## Essential University Physics: Volume 1 (3rd Edition)

We know the following equation for the R-factor: $R-factor = \frac{\Delta x}{k}$ In this equation, $\Delta x$ is thickness, and $k$ is thermal conductivity. Using this equation, we obtain the following values: $R_{air}=5.56$ $R_{concrete}=.143$ $R_{fiberglass}=3.45$ $R_{glass}=.167$ $R_{Styrofoam}=5.0$ $R_{wood}=1.28$