$\backslash$table$[[$Step $2$:$,$Calculate the R$-$value of the Floor System Cross Section, $R_r,$Per specs isted.$]]$

Calculate the thermal resistance of the floor system, $R,$ from Figure $6,$ considering all insulating materials in the cross$-$section including any floor coverings. When determining $R_r$ nominal $R-$values shall be used for all materials, including insulation. $($Use the aggregate of manufacturer's nominal values for each component of the floor system. Some common materials and $R-$values are contained in Appendix III.$)$ If the floor cross$-$section and resulting thermal resistance of the floor system varies over its area, calculate $R,$ as the average over the perimeter $39$ inches $(1$ m $)$ of the floor. In superinsulated slabs, where the calculated $R,$ value exceeds R $-28,$ the designer must follow the design procedure for unheated buildings, since the heat from the building is substantially blocked from moving into the ground and protecting the foundation.

$R_r={5\mathrm{.}05}_{?}$