Will this work to insulate and air seal under a bay window

A homeowner on a building science forum asked for feedback on a project sealing and insulating the floor under a bay window, a spot that often lets in cold air and loses heat because it juts out past the house's foundation. The approach described: strip old sheathing and replace it with Zip System sheathing (a panel with a built-in weather barrier), frame the space with 2x6 lumber, add a half-inch of rigid foam board sealed at the edges along the sill, then fill the rest of the gap with rockwool (a mineral-wool insulation). The seams get sealed with liquid flashing, and the whole underside is covered with a thin white plastic sheet, also sealed at the edges. The poster asked whether the job also needs screened vents underneath.

At the time this was posted, no one had answered yet, so there's no expert verdict on whether this method is sound or whether venting is needed.

For homeowners with a bay window, this is a reminder that the floor cavity under one of these windows is a common weak spot for drafts and heat loss, and that fixing it involves both insulation and careful air sealing of the seams and edges, not just stuffing in more material. If you have a drafty bay window, the underside is worth checking, since gaps there can undercut insulation upgrades elsewhere in the house.