Question for the

2/12 residential single story with 2 inch car decking running vertically...no insulation is installed. What type of insulation should I use if I am going to use TPO product?>>>

Expanded Polystyrene and Extruded Polystyrene are the synonyms for the styro-foam you are looking for.

Expanded is less dense of a cellular structure, while the extruded is a firmer product.

They are most commonly used with EPDM ballasted roof systems.

I am not following what you are asking regarding the types of roof structures in the second part of your question.

Please clarify.

Ed>>>