Chapter 44 — REFERENCED STANDARDS

Section BK109 — THERMAL PERFORMANCE

2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · ingested 2026-07-07 · California

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BK109.1 Thermal characteristics.

BK109.1 Thermal characteristics. Cob walls shall be classified as mass walls in accordance with Section N1102.2.6 and shall meet the R -value requirements for mass walls in Table N1102.1.3.

BK109.2 Thermal resistance.

BK109.2 Thermal resistance. The unit R -value for cob walls with a density of 110 pounds per cubic foot (1762 kg/m [3] ) shall be R-0.22 (RSI 0.0387) per inch of cob thickness. The unit R -value for cob walls with a density of 75 pounds per cubic foot (1201 kg/m [3] ) shall be R-0.54 (RSI 0.095) per inch of cob thickness. Linear interpolation is permitted. Extrapolation is not permitted. Walls that vary in thickness along their height or length shall use the average thickness of the wall to determine its R -value. The thermal resistance values of air films and finish materials or additional…

BK109.3 Additional insulation.

BK109.3 Additional insulation. Where insulating materials are added to the face of a cob wall, the combination of additional insulation and any associated connecting, weather-resisting or protective materials shall comply with Section BK104.1.2, Items 1 through 4.