Shoddy Pad Insulation Alternative

I ran the single aluminum backed stuff in my 67 Dart and on my 71 Vette. Didn't necessarily need foil on both sides since I was just laying it under carpet and the foil is really more for radiation style heat shielding, but I suppose it also helps with moisture control and just general ease of installation. I only put it under my carpet though, haven't run any up the firewall or anything like that. I do like the idea of covering more surfaces and sealing things off to keep the noise down though. Will have to look into that one of these days.