Spray foam insulation provides better thermal resistance, air sealing, and moisture control than fiberglass. In modern residential construction, where energy efficiency and structural resilience are key, closed-cell spray foam consistently delivers superior performance. It prevents air leakage, resists water infiltration, and adds rigidity to framing cavities—unlike fiberglass batts, which often allow airflow and lose effectiveness over time.
This article presents clear comparisons backed by field experience and building science data. Insights reflect hands-on installation and performance results across residential, commercial, and agricultural projects throughout Minnesota’s variable climate.
Why Spray Foam Performs Better Across Key Metrics
The physical properties of spray foam allow it to serve both as insulation and air barrier in one step. In comparison, fiberglass typically requires additional sealing steps, which are often skipped or poorly executed. The data below highlights the difference:
Performance Differences Between Spray Foam and Fiberglass
| Feature | Closed-Cell Spray Foam | Fiberglass Batt |
|---|---|---|
| R-Value per Inch | R-6.5 to R-7 | R-2.9 to R-3.8 |
| Air Barrier | Yes | No |
| Moisture Resistance | High (closed-cell structure) | Low (absorbs moisture) |
| Structural Reinforcement | Adds wall strength | None |
| Lifespan | 50+ years | 10–20 years |
| Thermal Drift Over Time | Minimal | Moderate to High |
| Seamless Application | Expands to fill voids | Requires cutting and fitting |
| Mold Resistance | Excellent | Poor if damp |
Bonus Tip: In cold regions like southern Minnesota, spray foam prevents condensation inside wall cavities by keeping interior surfaces warmer.
Technical Specifications Overview
Key Physical Properties of Closed-Cell Spray Foam
| Specification | Value Range | Relevance |
|---|---|---|
| R-Value per Inch | 6.5 – 7.0 | High thermal resistance in tight spaces |
| Water Vapor Permeance | < 1.0 perms (at 1.5 inches) | Acts as a vapor retarder |
| Compressive Strength | 25 – 30 psi | Reinforces structural assemblies |
| Air Impermeability | < 0.02 L/s·m2 @ 75 Pa | Meets ASTM E283 air barrier criteria |
| Flame Spread (with intumescent) | < 25 (ASTM E84) | Code-compliant with fire protection paint |
Climate Considerations in Minnesota
Southern Minnesota experiences wide seasonal temperature swings and frequent freeze-thaw cycles. Spray foam’s ability to seal gaps and prevent thermal bridging reduces heat loss in winter and keeps homes cooler in summer. Fiberglass often leaves cold spots due to compression, gaps, or air bypass.
Bonus Tip: Closed-cell spray foam adheres tightly even to cold substrates, making it installable during winter construction projects with minimal performance loss.
Things to Know Before Choosing Insulation
Homeowners evaluating insulation options should consider the following:
- Air Leakage: Air movement through fiberglass reduces its R-value in real-world settings.
- Installation Quality: Spray foam requires trained applicators but eliminates many manual error points.
- Space Constraints: Where wall cavity depth is limited, higher R-value per inch of spray foam delivers better efficiency.
- Moisture Risks: Fiberglass holds moisture, increasing risk of mold and rot.
- Future Renovation: Spray foam bonds permanently, which can complicate wall access later.
Services Provided for Insulation Upgrades
Foam Worx Insulation delivers insulation solutions that match structural needs and building codes:
- Closed-Cell Spray Foam: High-performance insulation for walls, roofs, and foundations.
- Blown-In Attic Insulation: Efficient top-off option for attics to reduce heating loss.
- Intumescent Paint: Fire-resistant coating required over foam in exposed areas.
- Residential Insulation: Energy-efficient retrofits and new construction applications.
Before You Choose: Immediate Questions to Ask
Do current walls or attic have proper air sealing?
Proper air sealing is crucial before adding insulation. If gaps, cracks, or penetrations around pipes, wiring, or framing aren’t sealed, you could lose conditioned air and reduce the insulation’s effectiveness. A professional inspection can reveal whether air sealing is needed before moving forward.
Are there signs of moisture problems or drafts?
Yes, signs like mold, mildew, damp insulation, or cold drafts could indicate moisture infiltration or air leakage. These issues should be addressed first, as insulation installed over moisture-prone areas can lead to long-term damage or decreased performance.
How much insulation space is available?
The available space—such as stud bay depth, attic joist height, or crawlspace clearance—will determine what type and thickness of insulation is suitable. Some materials like spray foam can fit tight or irregular areas, while others may require more room to meet R-value targets.
Is long-term efficiency more important than installation speed?
If your priority is energy savings, durability, and comfort over time, investing in a higher-efficiency material like spray foam or dense-pack cellulose may be worthwhile—even if installation takes a bit longer. But if you need a quick solution, batts or blown-in fiberglass may offer faster turnaround with decent performance.
Final Thoughts on Choosing the Right Insulation
Closed-cell spray foam outperforms fiberglass in energy efficiency, air control, and durability. The material’s tight seal and moisture resistance make it a better fit for modern building standards especially in Minnesota’s climate. Fiberglass can still serve specific needs but falls short in airtightness and longevity.
Evaluate insulation based on performance, application needs, and building design. Short-term installation ease shouldn’t override long-term results.
Contact Foam Worx Insulation for Expert Help
For more information on selecting the right insulation or to schedule a service inspection, contact Foam Worx Insulation. Email [email protected] or call (507) 407-0678. The team will help determine the most effective solution based on your home structure and climate zone.
Long-Term Questions Answered
How long does spray foam last without degrading?
Spray foam maintains performance for 50 years or more under normal conditions. It resists moisture, pests, and settling.
Can spray foam be applied in old homes?
Yes. It works well for retrofits. However, older homes may require prep work like knob-and-tube wiring inspection.
Does spray foam need additional vapor barriers?
Closed-cell spray foam at sufficient thickness acts as its own vapor barrier. No additional membrane is typically needed.
Is fiberglass ever a better option?
In open, ventilated attic spaces where cost and ease of removal matter, fiberglass may be used—but it’s less effective for walls.
What happens if spray foam is installed improperly?
Incorrect ratios or coverage can affect curing. Always work with certified installers to meet code and ensure performance.