All material selections including the r-values of walls, ceilings, and floors can be adjusted in step 2. First start by expanding the system > zone > and room section headers to unhide the section you would like to edit. Section headers are expanded and collapsed by clicking anywhere on the header. Below is a screenshot showing what the sections look like when they are expanded.
Once you expand the section header for above grade walls you will see options to adjust the cavity insulation r-values as well as the board insulation r-values. Once you make a change simply collapse the section header and the loads will update. Below is a screenshot showing the expanded above grade wall section.
You can follow the same procedure to edit the r-values for ceilings and floors.