How many inches of blown insulation equals R30 depends on the material, but it is significantly less than R49. For blown fiberglass loose-fill at about R-2.5 to R-2.8 per inch, R30 requires roughly 10.5 to 12 inches of depth. For example, many fiberglass charts list R30 at 10.25 inches at 0.40 pounds per cubic foot density. For blown cellulose at about R-3.2 to R-3.8 per inch, R30 requires about 8 to 9.5 inches of depth, with most manufacturers listing R30 at 8.2 inches. For blown mineral wool or rock wool at about R-3.0 to R-3.3 per inch, R30 requires about 9 to 10 inches. These are installed thicknesses after settling, so installers typically blow a little extra to account for initial settling of cellulose. R30 is considered the minimum code for attics in some older southern codes, but current Energy Star and IECC codes in most climates now require R-38 to R-60, so R30 is usually insufficient for new construction. If you currently have R-19, adding about 4 to 6 inches of cellulose or 5 to 7 inches of fiberglass will bring you up to R-30.
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