The R-value of rigid insulation per inch is typically around 4.0 to 6.0.
The R-value per inch of rigid insulation is typically around 4.0 to 6.5, depending on the specific type and brand of insulation.
The R-value of rigid foam insulation typically ranges from 4 to 8 per inch of thickness, indicating its effectiveness in resisting heat flow.
The R-value of mineral wool insulation typically ranges from 3.0 to 3.7 per inch of thickness.
The insulation value of stucco is relatively low compared to other building materials, typically ranging from R-0.2 to R-0.5 per inch of thickness.
The R-value of thin fiberglass insulation can vary, but it typically ranges from about 2.2 to 3.7 per inch of thickness. Thicker fiberglass insulation will generally have a higher R-value.
While drywall, or gypsum board, does give insulation value it is not a high amount, a 1/2" piece of drywall will only raise the r-value by .45, if you are looking to improve the insulation of a wall you are much better off using rigid foam insulation. An extruded polystyrene board, that's Styrofoam, of 1" thickness gives you an R-value of 5.00, which is over 5 times greater per inch than that of drywall. You can further improve the insulation value of a wall by add some kind of batt insulation in-between the studs.
Among the following materials, the one with the highest R-value per inch of thickness is typically closed-cell spray foam insulation.
Closed cell spray foam insulation is denser and provides a higher R-value per inch, making it more effective at insulating against heat transfer. It also acts as a vapor barrier and is more rigid, providing structural support. Open cell spray foam insulation is less dense and has a lower R-value per inch, but it is more flexible and allows for better sound absorption. It does not act as a vapor barrier and is typically used in interior applications.
From everything I have seen it would be about 12 inches for conventional fiber glass insulation available from Home Depot or Lowes. Polyiso insulation can give up to r-6 per inch. That equates to 7 inches for r-42.
The R-value of stucco typically ranges from 0.2 to 0.5 per inch of thickness. This is lower than most other insulation materials such as fiberglass or foam board, which have higher R-values ranging from 3.0 to 7.0 per inch. Therefore, stucco is not as effective as these materials in providing insulation against heat transfer.
As strange as it may sound dead or still air is one of the best insulators. Insulation such as fiberglass or rock wool and styrofoam work because they are fluffy with trapped air. If you have a sheet of four inch thick R40 fiberglass and squeeze it into a wall made of 2X3 studs you will have less R value than than a 3 inch piece of fiberglass insulation. So the highest R value goes to the insulation that traps the most dead air per inch of thickness and is installed propperly.
The R-value of standard Batt insulation typically ranges from R-3.1 to R-3.7 per inch of thickness. However, the actual R-value can vary based on the specific materials and thickness of the insulation.