WAC 51-11C-61014. Section A101.4 — Compression of insulation

A101.4 Compression of insulation. Insulation which is compressed shall be rated in accordance with Table A101.4 or reduction in value may be calculated in accordance with the procedures in the ASHRAE Fundamentals Handbook. Table A101.4 R-value of Fiberglass Batts Compressed Within Various Depth Cavities Insulation R-Values at Standard Thickness Rated R-Value 82 71 60 49 38 30 22 21 19 15 13 11 Standard Thickness, Inches 26.0 22.5 19.0 15.5 12 9.5 6.5 5.5 6 3.5 3.5 3.5 Nominal Lumber Sizes, Inches Actual Depth of Cavity, Inches Insulation R-Values when Installed in a Confined Cavity Truss 26.0 82 — — — — — — — — — — — Truss 22.5 — 71 — — — — — — — — — — Truss 19.0 — — 60 — — — — — — — — — Truss 15.5 — — — 49 — — — — — — — — Truss 12.0 — — — — 38 — — — — — — — 2 x 12 11.25 — — — — 37 — — — — — — — 2 x 10 9.25 — — — — 32 30 — — — — — — 2 x 8 7.25 — — — — 27 26 22 21 19 — — — 2 x 6 5.5 — — — — — 21 20 21 18 — — — 2 x 4 3.5 — — — — — — 14 — 13 15 13 11 2.5 — — — — — — — — — — 9.8 — 1.5 — — — — — — — — — — 6.3 6.0 Insulation R-Values at Standard Thickness Rated R-Value 82 71 60 49 38 30 22 21 19 15 13 11 Standard Thickness, Inches 26.0 22.5 19.0 15.5 12 9.5 6.5 5.5 6 3.5 3.5 3.5 Nominal Lumber Sizes, Inches Actual Depth of Cavity, Inches Insulation R-Values when Installed in a Confined Cavity Truss 26.0 82 — — — — — — — — — — — Truss 22.5 — 71 — — — — — — — — — — Truss 19.0 — — 60 — — — — — — — — — Truss 15.5 — — — 49 — — — — — — — — Truss 12.0 — — — — 38 — — — — — — — 2 x 12 11.25 — — — — 37 — — — — — — — 2 x 10 9.25 — — — — 32 30 — — — — — — 2 x 8 7.25 — — — — 27 26 22 21 19 — — — 2 x 6 5.5 — — — — — 21 20 21 18 — — — 2 x 4 3.5 — — — — — — 14 — 13 15 13 11 2.5 — — — — — — — — — — 9.8 — 1.5 — — — — — — — — — — 6.3 6.0