R-values and U-factor
What the Thermal panel's rated and effective R-values mean, and which one the code check counts.
The Thermal panel in the side panel sums up how well the assembly insulates. Every number is worked out from the layers as you edit. Nothing here is typed in by hand.
These values are planning aids. They use rated R-values and simplified methods, so have them checked by a licensed professional before you rely on them.
The rated values #
- Rated cavity R: the labeled R of the insulation in the stud bays and any batt layers. This is what the prescriptive code check counts.
- Continuous insulation (ci): the R of the continuous boards (rigid insulation and mineral wool board).
- Assembly R (rated, layers): every layer's R added up. Insulated framing counts as its fill's labeled R, not the stud's.
- Rated R with air films: the assembly R plus the inside and outside air films.
Assembly R (rated) also shows in the toolbar next to Overall, the total thickness.
Effective R and U #
- Effective R (with framing): the whole-wall R once the studs are counted, air films included. Wood studs use the parallel-path method; steel studs use the ASHRAE 90.1 Appendix A correction for the bay. Hover over the label for the details.
- U (effective): one divided by the effective R.
Use effective R and U as the realistic figure for the wall. Rated R is what the prescriptive code paths compare against.
When a steel stud bay is insulated, a note under the totals says how much of its rated R it keeps once the steel's heat bridging is counted.
Assemblies saved with the older method #
An assembly saved before the framing-aware method also shows U (clear-cavity — ignores studs), the number it showed before. See Assemblies saved with the older check to move it to the current method.