Insulation Science: R-Values, Spray Foam vs Batts, Attic Ventilation

R-Value Basics Explained

R-value measures thermal resistance — the higher the number, the better the insulation. For most US climates, you want R-38 to R-60 in your attic and R-13 to R-21 in exterior walls.

Spray Foam vs Fiberglass Batts

• Fiberglass batts: R-3.1 per inch, DIY-friendly, $0.40-$1.50/sq ft
• Open-cell spray foam: R-3.5 per inch, seals air leaks, $0.60-$1.20/sq ft
• Closed-cell spray foam: R-6.0 per inch, acts as vapor barrier, $1.50-$3.00/sq ft

Attic Ventilation Strategies

1. Soffit vents + ridge vent = natural convection airflow (best for most homes)
2. Gable vents alone are insufficient — they create short-circuiting air paths

Climate Zone Recommendations

In cold climates (zones 5-8), prioritize attic insulation to R-60. In hot-humid zones (3-4), focus on exterior wall insulation and vapor barriers to prevent condensation.