Roof detail for cedar shakes with natural insulation?

My wife and I were recently able to purchase a dream property. The propert is off grid and there's a well and a small cabin, but the infrastructure is old and needs quite a bit of work before we can move there full time.

My first construction project is probably going to be building a new well house to protect the well head and associated equipment.

We're in western washington state near the ocean, so freezing isn't super common, but it does occasionally get down to ~10F/-12C and past freezes have damaged some of the exisiting equipment so I want to insulate the shed so that I can hopefully keep it warm with a minimum of electricity or fuel.

I'd like to avoid things that won't decompose after they have served their purpose so I'm thinking I'll go with cedar shakes for the roof and I'm thinking possibly wool for insulation.

Has anyone used this combination? A shed like this wouldn't normally get a finished roof, so the insulation would need to go in the joist bays, but both cedar and wool need to breath and not have trapped moisture. I'm considering using twine or something to try to keep the wool contained below the top of the  joist bay so that there's ~1" of empty space and laying skip sheathing on top to fasten the shingles.

Does that sound like it would work, or do people have ideas about other ways to deal with this?