EPS

Expanded polystyrene is a rigid cellular plastic made by heating polystyrene pellets with a blowing agent, usually pentane, until they puff up and fuse together. The result is a white or gray block that is roughly 98 percent air by volume. EPS density typically ranges from 10 to 30 kilograms per cubic meter, making it one of the lightest structural materials in common use.

The material's primary jobs are thermal insulation and shock absorption. In construction, EPS boards are cut to fit wall cavities, roof spaces, and foundation perimeters, where they provide an R-value of about 3.6 per inch of thickness. In packaging, loose-fill peanuts and molded shells protect fragile goods during transport. It also appears in refrigerated shipping containers, flotation devices, and as a core in sandwich composite panels.

Handling and processing

EPS is cut with hot-wire tools that melt the plastic into the desired shape, or with bandsaw blades if precision edges are needed. The material is flammable and will ignite at around 400 degrees Celsius, though manufacturers often treat it with flame retardants. It degrades in direct sunlight over time, becoming brittle and losing thermal performance. Moisture absorption is minimal, which is why it resists degradation in damp basements or coastal climates better than some competing insulants.

The main limitation is mechanical weakness: EPS compresses easily under point loads and has low shear strength. For this reason it is rarely used alone in load-bearing applications. Ground contact or burial also degrades it; soil contact with certain chemicals, such as gasoline or strong solvents, will dissolve the material almost instantly. Installation often requires a vapor barrier on the warm side in cold climates to prevent moisture from condensing within the foam.

EPS is cheaper than polyurethane foam or phenolic foam by a significant margin, which explains its dominance in budget insulation projects. Its low density and ease of cutting make it popular for non-structural thermal work in residential building. Recovery and recycling of EPS waste streams remains limited, though loose-fill material is increasingly being collected and compressed into new boards.