Probably in more place than you think.
Insulating attic and porch.
Your porch being open on one side doesn t really need to be insulated at all.
Insulating attic floors unfinished or uninsulated attics need a layer of protection against air migration.
But if the floor is covered in plywood you can t stuff enough insulation beneath it to do the job sufficiently not even in warm climates.
Is the porch heated.
You actually want the attic to stay relatively close to the outside temperature to prevent ice problems in the winter or overheating in the summer.
Not sure where exactly to insulate.
The important thing is that the ceiling above your living space is insulated because that s the area you heat cool.
The insulation should fit snugly to prevent air from getting through.
Because the simplest and cheapest way to insulate an attic is to add material to the floor.
In addition to walls and attics insulation should be installed in ceilings with unheated spaces basement walls floors above vented crawl spaces cathedral ceilings floors over unheated garages or porches knee walls and in between interior walls especially bathrooms as well as ceilings and floors.
Plan to pull up the flooring and layer new insulation on top of the old.
If you can crawl under your porch insulate from below by nailing plywood boards to cover any openings.
Install batting between the attic s floor joists.
The purpose of insulation is not to keep the attic warm but to keep the house warm or cool.
If not then don t bother.