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 insulation and attic insulation services.
Frequently Asked Questions
Open cell is generally preferred for Nebraska attics. It allows the roof deck to breathe, which helps manage moisture in Nebraska's zone 5A climate. It's also less expensive and provides good R-value for attic applications.
Nebraska's high soil moisture means crawl spaces need a vapor barrier. Closed cell foam at 2+ inches provides both insulation and vapor resistance. Open cell foam would absorb moisture and fail in a below-grade application.
Open cell spray foam provides R-3.5 to R-3.7 per inch. Closed cell provides R-6 to R-7 per inch — nearly double. For Nebraska's zone 5A, this means you need about 13 inches of open cell or 7 inches of closed cell to reach R-49 in an attic.
Usually not. Unless you're creating a conditioned (unvented) attic, open cell provides adequate performance at a lower cost. Save the closed cell budget for your crawl space and rim joists, where it's required and makes a bigger difference.
Yes — many Lincoln homeowners use closed cell in the crawl space and rim joists, and open cell in the attic. This hybrid approach gives you vapor protection where it's needed and cost savings where performance allows.
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