Sintered Expanded Polystyrene (EPS) has democratised energy efficiency. It is the backbone of building renovation (Superbonus), enabling the entire building to be wrapped in a continuous thermal layer that eliminates thermal bridges at a fraction of the cost of other insulators.
Via high-temperature steam injection and a blowing agent (pentane), polystyrene beads expand up to 50 times their original volume. In a closed mould, a second steam burst permanently fuses the bead edges (sintering), creating a block of a billion microscopic closed cells. These cells trap air, stopping convective movement: EPS becomes a masterful insulator while being 98% air and only 2% actual plastic material.
Unlike totally closed-cell polyurethanes, standard white EPS maintains reasonable vapour permeability (mu 30 to 70), similar to dense wood. Its main limitation is UV sensitivity (left raw in sunlight it yellows and crumbles to dust in months) and instant dissolution in contact with chemical solvents.
Standards
European and international references applicable.
Physical properties
Usage environment
GREY EPS: do not leave exposed to direct sun without shade netting before rendering. The graphite overheats (>80 degrees C) causing panel warping (U-shape bowing) that will violently debond from the wall. SOLVENTS: a spray of nitro thinner dissolves an entire block instantly. On site, prohibit any solvent-based paint or adhesive nearby.