What is the R-value of 3-1/2 inch batt insulation?

What is the R-value of 3-1/2 inch batt insulation?

• A. 11
• B. 13
• C. 15
• D. 17

Answer: (B)

R-value shows how well insulation resists heat flow. For batt insulation, you multiply the material’s resistance per inch by its thickness. Fiberglass batt is typically about 3.7 per inch, so for 3-1/2 inches the calculation is 3.7 × 3.5 ≈ 12.95, which rounds to about 13. In practice, that means 3-1/2 inches of fiberglass batt is commonly rated around R-13. The other numbers would require using a lower per-inch rating or a different rounding; 11 would come from a lower per-inch value, while 15 or 17 would need a noticeably higher per-inch rating or more thickness.

R-value shows how well insulation resists heat flow. For batt insulation, you multiply the material’s resistance per inch by its thickness. Fiberglass batt is typically about 3.7 per inch, so for 3-1/2 inches the calculation is 3.7 × 3.5 ≈ 12.95, which rounds to about 13. In practice, that means 3-1/2 inches of fiberglass batt is commonly rated around R-13. The other numbers would require using a lower per-inch rating or a different rounding; 11 would come from a lower per-inch value, while 15 or 17 would need a noticeably higher per-inch rating or more thickness.