General Contractor Practice Exam

What is the R value of fiberglass batt insulation used to fully insulate a 2 x 6 wall?

1. 15

2. 19

3. 21

4. 24

The correct answer is: 19

The R-value measures the thermal resistance of insulation, indicating how well it can resist heat flow. For fiberglass batt insulation designed for 2 x 6 wall assemblies, the typically accurate R-value is around 19. This is because the depth of the wall allows for a greater thickness of insulation material compared to a standard 2 x 4 wall, which commonly accommodates batt insulation with a lower R-value. Insulation materials vary, and while some may offer higher R-values, the standard fiberglass batt insulation used in 2 x 6 walls has been established to provide an effective R-value of 19, making it suitable for regulatory building codes and energy-efficient design objectives. This means that the insulation will perform adequately in providing warmth during colder months and keeping interiors cooler in warmer seasons, aligning with energy efficiency guidelines. Other R-values listed, such as 15, 21, and 24, represent either less effective insulation solutions or specialized products not typically used in standard applications for a 2 x 6 wall configuration. Hence, R-value 19 stands as the correct and widely acknowledged standard for fiberglass batts in this application.