R-Value Insulation: Definition and What it is

What is R-Value Insulation?

R-value measures an insulation material's resistance to heat flow—the higher the R-value, the better the insulation performs. It's the standard metric for comparing insulation products and determining how much insulation your home needs based on climate zone.

The "R" stands for resistance to heat transfer. R-value is expressed per inch of thickness, so R-19 fiberglass batt is approximately 6 inches thick (R-3.2 per inch), while R-19 spray foam is only 3 inches thick (R-6 per inch). Building codes specify minimum R-values for different climates and building components. For example, attics in cold climates typically require R-49 to R-60, while southern climates may require R-30 to R-38. Understanding R-value helps you select the right insulation type and thickness for maximum energy efficiency and code compliance.

R-Value by Insulation Type (per inch)

• Closed-Cell Spray Foam: R-6.0 to R-7.0 per inch (highest performance)
• Open-Cell Spray Foam: R-3.5 to R-3.7 per inch
• Polyiso Rigid Foam: R-5.6 to R-6.5 per inch
• XPS Rigid Foam: R-5.0 per inch
• Cellulose (dense-pack): R-3.6 to R-3.8 per inch
• Fiberglass (batts): R-2.9 to R-3.8 per inch
• Mineral Wool: R-3.0 to R-3.3 per inch

Recommended R-Values by Climate Zone

Energy Star recommends R-values based on climate zones. Cold climates (zones 6-7): attic R-49 to R-60, walls R-20 to R-21, floors R-25 to R-30. Moderate climates (zones 3-5): attic R-38 to R-49, walls R-13 to R-20, floors R-19 to R-25. Hot climates (zones 1-2): attic R-30 to R-49, walls R-13 to R-15. Always meet or exceed local building codes. Remember that R-value alone doesn't tell the whole story—air sealing is equally important for energy performance.

Benefits of R-Value Insulation

• Standardized metric for comparing insulation products
• Helps calculate energy savings and payback periods
• Ensures code compliance and energy efficiency
• Guides proper material selection for climate zones
• Allows accurate cost-benefit analysis of upgrades
• Critical for building performance and comfort

R-Value Insulation Cost

Higher R-values generally cost more, but the relationship between cost and R-value varies by material type.

• Material type (spray foam costs more per R-value than fiberglass)
• Installation method (blown-in vs. batts vs. spray)
• Target R-value for your climate zone
• Available cavity depth (limited depth may require higher R-value per inch)
• New construction vs. retrofit applications
• Regional material and labor costs

Related Services and Resources

Related Terms

• Thermal Insulation: Definition and What it is

References

• Wikipedia - R-value (Insulation)
• Energy.gov - R-Value Recommendations
• Wikipedia - Thermal Insulation
• Energy.gov - Insulation (Energy Saver)
• National Insulation Association - Insulation Basics
• ICAA - Insulation for Consumers