Open Cell
Spray Foam Insulation: Open‑Cell Benefits, Costs & Best Uses
Looking for a cost-effective way to seal your building envelope and improve indoor comfort? Open cell spray foam insulation may be exactly what you need. With its lightweight structure and high expansion rate, this type of spray foam fills every crack and cavity—making it a powerful solution for air sealing, soundproofing, and thermal performance. In this guide, we’ll explore what open cell foam is, how much it costs, and where it performs best.
What Is Open Cell Foam?
Open cell foam is a light-density (≈0.5 lb/ft³) polyurethane foam that expands rapidly upon application. Its open, interconnected cell structure traps air, resulting in a flexible insulation material. Despite its lower R‑value per inch than closed‑cell spray foam, open cell offers excellent air-sealing capabilities and sound-dampening qualities.
It typically delivers an R‑value of ~3.6 per inch. For a detailed comparison of spray foam types, check this guide from energy.gov
Benefits of Open‑Cell Spray Foam Insulation
Expands to Seal Gaps Completely
Open cell can expand up to 100× its liquid volume. That means it seals tight around wires, plumbing, and odd framing angles.
Air Sealing with Energy Efficiency
According to Energy Star, air leakage accounts for up to 40% of energy loss in homes. Open cell forms a tight barrier that helps cut down on drafts and utility bills.
Sound Control & Acoustic Benefits
Its soft structure absorbs sound waves and reduces airborne noise—ideal for media rooms, bedrooms, and home offices.
More Affordable Than Closed‑Cell Spray Foam
For projects where a vapor barrier isn’t required, open‑cell foam provides a more budget-friendly insulation solution.
Spray Foam Insulation Cost Breakdown
The cost of open cell depends on thickness and application. On average, here’s what to expect:
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3.5" (R‑13): $0.95–$1.50/sq ft
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5.5" (R‑20): $1.50–$2.15/sq ft
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8" (R‑30): $1.95–$3.00/sq ft
These figures are competitive compared to other spray foam systems.
Open Cell Applications
Metal Buildings & Barndominiums
Not Recommended Direct-to‑Metal
Open‑cell foam depends on layered protection. Most metal buildings only have a single metal skin, which can allow water intrusion. If moisture penetrates the panel, the foam can saturate and lose its performance.
Hybrid System Preferred
For best results, we recommend this combo:
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1.5" of closed‑cell foam for moisture control
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3.5" of open‑cell foam for R‑value and sound control
This ensures long-lasting durability without compromising cost or acoustic benefits.
Open‑Cell Spray Foam Insulation Applications
Best for Interior Walls in New Construction
Open‑cell foam is ideal for 2×4 or 2×6 framed walls. It expands to fill gaps and wraps around wiring without leaving air pockets.
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Cavity Fill Efficiency: Fully conforms to wall cavities
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Moisture Advisory: Use only in dry, protected assemblies
Great for Roof Decks and Attic Conversions
Applying spray foam to the underside of the roof deck creates a sealed thermal envelope and transforms unconditioned attics into usable space.
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Conditioned Attic Space: Helps regulate temperatures
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No Venting Required: Supports unvented roof assemblies
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Lightweight Load: Ideal for older homes and retrofits
Hybrid Systems for Metal Buildings
Direct-to-metal application isn’t recommended due to moisture risk. Instead, we recommend a two-layer spray foam system:
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1.5" closed-cell spray foam: Vapor barrier + strength
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3.5" open‑cell spray foam: R‑value + acoustic control
This approach is perfect for metal buildings, barndominiums, and commercial interiors.
Superior Soundproofing Performance
Spray foam also shines in noise-sensitive areas.
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Noise Dampening: Reduces echo, chatter, and room-to-room noise
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Vibration Control: Great for floors and ceilings in multi-story homes
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Privacy Barrier: Effective in partition walls and shared spaces
Spray Foam Comparison: Open‑Cell vs Closed‑Cell
Here’s how open‑cell foam stacks up against its dense counterpart:
R‑Value per Inch
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Open‑Cell: ~3.6
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Closed‑Cell: ~6.5
Vapor Barrier
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Open‑Cell: No
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Closed‑Cell: Yes
Density
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Open‑Cell: ~0.5 lb/ft³
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Closed‑Cell: ~2 lb/ft³
Cost
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Open‑Cell: Lower
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Closed‑Cell: Higher
Flexibility
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Open‑Cell: Soft and pliable
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Closed‑Cell: Rigid and structural
Ideal Applications
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Open‑Cell: Walls, attics, soundproofing
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Closed‑Cell: Metal roofs, basements, crawlspaces
Installation Tips for Spray Foam Projects
Before any spray foam is applied, a licensed contractor should evaluate your home’s structure, climate zone, and local code compliance.
Expect proper masking, ventilation, and equipment—especially for high-volume installs. Be sure to ask about warranty details and post-installation curing times.
Final Thoughts: Is Open‑Cell Spray Foam Right for You?
If you're looking for an affordable, high-performance insulation that improves comfort, energy savings, and noise control, open‑cell spray foam is a strong choice. It's especially effective in new construction walls, roof decks, and partition walls for soundproofing.
👉 Curious how much spray foam insulation would cost for your project? Contact Truly Sealed today to get a quote and personalized advice
Next Steps
- Project Assessment
We evaluate your building type, climate considerations, and code requirements to recommend the right thickness and system. - Professional Installation
Our licensed crews use calibrated proportioners to ensure consistent density and performance. - Lifetime Warranty
All open‑cell foam installations are backed by a comprehensive lifetime warranty—giving you long‑term peace of mind.
Get Started Today
Are you ready to improve your home or commercial space with the best insulation available? Contact Truly Sealed today for a free, no-obligation estimate tailored to your project needs.