Continuous exterior insulation with plywood sheathing and cement plank siding – GreenBuildingAdvisor

“Does the rigid foam have to go directly on the studs under the sheathing like zip”

NO It would not be allow. Zip can do it because they jumped thru the hoops to get their product approved. Random combinations of material are unlikely to perform as well as the highly engineered and thoroughly tested commercial products.

If your code officials are doing their jobs that would reject this plan without an engineer’s stamp.

Installing insulation outside of the sheeting should not be a problem. Covering the insulation with Hardie Plank would require you look up and follow the manufactures instructions for exterior insulation that varies by type and thickness.

https://www.greenbuildingadvisor.com/article/how-to-design-a-wall-to-meet-energy-code-requirements

https://www.greenbuildingadvisor.com/article/how-to-design-a-wall

Walta