The two most common types of insulation for commercial roof systems are Polyisocyanurate (Polyiso) and Expanded Polystyrene (EPS). Both are available in a variety of thicknesses and can be used in multiple applications. Polyiso is used in new construction designs more than EPS, though EPS still has it’s advantages. 

Here is a quick comparison: 

So which is best? 

While the winner may not be so clear, both insulation types have their pros and cons. When it's time for a new roof, contact your local roofing contractor to help you determine which insulation is best for your building and performance needs.