Cantilevered floor–Comfortboard outsulation? – GreenBuildingAdvisor

I’m working to air seal & insulate a small cantilevered floor system in climate zone 4C (western WA). It’s about 6’x8′ and framed with 2x8s, between which is some unfaced fiberglass; 1/2″ ply is nailed on the underside of the joists. Access is reasonable, with about 30″ of clearance from slab to the bottom of the joists.

I’m looking at a time-efficient way to improve this assembly and was wondering if anyone has done an outsulation approach to cantilevered floor systems. My thought is to:

1) retain the existing assembly

2) seal any seams & penetrations in the plywood soffit and perimeters

3) install a self-adhered WRB

4) add 2″ Comfortboard on the bottom, leaving it exposed.

Is this a reasonable idea?

Thanks for any ideas!

Kurt