Originally Posted by ColoRockiesFan
Thanks, it is a bit of a challenge. I'm leaning toward the Thinsulate ... I think it will work best for these walls. Would polyiso even work with these surfaces?
No, polyiso rigid foam board wouldn't really work for the walls pictured- I guess I was being optimistic and don't like to say no or never. But, it only makes sense if there is a large flat surface areas. IMO, Thinsulate or spray foam insulation seams the best choices.
But, if you decide to insulate the floor, 1" polyiso rigid foam board would be an ideal choice under a subfloor.
I did 1" floor insulation in my build because I plan on 4-season use with winter camping in cold climates for snowboard trips. I did 1" instead of 1/2" because I thought it might be sturdier and less likely to compress (I also put strips of 1/4" plywood in the grooves of my bare floor to create a flat surface to support the rigid board). But if you have a sturdy subfloor 1/2" or more, I think it would be fine with 1/2" or 1" insulation. I have a mid-top roof that does not allow full standing height, so I decided I didn't care about losing any ceiling height with floor insulation (I'll also be doing 1" rigid board on the ceiling of my fiberglass roof too).
Before I started, I saw many vans without floor insulation. And that's totally fine if you're in California or the south and not doing much wintering and don't want to lose standing height.
Also, hot air rises, so really, for winter, roof and ceiling insulation is probably a bit more important than floor insulation to keep warm air in- I think. I have no degree in thermodynamics here. All my advice should be taken with a grain of salt- I have a bachelor of arts degree- ha! But, I try my best researching the forums and blogs.
Whatever you do, don't waste your time and money putting Reflectix right against the van wall or floor. Reflectix is most effective at reflecting radiant heat and it needs an air gap to do that (1/8" or more I think). Reflectix is also very effective to hang for your windows, there's an air gap, and the foil reflects the sun's radiant heat. But if it's pressed up against hot metal van walls or floors, it's conducting and not gonna do much, it's essentially the small R-value of bubble wrap, no need for the foil. That's my understanding at least.
That said, I think Flux' use above (Thinsulate first and holding it in with a layer of Reflectix) is good and sound.
In a similar way, I've been considering an outer layer of Reflectix attached to the backside of my 1/4" birch paneling for my walls. I don't know if it would be effective and worth it though???
It would have some air gap between the paneling and my 1" of polyiso board insulation adhered to the metal van walls, especially at the bottom of the wall where the van is wider.