I used the double bubble reflectix material during the rehab of my 1963
Overlander. Last week in Austin TX,at 105 n teh shade, the interiro walls of the trailer were barely warm to the touch, while the outside walls were almost too hot to touch. I did provide an airspace on both sides, and took gret care to tape all seams painstakingly with aluminum tape. I believe that teh results speak for themselves - it works flawlessly.
The noise reduction is actually better than I had expected. It is not as good as fiberglass, but it does attenuate outside noise to a satisfactory level.
Check my threrad for pictures - a 63 for me -