# what insulation to use for a pole barn ?



## Guap0_ (Dec 2, 2017)

I don't anything about that insulation except for the quick google search that I just did. The first thing was that it's made from polyurethane. I'd be concerned with outgassing. When spray foam first started in the 60s, 60 Minutes had a segment on it. A family had to leave their home due to the smell. I know that they have drastically improved over the years but I would be concerned with polyurethane.


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## Windows on Wash (Aug 30, 2011)

Foam is going to be at least 2X to your fiberglass cost. 

If you aren't living in the space, I see no reason to foam it.

You can use Roxul and a combination of rigid foam (exterior sheathing) to get better performance than the standard fiberglass.


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## Porsche986S (Dec 10, 2017)

Windows on Wash said:


> Foam is going to be at least 2X to your fiberglass cost.
> 
> If you aren't living in the space, I see no reason to foam it.
> 
> You can use Roxul and a combination of rigid foam (exterior sheathing) to get better performance than the standard fiberglass.


That is kind of what I thought but needed to hear it from someone else :biggrin2: I'll go conventional R19/R21 and maybe some 1/2 " foam on the exterior before my final exterior siding . Thanks for the reply .


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## dmorean (Jan 18, 2018)

How did this work out for you?


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## Porsche986S (Dec 10, 2017)

dmorean said:


> How did this work out for you?


I'm not ready for insulation yet I'm still installing plywood on the exterior . The cold weather has slowed me down . But I will go with either R19 or R21 Kraft faced insulation and house wrap on the exterior before the siding . But I'm quite a ways away from that after I get it sheathed then I have to arrange getting the electrical installed .


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## Porsche986S (Dec 10, 2017)

Next set of questions is regarding what to do for ceiling/attic insulation . Being a pole barn the construction is 2 x 4 rafters set at a spacing of aprox. 5 ' - 6 ' apart . On top of the rafters are 2 x 4 perlons laying on their sides and screwed to the rafters . My plan is to go with full length ventilated soffits on both sides of the building . 

1.My original plan was to staple to the bottom of the rafters some 4 ' wide reflective barrier . I have enough left over from my previous garage to do this one . My intent with the foil barrier is to reduce or eliminate any condensation . I would then insulate the ceiling with conventional fiberglass insulation I believe kraft faced for the first layer . I would insulate to R30 .

2.Alternate plan would be to install 2 " thick poly iso foam panels on the perlons or rafters . If I were to mount the foam to the bottom of the perlons the air gap would only be the offset of the raised ridges of the metal roof panels is that enough ? The other way I could install the iso panels would be to install maybe a 1.5 " wood spacer on the rafters but tight to the bottom of the perlons , this obviously would create a 1.5 " air gap which I would think would flow air better from soffit to ridge vent .

I can get 2 " used poly iso panels locally for around $16.00 per panel and they are around R15 - R16 . If I went with the poly iso panels I would still insulate the ceiling but I " think " I would not have to go with R30 maybe I could go with R19 ? So from an overall vapor barrier and insulation standpoint which way would you go ? Or is there a better way than the two I described ? The ceiling will be white metal roofing panels and the space will be heated/cooled . And like anyone else I need to control costs the best I can :biggrin2:


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## Bryan n Deb (Jan 7, 2018)

I am planning a pole barn house and I talked to a guy here who said he would probably do 3 inches of foam in the walls and blown in in the ceiling. Walls being over 6 inches will there just be airspace as well?


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## user_12345a (Nov 23, 2014)

Don't use paper faced insulated, use a proper vapour barrier.

If you put foam on the outside, watch out - the wrong type not made for that use will trap moisture and prevent drying. With a complete thermal break it's not nearly as important due to reduced condensation risk, but still best to have drying potential.

There's a product called roxul board and can be used on exterior to reduce thermal bridging. It's very safe, doesn't burn, has good drying potential, a great alternative to foam.

Roxul in general is a fantastic material, at least on paper. The r-value per inch is lower than foam but higher than fiberglass - their 2x6 batts rate out at R24, put R5 to 10 on the outside and it'll be a very energy efficient structure.


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## Porsche986S (Dec 10, 2017)

Maybe I'm not explaining properly so let me try again . I am only talking about ceiling insulation/vapor barrier and the control of possible condensation on the bottom of the metal roof panels . If I staple the 4 ' wide reflective barrier to the bottom of the 2x4 rafters there will be an " air space " of 5 " to the bottom of the roof metal . If the eaves have full soffit vents and the roof peak has a full length vent will the ventilation and the barrier be enough to stop condensation ? This would be above a metal ceiling and R30 kraft faced conventional insulation . The garage space below the ceiling will have AC and heat . 

The 2nd way I'm thinking about doing this is take three 2x4's laying flat and mount them to the bottom of the perlons in each cavity between the rafters running from the soffits to the peak of the roof . That would give me a surface to install the 2 " poly iso panels to AND will provide an air space of 3 " to the bottom of the metal roof panels . Again the same ventilation as above . In this scenario I " might " only have to insulate the ceiling with R19 to still have R30 + in that space because of the poly iso . In both scenarios kraft faced insulation would be directly in contact with the metal ceiling panels . 

So which of these methods would give the best results for control of condensation and insulation value ?


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## user_12345a (Nov 23, 2014)

Roofs are different, no drying potential.

Foam is best, complete thermal break - i wouldn't bother with batts, especially with kraft paper.

Paper faced batts aren't available in canada - the paper doesn't work. Americans are behind and have worse regulations.

Need a proper plastic vapour barrier, properly sealed when using batts, but with a roof, it's not a good way to insulate because of the lack of drying potential.

I wouldn't do a vented roof with insulation at the deck, that's reserved for normal attics. The air movement behind the insulation will render it less effective, especially if batts.

The platic barrier never goes on the cold side.


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## Bryan n Deb (Jan 7, 2018)

user_12345a said:


> The plastic barrier never goes on the cold side.


Heres my wifes question. What side is the cold side? Winter or summer?:vs_laugh:


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## user_12345a (Nov 23, 2014)

^Is it more extreme in the winter or summer? That determines which side it goes on.

In the summer, if you have a dewpoint of 72 outside - pretty high, to get condensation issues inside it would have to be kept below that temp.

In the winter, in any climate that has real winters, the indoor dewpoint at like 70 degrees would be well above the outdoor temp, so barrier needs to go on the inside.


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## Porsche986S (Dec 10, 2017)

I believe my building is the same as a conventional stick built building it just started life as a pole barn . All four walls are studded with 2x6 studs . There will be CDX plywood installed on the interior and exterior of those walls . There will be R19 or R21 kraft faced fiberglass insulation in the stud cavities . Exterior will get house wrap and whatever final siding product I choose . So in every way a conventional build .

The only difference in the roof is it is metal panels installed on perlons vs. a plywood decking . It has a full length ridge vent and will have full length soffit vents on both sides . Air movement should be sufficient for North Ga. climate . I have made up my mind I am going to staple the radiant barrier I have to the underside of the roof rafters and use R30 insulation on the ceiling . Thanks everyone that chimed in .


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