These days, lots of builders are installing a continuous layer of rigid foam on the exterior side of their wall sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen.
. The usual approach is to sheathe the wall with OSB or plywood, and then to install one or more layers of rigid foam outboard of the sheathing.
Some builders are beginning to simplify this process by switching to nailbase panels — rigid foam panels with a layer of OSB or plywood glued to one side. Since nailbase panels provide sheathing and foam insulation in a single panel, they should (in theory) simplify the construction process.