What is the density of styrofoam?

Answer 1

Styrofoam is, strictly speaking, extruded polystyrene foam (XPS) and made by Dow, but the name is often used for expanded polystyrene foam (EPS) as well, though they are not the same. Wikipedia gives data for EPS, but there it gives a wide range of densities from 25 to 200 kg/m3, so that is not very useful. I suspect Styrofoam is a more uniform product but can't find a figure. If flagging this answer does not produce any more info, you may have to go to Dow directly. That is, if you really mean XPS and not EPS.
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EPS can be ordered to many different weights. In the US, it is commonly ordered as "2Llb EPS" meaning 2lb per FT³. I have ordered it as low as 1lb/ft³ and as high as 5lb/ft³. I forget exactly how dense you can order it. Try calling a local EPS supplier like insulfoam.