Which insulation material is not recommended to separate polystyrene and built-up roofing?

Which insulation material is not recommended to separate polystyrene and built-up roofing?

• A. glass fiberboard insulation
• B. wood fiberboard insulation
• C. perlitic board insulation
• D. non venting base ply

Answer: (D)

The main idea is choosing a separation layer that is chemically compatible with polystyrene and the bitumen in a built-up roof, while also managing moisture so the foam isn’t damaged. Polystyrene insulation can be attacked by asphalt solvents and can suffer from moisture entrapment, so the separation layer must resist bitumen and allow drying. A non-venting base ply is not recommended because it acts as a barrier that traps moisture between the insulation and the roofing, and its bituminous composition can interact with the foam. This trapped moisture and potential solvent exposure can degrade the polystyrene and reduce performance. The other options are rigid boards designed to provide a compatible separation surface that resists asphalt and supports drying, making them suitable in this role.

The main idea is choosing a separation layer that is chemically compatible with polystyrene and the bitumen in a built-up roof, while also managing moisture so the foam isn’t damaged. Polystyrene insulation can be attacked by asphalt solvents and can suffer from moisture entrapment, so the separation layer must resist bitumen and allow drying.

A non-venting base ply is not recommended because it acts as a barrier that traps moisture between the insulation and the roofing, and its bituminous composition can interact with the foam. This trapped moisture and potential solvent exposure can degrade the polystyrene and reduce performance. The other options are rigid boards designed to provide a compatible separation surface that resists asphalt and supports drying, making them suitable in this role.