Closed Cell Spray Foam R-Value Explained
Spray foam R-value calculations have gotten complicated with all the product variations, thickness requirements, and performance claims flying around. As someone who has insulated everything from crawl spaces to cathedral ceilings, I learned everything there is to know about getting the numbers right. Today, I will share it all with you.
What Is Closed Cell Spray Foam?
Probably should have led with this section, honestly—closed cell spray foam is polyurethane foam where each cell is completely sealed. This makes it denser and more rigid than open cell foam, adding both insulating properties and structural strength.
Composition
Closed cell foam consists of polyol resin and isocyanate that react to form rigid foam. The density ranges from 1.7 to 2 lbs per cubic foot, contributing to both rigidity and thermal resistance.
Installation
The foam is sprayed onto surfaces, expanding on application and solidifying quickly into an airtight, waterproof barrier. Proper application ensures maximum efficiency.
Understanding R-Value
That’s what makes R-value endearing to us energy-conscious builders—it measures thermal resistance. Higher R-values mean better insulation due to lower heat transfer rates.
Measuring R-Value
R-value depends on thickness, density, and thermal properties. For closed cell spray foam, expect about 6 to 7 R-value per inch—higher than fiberglass or cellulose.
Factors Affecting Performance
Density and Thickness
Denser materials generally insulate better. Two inches of closed cell spray foam yields R-12 to R-14.
Application Quality
Properly applied foam expands uniformly, covering all gaps. Poor application creates air pockets and uneven surfaces that reduce efficiency.
Environmental Factors
Temperature and humidity during installation affect expansion and curing. Follow manufacturer guidelines for optimal conditions.
Benefits
- Energy Efficiency: Reduces winter heat loss and summer heat buildup, lowering energy costs
- Air and Moisture Barrier: Reduces air leaks, resists water vapor, prevents mold
- Structural Support: Rigid foam adds strength to walls and roofs
Comparison with Other Materials
- Fiberglass Batts: R-2.2 to R-3.8 per inch, less effective air barrier
- Cellulose: R-3.2 to R-3.8 per inch, can settle over time
- Open Cell Foam: R-3.5 to R-4 per inch, better sound dampening
Cost Considerations
Closed cell spray foam costs more than other insulation types. The high R-value and additional benefits justify the investment for many projects. Long-term energy savings offset initial costs, and quality installation ensures expected performance.
Environmental Impact
Manufacturing involves chemicals that may release emissions, though modern formulations use more environmentally friendly blowing agents. Improved energy efficiency can lower a building’s carbon footprint over time.
Disposal can be challenging since the foam is not biodegradable. Recycling programs exist but are not widely available.
