Expanded Polystyrene (EPS) Insulation
Expanded polystyrene (EPS) is the most affordable rigid foam insulation and is produced by expanding polystyrene beads with steam and then molding them into boards. The white, bead-like appearance distinguishes it from the smooth surface of XPS. EPS provides R-3.9 per inch in standard densities, though higher-density versions can reach R-4.2 per inch. Unlike polyiso, EPS maintains its R-value in cold temperatures, making it a reliable choice for exterior continuous insulation in cold climates. EPS absorbs slightly more moisture than XPS over time, but it dries readily and does not lose structural integrity. Structural insulated panels (SIPs) commonly use EPS as their core material.
Expanded Polystyrene (EPS) Specifications
Best Applications for Expanded Polystyrene (EPS)
Expanded Polystyrene (EPS) is recommended for the following building components. Each application link shows the specific R-value requirements by climate zone and how Expanded Polystyrene (EPS) compares against other insulation options for that component.
Thickness Required by Climate Zone
The table below shows the thickness of Expanded Polystyrene (EPS) needed to achieve the DOE recommended R-value for each building component in every climate zone. Cells showing "N/R" indicate that insulation is not required for that component in that zone. Use this table to quickly determine how much Expanded Polystyrene (EPS) you need for your specific zone and application.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement | Crawlspace | Cathedral | Garage |
|---|---|---|---|---|---|---|---|---|
| Zone 1 | 7.7" | 3.3" | N/R | 3.3" | N/R | N/R | 5.6" | 4.9" |
| Zone 2 | 9.7" | 3.3" | N/R | 3.3" | N/R | N/R | 5.6" | 4.9" |
| Zone 3 | 9.7" | 3.3" | N/R | 4.9" | 1.3" | 1.3" | 7.7" | 4.9" |
| Zone 4 | 12.6" | 3.3" | 1.3" | 6.4" | 2.6" | 2.6" | 9.7" | 7.7" |
| Zone 5 | 12.6" | 3.3" | 1.3" | 6.4" | 2.6" | 2.6" | 9.7" | 7.7" |
| Zone 6 | 15.4" | 3.3" | 2.6" | 6.4" | 3.8" | 2.6" | 12.6" | 9.7" |
| Zone 7 | 15.4" | 3.3" | 2.6" | 6.4" | 3.8" | 2.6" | 12.6" | 9.7" |
| Zone 8 | 15.4" | 3.3" | 3.8" | 6.4" | 4.9" | 2.6" | 12.6" | 9.7" |
Cost Estimates by Climate Zone (per 1,000 sq ft)
Material cost estimates for Expanded Polystyrene (EPS) at the DOE recommended R-value for each climate zone and component. These are material costs only and do not include labor. Professional installation typically adds 30-50% to the material cost shown below.
| Zone | Attic | Wall Cavity | Wall Cont. | Floor | Basement |
|---|---|---|---|---|---|
| Zone 1 | $3,600 | $1,560 | N/R | $1,560 | N/R |
| Zone 2 | $4,560 | $1,560 | N/R | $1,560 | N/R |
| Zone 3 | $4,560 | $1,560 | N/R | $2,280 | $600 |
| Zone 4 | $5,880 | $1,560 | $600 | $3,000 | $1,200 |
| Zone 5 | $5,880 | $1,560 | $600 | $3,000 | $1,200 |
| Zone 6 | $7,200 | $1,560 | $1,200 | $3,000 | $1,800 |
| Zone 7 | $7,200 | $1,560 | $1,200 | $3,000 | $1,800 |
| Zone 8 | $7,200 | $1,560 | $1,800 | $3,000 | $2,280 |
Advantages and Limitations
Every insulation type has trade-offs that affect its suitability for different applications. Understanding these trade-offs helps you select the right insulation for your specific project requirements, budget, and installation constraints.
Advantages of Expanded Polystyrene (EPS)
- Low material cost makes it budget-friendly for large areas
- Suitable for DIY installation, reducing labor costs
- Well-suited for: Wall Continuous (Exterior), Attic, Floor (Over Unconditioned Space)
Limitations of Expanded Polystyrene (EPS)
- Combustible material requires thermal barrier coverage in occupied spaces
Compare Other Insulation Types
Browse specifications and cost analysis for other insulation materials to find the best option for your project.