Structural Insulated Panels (System)...good starting point to learn about 'em: https://en.wikipedia.org/wiki/Structural_insulated_panelwhat is SIPS??
Be aware of this problem with OSB SIPS and "hot roof" designs: http://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/how-make-sip-roof-better
And note that the underlying problem there is moisture. Moisture management is key factor in design & construction of structures. Especially any kind of earth-sheltered structures.