Choosing between open cell and closed cell spray foam depends heavily on where in your home you're insulating — and in Nebraska, climate zone 5A makes some of those choices for you. This guide covers everything a Lincoln-area homeowner needs to know before calling a contractor.
What Is Open Cell Spray Foam?
Open cell spray foam is a softer, lower-density foam that expands dramatically on application. The cells are "open," meaning they're not completely enclosed — this gives the foam a spongy texture and allows it to breathe. In Nebraska, open cell foam is most commonly used in attics and interior walls.
Key specs for open cell:
- R-value: R-3.5 to R-3.7 per inch
- Installed cost: $1.50–$3.50 per square foot
- Vapor permeance: High (allows some moisture movement)
- Density: 0.5 lb per cubic foot
- Expansion: Up to 100 times its liquid volume
What Is Closed Cell Spray Foam?
Closed cell spray foam is denser, harder, and has fully enclosed cells that trap a blowing agent — giving it significantly higher R-value per inch. It also acts as a vapor barrier, which is critical in Nebraska's high-humidity environment, especially below grade.
Key specs for closed cell:
- R-value: R-6 to R-7 per inch
- Installed cost: $3.00–$5.00 per square foot
- Vapor permeance: Very low (acts as vapor barrier at 2"+)
- Density: 2 lb per cubic foot
- Added structural rigidity: Yes
Side-by-Side Comparison
| Feature | Open Cell | Closed Cell |
|---|---|---|
| R-Value per inch | 3.5–3.7 | 6–7 |
| Cost per sq ft | $1.50–$3.50 | $3.00–$5.00 |
| Vapor barrier | No | Yes (at 2"+) |
| Water resistant | No | Yes |
| Structural support | Minimal | Yes |
| Sound attenuation | Excellent | Good |
| Best locations | Attics, interior walls | Crawl spaces, basements, below-grade |
Nebraska-Specific Guidance: Climate Zone 5A
Nebraska sits in climate zone 5A — a mixed-humid zone that sees harsh winters (around 6,000 heating degree days in Lincoln) and hot, humid summers. This climate has direct implications for which foam you choose:
- Below-grade applications (crawl spaces, basements): Closed cell is required. Nebraska soil moisture is high, and open cell foam would absorb water, lose R-value, and eventually fail.
- Attics: Open cell works well in Nebraska attics. The roof deck needs to breathe in winter to prevent ice dams, and open cell allows that moisture movement. Always use open cell in vented attics.
- Rim joists: Closed cell is strongly preferred — these are exposed to exterior conditions and need the vapor barrier and higher R-value per inch that closed cell provides.
- Interior walls: Either type works. Open cell is typically chosen here for cost savings and better sound attenuation.
Which Should You Choose?
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 and any interior walls. This hybrid approach maximizes performance where it matters while keeping costs reasonable.
The only location where you might need closed cell in the attic is if you're creating a conditioned (unvented) attic — in that case, your contractor will specify closed cell on the roof deck.
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Frequently Asked Questions
Open cell spray foam is generally preferred for Nebraska attics. It allows moisture movement through the roof deck, which helps prevent ice dams and condensation issues in zone 5A winters. It's also significantly less expensive and provides good R-value for attic applications.
Nebraska's high soil moisture means crawl spaces are exposed to significant humidity. Open cell spray foam is not vapor-resistant and would absorb moisture, swell, and eventually fail in a below-grade application. Closed cell foam at 2–3 inches creates a proper vapor barrier and air seal.
For Nebraska climate zone 5A: attics need at least R-49 (about 13 inches of open cell), crawl spaces need R-15 to R-19 at the walls (about 2–3 inches of closed cell), and rim joists need at least R-15 (about 2 inches of closed cell).
In below-grade applications like crawl spaces and basements, yes — closed cell is worth it because open cell would fail. In above-grade applications like attics, open cell is usually the better value. For rim joists, most Lincoln contractors recommend closed cell despite the higher cost.
Yes, and this is actually the most common approach for whole-home insulation in Lincoln. Many homeowners use closed cell in the crawl space and rim joists, then open cell in the attic and interior walls. Your contractor can quote both applications on the same job.