renovating unisulated attic

we will start to renovate an uninsulated attic........
the floor is presently insulated ( living area ceilings) with loose insulation
placing new floor over that
the question is , should we place that thin polyfoam sheeting for venting up in the rafters as well as use batts.....
and we will be sheet rocking the ceiling .........should we use open faced ,,kraft faced .or foil faced insulation

to many varied answers so far from lumber yards to contractors
thanks

You want a vapor barrier on the living space side of the finished walls/ceilings.

Keep in mind that attics are often not designed for people loads...the joists should hold the ceiling up and keep the walls and roof from spreading, but may not be deep enough to support either a live or dead load (the new floor might be quite springy).

If you have soffit vents and a roof vent, the yes, you should maintain airflow between them in the roof, so the channels are probably a good idea. The concept here is to keep the roof deck close to ambient so you don't melt snow and cause ice dams in the winter, or cook the roof in the summer. In theory, a really good insulation job without the air channels could work too.

Finishing an attic space when it isn't designed for it in the first place may not be a great idea or could require a lot of structural work.

What he said.

Someone should analyze the structure to see if the joists will handle the load. Ceilings are usually designed for 20 #/sq ft and floors for 40 #/sq ft though you could probably get by with 30 for a floor with no refrigerators or stuff like that.

There is a risk of damaging the ceiling finish underneath if it is not stiff enough.

If there is enough depth of rafters you can put the insulation on the inside edge of the rafters (example 3.5" insulation of 5.5" rafters) with the vapor barrier and even a supplemental vapor barrier inside. That is not a lot of insulation but it leaves the vent space.