Insulated wood concrete forms are stay-in-place formwork for energy-efficient, cast-in-place reinforced-concrete walls. The forms are interlocking modular units that are dry-stacked without using mortar and filled with concrete. The forms lock together somewhat like Lego bricks and serve to create a form for the structural walls of a building. Concrete is pumped into the cavity to form the structural element of the walls. Usually, reinforcing steel or rebar is added to give the resulting walls flexural strength, similar to bridges and high-rise buildings made of concrete.