Spray polyurethane foam is better than any other type of insulation for reducing air leakage, and it's high R-value doesn't diminish.
What is the R-Value of Spray Foam Insulation?
r-value-chart2 - EcoTek Spray Foam Insulation
How Much Home Insulation Do I Need in Ohio?
What R-Value Will a Roof Have After Applying Spray Polyurethane Foam?
Blown Spray foam Insulation vs Fiberglass Costs and R-Values
Spray Foam Insulation Cost - Attic Insulation Costs in NY.
Spray Foam R-Value Spray foam, Spray foam insulation, Foam insulation
What is the R value of 2 Inches of Spray Foam Insulation?
Vega Bond V600 Closed Cell Spray Foam Fast Rise 600 Board Feet Kit