Spray Foam Insulation: Definition and What it is

What is Spray Foam Insulation?

Spray foam insulation is a two-component polyurethane product that's mixed and sprayed as a liquid, rapidly expanding to fill cavities and create a seamless air barrier. It's available in open-cell and closed-cell formulations, each offering distinct performance characteristics and applications.

Spray foam revolutionized insulation by combining thermal resistance with air sealing in a single application. Traditional insulation materials require separate air sealing steps, but spray foam expands into every crack and gap, creating an airtight envelope. This dual function makes homes significantly more energy-efficient—studies show spray foam homes use 40-50% less energy than homes with traditional insulation. The material adheres to framing, sheathing, and other surfaces, and won't settle, sag, or degrade over time.

Types of Spray Foam Insulation

• Open-Cell Foam: R-3.5 to R-3.7 per inch, lighter, vapor-permeable, excellent for interior walls and sound dampening
• Closed-Cell Foam: R-6 to R-7 per inch, dense, moisture-resistant, adds structural strength, ideal for exterior applications
• Flash-and-Batt: Thin spray foam layer for air sealing, topped with fiberglass batts for cost savings
• High-Density Roofing Foam: Specialized closed-cell for commercial roofing applications

Choosing Between Open-Cell and Closed-Cell

Open-cell foam costs less, provides excellent soundproofing, and works well in interior applications where moisture isn't a concern. It requires a separate vapor barrier in cold climates. Closed-cell foam costs more but offers higher R-value per inch, moisture resistance, and structural benefits. Use closed-cell for exterior walls, below-grade applications, cathedral ceilings, and anywhere moisture is a concern. For new construction, spray foam in rim joists and attic roof decks provides exceptional performance. Ensure proper ventilation during installation and allow adequate cure time before occupying spaces.

Benefits of Spray Foam Insulation

• Exceptional air sealing eliminates drafts and infiltration
• Highest R-value per inch available (closed-cell)
• Fills irregular cavities and hard-to-reach areas completely
• Long-lasting performance with no settling or sagging
• Moisture barrier properties prevent condensation (closed-cell)
• Can reduce energy bills by 40-50% compared to traditional insulation

Spray Foam Insulation Cost

Spray foam is the most expensive insulation but offers the best performance and energy savings.

• Foam type (open-cell: $1.50-$3/sq ft; closed-cell: $3-$7/sq ft)
• Target R-value and required thickness
• Project size and scope (larger projects cost less per square foot)
• Application area and accessibility
• Regional contractor availability and market competition
• Need for additional prep work or removals

Related Services and Resources

Related Terms

• Closed Cell Insulation: Definition and What it is
• Open Cell Insulation: Definition and What it is
• Polyurethane Foam Insulation: Definition and What it is
• R-Value Insulation: Definition and What it is

References

• Wikipedia - Spray Foam
• Energy.gov - Foam Insulation (Types)
• Wikipedia - Thermal Insulation
• Energy.gov - Insulation (Energy Saver)
• National Insulation Association - Insulation Basics
• ICAA - Insulation for Consumers