I'm looking for ways to make a natural insulated roof

Situation: Tiny home in a cold/frigid climate for year round living.  Desiring natural building techniques, metal is ok.  Roof pitch limited to around 6:12.  Cathedral ceiling preferred but attic is ok if needed.

The walls will be tongue and groove wood on the inside, planer shavings, borax and maybe clay slip as the insulation (4" on walls, 6" on floor and roof), and board and batten or t&g exterior boards.  

The floor will be wood boards on 6" floor joists with the same insulation as in the walls.  The exposed surface underneath will be metal roofing, partially for mouse prevention.

In a cathedral ceiling situation, the ceiling will be wood boards and the same insulation.  My simple thought is to use metal roofing and pack the shavings fully between the ceiling and roofing.  But, I'm worried about condensation on the underside of the metal getting the insulation wet and leading to rot/mold.  If I leave an air gap, the condensation will likely still form and some may run down hill and exit but some undoubtedly would get into the insulation.  I've heard that if the dew point is reached "in" the insulation you don't have anything to worry about but I'm not sure if that's with styrofoam or any kind of insulation.

In an attic situation, I could do ceiling boards, insulation and then more boards on top to contain the insulation and block airflow.  Then have a well vented attic with a metal roof.  Would that greatly reduce the condensation to the point of not having to worry? Plus it would drip on boards instead of insulation so it probably would evaporate?

Alternately, is there a natural sort of vapor barrier I could use to keep humid house air from reaching the roof metal?  Perhaps rosin paper or single ply cardboard?

Alternately, is there another form of roofing that would not have the condensation problem? Thatch isn't a solution for my area/expertise.  Wood shingles might be...

I'm hoping the floor wouldn't have the same problem....

Thanks!!!

My simple thought is to use metal roofing and pack the shavings fully between the ceiling and roofing.  

Insulation works because the unconnected cells of air. I doubt compacted shavings will work at all.
Have you investigated the R value for what you propose?
I did a quick google search and found this ;
"Packed wood shavings have an estimated R-value of roughly 2.0 to 2.2 per inch of thickness when dry.
Insulation Performance and Risks
Using wood shavings as a building insulation material is rarely done today.
While dry shavings trap air effectively, they carry several major drawbacks
:Low thermal efficiency
: An R-value near 2 per inch falls well below modern standards like fiberglass (3.5–3.8 per inch) or spray foam.
Settling
: Shavings compress and shift over time, which leaves gaps at the tops of walls or ceilings.Moisture absorption
: They absorb water easily, leading to mold, rot, and a total loss of insulating value.
Fire hazard: Loose or packed wood shavings are highly flammable and create a severe fire risk.
Pests: Organic materials can attract rodents, termites, and insects unless heavily treated with additives like borax or lime."

VAPOUR BARRIERS
The use of vapour barriers is becoming better understood and I doubt the are any natural versions available.

I'm open to suggestions but I'm trying to stick with something affordable and that I can get my hands on.  Houses around here are often insulated with blown in cellulose insulation which is paper fibers treated with stuff.

Planer shavings are fluffier than general wood shavings with what I believe to be good air gap properties, even when packed down.  Saw dust wouldn't be as good in my opinion.

I tested a clay slip shaving at a recent permaculture convergence and it packed nicely and stayed put.  It "seemed" like it wouldn't settle with how hard it was packed.  The session leader said that 1 cup of borax in 20 gallons of clay slip (or water) mixed in with the shavings is enough for bug discouragement.  

I'll take a R 2.1 any day for a free insulation option.  That would give me R8.4 in the walls and R 12.6 in the floor and ceiling.  Plus another R2 for the boards that make up the interior and exterior cladding. I'd be very happy with that.  

I agree that loose shavings are a great fire starter but if they're packed in a wall cavity, I'm not worried about fire.  

Water is my biggest concern, thus the focus of my questions above