Yes, you can go all the way up, just like an ICF would, right? You can parge with synthetic or real hard coat stucco. Or you could use a cement board to protect the outside.
But that seems like a lot of extra work when you can make it easier by stopping the blue board just below grade and insulating the top of the wall on the inside with spray foam making sure to hit the rim on the inside as well.
Regarding the type of foam to use, here's an excerpt of an article on rigid foam that we haven't published yet on
www.GreenBuildingAdvisor.com yet (coming soon):
Expanded polystyrene
The least expensive of the three, EPS has an R-value of about 4 per in. It can be manufactured in different densities to in-crease its compressive strength but it’s still not as strong as extruded board and it’s more susceptible to crumbling at the edges and to other job-site damage. EPS is relatively open to the passage of water vapor with a permeance of 2 to 5, depending on the density of the board. This makes ita semi-permeable material. EPS can absorb more water than either of the other two types, from 2% to 4% by volume, making it a second choice for below-grade installations. EPS is often used on walls and roofs and commonly as the core material in structural insulated panels and in insulated concrete forms.
Extruded polystyrene
Stronger and more expensive, extruded polystyrene (XPS) also is a better thermal insulator, rated at R-5 per in. It’s more water-resistant than EPS and has much lower permeance to water vapor(1.1 per in.). When the thickness is increased to 2 in., the permeance drops to 0.55, making this a semi-impermeable material. Because of its higher strength and water resistance, XPS is often used below grade to insulate slabs and foundation walls.
PolyisocyanurateWith higher insulating values (up to R-6.5 per in.) and the elimination of ozone-depleting blowing agents, polyiso board has some advan-tages over XPS for above-grade use (it’s not recommended for below-grade applications because it can absorb water). Polyiso often comes with
a foil facing, which gives the material a very low vapor permeance of 0.03.
Good luck,
Dan