The department of energy provides a service to determine the exact r value required based on zip code and type of heating fuel.
R value concrete wall basement.
You are confusing the minimum thickness of foam on the outside of above ground framing with the code required r value for basement wall insulation using foam.
Brian doe s wall foam r value question brian.
Consider adding insulation to the outside of the basement wall this can serve as protection for your waterproofing also.
By doubling the thickness of the wall to 16 inches the r value only increases by 0 50.
Foam insulation is preferred over fiberglass as it has a higher r value is resistant to moisture.
Generally zones 1 and 2 cover the southern states which suggest no necessary values to r 10 for basement walls.
Zones 3 and 4 include the midwest and northern regions requiring r 10 to r 19 values.
These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation.
The code cited by martin is for basement walls.
The chart you cite is for the above ground framing.
For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3.
Concrete block makes a cost effective and structurally sound wall but it has.