According to the drawings, that Engel drop in unit has 2.2 inches of insulation
at the bottom, and 1.57 on each side. The top doesn't look to have any at all, it looks to be laminated from some material. This causes me to wonder about their performance specs. Has anyone seen a review of this unit? However, looking at the straight forward slab sided design, I see no reason why you couldn't glue on some extra 2 inch thick sheets
around it or make a box of foam for it to fit into.