EPS / Thermocol Sheets — Complete Guide
EPS (Expanded Polystyrene) — popularly called Thermocol in India — is a rigid, lightweight, closed-cell foam insulation made by expanding polystyrene beads with steam. Composed of ~98% trapped air, it is an excellent, economical thermal insulator. EPS is widely used for roof & wall insulation, cold storage, sandwich panels, geofoam fill, packaging and lost-formwork. It is light, easy to cut, moisture-resistant and cost-effective.
Indian EPS follows IS 4671 (Expanded Polystyrene for Thermal Insulation). Major brands: BASF Styropor, Beardsell, Supreme, Cohinoor, Styrene Packaging, Premier Polyfilm.
What is EPS?
EPS is produced by expanding polystyrene beads (containing pentane blowing agent) with steam, then moulding them into blocks / boards. The result is a closed-cell foam that is ~98% air, giving low density & low thermal conductivity. It is rigid (unlike loose wools), making it suitable for boards, panels & structural fill.
Key Characteristics
- Lightweight (10–30 kg/m³)
- Low thermal conductivity (0.033–0.040 W/m.K)
- Rigid, easy to cut / shape
- Moisture-resistant (closed cell)
- Economical
- Recyclable
Density Grades & Properties
| Grade / Density | Compressive Strength | Use |
|---|
| Grade I / SD (15 kg/m³) | ~70 kPa | Packaging, light insulation |
| Grade II / MD (20 kg/m³) | ~100 kPa | Roof / wall insulation |
| Grade III / HD (24 kg/m³) | ~150 kPa | Cold storage, panels |
| Grade IV (30 kg/m³) | ~200 kPa | Floor / load-bearing, geofoam |
| Property | Value |
|---|
| Thermal Conductivity (k) | 0.033–0.040 W/m.K |
| Water Absorption | Low (1–3%) |
| Max Service Temp | ~75–80 °C |
| Fire Behaviour | Combustible (use FR grade) |
| R-Value (50 mm) | ~1.3–1.5 m²K/W |
| Lifespan | 30–50 years |
Forms & Applications
| Form | Use |
|---|
| Sheets / Boards | Roof, wall, floor insulation |
| Blocks | Geofoam fill, cutting to shape |
| Sandwich Panels (EPS core) | PEB walls / roofs, cold rooms |
| Moulded Shapes | Packaging, void formers |
| EPS Beads | Lightweight concrete, fill |
| Lost Formwork (ICF) | Insulated concrete forms |
| FR (Fire Retardant) Grade | Building applications |
Where to Use
- Roof & terrace thermal insulation (under screed / over deck)
- Wall insulation (cavity / external)
- Cold storage & freezer rooms (sandwich panels)
- PEB / prefab walls & roofs (sandwich panels)
- Floor insulation
- Geofoam (lightweight fill for embankments)
- Void formers (slabs / beams)
- Lightweight concrete blocks
- Packaging
- False ceiling / decorative (light)
EPS vs XPS
| Parameter | EPS | XPS |
|---|
| Process | Expanded beads (steam) | Extruded continuous |
| Structure | Closed cell (bead boundaries) | Uniform closed cell |
| Thermal k | 0.033–0.040 | 0.028–0.035 (better) |
| Compressive Strength | Lower | Higher |
| Water Absorption | 1–3% | < 0.7% (better) |
| Cost | Lower | Higher |
| Best For | General, cost-effective | High-load, wet, high-performance |
See XPS Boards for the higher-performance extruded version.
Advantages
- Excellent thermal insulation (low k)
- Very lightweight
- Economical (lowest cost rigid insulation)
- Rigid — easy to cut / shape / handle
- Moisture-resistant (closed cell)
- Doesn't rot / decay
- Versatile (boards, panels, fill, formwork)
- Recyclable
- Good for cold storage & sandwich panels
- Long lifespan
- Available in FR grade
Disadvantages
- Combustible (use FR grade; toxic smoke on burning)
- Low temperature resistance (~80 °C)
- Poor acoustic insulation
- Lower compressive strength than XPS
- Damaged by solvents / petroleum
- UV degrades surface (needs covering)
- Brittle — can crumble
- Higher water absorption than XPS
- Not load-bearing (low grades)
Top Brands
| Brand | Products |
|---|
| BASF Styropor | EPS raw material / FR grade |
| Beardsell | EPS boards, panels |
| Supreme Industries | EPS & sandwich panels |
| Cohinoor / Premier | EPS sheets & packaging |
| Styrene Packaging | EPS products |
Installation & Best Practices
- Use FR (fire retardant) grade for buildings
- Choose density per load & application
- Protect from UV (cover / plaster / cladding)
- Keep away from solvents / petroleum
- Provide fire barriers (EPS is combustible)
- Seal joints for continuous insulation
- Use over-deck with screed protection on roofs
- For cold storage, use sandwich panels with metal skins
- Combine with reflective foil for radiant heat
- Don't expose to high temperature (> 80 °C)
Tests & Standards
| Standard | Description |
|---|
| IS 4671 | Expanded Polystyrene for Thermal Insulation |
| IS 3346 | Thermal Conductivity Test |
| ASTM C578 | Rigid Cellular Polystyrene Thermal Insulation |
| IS 8183 | (related insulation standard) |
| ASTM E84 / IS 12777 | Surface Burning / Fire |
| ECBC 2017 | Building Insulation Requirements |
Cost (Approximate, Indian Market, 2025-26)
| Type | Cost |
|---|
| EPS Sheet 50 mm 16 kg/m³ (per sqm) | Rs 60 – 120 |
| EPS Sheet 50 mm 24 kg/m³ (per sqm) | Rs 100 – 180 |
| EPS Block (per cubic ft) | Rs 80 – 160 |
| EPS Sandwich Panel (per sqm) | Rs 600 – 1,400 |
| FR Grade EPS (premium) | + 15–30% |
| Installed (per sqft, roof) | Rs 20 – 50 |
Conclusion
EPS / Thermocol is the most economical rigid thermal insulation — widely used for roof & wall insulation, cold storage, sandwich panels, geofoam and lost-formwork. It is light, easy to handle and moisture-resistant, but combustible (use FR grade), low-temperature limited and poor acoustically. Always protect from UV & solvents and provide fire barriers.
For higher compressive strength & lower water absorption, choose XPS boards; for fire / high-temperature, use rock wool; for acoustic + thermal, glass wool; for radiant heat, reflective foil; for gap-filling, PU foam.