R-Value
UNDERSTANDING R-VALUE
- R means resistance to heat flow. The higher the R-value, the greater the insulating value.
- Nominal R-values are the rated/labeled values of insulation products. Nominal R-values do NOT consider the effectiveness of the insulation when it is combined with framing members and other conventional building materials.
- Effective or In-Service R-values are the TOTAL resistances provided by all components in a wall assembly, i.e., sheetrock, metal sheathing, wood or steel framing members, OSB, etc.
Thermal bridging (heat transfer through framing members), air infiltration, radiant heat loss or gain, and moisture impact the effective R-value of building assemblies. Typically, these factors REDUCE the effectiveness of the labeled R-value of conventional cavity-fill Insulation.
