# Insulating Pole barn



## HUBBHUNTER (Aug 8, 2007)

Can I put the foam board against the OSB like pictured below? (thats just a pic I found on line to show what I mean) I was told I would have to put the foam board on the rafters because of moisture issues but if I have the option I'd like to keep an open ceiling and easier access to store things in the rafters. Also, there is a ridge vent but no vents on the gable ends. Will that be enough for air flow?


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## Luv2hunteup (Mar 22, 2003)

You need to put an air space for ventilation from the eve vent up to the ridge vent. You have to have ventilation. You can also use insulation baffles between the roof boards and insulation. A vapor barrier between the warm space and insulation is recommended.


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## storman (Mar 12, 2008)

Yes you can do that houses and barns are spray foamed every day on the underside of the roof deck and many buildings have non vented nailbase insulation which is foam laminated to the wood sheeting as a composite.

Foam if sealed works great.

My home has had spray foam installed on sheeting with no venting for the last 12 years i have no ill effects no shingle curling cracking etc. I still have an attic space in parts of my home with drywall then dead air up to the sheeting and temps summer or winter are close to living space temp.

I do not have any ice dam issues either.

My pole barn is done the same way and has no issues as well.


Sent from my SM-N970U using Michigan Sportsman mobile app


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## Ronnie D (Dec 8, 2020)

I'd place an exhaust fan in that space. One hole termination and with a stove in that space you'll get a lot of moisture when the burners are lit not to mention the smoke and odors. A temp control in the eves will cycle it automatically and you can add a switch near the stove for manual operation. If ya need help on sizing one pm me and I'll give ya the specs.


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## HUBBHUNTER (Aug 8, 2007)

storman said:


> Yes you can do that houses and barns are spray foamed every day on the underside of the roof deck and many buildings have non vented nailbase insulation which is foam laminated to the wood sheeting as a composite.
> 
> Foam if sealed works great.
> 
> ...


I left out that there are soffit vents as well as the ridge vent.

So basically sealing up tight to the roof deck and trusses will be just fine?


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## bjacobs (Feb 8, 2007)

HUBBHUNTER said:


> I left out that there are soffit vents as well as the ridge vent.
> 
> So basically sealing up tight to the roof deck and trusses will be just fine?


Not always. The safest construction would be to have an air space between the roof sheathing and the insulation. Take the rigid insulation the way that is shown in the picture and install it flush with the bottom of the top cord of the truss. If you use 2" rigid it would leave an 1.5" air space all the way from the soffit vents to the ridge vents.

Putting the foam tight to the underside of the roof deck renders your soffit and ridge vents useless, and if you don't seal the foam perfectly, can create some moisture issues. Having an air space under the roof deck helps to alleviate any potential moisture issues. 

Get a box off shims and use that to temporarily wedge the insulation between the trusses and then use a can of one-component spray foam to seal the edges and hold it in. Then come back after the foam cures and pull out the shims and seal the gaps that the shims created. This also allows you (depending on truss heel size) to extend the foam out beyond the top plate and into the soffit area, which will ensure that the top of the wall is adequately insulated. I did this in my new construction barn last fall and then had the whole underside spray foamed and couldn't be happier.


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## MossyHorns (Apr 14, 2011)

I would be more concerned about the barn catching fire. A fire would spread very fast with exposed foam.


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## bowjack (Nov 20, 2011)

When researching a similar application I read that while you can use spray foam directly to the undersheeting like storman has ridgid foam needs that air space. I would nail a 2x2 cleat to the inside of the rafters to fasten the foam board to and allow for the air space above.


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## bjacobs (Feb 8, 2007)

MossyHorns said:


> I would be more concerned about the barn catching fire. A fire would spread very fast with exposed foam.


I agree to an extent. Polyiso foam would be better than polystyrene for that reason.


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## bjacobs (Feb 8, 2007)

bowjack said:


> When researching a similar application I read that while you can use spray foam directly to the undersheeting like storman has ridgid foam needs that air space. I would nail a 2x2 cleat to the inside of the rafters to fasten the foam board to and allow for the air space above.


I started with that "cleat" idea at first but ended up abandoning it for a friction fit. Installing the cleats seemed pretty time consuming and the friction fit held it in place good enough until the foam cured.


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## aphess223 (Aug 1, 2001)

This is probably more than you want to know it's the currant building code for State of Michigan it's three hours long
broken into 3 one hour video's this is just the first one.


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## bjacobs (Feb 8, 2007)

aphess223 said:


> This is probably more than you want to know it's the currant building code for State of Michigan it's three hours long
> broken into 3 one hour video's this is just the first one.


But the insulation part of the code most likely doesn't apply here.


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## aphess223 (Aug 1, 2001)

bjacobs said:


> But the insulation part of the code most likely doesn't apply here.


The only thing I was suggesting was currant best practice as the code is minimum requirement and they due talk about remodel or alteration.


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## brushbuster (Nov 9, 2009)

bjacobs said:


> I started with that "cleat" idea at first but ended up abandoning it for a friction fit. Installing the cleats seemed pretty time consuming and the friction fit held it in place good enough until the foam cured.


I did all mine with cleats


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## brushbuster (Nov 9, 2009)

I nailed1 inch cleats up then installed foil backed 1 inch foam board. spray foamed all the seams, then friction fit fiberglass batts. I did this on my house though and not pole barn.


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## TrailMarker (Dec 8, 2012)

MossyHorns said:


> I would be more concerned about the barn catching fire. A fire would spread very fast with exposed foam.


I wonder if the barn caught fire that the fire might spread quickly anyway? I mean, a fire is a fire, and I doubt the fire department is going to be able to save a pole barn.


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## MossyHorns (Apr 14, 2011)

TrailMarker said:


> I wonder if the barn caught fire that the fire might spread quickly anyway? I mean, a fire is a fire, and I doubt the fire department is going to be able to save a pole barn.


A pole barn doesn't have much wood like a house. Foam would definitely make it spread faster.


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## Waif (Oct 27, 2013)

TrailMarker said:


> I wonder if the barn caught fire that the fire might spread quickly anyway? I mean, a fire is a fire, and I doubt the fire department is going to be able to save a pole barn.


At least a fire would get the mice out of the foam.... Maybe.


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