New guidance for slabs with missing perimeter insulation is posted on the Rater Field guide page.
Partial slab edge insulation:
A slab without a fully insulated perimeter (e.g. no insulation between main body of home and garage and/or porch) should be modeled as follows: Determine the percentage of slab perimeter that is insulated and the percentage that is uninsulated (linear feet). Model two slabs, one insulated and one uninsulated, with areas divided proportionally according to the perimeter percentages.
E.g - 900 sf slab; 120' perimeter, with 30' uninsulated (25% uninsulated vs. 75% insulated)
Model 2 slabs: 1 slab with 30' perimeter and 225 sf area (25% of 900); 1 slab with 90' perimeter and 675 sf area (75% of 900)