder if the building is located in Climate Zone 5 or anywhere colder.

Q. "Will I need to add a vapor barrier?"

A. No, you won't need a vapor barrier. But you will definitely need a layer of gypsum drywall on the interior side of the spray foam for fire safety reasons. (Most codes require this barrier.) The drywall should be taped. It wouldn't hurt to install a layer of vapor-retarder primer (paint) to the gypsum drywall. A vapor retarder is a less stringent layer than a vapor barrier.

Read more: http://www.greenbuildingadvisor.com...foam-require-additional-vapor-b#ixzz4oi352lPx
Follow us: @gbadvisor on Twitter | GreenBuildingAdvisor on Facebook

 

[Huntdux]

Whoever built my pole barn stapled plastic on the inside of the framing with paper faced fiberglass insulation behind the plastic on the walls AND CEILING! OSB walls. So picture OSB-plastic-insulation (paper side in)-Steel. Then picture green stuff growing on your wood handled tools. Here in East TN summers are HOT and HUMID! Winters can get cool at times and are much drier. Most things I find say to put the plastic on the heated side which could be either depending on the season. So I'm in the process of ripping down all the plastic from the ceiling now and trying to decide whether I should leave the plastic behind the OSB or rip it out too. All that to say, it sounds like you're in a similar boat.

 

[Marctrees]

Huntdux - If you AC cool your interior, ---In your location --- .....it is best to not have that interior vapor barrier.

If you do NOT cool the interior, I'd leave it alone as good enough, still not ideal... but I'd leave it IF no AC inside. Marc

 

[Marctrees]

Hunt - An option for incorrectly placed VB, whether Poly, Kraft( it has "tar" layer inside)
is to slash all over w razorknife.

That may help some if the VB is exposed, but not if covered.

For example, one could, in some cases, leave a poly in place that makes the whole wall "cleaner" while holding back insul, by carefully slashing in a pattern, NOT "ALL" over criss crossing like a Drunken Sailor ( or Drunken Marine, or Drunken Grunt, or any Drunken Service member of choice... including a Civilian Drunk)

But behind OSB, I dunno, what a PIA mess.

That's the only reason I say leave it as good enough (far as I know, and I HAVE studied this) if it's covered, not accessible. Marc

 

[bdk1976]

Not sure if you're aware, but they make closure strips that match the profile of the ribs in the metal and will fit/seal a lot better than your foam rod solution and likely won't require spray foam to fill the gaps.


Sent from my iPhone using Tapatalk

 

[Huntdux]

Thanks Marc. I'll look into all of this.