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Discussion Starter #1
30x40 steel pole barn with wood frame and trusses, located in eastern Nebraska, 13' to the bottom of the trusses. I've been building 8' wall around shop so I can run electrical, put in workbench, and mezzanine. Insulating the walls with R-19 fiberglass batts, covered by 7/16th OSB. Did not include a vapor barrier in the walls.

I did use spray foam to seal gaps / seams at bottom of walls and at the wainscoting before building walls.

Down the road I would like to finish and insulate the walls up to trusses, then install ceiling at bottom of trusses, blown in insulation above that. Will likely heat the shop only...no AC plans at this time.

Been reading and considering vapor barriers and have seen different opinions.

Based on my climate "Zone" the local extension suggested putting a single vapor "retarder" on the inside of the walls, between heat source and insulation. They also said vapor barrier not necessary or required.

Other message boards are big on vapor barriers, suggesting they are needed.

Your thoughts on vapor barriers?
 

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If the walls are still open it is cheap.

If doing full spray insulation it is probably overkill but it looks like you sprayed the gaps and such and are doing batt insulation (if I read that right). In that case and you haven't put anything up on the walls yet (sheetrock or whatever you are doing on the inside) then I would put up a VB. If you already did rock the walls (or OSB I think you mentioned) then it might be a lot of work to go back and do it now. You probably won't see much return on your investment (mostly time and labor) at this point to mess with it.

For what it is worth my garage build is the same size space and I will be doing a VB before it is rocked. My ceiling is a bit lower (10.5') but that doesn't change much. I am a little on the fence if I do full spray insulation vs batt for my walls. Most likely will be a combination like you did and if that is the case then I will for sure do the VB.

Another thing we did is all electrical boxes are the barrier style with a foam seal against the rock.

Like these.

Arlington FN102F Switch/Outlet Box with Vapor Barrier, 2-Gang, Nail-On: Amazon.com: Industrial Scientific
 

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Vapor barrier. :good2:
 

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In my opinion, whenever you have a heated building envelope you should have a vapor barrier. Without it, warm humid air infiltrates into the insulation, and the moisture will condense out as the air cools.
 

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In my opinion, whenever you have a heated building envelope you should have a vapor barrier. Without it, warm humid air infiltrates into the insulation, and the moisture will condense out as the air cools.

exactly rendering the insulation much much less effective....IE typical house batt insulations have a VB on the living side of things..
 

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I’ve done spray foam insulation on two steel buildings now. It’s worth every penny if the walls are still open. I wouldn’t be without it.
I thought spray foam insulation has the built in properties of the vapor barrier... :dunno:
 

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I thought spray foam insulation has the built in properties of the vapor barrier... :dunno:
I read it as he used the crack filler type spray foam, for filling gaps he had. True spray foam insulation, ie, covering the entire wall, etc. does not need a VB. Blown in insulation should have a VB. It doesn't cost much and it sure won't hurt anyway.
 

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Discussion Starter #9
Here are some pics...

Walls are built, insulated, and faced with OSB.



Sent from my SM-G930V using Tapatalk
 

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Your insulation is faced. That will be good enough for your application.
yep the faced will work fine...


personally on mine i went with a plastic bagged type as shown....my thoughts were it might provide a additional layer of moisture proofing from the exterior metal sheeting if needed....if i did it again i would use the closed cell foam but this works well and is easier to handle
 

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Discussion Starter #15
Hit Menards this weekend, loaded up on lumber and got 2/3rds of the mezzanine built. Tricky getting those first beams up by myself. But managed to get it done.

Buddy has a 40x60 pole barn, and had mezzanine installed when it was built. I modeled mine after his...three 2x8's screwed together are the main beams, 2x6's @ 16" on center. 3/4" tongue and groove OSB for the floor. Posts are three 2x6's screwed together. Heck, the whole damn thing is screwed together...not a one nail in it.

My retired carpenter Dad is going to help lay out the stairs that will run up the left side near wall. I'm happy the way it turned out.

A few repairs to the boat cover, then it will be moved outside...and the Green Truck project will start...
 

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Looks good.:bigthumb:

The rest of it gives me flashbacks.:mocking:
 

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Please keep us updated on your green truck project!!

Back to the vapor barrier question, I would be hesitant to use a traditional plastic vapor against metal siding.

The moisture would have no where to go, thus causing big problems down the road.

When I had my 30x40 pole barn built, I used spray foam on the walls and roof, made a huge difference!!
 

