The principle behind soffits is to allow air to circulate in and around the attic.
How to insulate a roof and soffit.
Staple plastic or foam baffles to the roof sheathing near the eaves to keep the material away.
Alternatively use two half sheets of 3 4 inch.
Lay strips of 3 4 inch plywood that are at least 24 inches wide across the floor of the attic.
The airflow from the soffits to the ridge vent keeps the roof cool and prevents ice dams and the material will block that flow.
For the same reason insulation shouldn t touch the roof s underside.
How to keep blow in insulation out of soffits.
To insulate the roof itself you either use spray foam or retrofit with it with rigid foam board.
Insulating and venting when there is no roof soffit.
Construct a soffit or eaves overhang combined with assuring that an opening is provided all along the top of the building wall by removing any blocking between roof rafters at the top plate combined with use of roof insulation baffles to assure an air inflow pathway under the roof deck.
The soffit vents are now installed but you still need to make sure there s no insulation blocking the new vents.
If the attic is insulated with fiberglass batts just pull back any that are blocking the flow of air.
Set the baffles inside the attic opening along with a loaded staple gun.
You need one baffle for each.