Every teardrop I’ve seen uses insulation in the top of the cabin. I think it will help, not so much with the cold -sweaters and hoodies are for that- but with the heat. It can get quite warm in October. I imagine I will be happy in the long-term to have joined the crowd. I see NO use for adding a layer to the walls; 3/4 plywood will do just fine by itself.
I’m using 3/4″ hard foam. One sheet does it all. A very sharp utility knife blade works well. I have read that a hot knife is super. Didn’t need it so one less tool to buy. (:
I drilled up through the ceiling to make a pilot hole and then used a router bit to cut the opening. Because I was cutting UP, I got COVERED with the sawdust, in my mouth, nose, ears, hair and shoulders. Ick. What a mess. BIG mistake to not use a mask. Glad I had my glasses on. The subsequent shower felt very good.