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As an inspector I don't have much to offer!!!!.. Remember VB's go on the heated side of the building not up against the outside sheathing as just stated. We have strict codes here in Ma and I am also a stretch code town so air sealing is also a must, not just a VB. Some spray foam insulation is not resistant to water infiltration and the manufacturer will state this in the literature of the product.. Most say to cover the foam with 1/2" sheetrock and low perm paint.. Guys around here use 6 mil poly and air seal boxes like the boxes listed above in one of the posts. I am not a fan of paper VB's, no way can you actually seal the paper to the air seal type box,, poly just goes right over the entire project and when the drywall guys come and cut the boxes out the poly is not compromised and no heat or air movement goes into the insulation around the boxes,, which is where you have the problems.. A cheap lousy insulation job is what rots plates in the walls, sheathing and siding along with the paint job on the siding.. Think of it this way,, warm air gathers on the outside walls if not done correctly and condensation develops with cold temps and then you have issues...
There are lots of web sites devoted to proper VB's and air sealing.. I would suggest anyone thinking of this go to one of those sites.. Your energy company will no doubt have one of those sites..
Good luck and to answer the question would I use a VB... Yes if you are heating the structure, especially with fiberglass. And no if you are using the spray foam the spray foam doesn't demand it.. My own home is an energy crafted house I built back in the early 80's and I have never had a ice dam or rotted anything. It works if properly done. Remember some of the foam is also not fire rated, so if you leave it exposed it may burn and emity toxic smoke,,, read the manufacturer's specs before you run into more than you bargained for. My .02 Don't beat me up, I'm only repeating what our codes state and 30 years experience as a builder before I retired to be a full time inspector..
 

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As an inspector I don't have much to offer!!!!.. Remember VB's go on the heated side of the building not up against the outside sheathing as just stated. We have strict codes here in Ma and I am also a stretch code town so air sealing is also a must, not just a VB. Some spray foam insulation is not resistant to water infiltration and the manufacturer will state this in the literature of the product.. Most say to cover the foam with 1/2" sheetrock and low perm paint.. Guys around here use 6 mil poly and air seal boxes like the boxes listed above in one of the posts. I am not a fan of paper VB's, no way can you actually seal the paper to the air seal type box,, poly just goes right over the entire project and when the drywall guys come and cut the boxes out the poly is not compromised and no heat or air movement goes into the insulation around the boxes,, which is where you have the problems.. A cheap lousy insulation job is what rots plates in the walls, sheathing and siding along with the paint job on the siding.. Think of it this way,, warm air gathers on the outside walls if not done correctly and condensation develops with cold temps and then you have issues...
There are lots of web sites devoted to proper VB's and air sealing.. I would suggest anyone thinking of this go to one of those sites.. Your energy company will no doubt have one of those sites..
Good luck and to answer the question would I use a VB... Yes if you are heating the structure, especially with fiberglass. And no if you are using the spray foam the spray foam doesn't demand it.. My own home is an energy crafted house I built back in the early 80's and I have never had a ice dam or rotted anything. It works if properly done. Remember some of the foam is also not fire rated, so if you leave it exposed it may burn and emity toxic smoke,,, read the manufacturer's specs before you run into more than you bargained for. My .02 Don't beat me up, I'm only repeating what our codes state and 30 years experience as a builder before I retired to be a full time inspector..
You are correct regarding placing the VB towards the heated area, I mistyped what I was trying to say. I still question having a plastic or non permeable material trapping moisture in a steel sided building.
 

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You are correct regarding placing the VB towards the heated area, I mistyped what I was trying to say. I still question having a plastic or non permeable material trapping moisture in a steel sided building.
It's ok to have issues with this question. Look at it this way, when you buy a steel structure they also sell the insulation for these structures and on a daily Basis, and that insulation has a VB on the inside of the insulation and in fact the insulation is applied along with the roofing and side walls at the same time so no penetrations are letting the transfer of water vapor to the steel outsides.. There is a reason for this and it is also engineered that way.. It's the transfer of water vapor that causes an issue with any sheathing, steel, wood, etc. That's why it's important to have a well sealed VB on the heated side.. I've seen the argument for both; no VB and yes imperative you have a VB.. it all depends on who you listen too,, our code requires it in our region for freezing issues plus our wonderful stretch code requirements.. Which we fought as inspectors.. we already have a pretty strict energy code so why do we need two codes? But people a lot smarter than us say so! :laugh: We lost the battle but we haven't totally lost the war yet! From field experiencing thousands of homes and also 46 years in this business that tells me a lot about how to build a safe, healthy house or structure.. Our electric company has been testing all types of conditions, houses and materials since the early 70's so they are pretty much convinced this is the way to go.. They want to save energy and also build safe healthy structures, so I guess I have to believe them... MY house is a good example and in fact it was being used as a model home by those people when it was being built. My barn and garage are built the same way except I used 18" of Cellulose in the attic of my garage. All wood structures. I Only have one steel structure and it is not heated nor insulated, storage only.
Build on....
 
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