Styrofoam is actually a brand name, just like saying scotch tape. The fact is they are all extruded polystyrene foam boards, panels, whatever (which is way different than the material that is commonly referred to as a "Styrofoam cup" or other similar materials). They all come in different densities which is why you seem to make a distinction between "Styrofoam" and "high density construction foam". Sorry if I confused you by using the term Styrofoam instead of foam panels, boards, whatever; it's like the scotch tape thing.
