Which is better for a 2x4 wall?

The Knauf R-11. At 3.5 inches it fits a 2x4 cavity; the Owens Corning R-21 is 5.5 inches and will not fit without compressing, which cuts its R-value.

Which is better for a 2x6 wall?

The Owens Corning R-21. It fills a 5.5-inch cavity at R-21, while the Knauf R-11 would leave a 2-inch gap and much lower performance.

Which gives more coverage for the money?

Per pack, the Knauf covers 155 sq ft and the Owens Corning covers 89.13 sq ft. Compare price per square foot at checkout, since the Owens Corning pack costs more for less area.

Does the Owens Corning batt block sound better?

Yes. Owens Corning lists acoustic insulation and noise absorption; Knauf lists thermal insulation only for this product.

Do both have a vapor barrier?

Both have kraft facing. Owens Corning explicitly lists its kraft facing as a vapor barrier for moisture control; Knauf does not make that claim for this batt.

Is the Owens Corning worth the extra weight and cost?

Only if you have 2x6 framing. You get R-21 and sound absorption, but each pack weighs 52 lbs and covers less area than the Knauf pack.

Knauf R-11 Kraft Faced Fiberglass Insulation vs Owens Corning R-21 Faced Fiberglass Insulation

Buy the Owens Corning R-21 for 2x6 walls and any wall where you want more R-value and some noise absorption. Buy the Knauf R-11 for 2x4 walls, tight bays, or a lower total cost per bay. The Knauf covers 155 sq ft per pack; the Owens Corning covers 89.13 sq ft, so the Owens Corning pack costs more per square foot at any price.

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