When it is reported that styrofoam is less efficient than
polyurethane they are referring to the white generic material used for
disposable items like coffee cups which are really expanded
polystyrene beads and not DOW's controlled density trademarked
polyurethane product. If you were to compare specification sheets of
extruded polystyrene insulation against polyurethane pressed board
insulation you will find polyurethane board has a 30% higher R value
over extruded polystyrene. The disadvantage to polyurethane as
insulation for a boats refrigerator is it is less moisture resistant
over time than extruded polystyrene.

Each boat and each owner's refrigeration needs are different, so one
system does not fit all. No one can answer a question about what is
the best refrigeration for you and your boat without knowing more
about the boat and how and were you will be using the boat. There are
from twenty to fifty different configurations of these new systems to
choose from, study your options then go for price. The slide show on
my web site will help guide you through the refrigeration selection
process and help you determine what will be needed to support it.
http://www.kollmann-marine.com.