Pole Barn insulation

[12voltsguy]

I recently had an uninsulated pole barn constructed. The roof has double bubble installed on the underside of roof sheet metal. I'd like to install a 1.5" foam insulation between the roof purlins then add a 6" vinyl faced blanket insulation to fill the top truss area. I was told the double bubble and vinyl face would create a dual vapor barrier and could possibly create moisture between the two. Does anyone have any experience with this? Should I remove the double bubble before installing the foam and faced blanket insulation?

 

[billconner]

I don't know your climate. If a heating climate and if a house with normal house activity, certainly a potential problem.

If moisture - air - gets past vinyl and past to the foam, it's likely to condense on the bubble wrap. Seems that the vinyl will be leaky. The rigid foam however - at least XPS or polyiso - might be enough to prevent condensation. Ideally, you might spray foam the purlins and foam.

And how warm and how consistently will you heat this space? Do you have a vapour barrier under slab? Do you store firewood in this space? Other moisture producers?

Probably safer to remove bubble but hard for me to be sure.

 

[12voltsguy]

Thank you for the reply. I'm located in mid state PA. We have fairly cold winters 20's - 30's but can fluctuate lower. I have 8 mil plastic sheeting covering under concrete with 4' foil bubble around perimeter folded up the entire 5" edge of concrete. There is 2" XPS foam on top of plastic and bubble foil. The concrete pad is 30'x40' with 4 sections of pex for future radiant heat. The building is not a full time residence, but have been using as 3 season getaway. Hopefull for winter use after insulating. I do not store wood, but do have indoor plumbing. A few pictures of floor attached.

 

[lkempf]

Can't answer your question, but i like your building. The trusses being built like that really make it seem more open.

 

[billconner]

I'm not sure. I think the foam against the deck makes that a vapor barrier - with or without the bubble wrap. Or, the foam makes removing the bubble wrap unnecessary. So is there a problem with foam against exterior an vinyl against interior, and I believe there is. Some of the most touted wall systems use continuous foam on exterior but no vapor barrier inside - cellulose or fibreglass with just drywall and latex inside so wall moisture can dry to the inside.

No solutions, but I think you could could have a problem with foam and vinyl.

 

[kj_mustang]

Are the soffits vented and do you have a roof ridge vent?

 

[12voltsguy]

Are the soffits vented and do you have a roof ridge vent?

There is a ridge vent and a cupula. Soffits are not vented. My original plan was to just use the vinyl faced blanket insulation without foam, but was told that could leave air gaps. I'm guessing near the purlins

 

[kj_mustang]

You have a couple decisions to make. If you put in a ceiling, then you created a space that will need to be considered. You have a ridge vent with no soffit venting so that newly created attic space can not vent well and moisture in the attic air becomes a concern. If you block off the ridge vent and insulate at the roof line, then you need to condition the inside air to control moisture levels.

 

[billconner]

Is your plan to leave the vinyl exposed?

 

[12voltsguy]

Is your plan to leave the vinyl exposed?

Yes, my hope was to leave the vinyl exposed. I like the openness feel of the building. I like seeing the exposed trusses.

 

[billconner]

I don't know how good or complete of a vapor barrier the vinyl is, but the bubble wrap and or foam on cold side and vinyl on warm side seems like a problem. If the yinyl is the priority, then remove bubble and do not add rigid foam.

It seems the best strategy is foam on exterior side, well sealed (like if not all spray, than rigid and spray seams, over purlins, around upper chords) and then fiber glass with a vapor permeable covering - like drywall with latex, but maybe fabric would work.

Not appealing but what I've learned from experience and more important listening to the best.

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[12voltsguy]

I don't know how good or complete of a vapor barrier the vinyl is, but the bubble wrap and or foam on cold side and vinyl on warm side seems like a problem. If the yinyl is the priority, then remove bubble and do not add rigid foam.

It seems the best strategy is foam on exterior side, well sealed (like if not all spray, than rigid and spray seams, over purlins, around upper chords) and then fiber glass with a vapor permeable covering - like drywall with latex, but maybe fabric would work.

Not appealing but what I've learned from experience and more important listening to the best.

National Home Performance Conference & Trade Show 2023 - Building Performance Association

Our annual national conference brings together thousands of industry stakeholders for the latest industry education.

events.building-performance.org

Thank you for all of the suggestions. I've heard many varying suggestions and it seems hard to know what the best approach is. I have lots to consider here.

 

[rburke65]

Why don’t you call a local insulation company for a quote n options?