Evaluating Thermal Resistance Insulation R-values and Climate Zones
The thermal resistance insulation R-values measure the thermal control of insulation. R-values can be misleading because they do not account for the effect of thermal bridging or how the product works when it is installed in an enclosure. Therefore, the term effective R-value can be used to state the R-value when thermal bridging is included in the R-value measurement.
For that reason, effective R-values can differ from the R-value rating listed in product materials or on the packaging.
Here is a graph comparing nominal to effective R-values:
Here is a climate map designating climate zones in North America:
Here is a chart with recommended R-values by zone for residential and commercial buildings: