On the foil: it can act as a heat shield, but not as an insulator. It'll stop convection if it's wall-to-wall, and it'll stop radiation if it's shiny. The "stops radiation" is why "space blankets" are shiny, and that's why they work.
If you look at the old pictures of the Gemini capsule in space, you'll see that the back of one of the sections was covered with gold foil -- that's because gold reflects infrared, which makes it a heat shield.
If you were to put the foil in contact with the electronics and all that in contact with the pipe, then you may as well not have the foil.
A thin balsa wall, with aluminum foil on the pipe side, shiny side toward the pipe, will provide insulation, it'll bounce the infrared back toward the pipe, it'll be light, and it should be easy to mount. Think on that...