Rigid Foam insulation and Drywall

[Pixiemoss]

Hello!

We live in PNW and have a 30 ft pacific yurt with snow and wind package. We want to add rigid foam

insulation

between the rafters and finish with drywall. On the exterior we will add board and batten siding.

Can someone recommend the best way to go about the rigid foam, in respects to air gaps and vapor barriers, that will reduce the likelihood of mold??

Thanks in advance for any tips, advice or thoughts ..