XPS (Extruded Polystyrene) is a premium rigid foam insulation board with a uniform closed-cell structure produced by a continuous extrusion process. Compared to EPS, XPS offers higher compressive strength, lower thermal conductivity, and very low water absorption — making it the preferred choice for demanding applications: inverted / protected roofs, podium decks, basement walls, cold storage floors, and any load-bearing or wet insulation situation.
XPS follows ASTM C578 / EN 13164. Major brands: Supreme INSUboard, BASF Styrodur, Owens Corning Foamular, Dow Styrofoam, Beardsell.
XPS is made by melting polystyrene resin with a blowing agent and extruding it as a continuous board with a smooth skin & uniform closed cells. The homogeneous closed-cell structure (no bead boundaries like EPS) gives superior moisture resistance & strength.
| Property | Value |
|---|---|
| Thermal Conductivity (k) | 0.028–0.035 W/m.K (best rigid foam) |
| Compressive Strength | 200–700 kPa (grade dependent) |
| Water Absorption | < 0.7% |
| Density | 28–45 kg/m³ |
| Max Service Temp | ~75 °C |
| R-Value (50 mm) | ~1.5–1.8 m²K/W |
| Fire Behaviour | Combustible (use FR grade) |
| Thickness | 20, 25, 30, 40, 50, 75, 100 mm |
| Lifespan | 50+ years |
| Parameter | XPS | EPS |
|---|---|---|
| Process | Extruded (continuous) | Expanded beads |
| Thermal k | 0.028–0.035 (better) | 0.033–0.040 |
| Compressive Strength | 200–700 kPa (higher) | 70–200 kPa |
| Water Absorption | < 0.7% (much better) | 1–3% |
| Structure | Uniform closed cell | Bead boundaries |
| Cost | Higher | Lower |
| Best For | Load-bearing, wet, high-performance | General, cost-effective |
See EPS / Thermocol for the economical alternative.
| Brand | Products |
|---|---|
| Supreme Industries | Supreme INSUboard XPS |
| BASF | Styrodur XPS |
| Owens Corning | Foamular XPS |
| Dow | Styrofoam XPS |
| Beardsell | XPS boards |
| Standard | Description |
|---|---|
| ASTM C578 | Rigid Cellular Polystyrene Thermal Insulation |
| EN 13164 | XPS Thermal Insulation Products |
| IS 3346 | Thermal Conductivity Test |
| ASTM D1621 | Compressive Properties of Rigid Foam |
| ASTM C272 | Water Absorption |
| ECBC 2017 | Building Insulation Requirements |
| Type | Cost |
|---|---|
| XPS Board 25 mm (per sqm) | Rs 120 – 220 |
| XPS Board 50 mm (per sqm) | Rs 220 – 420 |
| XPS Board 75 mm (per sqm) | Rs 350 – 600 |
| High-Strength Grade (per sqm) | + 20–40% |
| Installed (per sqft) | Rs 30 – 70 |
XPS boards are the high-performance rigid foam insulation — choose them where compressive strength, low water absorption and the best thermal performance matter: inverted roofs, podium decks, basements, cold storage floors and below-grade. They cost more than EPS but deliver superior durability in load-bearing & wet conditions. Use FR grade, protect from UV & solvents, and seal joints.
For economical general insulation, use EPS; for fire / high-temperature, rock wool; for acoustic, glass wool; for radiant heat, reflective foil; for gap-filling, PU foam.