Open Cell vs. Closed Cell Spray Foam Insulation in Nebraska
Nebraska's climate zone 5A changes the open vs. closed cell decision. Here's what Lincoln homeowners need to know.
Quick Answer: In Nebraska, use open cell spray foam in attics and interior walls (R-3.7/inch, $1.50–$3.50/sq ft). Use closed cell spray foam in crawl spaces, basements, rim joists, and any below-grade application (R-6.5/inch, $3.00–$5.00/sq ft). Closed cell is required below grade — open cell absorbs moisture and fails in those conditions.
What Is Open Cell Spray Foam?
Open cell spray foam is a soft, lower-density foam that expands dramatically on application — up to 100 times its liquid volume. The foam cells are "open," meaning they're interconnected and allow some air and moisture movement. This makes it breathable and excellent for sound attenuation.
- R-value: R-3.5 to R-3.7 per inch
- Cost: $1.50–$3.50 per square foot installed
- Density: About 0.5 lb per cubic foot
- Vapor permeance: High — not a vapor barrier
- Best for: Attics, interior walls, soundproofing
What Is Closed Cell Spray Foam?
Closed cell spray foam is harder, denser, and has fully enclosed cells that trap a blowing agent — giving it nearly double the R-value per inch of open cell. At 2+ inches thick, it acts as a Class II vapor retarder, which is critical for Nebraska's moisture management needs below grade.
- R-value: R-6 to R-7 per inch
- Cost: $3.00–$5.00 per square foot installed
- Density: About 2 lb per cubic foot
- Vapor permeance: Very low — acts as vapor barrier at 2"
- Best for: Crawl spaces, basements, rim joists, exterior walls
Side-by-Side Comparison
| Feature | Open Cell | Closed Cell |
|---|---|---|
| R-Value per inch | 3.5–3.7 | 6–7 |
| Cost per sq ft installed | $1.50–$3.50 | $3.00–$5.00 |
| Vapor barrier | No | Yes (at 2"+) |
| Water resistant | No | Yes |
| Structural support added | Minimal | Yes |
| Sound attenuation | Excellent | Good |
| Expansion on application | Up to 100x | 30–40x |
| Suitable below grade | No | Yes |
Nebraska-Specific Guidance: Climate Zone 5A
Nebraska sits in climate zone 5A — a mixed-humid zone with approximately 6,000 heating degree days per year in Lincoln and hot, humid summers. This climate directly affects your foam choice:
Crawl Spaces: Closed Cell Required
Nebraska soil moisture is high. Open cell foam would absorb ground moisture, swell, lose R-value, and eventually fail in a below-grade crawl space. Closed cell at 2–3 inches is the only acceptable choice.
Attics: Open Cell Preferred
In a vented attic, the roof deck needs to breathe in winter to prevent ice dams and condensation. Open cell allows this moisture movement while still air-sealing the attic floor. Exception: if creating an unvented (conditioned) attic, use closed cell on the roof deck.
Rim Joists: Closed Cell Required
Rim joists are exposed to exterior temperatures and exterior moisture. Closed cell provides the vapor barrier and higher R-value needed at this critical thermal bridge. This is often the highest-ROI project in older Lincoln homes.
Interior Walls: Either Type Works
For interior wall soundproofing or air sealing, either foam works. Open cell is typically chosen for cost savings and better sound attenuation (its spongy texture absorbs sound waves more effectively).
Not Sure Which Foam You Need?
Our crew will assess your home and recommend the right foam for each application — at no cost.
Which Should You Choose for Your Lincoln Home?
For most Lincoln homeowners, the answer is both. A typical full-home insulation project uses closed cell in the crawl space and rim joists, and open cell in the attic. This hybrid approach maximizes performance where it matters (below grade) while keeping costs reasonable above grade.
Learn more about spray foam insulation costs in Lincoln, NE or explore our specific crawl space encapsulation and attic insulation services.
Frequently Asked Questions
Open cell is the right call for Nebraska attics in most cases. Here's the reasoning we walk homeowners through: Nebraska's climate zone 5A creates vapor pressure differentials in winter that need to escape through the roof deck. Open cell foam allows that moisture movement, preventing condensation buildup in the roof assembly. Closed cell on a roof deck can trap moisture and cause structural damage over time in our climate. Open cell also delivers R-49 for significantly less money — important for an area that doesn't need the structural rigidity closed cell provides.
Nebraska's soil stays consistently moist — a legacy of the Platte River basin and Lancaster County's clay soils. We've pulled out failed open cell installations from Lincoln crawl spaces where the foam had absorbed ground moisture, lost thermal performance, and begun harboring mold. Closed cell at 2+ inches is impermeable to water, acts as a Class II vapor retarder, and handles Nebraska's below-grade moisture environment without degrading. It's not a recommendation — for crawl spaces in Nebraska, it's the technically correct solution.
Open cell spray foam delivers R-3.5 to R-3.7 per inch. Closed cell delivers R-6 to R-7 per inch — nearly double the thermal resistance in the same thickness. In practical terms for Nebraska's zone 5A R-49 attic requirement: you'd need about 13–14 inches of open cell, or just 7–8 inches of closed cell. For tight spaces like rim joists (typically 2–3 inches of accessible depth), closed cell's higher R-value per inch makes it the only viable choice.
For a standard vented attic in a Nebraska home, no — the premium isn't justified. Open cell does the job at a lower cost per square foot, and the breathability actually improves performance in our climate. The one exception: if you're converting to a conditioned (unvented) attic to house HVAC equipment above the ceiling, closed cell on the underside of the roof deck is often required. Your contractor will tell you which scenario applies. In every other attic situation, spend the closed cell budget on the crawl space and rim joists where it's genuinely necessary.
Yes — and the hybrid approach is what we recommend to most Lincoln homeowners who are doing both attic and crawl space work. Use open cell in the attic (lower cost, breathable, R-49 easily achieved). Use closed cell in the crawl space and rim joists (vapor barrier, structural rigidity, correct for below-grade). You get the right foam in each location rather than paying closed cell prices everywhere. This hybrid approach is common among experienced Nebraska contractors.
Areas We Serve in Nebraska
Lincoln Spray Foam serves Lincoln and surrounding communities throughout Lancaster County and beyond. Free estimates are available for all service areas listed below.
- Spray foam insulation in Lincoln, NE — all Lincoln neighborhoods and Lancaster County
- Spray foam insulation in Waverly, NE — 12 miles northeast of Lincoln, no travel surcharge
- Spray foam insulation in Hickman, NE — south Lancaster County, new construction and retrofits
- Spray foam insulation in Beatrice, NE — Gage County, older home retrofits and ag buildings
- Spray foam insulation in Seward, NE — 25 miles west of Lincoln in Seward County
- Spray foam insulation in Papillion, NE — Sarpy County, residential and new construction
Don't see your city? Call (402) 799-4760 — we serve communities throughout southeast Nebraska.
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Call or request a quote online. We serve Lincoln and all of Lancaster County.