Use a premade kit for this type of project.
Foam board roof vent.
In an un vented roof foam can serve as the air barrier and vapor retarder and prevent moisture from getting in to the roof.
Spray foam the iso board would be a lot cheaper especially if this is a diy project.
Of airflow per linear ft.
Additionally raft r mate attic vent has an optional bend down air stop or insulation block at the top plate of the wall in one easy to install product.
As for iso board vs.
The plyco quick vent is non wicking highly pliable while still providing a superior airflow.
Cathedral roofs especially need a lot more insulation between the ceiling and the rafters because there usually isn t.
Simply peel the backing and install.
Just peel the backing as you install.
So an unvented roof is probably your best option.
The superior adhesive helps make a complete seal.
All insulation materials require proper venting.
For new construction use rigid boards to insulate slabs and the outside of foundation walls.
Owens corning raft r mate attic vent is an extruded polystyrene foam vent designed to assure unrestricted airflow from the soffit to the ridge vent.
Intended for a roof pitch of 6 12 and higher it is recommended to use the cv3 vent for a roof pitch of 5 12 and lower installed without cutting or altering the roof structure made with fiberglass screen making it a mold and mildew free permanent solution to your ventilation needs while providing over 7 sq.
In a vented roof foam can seal the openings and serve as an air barrier and a vapor retarder in addition to its insulating function.
Today there are more options.
Foam insulation can play an important role in both vented and un vented roof assemblies.
Foam board insulation with rigid panels polystyrene and styrofoam boards are low cost and quick and easy to fit to the large panel in the camper van.
If you want to install rigid foam above your roof sheathing in climate zone 3 then 1 2 inch of rigid foam board is not ideal this rigid foam layer needs a minimum r value of r 5 and that s impossible with 1 2 inch of foam.
For a basement remodeling project consider insulating basement walls with foam board.
Some people nail flat 2x4s on top of their existing roof and build a new roof to create a vent space but it would be hard to justify the cost for a workshop.
Vent a foam insulated roof there used to be a time when the only insulation available was pink fiberglass.
No more foam flapping in the wind.
Plyco quick vent comes in 2 x 10 lengths for quick and easy installation.