R-20 vs R-23 Insulation: Which Do You Need? Choosing between R-20 and R-23 insulation is a common decision for DIY builders finishing a 2x6 wall, upgrading an older home, or specifying insulation for a tiny house. This article on r20 vs r23 insulation explains what the numbers mean, how much real-world difference 15% more R-value makes, and which materials and assemblies hit those targets without unnecessary cost. Readers will get a clear comparison of fiberglass batts, mineral wool, rigid foam, closed-cell spray foam, and blown-in cellulose — plus scenario-based recommendations for cold climates, mild retrofits, and small-cavity builds. TL;DR: - R-23 provides about 15% higher thermal resistance than R-20 (R-23 ÷ R-20 = 1.15), but energy savings are smaller and depend on climate, orientation, and fuel type. - Best cost-performance: in mild climates, install R-20 cavity fill and focus on air sealing; in cold climates or thin assemblies, use continuous exterior foam or high R/inch materi...