Which is better for a 2x6 wall?

The R-23 ComfortBatt. Its 5.5-inch thickness fills a 2x6 cavity and gives R-23; the R-15 is a 3.5-inch batt meant for 2x4 walls.

The R-15 at $80.42 at Cowls Building Supply as of November 7, 2026, versus $89.98 for the R-23 at The Home Depot as of November 7, 2026.

Is the R-23 worth the extra money?

Yes for 2x6 framing. You get roughly 50% more R-value per cavity, which matters more than the $9.56 price gap.

Does either fit 24-inch stud spacing?

The R-15 is 24 inches wide and fits 24-inch on-center framing. The R-23 is 15-1/4 inches wide and fits 16-inch on-center framing.

Both are stone/mineral wool and do not rot or support mold. Service life depends on installation and moisture control, not on the R-value.

Can I mix them in one house?

Yes. Use R-23 in 2x6 exterior walls and R-15 in 2x4 interior or partition walls where code allows.

Rockwool Comfortbatt R-23 Stone Wool Insulation vs ROCKWOOL RXCB3523 R15 Bat Insulation

Buy the R-23 ComfortBatt for 2x6 walls and attic ceilings where you need the higher R-value; it costs $89.98 at The Home Depot as of November 7, 2026. Buy the R-15 24-inch batt only if you have 2x4 framing or need the wider 24-inch width, at $80.42 at Cowls Building Supply as of November 7, 2026. The R-15 is cheaper per pack but covers less thermal resistance, so it is not the better value for a 2x6 cavity.

Today the ROCKWOOL RXCB3523 R15 Bat Insulation costs $9.56 less at its best price.

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