I ordered a Jotul 350 insert in blue/black enamel this morning and it will be 3 days to 3 weeks depending on where they can find one. Meantime I'm working on my "hole in the wall" firebox. Because it's an external fireplace, I'll be lining the sides, back and top with 3 in roxul and durorock. I have plenty of room, it's a big hole. Does it make sense to put a foil face on the durorock facing the inside. Would that help radiate energy back toward the front?