Best self-adhesive foil insulation

Start with the EcoFoil single-sided perforated foil. It's the most versatile of the bunch: a big roll of 97%-reflective foil with a white perforated face, so it can go on walls, ceilings and attic rafters without trapping moisture, and it's sold at several stores.

Who the others suit:

• Small jobs and quick fixes (window panes, RV walls, a shed door): the SmartSHIELD or TWCUSEP bubble-foil rolls — thin, easy to cut, and they add a little padding as well as reflection.
• Big attic or garage-door runs: the 4' x 125' solid or perforated EcoFoil rolls, or Arma Foil if you need a stated Class A fire rating.
• Tight budgets: the small reflective sheets and film rolls are fine for patching, but check the size before you buy — several are only a few feet.

One caveat: most of these are radiant barriers, not thick insulation. They reflect heat rather than fill a cavity, so pair them with existing insulation for real R-value. Look for a foil with an adhesive backing or foil tape if you want it to stick down flat.