R value
The thermal resistance of insulation material can be characterized by its R-value. R is defined as the temperature difference across the insulation by the heat flux going through it:
The typical space inside the residential frame wall is 3.5 in. Find the R-value if the wall cavity is filled with fiberglass batt. (k=0.046 W/m.K=0.027 Btu/h.ft.R)