Exterior insulation on 2×4 framed home kit with metal siding – GreenBuildingAdvisor

Hello!

I am looking at the following great american home kit https://overmanbuildings.com/house-kit-48r/

The kit comes with corrugated metal siding and house wrap over 2×4 framed walls, no sheathing.

My question is how to achieve a R-20 wall assembly for climate zone 4a with R-15 batt insulation in stud cavaties and some type of exterior foam board under the metal and house wrap? My research shows you can’t attach vertical metal siding directly through foam board to studs. I was thinking of running 2×4 perlins/girders horizontally every 24″ over the studs and installing 1 1/2″ eps foam between these girders to the studs. Then house wrap covering the foam and girders then metal siding. Windows would be flush with the girders and foam board for house wrap detail. This assembly would not include any sheathing, metal would be fastened to horizontal girders.

Proposed assembly (outside to inside):

Metal siding vertical

house wrap

horizontal perlins 24″ o.c with 1.5″ eps in between

2×4 studs with R-15 batt in between

drywall

Thanks for any insight!