Ever wonder if a radiant barrier is worth it?

I believe the benefit you are getting is from bubbles in the rap. If I were building this I would put the radiant rap on the inside which would also act as a vapor barrier and tyvek the outside which breaths. Any and all insulating improvements will pay off as time goes buy and with the increases in electric and gas bills coming in the future with the switch to green energy(solar, wind and the such) which cost twice the money to produce than with conventional means(coal, natural gas).

The biggest mistake I see folks make when rapping buildings in tyvek is they do not side or cover it immediately and uv light breaks down the rap reducing it insulating and breathable sealing properties. I’m also not fond of the idea of stapling it up. Better to tape it up and keep holes in it to a minimum.