Looking for Pole Barn Insulation Advice

[RonRock]

I want to insulate a section of my pole barn ceiling. In this section of the PB I have a vaulted ceiling. This was accomplished with scissor trusses. On the top cord of the truss is a 2X4 purlin standing on edge with the steel roof screwed into the purlin edge. I plan to use OSB as a ceiling material. And blown in fiberglass insulation.

My question is should I place 1/2" foam board on the bottom of the purlins to create an air space on the inside with the blown in insulation filling the space between the ceiling and foam board? Or can I omit the foam board and simply blow in the insulation to fill the void at the wall angle.

I am in Iowa with cold winters, so will insulate to R38. It will not have room to reach that depth at the wall. Approximately 15 inches from ceiling to inside of roof.

Here is a poorly drawn sketch,

I should add. There is no over hang on the walls. Just a bad drawing.

 

[RonRock]

Here is an outside picture,

 

[brokenknee]

I can't answer your question, but have you checked into spray foam. I would think for that application it would be your best bet.

 

[RonRock]

Spray foam would be great for this. But from what I have found it is crazy expensive. If anyone has a source for it that is affordable I would like to know about it. I would like to use some in my basement around the rim joist.

 

[kj_mustang]

If your trusses are set on 4' spacing, than you can not hang osb on them. I am sure they were not designed for that much weight. If they are 2' spacing, than you probably can. Spray foam directly to the metal roof if it was left unvented. If the roof is vented, metal siding or osb hung on the bottom of the truss and blown in insulation on top of it.

 

[RonRock]

Thanks for the advice kj. My trusses are on 4' center, but they were designed for a load. They have 2X8 cords, top and bottom. Been several years since I built the building so I don't recall the exact load specs. But I did plan to finish the ceiling.

I have a full length ridge vent but no eves therefore no eve vents. The ridge vent will be partially blocked off when the ceiling is put up. As it is there seems to be too much ventilation and when conditions are right it will let rain and snow blow in. I plan to block off most of the ridge vent leaving smaller vent openings in the length of the building.

 

[swvega]

I'VE GOT A 30X60 MORTON IN MN. SO A LITTLE COLDER THAN YOU ARE. My trusses are at 7'6'' what I did was run a 2x4 on the bottom of the truss every 2' then put up vapor barrier and then my tin screwed to the 2x4s. Was told I could just put tin to trusses but didn't like that much span. I've got r-19 in side walls and r-40-50 in ceiling. Mine has inclosed eves with vents. You will have to find a way to vent if you inclose yours

 

[RonRock]

How do you like the tin ceiling? After looking around the forum a bit, I'm seeing several metal ceilings. I never gave steel ceiling much thought, but now I am considering it.

 

[samert111]

I have a full length ridge vent but no eves therefore no eve vents. The ridge vent will be partially blocked off when the ceiling is put up. As it is there seems to be too much ventilation and when conditions are right it will let rain and snow blow in. I plan to block off most of the ridge vent leaving smaller vent openings in the length of the building.

You will need to allow for sufficient air flow above your insulation or you're going to have condensation issues up there and excessive snow melt off your roof. At your eves, are the ribs in the metal roofing closed up or open? If open, then that would allow for air flow up thru there. The foam board on the bottom of the roofing purlins should give you the air pocket you need and allow you to fill in space between with blown in insulation.

 

[RonRock]

I put the foam strips in the void on the roof panels at the outside walls. Although they could be removed.

 

[samert111]

I put the foam strips in the void on the roof panels at the outside walls. Although they could be removed.

I would leave them in, otherwise the bees will be getting in there and building nests up in your attic area.

Maybe you could put vents in the gabled ends above the insulation line. Or have it spray foamed directly on the underside of your roof. That will seal everything up tight and you can either put in a ceiling or not. No need to insulate above the ceiling then.

 

[D KRAGER]

I put foam (3/4") up against the roof tin to keep it from sweating and dripping.

Then I dropped the ceiling and blew in cellulose. R-40

My walls I basically did the same thing. I put 1 1/2" foam between the girts against the tin. Then studded out the wall, left it open to the attic on top, then blew in cellulose.

I my mind you want some type of foam product up next to the tin in case there is any condensation issues.