R-19 fiberglass batt insulation is the standard for 2x6 exterior wall cavities. Manufactured by Owens Corning, CertainTeed, Knauf, Johns Manville. Properties: R-value 19 per 6.25 inches. Density approximately 0.5-1.0 pcf. Non-combustible per ASTM E136. Class A fire rating. Sound attenuation: STC improvement of 3-5 points in wall assembly. Installation: friction fit between studs, no gaps or compression (compression reduces R-value). Kraft facing acts as vapor retarder — face toward conditioned space in heating climates. Unfaced used when separate vapor barrier installed. IECC 2024 minimum wall insulation by climate zone: Zone 1-2: R-13, Zone 3: R-20 or 13+5ci, Zone 4: R-20 or 13+5ci, Zone 5-8: R-20+5ci or 13+10ci. For Zone 5+ compliance, fiberglass alone may not meet code without continuous insulation.