Do not place a vapor barrier under blown in insulation.
Insulate pole barn roof or not.
Some things to consider when insulating a pole barn include.
It ranges from r 5 to an r 16 value depending on the type.
Make sure the attic space above the insulation is adequately vented.
There most common options for insulation are fiberglass blankets and spray foam.
The best way to insulate your ceiling is to blow in cellulose or fiberglass to at least r45 if not r60.
This will provide a greater r value than r19 batts and provides a vapor barrier.
Pole barn insulation thickness one or two inches one or two inch insulation can be placed on the exterior of the building underneath the steel.
This blanket comes in 3 4 6 and 8 widths and provides a minimum of r19 installed.
Condensation issues and the specific thicknesses and types of roofing and wall insulation materials.
Pole building ceilings the most common way to insulate the roof of a pole barn or pole building is to place the insulation blankets at the bottom of the truss.
For any pole barn unfinished wall system we sell 6 thick friction fit insulation that is installed between the posts from the inside after the building is erected.
Closed cell spray foam insulation would need to be added in the area closest to eave sidewalls.
Weighing what you have to start with my recommendation is to spray three inches of closed cell foam insulation below your roof sheathing.
This is typically done by placing metal banding 30 apart down the length of the pole building.